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Lipid biomarkers indicate different ecological niches and trophic relationships of the Arctic hyperid amphipods Themisto abyssorum and T. libellula
Abstract
The hyperiid amphipods Themisto libellula and T. abyssorum are important components of Arctic pelagic ecosystems. Both species are carnivorous and prey on mesozooplankton. They represent a substantial food source for marine vertebrates and are a key link between zooplankton secondary production and higher trophic levels. We present data on the total lipid content, lipid class and fatty acid composition of T. libellula and T. abyssorum from northern Fram Strait and the central Arctic Ocean. Both species had moderate to high lipid contents of 14-42% of body dry mass. In T. abyssorum, total lipid content was correlated to body mass, while T. libellula showed sex-related differences in lipid content. Despite their smaller body size, females of T. libellula had higher lipid contents than males. Wax esters represented the major lipid class in both species with 41-43% of total lipid, while triacylglycerols contributed 23-32%. The fatty acid composition was dominated by the long-chain polyunsaturated moieties 20:5(n-3) and 22:6(n-3), short-chain saturated compounds (16:0 and 14:0) and monounsaturated fatty acids of varying length, i.e. 16:1(n-7), 20:1(n-9), 18:1(n-9) and 22:1(n-11). Species-specific and geographic variations in the fatty acid and alcohol patterns were apparently linked to differences in diet and life-cycle. High amounts of the fatty acids and alcohols 20:1(n-9) and 22:1(n-11) in T. libellula indicate predation on herbivorous Calanus copepodids. In addition, elevated levels of 20:5(n-3) in T. libellula indicate a close connection with ice-algal production and the importance of cryo-pelagic coupling processes (i.e. exchange processes between the sea ice and the pelagic communities) for the nutrition of this high-Arctic epipelagic species. In contrast, T. abyssorum is characterised by lower amounts of 20:5(n-3) and its biomarker ratios indicate a higher trophic level. This observation is consistent with the subarctic-boreal origin of T. abyssorum and its occurrence in deeper layers of the Arctic Ocean, where it may feed on omnivorous and/or carnivorous prey.
... Both T. libellula and T. abyssorum are preyed upon by fish, seabirds and marine mammals throughout the Arctic (reviewed in . They are visual predators of mesoand microzooplankton and although their geographical distributions overlap, they occupy different ecological niches (Auel et al., 2002). ...
... Themisto abyssorum (Figure 2b) is largely found in waters of Atlantic origin (Mumm et al., 1998) in the marginal Arctic seas and has a life cycle of up to 2 years . It is smaller than T. libellula, and while lipid content by body mass is comparable, its smaller body size makes it an overall less nutritious prey (Auel et al., 2002). Previous studies indicate that the diet of T. ...
... abyssorum is less sea ice-dependent than that of T. libellula, with a wider prey spectrum and a higher trophic position in the Arctic food web (Auel et al., 2002;Kohlbach et al., 2016). ...
Rapid warming in the Arctic is drastically impacting marine ecosystems, affecting species communities and food-web structure. Pelagic Themisto amphipods are a major component of the Arctic zooplankton community and represent a key link between secondary producers and marine vertebrates at higher trophic levels. Two co-existing species dominate in the region: the larger Themisto libellula, considered a true polar species and the smaller Themisto abyssorum, a sub-Arctic, boreal-Atlantic species. Recent changes in abundance and distribution ranges have been detected in both species, likely due to the Atlantification of the Arctic. The ecology and genetic structure of these species are understudied, despite their high biomass and importance in the food web. For both species, we assessed genetic diversity, patterns of spatial genetic structure and demographic history using samples from the Greenland shelf, Fram Strait and Svalbard. This was achieved by analysing variation on the mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI). The results revealed contrasting levels of mtCOI diversity: low levels in T. libellula and high levels in T. abyssorum. A lack of spatial genetic structure and a high degree of genetic connectivity were detected in both species in the study region. These patterns of diversity are potentially linked to the impacts of the Last Glacial Maximum. T. libellula populations may have been isolated in glacial refugia, undergoing gene flow restriction and vicariant effects, followed by a population expansion after deglaciation. Whereas T. abyssorum likely maintained a stable, widely distributed metapopulation further south, explaining the high diversity and connectivity. This study provides new data on the phylogeography of two ecologically important species, which can contribute to predicting how zooplankton communities and food-web structure will manifest in the rapidly changing Arctic.
... Four biomarker ratios of interest were also cal culated: C16:1n7/C16:0, C18:1n9/C18:1n7, C20:5n3/C22:6n3, and C22:1n11/C20:1n9. C16:1n7 and C20:5n3 are indicators of pelagic or sympagic diatoms (ice algae), while C22:6n3 indicates a flagellate-based diet (Auel et al. 2002). C18:1n7, which is formed by elongation of the precursor C16:1n7, is an indicator of herbivorous feeding on diatoms, while C18:1n9 indicates carnivorous feeding and is a proxy for trophic level (Graeve et al. 1997). ...
... All individuals but one had C22:1n11/C20:1n9 ratios > 1.8 which suggests that C. hyperboreus is the most important calanoid copepod species in the diet of the sampled individuals (Falk-petersen et al. 2009), regardless of the region occupied during summer and fall. High values of C16:1n7/C16:0 found in this study are consistent with findings from Pomerleau et al. (2014) and confirm that diatoms are the main type of phytoplankton at the base of these food webs in which EC-WG bowhead whales forage (Auel et al. 2002). Carnivorous marine mammals are thought to be highly adapted in the digestion and incorporation of marine-specific FAs without any modification (Iverson 2008), meaning that inter-individual differences in FA composition can be attributed to differences in diet. ...
... While prey sampling would have been necessary to identify specific prey items from FAs in the outer blubber of bowhead whales, the significant differences in FA ratios between individuals using different habitats support the results from the SI ratios of distinct diet compositions between habitats used. Variability in C20:5n3/C22:6n3 and C18:1n9/C18:1n7 could not be explained by any predictors or combination of predictors, but the values of C20:5n3/C22:6n3 and C18:1n9/C18:1n7 >1 indicate carnivorous feeding in a diatom-based food web (Graeve et al. 1997, Auel et al. 2002 which is consistent with the current knowledge on the diet of bowhead whales from this population. ...
Shifts in zooplankton quantity and quality caused by climate change could challenge the ability of bowhead whales to meet their energetic requirements. When facing such selection pressure, intra-population variation dampens the negative effects and provides population-level resilience. Previous studies observed inter-individual diet variation in bowhead whales, but the mechanism responsible for the variation was undetermined. We investigated foraging variability in Eastern Canada-West Greenland bowhead whales using dietary biomarkers (stable isotopes, fatty acids) and movement data (satellite telemetry with time-depth recorders) from the same individuals. We found that bowhead whale individuals using distinct summer and fall foraging habitats displayed differences in horizontal movements, foraging dive depth, and diet. For individuals using the Canadian Arctic Archipelago habitat (Foxe Basin, Gulf of Boothia, Prince Regent Inlet, Lancaster Sound and Admiralty Inlet, Nunavut), they performed long distance movements across regions, and their foraging dive depth was generally shallow, but increased from July to November. These whales displayed higher δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Individuals using the West Baffin Bay habitat (Cumberland Sound, Baffin Bay, Davis Strait) were more localized in their horizontal movements and consistent over time in their foraging dive depth, which was generally deeper. These whales displayed lower δ ¹³ C and δ ¹⁵ N values and ratios of C16:1n7/C16:0. Overall, this inter-individual variation in diet and foraging behaviour could indicate some niche variation which would be beneficial for the population under changing habitats and prey availability.
... These two congeneric species, co-existing throughout the Arctic region, are an important food source for higher trophic levels, including fish, seabirds, harp seals and whales [23]. They are themselves efficient predators of zooplankton, believed to mainly prey on calanoid copepods [15,24]. Hence, Themisto amphipods build an important link between lower and higher trophic levels in the Arctic marine food web. ...
... According to previous studies [8,24,26,27] Themisto amphipods are believed to be opportunistic carnivores feeding on the most abundant zooplankton species, including copepods, euphausiids and chaetognaths. Nevertheless, studies of Auel et al. [24] and Kohlbach et al. [8] using lipid, fatty acid composition and stable isotopes, found evidence for a niche segregation between T. libellula and T. abyssorum in the Arctic ecosystem, with T. libellula being more dependent on the ice-algal pathway, feeding on herbivorous copepods, whereas T. abyssorum occupies a higher trophic position, feeding on omni-and carnivorous prey. ...
... According to previous studies [8,24,26,27] Themisto amphipods are believed to be opportunistic carnivores feeding on the most abundant zooplankton species, including copepods, euphausiids and chaetognaths. Nevertheless, studies of Auel et al. [24] and Kohlbach et al. [8] using lipid, fatty acid composition and stable isotopes, found evidence for a niche segregation between T. libellula and T. abyssorum in the Arctic ecosystem, with T. libellula being more dependent on the ice-algal pathway, feeding on herbivorous copepods, whereas T. abyssorum occupies a higher trophic position, feeding on omni-and carnivorous prey. If these two sympatric species systematically occupy distinct trophic positions and display divergent feeding habits, we can assume that the two amphipods will be differently impacted by the consequences of climate change and sea-ice decline in the Arctic [23]. ...
The two congeneric hyperiids Themisto libellula and T. abyssorum provide an important trophic link between lower and higher trophic levels in the rapidly changing Arctic marine ecosystem. These amphipods are characterized by distinct hydrographic affinities and are hence anticipated to be differently impacted by environmental changes, with major consequences for the Arctic food web. In this study, we applied DNA metabarcoding on the stomach contents of these Themisto species, to comprehensively reveal their prey spectra at an unprecedented-high-taxonomic-resolution and assess the regional variation in their diet across the Fram Strait. Both species feed on a wide variety of prey but their diet strongly differed in the investigated summer season, showing overlap for only a few prey taxa, such as calanoid copepods. The spatially structured prey field of T. libellula clearly differentiated it from T. abyssorum, of which the diet was mainly dominated by chaetognaths. Our approach also allowed the detection of previously overlooked prey in the diet of T. libellula, such as fish species and gelatinous zooplankton. We discuss the reasons for the differences in prey spectra and which consequences these may have in the light of ongoing environmental changes.
... The fatty acid (FA) profile of C. scaura was characterized by the presence of four major FAs, 16:0, 18:1n-9, 20:5n-3 (EPA) and 22:6n-3 (DHA). These FAs were also found to be the most dominant in several other studies, either in caprellids [4,11,12,21] but also other groups of amphipods [15,[22][23][24]. Although content levels vary between locations and species, which is something to be expected, the consistent abundance of those four important FAs in amphipods shows that they actually could be a promising natural marine resource in the aquaculture sector. ...
... Based on the composition of the FA profile of amphipods, a wide range of ratios can be calculated which sometimes are considered as bioindicators of diet preference [22,27]. In the case of C. scaura from fish cages in Pagasitikos gulf, the ratio EPA/DHA which is an indicator of a diatom-based diet [22,27], was lower than the ratio 18:1(n-9)/ 18:1(n-7) which is an indicator for a more carnivorous preference [28]. ...
... Based on the composition of the FA profile of amphipods, a wide range of ratios can be calculated which sometimes are considered as bioindicators of diet preference [22,27]. In the case of C. scaura from fish cages in Pagasitikos gulf, the ratio EPA/DHA which is an indicator of a diatom-based diet [22,27], was lower than the ratio 18:1(n-9)/ 18:1(n-7) which is an indicator for a more carnivorous preference [28]. This finding is in agreement with the predation attribute which characterizes the feeding behavior of C. scaura [29][30][31][32]. ...
The total lipid and protein content of the invasive caprellid amphipod Caprella scaura, from the biofouling communities of fish farm cages in the Pagasitikos Gulf were analyzed and compared among seasons. Proteins were the most abundant component (48.5 – 49.3%). Lipid content was relatively lower, with a wider range (6.7 – 34%) and showed a distinct seasonal fluctuation with high values in the winter population and a gradual decrease in spring and summer, with the lowest values in Autumn. Composition of the fatty acids profile was consistent among the seasons, with palmitic (16:0), Oleic (18:1n-9), Eicosapentanoic (20:5n-3)(EPA) and Docosahexanoic acid (22:6n-3 )(DHA) being the most abundant fatty acids. The presence of high levels of EPA and DHA fatty acids makes the species a potential candidate for use of these organisms in aquaculture.
... biosynthesize the monounsaturated long-chained FAs 20:1 and 22:1 (all isomers), which then can indicate the importance of Calanus spp. as a food source for a consumer (Sargent and Falk-Petersen, 1988;Falk-Petersen et al., 1990). The FA 18:1(n-7) derives from the elongation of 16:1n-7 in algae (Falk-Petersen et al., 1990) whereas 18:1(n-9) can be produced by the consumers Nyssen et al., 2005), and ratios of 18:1(n-9)/18:1(n-7) (carnivory index) can further inform about the degree of carnivory in a consumer (Graeve et al., 1997;Falk-Petersen et al., 2000a;Auel et al., 2002). ...
... The two pelagic amphipods varied in their lipid class (Figures 2A,B) and FA compositions (Figures 4A,B) as well as seasonal variability of these parameters, which supports the notion that the two species differ in their lipid storage modes, carbon source composition and consequently their trophic interactions within the Arctic food web (Auel et al., 2002). ...
... During both seasons, concentrations of pelagic HBIs were higher (Figure 5B), whereas 18:1(n-9)/18:1(n-7) carnivory ratios were lower in T. libellula compared to T. abyssorum ( Table 3), suggesting that T. abyssorum occupied a higher trophic level than T. libellula, in agreement with the literature (Auel et al., 2002). In both amphipod species, heterotrophic prey had a greater contribution to their food composition in winter versus summer based on the higher carnivory ratios of 18:1(n-9)/18:1(n-7) and zoosterols to phytosterol ratios (Tables 3, 4). ...
The Barents Sea is a hotspot for environmental change due to its rapid warming, and information on dietary preferences of zooplankton is crucial to better understand the impacts of these changes on food-web dynamics. We combined lipid-based trophic marker approaches, namely analysis of fatty acids (FAs), highly branched isoprenoids (HBIs) and sterols, to compare late summer (August) and early winter (November/December) feeding of key Barents Sea zooplankters; the copepods Calanus glacialis, C. hyperboreus and C. finmarchicus and the amphipods Themisto libellula and T. abyssorum. Based on FAs, copepods showed a stronger reliance on a diatom-based diet. Phytosterols, produced mainly by diatoms, declined from summer to winter in C. glacialis and C. hyperboreus, indicating the strong direct linkage of their feeding to primary production. By contrast, C. finmarchicus showed evidence of year-round feeding, indicated by the higher winter carnivory FA ratios of 18:1(n-9)/18:1(n-7) than its larger congeners. This, plus differences in seasonal lipid dynamics, suggests varied overwintering strategies among the copepods; namely diapause in C. glacialis and C. hyperboreus and continued feeding activity in C. finmarchicus. Based on the absence of sea ice algae-associated HBIs (IP25 and IPSO25) in the three copepod species during both seasons, their carbon sources were likely primarily of pelagic origin. In both amphipods, increased FA carnivory ratios during winter indicated that they relied strongly on heterotrophic prey during the polar night. Both amphipod species contained sea ice algae-derived HBIs, present in broadly similar concentrations between species and seasons. Our results indicate that sea ice-derived carbon forms a supplementary food rather than a crucial dietary component for these two amphipod species in summer and winter, with carnivory potentially providing them with a degree of resilience to the rapid decline in Barents Sea (winter) sea-ice extent and thickness. The weak trophic link of both zooplankton taxa to sea ice-derived carbon in our study likely reflects the low abundance and quality of ice-associated carbon during late summer and the inaccessibility of algae trapped inside the ice during winter.
... The relative proportion of polyunsaturated FAs (PUFAs) can be used as an indicator of food quality of an algal community or as a herbivore index for a consumer based on the assumption that algae are the main producers of PUFAs (Stevens et al., 2004). Additionally, high ratios of 18:1(n−9)/18:1(n−7) indicate an omnivorous/carnivorous/detritivorous rather than herbivorous feeding mode (Graeve et al., 1997;Falk-Petersen et al., 2000;Auel et al., 2002). ...
... In previous studies, the link between the predominantly carnivorous T. libellula and sea-ice primary production varied during summer in the Bering Sea (mean contribution of ice-associated carbon between 38 and 79%, depending on stable isotope model parameters; Wang et al., 2015) and the CAO (mean contribution of ice-associated carbon between 23 and 55%, depending on stable isotope parameters; Kohlbach et al., 2016). In this study, sea ice algae-associated and pelagic/MIZ HBIs were detected in both Themisto species, showing that they utilized carbon of different origin, likely by preying on Calanus spp., based on their high proportions of copepod-associated FAs and elevated wax ester levels (Scott et al., 1999;Auel et al., 2002) and/or possibly also on krill and pteropods (Marion et al., 2008) based on the presence of HBIs in these taxa. Differences in lipid class, FA composition and HBI concentrations between T. abyssorum and T. libellula, however, reflect differences in energy storage mode and their highly diverse feeding behavior (Auel et al., 2002;Havermans et al., 2019). ...
... In this study, sea ice algae-associated and pelagic/MIZ HBIs were detected in both Themisto species, showing that they utilized carbon of different origin, likely by preying on Calanus spp., based on their high proportions of copepod-associated FAs and elevated wax ester levels (Scott et al., 1999;Auel et al., 2002) and/or possibly also on krill and pteropods (Marion et al., 2008) based on the presence of HBIs in these taxa. Differences in lipid class, FA composition and HBI concentrations between T. abyssorum and T. libellula, however, reflect differences in energy storage mode and their highly diverse feeding behavior (Auel et al., 2002;Havermans et al., 2019). HBI concentrations in T. abyssorum were only analyzed for samples from the ice-covered stations P6 and P7, so that a strictly pelagic feeding style of this species in the more southern Barents Sea cannot be excluded. ...
We investigated diets of 24 Barents Sea zooplankton taxa to understand pelagic food-web processes during late summer, including the importance of sea ice algae-produced carbon. This was achieved by combining insights derived from multiple and complementary trophic marker approaches to construct individual aspects of feeding. Specifically, we determined proportions of algal-produced fatty acids (FAs) to reflect the reliance on diatom- versus dinoflagellate-derived carbon, highly branched isoprenoid (HBI) lipids that distinguish between ice-associated and pelagic carbon sources, and sterols to indicate the degree of carnivory. Copepods had the strongest diatom signal based on FAs, while a lack of sea ice algae-associated HBIs (IP25, IPSO25) suggested that they fed on pelagic rather than ice-associated diatoms. The amphipod Themisto libellula and the ctenophores Beroë cucumis and Mertensia ovum had a higher contribution of dinoflagellate-produced FAs. There was a high degree of carnivory in this food web, as indicated by the FA carnivory index 18:1(n−9)/18:1(n−7) (mean value < 1 only in the pteropod Clione limacina), the presence of copepod-associated FAs in most of the taxa, and the absence of algal-produced HBIs in small copepod taxa, such as Oithona similis and Pseudocalanus spp. The coherence between concentrations of HBIs and phytosterols within individuals suggested that phytosterols provide a good additional indication for algal ingestion. Sea ice algae-associated HBIs were detected in six zooplankton species (occurring in krill, amphipods, pteropods, and appendicularians), indicating an overall low to moderate contribution of ice-associated carbon from late-summer sea ice to pelagic consumption. The unexpected occurrence of ice-derived HBIs in pteropods and appendicularians, however, suggests an importance of sedimenting ice-derived material at least for filter feeders within the water column at this time of year.
... Due to the impact of maternal diet on larval quality 12 , we also explored fatty acid trophic markers (FATM). Eggs originating from the salt marsh exhibited the highest EPA:DHA ratio suggesting a lower maternal trophic position 31,39 than conspecifics in the dock and mangrove habitats (p < 0.001; Fig. 5a), whose eggs did not differ in this measure (p = 0.078). Instead, eggs from the salt marsh displayed higher concentrations of odd-numbered www.nature.com/scientificreports ...
... This is reflected by eggs from docks exhibiting higher concentrations of the developmentally critical Ω-3s, EPA, DHA, Ω-3:Ω-6 31,41 , and HUFAs 43,44 , all of which indicate a higher quality investment deriving from a high-quality diet 30,42 . The low EPA:DHA ratio of eggs from docks further supports this hypothesis by indicating a higher trophic position 31,39 . This suggests the dietary origin of the improved investment is animal material, a high-quality food source preferred by A. pisonii 18 which is likely an important dietary component on docks 8 . ...
... This included the total Ω-3s, the individual Ω-3s EPA, DHA, and ALA, the Ω-3:Ω-6 ratio, and the HUFA concentration; all indices which correlate positively with larval quality 30,31,41,49,50 . We also explored the fatty acid trophic markers (FATM) of EPA:DHA ratio, a measure of trophic position 31,39 and the concentration of OFA, a measure of relative detritivory 31 . We compared the concentration of the FAs, FA groups, and FATMs between habitats using individual LMs. ...
When a range-shifting species colonizes an ecosystem it has not previously inhabited, it may experience suboptimal conditions that challenge its continued persistence and expansion. Some impacts may be partially mitigated by artificial habitat analogues: artificial habitats that more closely resemble a species’ historic ecosystem than the surrounding habitat. If conditions provided by such habitats increase reproductive success, they could be vital to the expansion and persistence of range-shifting species. We investigated the reproduction of the mangrove tree crab Aratus pisonii in its historic mangrove habitat, the suboptimal colonized salt marsh ecosystem, and on docks within the marsh, an artificial mangrove analogue. Crabs were assessed for offspring production and quality, as well as measures of maternal investment and egg quality. Aratus pisonii found on docks produced more eggs, more eggs per unit energy investment, and higher quality larvae than conspecifics in the surrounding salt marsh. Yet, crabs in the mangrove produced the highest quality larvae. Egg lipids suggest these different reproductive outcomes result from disparities in the quality of diet-driven maternal investments, particularly key fatty acids. This study suggests habitat analogues may increase the reproductive fitness of range-shifting species allowing more rapid expansion into, and better persistence in, colonized ecosystems.
... The hyperiid amphipod Themisto libellula is an important component of Arctic pelagic ecosystems (Auel et al., 2002), and a key prey of polar cod Boreogadus saida (Dolgov et al., 2011;Dalpadado et al., 2016;Kohlbach et al., 2017;ICES, 2021). In our study, T. libellula dominated the amphipod catches in the northern Barents Sea, with a peak in early winter (Q4). ...
... Therefore, the strong difference in T. libellula biomass between Q4 and Q1 may to a large extent be a year-effect, rather than seasonal dynamics. T. libellula is predominantly carnivorous, preying mostly on mesozooplankton including copepods (Auel et al., 2002;Dalpadado et al., 2008b). The presence of adults with marsupium and young individuals (ca. ...
... Additionally, an increased length and weight of age 4 cage-associated G. morhua was consistent with an increased length, weight, and condition of adult cage-associated wild fish observed elsewhere (Skog et al. 2003, Fernandez-Jover et al. 2007, 2011b). An increased length and weight of age 4 cage-associated G. morhua could be attributed to (Auel et al. 2002, Dalsgaard et al. 2003, though alternatively in agreement with Saether et al. (2012), who observed ontogenetic shifts away from direct pellet feeding in adult G. morhua. Bagdonas et al. (2012), observed similar behaviour in cage-associated G. morhua in Norway, with smaller G. morhua feeding on waste feed and larger G. morhua feeding on aggregated prey fish. ...
... must be acquired through the diet and large proportions of LA, ALA and ω6 FAs in aquafeed, but trace proportions in marine environments allows their use as biological tracers for primary consumption, though multiple dietary and FA sources can lower their applicability in tracing secondary and tertiary consumption(Auel et al. 2002, Dalsgaard et al. 2003. However, elevated proportions of OA are common in marine consumers(Falk- Petersen et al. 1990), and elevated OA proportions in cage-associated adult G. morhua may be attributed to increased prey aggregations in the area of sea cages (Serra-Llinares et al. 2013), including juvenile G. morhua that may have been feeding on waste feed themselves. ...
Sea cage aquaculture can alter the spatial distribution of wild fish populations; however, little is known about the dietary habits and subsequent effects on wild fish. In this thesis, I used stable isotopes δ 13 C and δ 15 N values and proportions of vegetable oil-based fatty acids (VOFAs) to investigate the dietary habits of wild cage-associated Atlantic cod Gadus morhua and Atlantic redfish Sebastes fasciatus. Furthermore, I compared the length, weight and condition of cage-associated G. morhua ages 2-4 years old to reference sites within the local division and outside divisions removed from aquaculture, and used VOFAs as biomarkers for waste feed consumption to identify any role(s) in explaining differences in length, weight and condition among age classes. Juvenile G. morhua captured around sea cages had depleted δ 13 C and δ 15 N values and elevated proportions of VOFAs consistent with waste feed consumption and sea cage residency, whereas differences in δ 13 C, δ 15 N, and VOFAs in cage-associated adult G. morhua and S. fasciatus were predominately absent. Interestingly, waste feed consumption by age 2 cage-associated G. morhua resulted in lower condition than age 2 G. morhua from the local reference division; however, age 4 cage-associated G. morhua were longer and heavier than the local reference division, despite no evidence to support direct or indirect waste-feed consumption. Overall, the results of this thesis suggest that δ 13 C, δ 15 N and VOFAs are suitable biomarkers for tracing sea cage residency and dietary habits of cage-associated wild fish, but waste feed consumption patterns and subsequent effects on wild fish were paradoxical and dependent on species and life stage.
... S. beanii muscles contained comparatively high amounts of OLE, 18:1(n-7), and 16:1(n-7) FAs, which are plentiful in Arctic hyperiid amphipods Themisto sp. foraging on mesozooplankton [102]. ...
... L. macdonaldi probably uses another strategy in its compensatory response to changes in environmental conditions during vertical migrations. The low percentage similarity between S. beanii and other mesopelagic fishes in the study may be due to a greater exogenous supply of EPA since this acid, together with some MUFAs, is plentiful in Arctic hyperiid amphipods [102]. Similar build-up of EPA and DHA towards greater depths has been described in our previous studies on beaked redfish [75]. ...
The lipid and fatty acid composition of muscles of mesopelagic fish species Lampanyctus macdonaldi, Bathylagus euryops, Serrivomer beanii, Scopelogadus beanii in the Irminger Sea at deep range were
studied. The contents of the total lipids (TLs), total phospholipids (PLs), monoacylglycerols (MAGs), diacylglycerols (DAGs), triacylglycerols (TAGs), cholesterol (Chol), Chol esters, non-esterified fatty acids (NEFAs), and wax esters were determined by HPTLC; the PL classes were determined by HPLC; and fatty acids (FAs) were determined using GC. It was found significant differences in lipid
profile of the studied fishes: Chol esters and waxes were dominant in L. macdonaldii and S. beanii, fish species with diel vertical migrations (DVM), while TAGs were prevalent in B. euryops and Sc. beanii—non-migratory species. It was revealed the species-specific differences in FAs profiles of the studied fish. Along with this, it was detected the similarity of FAs in fish, which is associated with food sources. A comparative analysis of lipids and FAs among L. macdonaldi and S. beanii collected in the Irminger Sea and L. alatus and S. beanii collected in the Tropic Seamount revealed similar biochemical strategies for the accumulation of certain lipids characterized the mesopelagic inhabit despite latitude differences of the area of study.
... In the Arctic Ocean, two hyperiid amphipods, Themisto libellula and T. abyssorum (Fig. 30.1), are important components of pelagic ecosystems. They represent a substantial food source for marine vertebrates and are a key link between zooplankton secondary production and higher trophic levels (Auel et al. 2002). Both species are carnivorous and prey on mesozooplankton; however, their prey animals are not identical, although both species co-occur sympatrically in large areas of the Arctic Ocean and adjacent seas. ...
... In contrast, T. abyssorum is characterized by lower amounts of EPA, and its biomarker ratios indicate a higher trophic level. This observation complies with the subarctic-boreal origin of T. abyssorum and its occurrence in deeper layers of the Arctic Ocean, where it feeds on omnivorous and/or carnivorous prey (Auel et al. 2002). ...
Central of the trophic transfer is its efficiency, the ratio between production of one trophic level and that of the previous one. Long-chain polyunsaturated fatty acids (LC-PUFAs), particularly docosahexaenoic acid (DHA), are preferentially retained by higher trophic levels in disfavor of nonessential FAs and bulk carbon. Traditional beliefs have to be revised: Autochthonous LC-PUFA sources prevail even in lotic headwater food webs. The hypothesis that (marine) single-cell factories, sensitive to global warming, are the sole source of ω3 LC-PUFAs is being challenged by the identification of the widespread occurrence of ωx genes in animals and by finding potentially additional sources.
... In the tissue of marine primary producers, Dalsgaard et al. (2003) discovered unique fatty acid patterns that can be unchangeably passed to species with a higher trophic level. Availability of 20:1 And 18:2n6c in marine bivalves indicates the presence of herbivore zooplankton, algae, and fungi as a dietary source in their habitat (Auel et al., 2002;Erwin, 1973;Kayama et al., 1989). Withal, dinoflagellates as a major food source is reflected by higher level of 22:6n3 in tissues (Joseph, 1975;Sargent et al., 1977). ...
... Withal, dinoflagellates as a major food source is reflected by higher level of 22:6n3 in tissues (Joseph, 1975;Sargent et al., 1977). On the other hand, presence of 20:5n3 and 16:1 intimate the dominance of diatoms (Graeve et al., 1997), whereas the presence of 22:6n3, 20:1, and 14:0 reflect the abundance of dinoflagellates, herbivorous zooplankton and diatoms (Auel et al., 2002;Graeve et al., 1997;Joseph, 1975;Sargent et al., 1977). Abundance of bacteria, algae, fungi, and diatoms are reflected in the concentration of 20:4n6, 18:2n6c, and 17:0 in marine bivalves (Ackman, 1989;Erwin, 1973;Kayama et al., 1989;Kharlamenko et al. 2001). ...
Oyster meat is consumed for its high nutritional value. Marine oysters (several species under the genus Crassostrea) have been commercially cultured long since around the world to satisfy the increased demand of oyster. Bangladesh has taken approaches to initiate oyster mariculture. Three pilot commercial oyster (Crassostrea spp.) farms were constructed by District Fisheries Office, Cox’s Bazar at Nunia Chara (NC – 21°28ˈ19.5" N, 91°57ˈ42.7" E), Chowfoldandy (CD – 21°30ˈ44.1" N, 92°01ˈ00.1" E) and Sonadia Island (SI – 21°30ˈ18.7" N, 91°53ˈ43.3" E) in Cox’s Bazar, Bangladesh. Live oysters were collected from the farm and taken to the laboratory maintaining cold chain to analyse proximate and fatty acids. Data on yield as well as cost-benefit were collected from the District Fisheries Office, Cox’s Bazar to analyse yield performance and economic viability. Biological yield was observed 19.9 ± 5.7 kg/m2 and economic yield was observed 11.3 ± 2.5 kg/m2. Moisture, protein, lipid, carbohydrate, ash and fiber was found 79.2 ± 0.2%, 58.1 ± 2.1%, 10.2 ±
0.7%, 13.5 ± 1.4%, 12.3 ± 0.7% and 0.4 ± 0.0%, respectively, while moisture was determined in wet weight basis and rests were determined in dry weight basis. Saturated fatty acid, monounsaturated fatty acid, omega-3 fatty acid, omega-6 fatty acid and polyunsaturated fatty acid were observed 35.22 ± 10.91%, 13.77 ± 4.36%, 7.39 ± 4.00%, 43.62 ± 19.21, 51.01 ± 15.23% of total
fatty acid, respectively. Annual net profit of the farms was found 34557 ± 5636 BDT and payback period was found 2.6 ± 0.4 years. Thus, oyster farming was found to be potential for high food value as well as an economically viable oyster farm enterprise.
... Furthermore, determining fatty acid profiles can help in monitoring ecosystem dynamics in the face of global climate change, reflecting baseline food web dependencies (Auel et al., 2002;Dalsgaard et al., 2003). In a changing ocean, studies of the fatty acid profiles of forage fish, complemented with other physiological measures such as oxidative stress balance, could help reveal shifts in primary productivity and consequently lead to a system-level understanding of marine trophodynamics (Litzow et al., 2006;Pethybridge et al., 2014;Queiros et al., 2019). ...
... In order to assess trophic relationships, we computed the following ratios (Auel et al., 2002;Dalsgaard et al., 2003): palmitoleic acid/palmitic acid (16:1 n-7/16:0; or PO/P) and EPA/DHA (20:5 n-3/22:6 n-3). High values of these ratios indicate a diatom-based diet, whereas low values indicate a dinoflagellate-based diet. ...
The status of sardine and anchovy populations in the northern Mediterranean Sea has been declining in recent decades. In this study, fatty acids and parasitism at different reproductive and feeding stages in these two species were assessed using specimens caught along the northern Catalan coast, in order to assess the links between lipid dynamics, reproduction and feeding in these two species and to contribute towards an explanation of the potential causes of the current poor situation of the stocks. The results support the use of fatty acid levels as indicators of the body condition of sardine and anchovy at different reproductive and feeding stages, as well as that of the pelagic environmental conditions. In particular, the relatively low n-3 polyunsaturated fatty acid levels found in spawning sardines compared to spawning anchovies indicate a poorer reproductive health status of sardine. By comparing the current total lipid content values with those recorded in other Mediterranean and North Atlantic areas, and others from more than 10 years ago, in the adjacent area of the Gulf of Lion, our study reveals the persistent poor condition of sardine and anchovy in the northern Catalan Sea. Furthermore, the low levels of diatom fatty acid markers observed throughout the spawning and non-spawning seasons in both sardine and anchovy indicate a diet poor in diatoms. Moreover, the results indicate that it is very unlikely that parasitism is a significant factor in the decline in condition of sardine and anchovy in the northern Catalan Sea. In fact, the results, which we believe provide useful insights for the management of small pelagic fisheries in the Mediterranean, suggest that the current poor condition of sardine and anchovy in the northern Catalan Sea has probably been exacerbated by a decrease in plankton productivity and/or a shift in the taxonomic composition of phytoplankton communities, adding to the ongoing effects of overfishing.
... T. longicaudata, T. raschii, and Meganyctiphanes norvegica also contributing to the biomass (Eriksen et al., 2016). The dominant pelagic amphipod is the Arctic Themisto libellula, which is carnivorous and has copepods as important parts of the diet (Auel et al., 2002;Dalpadado, 2002). ...
... Positive bottom-up effect by copepods on amphipods is consistent with copepods being the key prey of the dominant amphipod in our samples, T. libellula (Auel et al., 2002). This finding complements previous studies based on shorter data time series, which have not been able to separate the correlated effects of high copepod biomass and large extent of Arctic waters (Dalpadado, 2002;Dalpadado et al., 2012), by suggesting that both factors contributed to explain the variation in amphipod biomass. ...
Reductions in Arctic sea ice affect marine food webs through a multitude of direct and indirect effects. We here analysed direct, indirect, and delayed associations between winter sea ice cover and year-to-year changes in biomasses of the main zooplankton groups (copepods, krill, amphipods) and planktivorous fishes (capelin, polar cod) in the central and northern Barents Sea from 1980 to 2015. Climate effects and species interactions were estimated jointly in a Bayesian state-space model framework. We found that population biomass of capelin increased in years with low sea ice cover, while biomasses of copepods and amphipods decreased. Furthermore, results suggested strong bottom-up effects by krill on capelin and by copepods on amphipods and top-down effects by polar cod on amphipods and by capelin on krill and copepods. Sea ice effects thereby cascaded through the food web through indirect and delayed effects. The indirect and delayed effects amplified the effects of sea ice cover on capelin, copepods and amphipods. For krill, low sea ice cover most likely increased biomass in the short-term but reduced biomass in longer terms because of increased predation pressure. These findings suggest that both bottom-up and top-down processes need to be considered when projecting effects of future climate change on ecosystems.
... Furthermore, determining fatty acid profiles can help in monitoring ecosystem dynamics in the face of global climate change, reflecting baseline food web dependencies (Auel et al., 2002;Dalsgaard et al., 2003). In a changing ocean, studies of the fatty acid profiles of forage fish, complemented with other physiological measures such as oxidative stress balance, could help reveal shifts in primary productivity and consequently lead to a system-level understanding of marine trophodynamics (Litzow et al., 2006;Pethybridge et al., 2014;Queiros et al., 2019). ...
... In order to assess trophic relationships, we computed the following ratios (Auel et al., 2002;Dalsgaard et al., 2003): palmitoleic acid/palmitic acid (16:1 n-7/16:0; or PO/P) and EPA/DHA (20:5 n-3/22:6 n-3). High values of these ratios indicate a diatom-based diet, whereas low values indicate a dinoflagellate-based diet. ...
The status of sardine and anchovy populations in the northern Mediterranean Sea has been declining in recent decades. In this study, fatty acids and parasitism at different reproductive and feeding stages in these two species were assessed using specimens caught along the northern Catalan coast, in order to assess the links between lipid dynamics, reproduction and feeding in these two species, and to contribute towards an explanation of the potential causes of the current situation of the stocks. The results support the use of fatty acid levels as indicators of the body condition of sardine and anchovy at different reproductive and feeding stages, as well as that of the pelagic environmental conditions. In particular, the relatively low n-3 PUFA levels (which are crucial for reproductive success) found in spawning sardines compared to spawning anchovies indicate a poorer reproductive health status of sardine. By comparing the current total lipid content values with those recorded in other Mediterranean and North Atlantic areas, and, others from more than ten years ago, in the adjacent area of the Gulf of Lion, our study reveals the persistent poor condition of sardine and anchovy in the northern Catalan Sea. Furthermore, the low levels of diatom fatty acid markers observed throughout the spawning and non-spawning seasons in both sardine and anchovy, indicate a diet poor in diatoms. Moreover, the results indicate that it is very unlikely that parasitism is a significant factor in the decline in condition of sardine and anchovy in the northern Catalan Sea. In fact, the results suggest that the current poor condition of sardine and anchovy in the northern Catalan Sea has been exacerbated by a decrease in plankton productivity and/or a shift in the taxonomic composition of phytoplankton communities, adding to the ongoing effects of overfishing.
... Based on the FA and Falc composition, several biomarker ratios have been calculated. Here, the 18:1(n-9)/18:1(n-7) ratio indicated carnivory in zooplankton (Graeve et al., 1997;Auel et al., 2002), while 20:5(n-3)/22:6(n-3) and 16:1(n-7)/16:0 ratios differentiated diatom and flagellate based diets, respectively (Graeve et al., 1994). We used the highly polyunsaturated vs. saturated fatty acids ratio (PUFA/SAFA) to track the flow of energy, and the 22:1(n-11)/20:1(n-9) ratio to differentiate within diets based on Calanus species (∼1.8 or higher refers to C. hyperboreus, 1.1 to C. finmarchicus, and 0.7 or lower to C. glacialis) (Falk-Petersen et al., 1990. ...
... Similarly, Petursdottir et al. (2008) demonstrated that beaked redfish in the Reykjanes Ridge (Iceland) fed predominantly on krill, while daubed shanny from Ullsfjorden (70 • N, Norway) fed on C. hyperboreus (Falk-Petersen et al., 1986). Themisto libellula in the Fram Strait (Auel et al., 2002) and off East Greenland (Kraft et al., 2015) also rely on C. finmarchicus as their main prey. ...
Mesopelagic sound scattering layers (SSL) are ubiquitous in all oceans. Pelagic organisms within the SSL play important roles as prey for higher trophic levels and in climate regulation through the biological carbon pump. Yet, the biomass and species composition of SSL in the Arctic Ocean remain poorly documented, particularly in winter. A multifrequency echosounder detected a SSL north of Svalbard, from 79.8 to 81.4°N, in January 2016, August 2016, and January 2017. Midwater trawl sampling confirmed that the SSL comprised zooplankton and pelagic fish of boreal and Arctic origins. Arctic cod dominated the fish assemblage in August and juvenile beaked redfish in January. The macrozooplankton community mainly comprised the medusa Cyanea capillata, the amphipod Themisto libellula, and the euphausiids Meganyctiphanes norvegica in August and Thysanoessa inermis in January. The SSL was located in the Atlantic Water mass, between 200–700 m in August and between 50–500 m in January. In January, the SSL was shallower and weaker above the deeper basin, where less Atlantic Water penetrated. The energy content available in the form of lipids within the SSL was significantly higher in summer than winter. The biomass within the SSL was >12-fold higher in summer, and the diversity of fish was slightly higher than in winter (12 vs. 9 species). We suggest that these differences are mainly related to life history and ontogenetic changes resulting in a descent toward the seafloor, outside the mesopelagic layer, in winter. In addition, some fish species of boreal origin, such as the spotted barracudina, did not seem to survive the polar night when advected from the Atlantic into the Arctic. Others, mainly juvenile beaked redfish, were abundant in both summer and winter, implying that the species can survive the polar night and possibly extend its range into the high Arctic. Fatty-acid trophic markers revealed that Arctic cod mainly fed on calanoid copepods while juvenile beaked redfish targeted krill (Thysanoessa spp.). The relatively high biomass of Arctic cod in August and of redfish in January thus suggests a shift within the SSL, from a Calanus-based food web in summer to a krill-based food web during winter.
... The turnover rate of FA is relatively fast in marine mammals, hence dietary shifts are estimated to be observable in whale blubber after one month (Budge et al., 2006). Ratios of FA can be used to interpret feeding strategies such as herbivory versus carnivory (Auel et al., 2002;Falk-Petersen et al., 1990). However, some saturated (SFA) and monounsaturated FA (MUFA) can be elongated or desaturated during the metabolic process, making interpretation of the specific origin difficult (Budge et al., 2006;Cook, 1991). ...
... Polar zooplankton taxa show different strategies to cope with such food limitation. Some amphipod and copepod species reduce their feeding rate or overwinter in a state of arrested development, referred to as diapause, relying on lipid storage (Hagen, 1999;Hagen and Auel, 2001;Auel et al., 2002). Recently, it has been shown that some crustacean zooplankton taxa such as under-ice amphipods switch to an omnivorous feeding mode, increasing their feeding flexibility (Kunisch et al., 2023). ...
Introduction
Currently, Arctic marine ecosystems are witnessing the most rapid physical changes worldwide, leading to shifts in pelagic and benthic communities and food web structure, concomitant with the introduction of boreal species. Gelatinous zooplankton or jellyfish represent one particular group of which several boreal species are prone to undergo significant poleward range expansions and population increases in the Arctic in the course of the ongoing changes. Historically, jellyfish were considered a trophic dead-end, but an increasing number of studies using modern tools have highlighted their role as major prey items in marine food webs. In this study, we aimed to verify the role of jellyfish and other metazoans as food sources in the Arctic polar night food web, when pelagic resources are limited.
Methods
We identified the diet of different bentho-pelagic amphipod species in the Atlantifying Kongsfjorden (West Svalbard) during the polar night. We regularly sampled lysianassoid and gammarid amphipods using baited traps and hand nets over a period of one month during the polar night and identified their diet spectrum by applying DNA metabarcoding (COI) to their stomach contents.
Results
We demonstrate that all investigated species are omnivorous. Fish species including polar cod and snailfish, likely in the shape of carrion, played an important role in the diet of the scavengers Orchomenella minuta and Anonyx sarsi. Predation and potential scavenging on jellyfish contributed to the diet of all four investigated species, particularly for the species Gammarus setosus and G. oceanicus, as evidenced by high read abundances and high frequencies of occurrence. Besides jellyfish, crustaceans and macroalgae were important components of the diet of the two Gammarus species.
Discussion
The diverse jellyfish community present in Kongsfjorden in the polar night is clearly being utilized as a food source, either through pelagic feeding or feeding on jelly-falls, albeit to a different extent in the local amphipod community. These findings provide novel insights into the Arctic food web during the polar night and represent the first evidence of feeding on natural (non-experimental) jelly-falls.
... Phytoplankton and phytodetritus may serve as potential food sources for deep-sea corals(Maier et al., 2019(Maier et al., , 2020Orejas et al., 2001Orejas et al., , 2016 and could thus directly account for these specific markers. Phytoplankton inputs are visible through a higher proportion of algal-related markers (EPA, DHA and slightly for 18:4(n-3)), especially in shallow corals (Figure 3a, Supporting InformationFigure S3,Dalsgaard et al., 2003;Harwood & Russell, 1984) and the ratio DHA/EPA indicates a diatom prevailed over dinoflagellate signal(Auel et al., 2002;Falk-Petersen et al., 1987;Radice et al., 2019;Scott et al., 2002) across sites (Figure 3a). This also coincides with a predominant pattern of diatom-zooplankton succession rather than dinoflagellate-zooplankton in the plankton communities of Chilean fjords(González et al., 2010;Montero et al., 2017) as reflected in the corals FATM ratio DHA/EPA signal. ...
Benthic suspension feeders like corals and sponges are important bioengineers in many marine habitats, from the shallow tropics to the depth of polar oceans. While they are generally considered opportunistic, little is known about their actual in situ diet. To tackle this limitation, fatty acid trophic markers (FATMs) have been employed to gain insights into the composition of their diet. Yet, these in situ studies have not been combined with physiological investigations to understand how physiological limitations may modulate the biochemistry of these organisms.
Here, we used the cold‐water coral (CWC) Desmophyllum dianthus in its natural habitat in Comau Fjord (Northern Patagonia, Chile) as our model species to assess the trophic ecology in response to contrasting physico‐chemical conditions (variable vs. stable) and ecological drivers (food availability) at three shallow sites and one deep site. We took advantage of the expression of two distinct phenotypes with contrasting performance (growth, biomass, respiration) coinciding with the differences in sampling depth. We analysed the corals' fatty acid composition to evaluate the utility of FATM profiles to gain dietary insights and assess how performance trade‐offs potentially modulate an organism's FATM composition.
We found that 20:1(n‐9) zooplankton markers dominated the deep high‐performance phenotype, while 20:5(n‐3) and 22:6(n‐3) diatom and flagellate markers, respectively, are more prominent in shallow low‐performance phenotype. Surprisingly, both energy stores and performance were higher in the deep phenotype, in spite of measured lower zooplankton availability.
Essential FA concentrations were conserved across sites, likely reflecting required levels for coral functioning and survival. While the deep high‐performance phenotype met with these requirements, the low‐performance phenotype appeared to need more energy to maintain functionality in its highly variable environment, potentially causing intrinsic re‐allocations of energy and enrichment in certain essential markers (20:5(n‐3), 22:6(n‐3)).
Our analysis highlights the biological and ecological insights that can be gained from FATM profiles in CWCs, but also cautions the reliability of FATM as diet tracers under limiting environmental conditions that may also be applicable to other marine organisms.
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... The fact that 18:1w9, EPA and DHA are the most abundant fatty acids may indicate that G. rufa prefers the members of Cryptophyceae, Dinophyceae, and Chlophyta as food sources in the Murat River. Moreover, the 16:1w7/16:0 ratio has been used to infer a diatom-dominated food chain base (Auel et al., 2002). While 16:1w7 is found in cyanobacteria, dinoflagellates, and a specific isomer, the trans one, is found in bacteria, 16:1w7 is most prevalently associated with diatoms (Parrish, 2013). ...
Specimens of Garra rufa were collected from a warm river and a cool stream in the Bingöl Province, Turkey, once a month over a period of one year. The effects of month, season, gender and location on the fatty acid composition in the muscle and the lipid content were investigated and dietary marker fatty acids were used to obtain dietary preferences in different locations (Ilıcalar, Garip) and periods. Total lipid change was seasonally significant (ANOSIM-R=0.49) at both locations and 18:1ω9, 20:5ω3 and 20:6ω3 were the most abundant dietary fatty acids. Although G. rufa are predominantly herbivores, they can also feed omnivorously on mixed diets depending on the presence and absence of their primary diet. The effect of season was significant on fatty acid composition, regardless of the location (Pperm=0.001). Significant seasonal changes in all the fatty acid compositions could be attributed to seasonal changes in the abundance and diversity of dietary sources in the environment due to the effect of temperature.
... This is also known to be the case for polar cod (Boreogadus saida) in Svalbard (Cusa et al. 2019). T. libellula is generally larger than T. abyssorum, which could explain this preference, though the two amphipods have similar energy/ lipid content per biomass (Percy and Fife 1981;Auel et al. 2002;Węsławski et al. 2006). It could also suggest that the two salmonids feed in areas with relatively high abundances of T. libellula, e.g., inner fjord basins, as seen in Kongsfjorden (Dalpadado et al. 2016;Hop et al. 2019). ...
During summer, native anadromous Arctic char (Salvelinus alpinus) and the alien species pink salmon (Oncorhynchus gorbuscha) now coexist in marine environments in Svalbard, following the introduction of the latter in the Barents Region. To investigate potential dietary competition between these two salmonid species, stomach contents from Arctic char (n = 301) and pink salmon (n = 28) were sampled from different areas within the archipelago. The most important prey in terms of biomass for both salmonid species were amphipods; Themisto libellula (B = 26.0%) for Arctic char and Onisimus litoralis (B = 35.0%) for pink salmon. Pianka’s niche overlap revealed that dietary overlap between the two species was moderately high (Oobs = 0.59); both species had strong associations with intertidal invertebrates in areas where direct comparisons were possible (Kongsfjorden/Krossfjorden). However, both salmonid species did also eat some fish, with Arctic char consuming more offshore pelagic fish, while the small number of fish eaten by pink salmon were primarily coastal demersal fish species. Arctic char was a more generalist feeder, while pink salmon was more of a dietary specialist. Furthermore, the diet composition of the Arctic char consisted of 32.9% Atlantic prey while the pink salmon, surprisingly, ate only Arctic species, likely due to their tightly coastal feeding habits. Even though the sample size for pink salmon was low, this study contributes new insights into salmonid diets in Svalbard and the potential for introduced species to compete with native Arctic endemics, particularly in the expected warmer Arctic of the future.
... All statistical analyses were run in the R v3.5.1 (R Development Core Team, 2008). We gathered all information required for the present study Bivalves and gastropods (Budge et al., 2007;Joseph, 1982) Carnivorous: 18:1ω9/18:1ω7 Carnivorous (Auel et al., 2002;El-Sabaawi et al., 2009;Graeve et al., 1997) Essential FA Role Reference ...
Multifactorial studies assessing the cumulative effects of natural and anthropogenic stressors on individual stress response are crucial to understand how organisms and populations cope with environmental change. We tested direct and indirect causal pathways through which environmental stressors affect the stress response of wild gilthead seabream in Mediterranean coastal lagoons using an integrative PLS-PM approach. We integrated information on 10 environmental variables and 36 physiological variables into seven latent variables reflecting lagoons features and fish health. These variables concerned fish lipid reserves, somatic structure, inorganic contaminant loads, and individual trophic and stress response levels. This modelling approach allowed explaining 30 % of the variance within these 46 variables considered. More importantly, 54 % of fish stress response was explained by the dependent lagoon features, fish age, fish diet, fish reserve, fish structure and fish contaminant load latent variables included in our model. This integrative study sheds light on how individuals deal with contrasting environments and multiple ecological pressures.
... All statistical analyses were run in the R v3.5.1 (R Development Core Team, 2008). We gathered all information required for the present study Bivalves and gastropods (Budge et al., 2007;Joseph, 1982) Carnivorous: 18:1ω9/18:1ω7 Carnivorous (Auel et al., 2002;El-Sabaawi et al., 2009;Graeve et al., 1997) Essential FA Role Reference ...
... All statistical analyses were run in the R v3.5.1 (R Development Core Team, 2008). We gathered all information required for the present study Bivalves and gastropods (Budge et al., 2007;Joseph, 1982) Carnivorous: 18:1ω9/18:1ω7 Carnivorous (Auel et al., 2002;El-Sabaawi et al., 2009;Graeve et al., 1997) Essential FA Role Reference ...
... Contrastingly, the two amphipod species we studied showed lower energy content than either krill species, as well as a greater difference between summer and winter. These amphipods are known to be predominantly carnivorous, with less dependence on energy stores to withstand the non-productive period (Auel et al. 2002). Despite showing a large decrease in energy content from summer to winter, both amphipod species have been found to feed during the polar night in some Svalbard fjords (Kraft et al. 2013). ...
Arctic zooplankton develop large energy reserves, as an adaptation to strong seasonality, making them valuable prey items. We quantified the energy content (kJ g⁻¹ dry weight) of abundant krill (arcto-boreal, Thysanoessa inermis and boreal, Meganyctiphanes norvegica) and amphipods (Arctic, Themisto libellula and sub-Arctic-boreal, Themisto abyssorum) in the Barents Sea in late summer (August) and early winter (December). Variation in energy content was attributed to species-specific traits and body size categories, the latter in part as a proxy for ontogeny. T. inermis had the highest energy content, (Aug: 26.8 ± 1.5 (SD) kJ g⁻¹) and remained similar from summer to winter. Energy content increased in M. norvegica and decreased in both amphipod species, with the lowest energy content being in T. abyssorum (Dec: 17.8 ± 0.8 kJ g⁻¹). The effect of body size varied between species, with energy content increasing with size in T. inermis and T. libellula, and no change with size in M. norvegica and T. abyssorum. The reproductive stages of T. libellula differed in energy content, being highest in gravid females. Energy content varied with species’ dependence on energy storage. Our findings highlight how phylogenetically and morphologically similar prey items cannot necessarily be considered equal from a predator´s perspective. Energetically, the northern T. inermis was higher quality compared to the more southern M. norvegica, and mostly so during summer. Ecological models and management strategies should consider such variation in prey quality, especially as Arctic borealization is expected to change species composition and the energetic landscape for predators.
... The high 16:0 FA content in TAGs may be evidence of a trophic connection to euphausiids [67,74,75]. The significant content of cis16:1(n-7) and cis18:1(n-7) (above 1 µg/mL in the TAG fraction or above 1% of total FAs in TLs) in the samples may also point to the consumption of small amounts of hyperiids of the genera Themisto and Parathemisto, which feed on mesozooplankton, as well as on detritus, as confirmed by the finding of biomarker FAs of bacterial origin (iso15:0, iso16:0, iso17:0, and cy17:0) in muscle tissues [65,76]. The content of cis18:4(n-3) in S. boa, M. niger, and Ch. ...
New data on the fatty acid compositions of the muscle tissues of the two most widespread families of the mesopelagic zone—the Myctophidae (Notoscopelus kroyeri and Symbolophorus veranyi) and Stomiidae (Chauliodus sloani, Stomias boa, Borostomias antarcticus, and Malacosteus niger) families — were obtained from the Irminger Sea (North East Atlantic). The fatty acids (FAs) in the total lipids (TLs), phospholipids (PLs), triacylglycerols (TAGs), and cholesterol esters and waxes were analyzed using gas–liquid chromatography with a mass-selective detector and flame-ionized detector (GC-MS and GC-FID, respectively). Species-specific differences in the FA/alcohol profiles of the studied fishes were revealed. A directed deep-vise trend in the changes in the content and performance of certain FAs for the studied species was found. Along with this, a general character of dominance for monounsaturated fatty acids (MUFAs), which were discussed as food tracers, was revealed. MUFAs in the muscle tissues included dietary markers of zooplankton (copepods)—20:1(n-9) and 22:1(n-11), the content of which varied in association with the species—such that the biomarker Calanus glacialis predominated in muscles of B. antarcticus and C. hyperboreus prevailed in other studied species.
Different strategies of compensatory adaptation to depth gradient in lipid metabolism among the studied species were discussed.
... An earlier sea ice breakup and thus melt onset (Markus et al., 2009) should result in earlier spring bloom progressions, which first consists of an ice algal bloom within the ice, where the majority of algal-derived biomass sloughed from the melting ice cover settles to the ocean floor where it is fed upon by benthic organisms (AMAP, 2017). Then follows a phytoplankton bloom typically commencing under a melting ice cover (Ardyna et al., 2020;Back et al., 2021), fueling the development of Arctic pelagic prey including calanoid copepodswhich can be found in substantial abundance in the study region (Nelson et al., 2019) and in turn carnivorous pelagic organisms like the amphipod Themisto libellula (Percy, 1993;Auel et al., 2002;Søreide et al., 2010). Ice cover in many areas of the Kitikmeot Sea broke up over 12 days earlier in the 2010s than in the 1990s, with breakup dates coinciding to June and early July at the earliest. ...
Managing Arctic marine resources to be resilient to environmental changes requires knowledge of how climate change is affecting marine food webs and fisheries. Changes to fishery resources will have major implications for coastal Indigenous communities whose livelihoods, health, and cultures are strongly connected to fisheries. Understanding these broad social-ecological changes requires a transdisciplinary approach bringing together contrasting and complementary disciplines and ways of knowing. Here, we examine climatic proxies, ecological, and fishery indicators (stable isotopes, fish condition, and lipid content), and interviews with Inuit fishers to assess how marine ecosystem changes have influenced Arctic Char (Salvelinus alpinus) ecology and fisheries over a 30-year time period (1987–2016) in the Kitikmeot region of the Canadian Arctic. Inuit fishers reported several observations of environmental changes, including longer ice-free seasons, warmer ocean temperatures, and the arrival of new marine species. Biophysical data revealed important changes toward earlier dates of ice breakup (>12 days in some areas) and a shift in isotopic niche reflecting a changing Arctic Char diet, with increased contribution of pelagic carbon and higher trophic level prey. Fish condition was improved in years with earlier ice breakup, as observed by both Inuit fishers and biophysical indicators, while lipid content increased through time, suggesting that longer ice-free seasons may have a positive effect on Arctic Char quality as reflected by both fish condition and lipid content. Long-term impacts of continuing climate change, however, such as the northward expansion of boreal species and increasing ocean temperatures, could have negative effects on fisheries (e.g., physiological impairment in fish if temperatures exceed their thermal range). Continuous community-based monitoring that directly informs fisheries management could help communities and managers adaptively, and sustainably, manage in the face of multiple interacting changes in Arctic marine systems.
... They are omnivorous, feeding on dinoflagellates but primarily mesozooplankton species such as Calanus (approx. prey size ≤7-8 mm) (Auel et al., 2002;Dalpadado et al., 2008;Kraft et al., 2013;Leinaas et al., 2016). The sympagic (ice-associated) A. glacialis feeds on ice algae and small detritus particles (Poltermann, 2001). ...
Some of the highest microplastic concentrations in marine environments have been reported from the Fram Strait in the Arctic. This region supports a diverse ecosystem dependent on high concentrations of zooplankton at the base of the food web. Zooplankton samples were collected during research cruises using Bongo and MOCNESS nets in the boreal summers of 2018 and 2019. Using FTIR scanning spectroscopy in combination with an automated polymer identification approach, we show that all five species of Arctic zooplankton investigated had ingested microplastics. Amphipod species, found in surface waters or closely associated with sea ice, had ingested significantly more microplastic per individual (Themisto libellula: 1.8, Themisto abyssorrum: 1, Apherusa glacialis: 1) than copepod species (Calanus hyperboreus: 0.21, Calanus glacialis/finmarchicus: 0.01). The majority of microplastics ingested were below 50 μm in size, all were fragments and several different polymer types were present. We quantified microplastics in water samples collected at six of the same stations as the Calanus using an underway sampling system (inlet at 6.5 m water depth). Fragments of several polymer types and anthropogenic cellulosic fibres were present, with an average concentration of 7 microplastic particles (MP) L⁻¹ (0–18.5 MP L⁻¹). In comparison to the water samples, those microplastics found ingested by zooplankton were significantly smaller, highlighting that the smaller-sized microplastics were being selected for by the zooplankton. High levels of microplastic ingestion in zooplankton have been associated with negative effects on growth, development, and fecundity. As Arctic zooplankton only have a short window of biological productivity, any negative effect could have broad consequences. As global plastic consumption continues to increase and climate change continues to reduce sea ice cover, releasing ice-bound microplastics and leaving ice free areas open to exploitation, the Arctic could be exposed to further plastic pollution which could place additional strain on this fragile ecosystem.
... The higher level of C14:0 and C20:5n3 in R. esculentum individuals (Table 1) reflects the characteristic of dietary tracer for diatoms (Parrish, 2013). The FA biomarker ratio of C16:1n7/C16:0 typically used to infer a dominant diatom versus dinoflagellate (Auel et al., 2002), was also significantly higher in R. esculentum (0.037 ± 0.038). ...
With the continuous development of jellyfish fisheries and food products around the world, an effective traceability system has become increasingly prominent. This study provides insight into the origin traceability and authentication of two commercially important jellyfish species, flame jellyfish Rhopilema esculentum and Nomura’s jellyfish Nemopilema nomurai, while investigating the intra- and inter-specific variation in fatty acid (FA) profiles and carbon and nitrogen stable isotope ratios (δ¹³C and δ¹⁵N). Results showed significant differences in FA profiles and isotopic values in fresh bell tissues between wild and farmed R. esculentum and among geographic origins, possibly due to different food sources, nutritional status, and energy costs that each group experiences at a given location. The linear discriminant analysis indicated that δ¹³C, δ¹⁵N, C16:0, C17:0, C18:0, C16:1n7, and C20:5n3 were suitable discriminatory variables with a high rate of correct classification for distinguishing origins of R. esculentum. In addition, inter-specific FA profiles/biomarkers, combined with isotopic values, suggests the variety of dietary sources and trophic positions of sympatric similar-sized R. esculentum and N. nomurai and the potential use of biomarkers, especially stable isotope analysis, for distinguishing sympatric jellyfish species. These results highlighted the complementarity of FA and stable isotope analyses and provide an alternative approach for improving the origin traceability and authenticity evaluation of untreated edible jellyfish. Furthermore, this study adds new information regarding the biochemical compositions of jellyfish species.
... In addition, natural fluxes in environmental δ 15 N values (Robinson 2001, Pereira et al. 2007) may have contributed to elevated redfish δ 15 N values. Essential and conditionally essential FAs must be acquired through the diet and large proportions of LA, ALA and ω6 FAs in aquafeed, but trace proportions in marine environments allows their use as biological tracers for primary consumption though multiple dietary and FA sources lowers applicability in tracing secondary and tertiary consumption (Auel et al. 2002, Dalsgaard et al. 2003. However, elevated proportions of OA are common in marine consumers (Falk-Petersen et al. 1990), and elevated OA proportions in cage-associated adult cod may be attributed to increased prey aggregations in the area of sea cages (Serra-Llinares et al. 2013), including juvenile cod that may have been feeding on waste feed themselves. ...
Sea cage aquaculture can alter the spatial distribution of wild fish populations, however little is known about the dietary habits of wild fish frequenting sea cages. We used wild juvenile cod (Gadus morhua) reared in the laboratory and fed either an aquafeed pellet or marine-based diet to determine trophic discrimination factors (TDFs) of stable carbon (𝛿13C) and nitrogen (𝛿15N) isotope values in white muscle tissue and baseline liver proportions of vegetable-oil based (VOB) fatty acids. We then used 𝛿13C and 𝛿15N and proportions of VOB fatty acids to investigate the dietary habits of wild cage-associated juvenile and adult Atlantic cod and adult Atlantic redfish (Sebastes fasciatus). Cod and redfish were collected in the immediate area of sea cages and reference areas of no aquaculture production. Juvenile cod captured around sea cages had both elevated 𝛿13C and 𝛿15N values and proportions of VOB fatty acids, and isotopic fractionation comparable to laboratory cod fed an aquafeed diet. However, differences in 𝛿13C and 𝛿15N and proportions of VOB fatty acids between cage-associated and reference site adult cod and redfish were predominately absent. Results suggest that sea cages may provide an energetic subsidy to juvenile cod but perhaps not at the level to sustain adult cod or redfish. Therefore, the lack of differences suggests that both adult groups may be using cage sites opportunistically and only for short duration, as isotopic values and fatty acid proportions were not consistent with waste feed consumption despite individuals being collected in close proximity to sea cages.
... In general, the values for 16:1ω7/16:0 were rather low in our data; values > 1 were only detected in two samples of Fabia subquadrata. Previous studies have shown the 16:1ω7/16:0 ratio may reach > 2 in herbivores and carnivores that depend on a diatom-based food chain (Cripps et al. 1999;Auel et al. 2002). However, PUFA indicative of diatoms (DIFA) reached > 10% in some crab larvae, particularly in April-June, consistent with the spring diatom peak in Puget Sound. ...
Fatty acid (FA) content and composition of zooplankton in Puget Sound, Washington (USA) was studied to investigate the nutritional quality of diverse zooplankton prey for juvenile salmon ( Oncorhynchus spp.) in terms of their essential fatty acid (EFA) content. The study focus was on eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and arachidonic acid (ARA) as these are key FA needed to maintain growth and development of juvenile fish. The different zooplankton taxa varied in their FA composition. Much of the variation in FA composition was driven by 18:1ω9 (a biomarker of carnivory), ARA, DHA, and FA characteristic of diatoms, which are linked to zooplankton diet sources. Gammarid and hyperiid amphipods contained the highest amount of EFA, particularly the gammarid amphipod Cyphocaris challengeri , while shrimp and copepods had much lower EFA content. Crab larvae, which are important prey for juvenile salmon in Puget Sound, had intermediate EPA + DHA content and the lowest DHA/EPA ratio, and were rich in diatom biomarkers. Temporal and spatial trends in zooplankton lipids were less apparent than the taxonomic differences, although the EFA content increased from spring to summer in Cancridae zoeae and the amphipod C. challengeri . These results on taxon-specific EFA content provide baseline information on the nutritional quality of zooplankton that can be applied in food web models. Combining zooplankton fatty acid data (quality) with taxon-specific zooplankton biomass data (quantity) enables development of new, sensitive indicators of juvenile fish production to help assess recent declines in salmon production in the Pacific Northwest and predict future adult returns.
... Permutational multivariate analysis of variance (PERMANOVA) [54] was used to test whether these differences in the FA composition were statistically significant among wild (before the start of the feeding experiment), starved (day 0) and in green algae and diatom treatments. Treatment and day (7,14,21,28) or lipid fractions (NLFA, PLFA) were used as factors in two factors PERMANOVA (Primer 7). Additionally, one factor (treatment) PERMANOVA was run for testing differences in the PLFA and NLFA fraction. ...
Gammarid amphipods are a crucial link connecting primary producers with secondary consumers, but little is known about their nutritional ecology. Here we asked how starvation and subsequent feeding on different nutritional quality algae influences fatty acid retention, compound-specific isotopic carbon fractionation, and biosynthesis of ω-3 and ω-6 polyunsaturated fatty acids (PUFA) in the relict gammarid amphipod Pallaseopsis quadrispinosa. The fatty acid profiles of P. quadrispinosa closely matched with those of the dietary green algae after only seven days of refeeding, whereas fatty acid patterns of P. quadrispinosa were less consistent with those of the diatom diet. This was mainly due to P. quadrispinosa suffering energy limitation in the diatom treatment which initiated the metabolization of 16:1ω7 and partly 18:1ω9 for energy, but retained high levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) similar to those found in wild-caught organisms. Moreover, α-linolenic acid (ALA) from green algae was mainly stored and not allocated to membranes at high levels nor biosynthesized to EPA. The arachidonic acid (ARA) content in membrane was much lower than EPA and P. quadrispinosa was able to biosynthesize long-chain ω-6 PUFA from linoleic acid (LA). Our experiment revealed that diet quality has a great impact on fatty acid biosynthesis, retention and turnover in this consumer.
... A rare exception seems to be Hyperia galba (Montagu, 1813), which may shift to a benthic mode of life when their host is scarce (Fleming et al. 2014). The ecological role of this diverse group is related to their predation impact over zooplankton (Auel et al. 2002;Dalsgaard et al. 2003;Yamada and Ikeda 2006;Pinchuk et al. 2013), and therefore acts as a link to higher trophic levels in polar and temperate regions (Dauby et al. 2003;Dalpadado et al. 2008;Weil et al. 2019). They are also known to be closely related to gelatinous zooplankton (Laval 1978(Laval , 1980Phleger et al. 2000;Nelson et al. 2001;Nishikawa et al. 2005;Aoki et al. 2013;Gasca et al. 2015;Riascos et al. 2015). ...
The subtropical region of the Southeast Pacific exhibits a strong onshore-offshore gradient in hydrographic conditions and biological production from the eutrophic upwelling zone to the ultra-oligotrophic oceanic area in the central South Pacific gyre (SPG). Across this gradient, zooplankton must cope with either gradual or abrupt changes in environmental conditions. Here, the distribution and diversity of hyperiid amphipods were assessed over this gradient in the upper 1000 m in relation to temperature, salinity, oxygen, chlorophyll-a, sea level anomalies, the bulk of mesozooplankton biomass and the biomass of salps, siphonophores, and other hydrozoans during October/November 2015 from the coastal zone off Chile (27° 00‵ S, 70° 52‵ W) to near Easter Island within the SPG (27° 10‵ S, 109° 20‵ W). The most frequent and abundant species were Hyperioides longipes Chevreux, 1900, Eupronoe minuta Claus, 1879, and Hyperioides sibaginis (Stebbing, 1888). Significant changes in abundance and community structure across the gradient with respect to the evaluated environmental variables and significant correlations of 17 hyperiid species with the gelatinous category other hydrozoans were found. These changes were closely linked to previously defined zonation patterns, which contained distinct species assemblages and a unique dominant species per zone. These zones represented ecoregions based on diversity patterns of hyperiids and other shared species among such ecoregions suggesting a possible ecological connectivity among the zones, promoted by mesoscale eddies travelling westward from the coastal upwelling zone to offshore waters. Environmentally forced zonation and the interactions with mesoscale features are thus suggested as the driving processes maintaining spatial patterns of diversity of the hyperiid community in the Southeast Pacific.
... However, a small increase in the relative levels of Calanus FATMs was observed, suggesting that the old seals might be eating more amphipods than young seals. The amphipod T. libellula, is a high energy prey, rich in lipids and contain large amounts of wax ester, obtained from feeding on Calanus finmarchicus (Auel et al., 2002;Krafft et al, 2015). Also, they are often found in dense swarms and therefore represent a very attractive high energy prey for the harp seals ...
In September 2016, a marine ecosystem survey covered all trophic levels from phytoplankton to seals in the Arctic Ocean to the west and north of Svalbard. At the ice edge, 26 harp seals were sampled to assess whether recent environmental changes had affected their diets and body condition by comparing our current results with previous investigations conducted 2-3 decades ago in the northern Barents Sea, when the ice edge was located much further south. Our results suggest that the body condition was slightly but significantly lower for one year and older seals in 2016 compared with seals sampled in the early 1990s. Furthermore, we confirmed previous findings that polar cod (Boreogadus saida) and the pelagic hyperiid amphipod Themisto libellula still dominate the seal diet. One consequence of current ice edge localisation north of Svalbard is that the water depth underneath is now 500 m and deeper, which probably explains the absence of bottom associated species, and the presence of species such as Atlantic cod (Gadus morhua) and blue whiting (Micromesistius poutassou) as alternative species in addition to polar cod and T. libellula in the seal diets. Stable isotope data also suggest possible long-term importance in the seal diet of T. libellula and of low trophic level benthopelagic prey such as the squid Gonatus fabricii over mid-trophic level pelagic fishes, but with a strong component of small, benthopelagic fish such as blue whiting. The long-term importance of pelagic crustaceans was also suggested from the fatty acid analyses. Assessment of the abundance of prey showed that T. libellula was by far the most abundant prey species in the upper water layers, followed by krill (mainly Thysanoessa inermis), Atlantic cod and polar cod. Prey-preference analyses indicated that polar cod was the most preferred prey species for the seals.
... These results are consistent with a consumer-prey relationship occurring between E1 humpback whales and Antarctic krill. This ratio is generally used to distinguish between a herbivorous and carnivorous diet 49,50 . Our results show that E1 humpback whales, their potential temperate prey species (N. ...
Southern hemisphere humpback whales are classified as high-fidelity Antarctic krill consumers and as such are vulnerable to variability and long-term changes in krill biomass. Evidence of heterogeneous feeding patterns of east coast of Australia migrating humpback whales has been observed, warranting a comprehensive assessment of interannual variability in their diet. We examined the lipid and fatty acid profiles of individuals of the east coast of Australia migrating stock sampled between 2008 and 2018. The use of live-sampled blubber biopsies showed that fatty acid profiles varied significantly among all years. The two trophic indicator fatty acids for Antarctic krill, 20:5ω3 and 22:6ω3 remained largely unchanged across the 10-year period, suggesting that Antarctic krill is the principal prey item. A distance-based linear model showed that 33% of the total variation in fatty acid profiles was explained by environmental variables and climate indices. Most of the variation was explained by the Southern Annular Mode (23.7%). The high degree of variability observed in this study was unexpected for a species that is thought to feed primarily on one prey item. We propose that the observed variability likely arises from changes in the diet of Antarctic krill rather than changes in the whale's diet.
... The ecological role of this diverse group is better known in polar and temperate regions where it constitutes an important resource in food webs (Armstrong et al., 2005;Dalpadado et al., 2008;Dauby et al., 2003;Hedd and Montevecchi, 2006). In particular, species belonging to the genus Themisto have been well studied because of their dominance in cold areas and their predation on mesozooplankton (Pakhomov and Perissinotto, 1996;Yamada and Ikeda, 2006) especially on copepods (Auel et al., 2002;Dalpadado et al., 2008;Dalsgaard et al., 2003;Havermans et al., 2019). In polar regions Themisto can perform "top down" control over copepods, krill and larval fish (Pinchuk et al., 2013;Watts and Tarling, 2012) but this genus is able also to feed on salps and switch from herbivory to carnivory (Havermans et al., 2019). ...
The structure of the pelagic food web is a key issue to understand the variability in C and N fluxes in the ocean. The trophic structure of the hyperiid amphipods and its spatial variation in the subtropical area of the Southeast Pacific was studied based on C and N isotope composition. Zooplankton were collected off northern and Central-southern Chile during September-November 2016 at the coastal zone and in oceanic areas. Measurements of δ 15 N and δ 13 C of individual hyperiids were used to estimate the trophic position for each species, and to assess the community isotopic niche for 3 pre-defined areas: the coastal upwelling (eutrophic) zone, the coastal transition (mesotrophic) zone and the oceanic (oligotrophic) zone, as well as three depth layers. Our results showed different assemblages of species among the 3 zones, but also a large overlap between the isotopic niche for all zones and depth layers. In the mesotrophic zone there was a noticeable increase in the trophic position of individual species. The trophic diversity of hyperiids over the study region was relatively high, including primary consumers, omnivores and carnivorous feeders, and was associated with the changes in productivity across zones. However, carnivory was more prevalent in the mesotrophic zone and in the mesopelagic (500-1000 m) layer. We suggest that such variations reflect both the biogeochemical processes controlling the productivity in each zone, and the life-traits of individual species.
... FA 18:1n9 is considered a carnivory marker (Sargent and Henderson, 1986;Graeve et al., 1994a;Nyssen et al., 2005), while 18:1n7 is synthesized by phytoplankton (Falk-Petersen et al., 1990). Subsequently, high values of this ratio indicate carnivorous feeding, while lower values indicate an herbivorous diet (Falk-Petersen et al., 1990;Graeve et al., 1997;Cripps and Atkinson, 2000;Bühring and Christiansen, 2001;Auel et al., 2002). High PUFA versus saturated FA (SFA) ratios are indicative of a relatively more carnivorous diet. ...
... Furthermore, the ratio between EPA and DHA is often used as an indicator of a diatom-or flagellate-based diet (St. John and Lund, 1996;Auel et al., 2002). The variations of this index are in total accordance with the evolution of other biomarkers. ...
Les recherches présentées dans cette thèse ont été menées au Laboratoire des sciences de l'environnement marin, Université de Bretagne occidentale (Plouzané, France), au Département de biologie théorique, Vrije Universiteit Amsterdam (Pays-Bas) et à l'Institut de recherche marine (Bergen, Norvège).
... A second data set of FAs was chosen to explain statistics and relationships between the FAs in animals of different feeding behavior, changing from herbivores to a mainly carnivorous animal. The pelagic amphipods are important congeners of the Arctic food web supplying lipid-based energy for higher trophic levels (Auel et al. 2002;Kraft et al. 2015). They partly feed on copepods and store Calanus derived lipids consisting of essential ω3 and ω6 FAs into storage and membrane lipids. ...
Fatty acid (FA) compositions provide insights about storage and feeding modes of marine organisms, characterizing
trophic relationships in the marine food web. Such compositional data, which are normalized to sum to
1, have values—and thus derived statistics as well—that depend on the particular mix of components that constitute
the composition. In FA studies, if the set of FAs under investigation is different in two separate studies, all the
summary statistics and relationships between the FAs that are common to the two studies are artificially changed
due to the normalization, and thus incomparable. Ratios of FAs, however, are invariant to the particular choice of
FAs under consideration—they are said to be subcompositionally coherent. Here, we document the collaboration
between a biochemist (M.G.) and a statistician (M.J.G.) to determine a suitable small set of FA ratios that effectively
replaces the original data set for the purposes of univariate and multivariate analysis. This strategy is applied
to two FA data sets, on copepods and amphipods, respectively, and is widely applicable in other contexts. The
selection of ratios is performed in such a way as to satisfy substantive requirements in the context of the respective
data set, namely to explain phenomena of interest relevant to the particular species, as well as the statistical
requirement to explain as much variance in the FA data set as possible. Benefits of this new approach are (1) univariate
statistics that can be validly compared between different studies, and (2) a simplified multivariate analysis
of the reduced set of ratios, giving practically the same results as the analysis of the full FA data set.
A video abstrat is available here: https://youtu.be/T09U5FzP7fg
... FAs are incorporated into consumers in a conservative manner (Dalsgaard et al., 2003;Stowaser et al., 2009), thereby providing information on predator-prey relations. FAs, as trophic markers, provide information on dietary intake and food constituents leading to the sequestering of lipid reserves over a long period of time (Auel et al., 2002). FA composition may be used to elucidate the dietary source of lipid reserves and have so far been used as qualitative and "semi-quantitative" food web markers, the latter in concert with other tracers such as stable isotopes (Dalsgaard et al., 2003;Iverson, 2009;Mourente et al., 2015). ...
Foraging habits of skipjack tuna, SKJ (Katsuwonus pelamis), were investigated in three Spanish marine regions (Balearic Sea, Alboran Sea and Gulf of Cadiz) using stomach content (SCA), stable isotope (SIA), and fatty acid (FA) analyses. The three methodological approaches yielded significant differences among locations. All the studied areas appear to serve as important foraging grounds for SKJ, but the diet composition significantly varied among them. The predominant prey species in the respective locations were the North Atlantic krill, Meganyctiphanes norvegica, in the Balearic Sea, the flyingfish, Exocoetus volitans, in the Alboran Sea, and the anchovy, Engraulis encrasicolus, in the Gulf of Cadiz. Regional differences were also found in δ13C and δ15N values; furthermore, the analysis of standard ellipse areas (SEAc) based on isotopic data showed that the broadest niche corresponded to SKJ from the Gulf of Cadiz, with no significant isotopic niche overlap between areas. Consistent with the SCA and stable isotope results, the FA composition varied among areas. Docosahexaenoic acid (DHA, 22:6n-3) was the most abundant FA in the SKJ muscle, showing its highest values in samples from the Gulf of Cadiz; this FA was the most effective in segregating SKJ geographical groups. In conclusion, this study provides evidence that SKJ in eastern Atlantic and western Mediterranean waters can easily adapt their diet to local prey availability. Furthermore, stable isotope signatures and FA profiles of muscle tissue prove to be reliable trophic markers that allow separation of populations occurring in different marine areas.
... Specific FA ratios were also calculated to obtain better insights in diet differentiation between krill species and among regions. The EPA/DHA ratio was calculated to differentiate diets mostly composed of diatoms or dinoflagellates (Graeve et al., 1994;Auel et al., 2002). The (Σ20:1+Σ22:1+18:1n9)/(EPA+DHA) ratio, named hereafter Σzooplankton/Σphytoplankton, characterize carnivory versus herbivory, and the 18:1n9/(Σ20:1+Σ22:1) ratio differentiates selectivity between Pseudocalanus spp. ...
Krill, as forage species, play a pivotal role in marine food webs by linking lower to upper trophic levels. Despite their ecological relevance, processes affecting their physiological condition and their feeding selectivity remain not well known. Here, we hypothesize that significant spatial fluctuations of environmental conditions in a Subarctic region affect the energy reserve content and feeding strategies of krill. To test this hypothesis, we assessed the fatty acid content and composition of two dominant northern krill species Meganyctiphanes norvegica and Thysanoessa inermis on a seasonal basis over more than 1000 km in the Estuary and Gulf of St. Lawrence (eastern Canada) and for the first time during the ice covered winter. M. norvegica exhibited large spatial variation of its energy reserve lipids, which were similar to seasonal variations found in a previous study in the same environment. In contrast, lipid content of T. inermis was much less affected by the spatial variations of environmental conditions but showed high seasonal variability. Feeding preferences assessed using fatty acid trophic markers highlight that the zooplankton standing stock could be more critical than phytoplankton to fulfill the metabolic requirements of these
krill species and to build lipid energy reserves. In addition, diet comparison between both species highlights that trophic niche partitioning is present in the Gulf of St. Lawrence, however, modulated by spatial differences in food supply and oceanographic conditions.
... John & Lund, 1996). The ratio 18:1ω9/18:1ω7 has been used as an index of carnivory, with higher values (>>2) indicating a more carnivorous diet (Auel, Harjes, Da Rocha, Stübing, & Hagen, 2002;Falk-Petersen, Hagen, Kattner, Clarke, & Sargent, 2000;Maazouzi, Masson, Izquierdo, & Pihan, 2007;Stevens, Deibel, & Parrish, 2004). ...
Ecology of the glacial relict macrocrustacean Gammaracanthus lacustris , a rare inhabitant of deep Fennoscandian lakes, is poorly understood. We studied the life cycle and trophic position of this cold‐stenothermic amphipod in Lake Paasivesi, eastern Finland. The study is based on intensive sampling and analyses of fatty acid composition as well as stable carbon (δ ¹³ C) and nitrogen (δ ¹⁵ N) isotope ratios.
Both day and night, the G. lacustris population occurred at depths below 25 m at temperatures <8°C, and the density increased towards the bottom of the lake, where it was 0.4–0.6 individuals/m ³ .
Gammaracanthus lacustris was observed to reach a length of >40 mm and live up to 4 years. The oldest and the largest individuals and females seemed to favour the deepest zones.
In October, almost 100% of females with length at least 25 mm (i.e. females presumably at least 1‐year‐old) had an embryo sack with 20–200 eggs or embryos—the larger the female, the more young it had.
The developing eggs of G. lacustris had a very high fatty acid content, indicating that the females invest heavily on provisioning their young. Furthermore, the fatty acid composition differed among life stages, and in particular the eggs had a higher proportion of eicosapentaenoic acid than juveniles or adults.
The stable δ ¹³ C and δ ¹⁵ N isotope ratios and fatty acid biomarkers of the food web, together with visual observations, indicate that G. lacustris is a carnivore that feeds mainly on zooplankton and other relict macrocrustaceans.
Due to its high content of essential polyunsaturated fatty acids, G. lacustris is a valuable prey for fish and other predators in the food web. However, as a glacial relict with strict habitat requirements the species is vulnerable to global warming and local environmental changes. These facts should be considered in the management of lakes and their catchments.
... Analysis of FAs trophic markers is a quantitative approach that can provide information on the integrated dietary sources in consumers on time scales of several weeks (Auel, Harjes, Rocha, Stübing, & Hagen, 2002;Boissonnot, Niehoff, Hagen, Søreide, & Graeve, 2016). ...
Increasing sea surface temperatures (SST) and blooms of lipid‐poor, filamentous cyanobacteria can change mesozooplankton metabolism and foraging strategies in marine systems. Lipid shortage and imbalanced diet may challenge the build‐up of energy pools of lipids and proteins, and access to essential fatty acids (FAs) and amino acids (AAs) by copepods. The impact of cyanobacterial blooms on individual energy pools was assessed for key species temperate Temora longicornis and boreal Pseudo‐/Paracalanus spp. that dominated field mesozooplankton communities isolated by seasonal stratification in the central Baltic Sea during the hot and the cold summer. We looked at (a) total lipid and protein levels, (b) FA trophic markers and AA composition, and (c) compound‐specific stable carbon isotopes (δ13C) in bulk mesozooplankton and in a subset of parameters in particulate organic matter. Despite lipid‐poor cyanobacterial blooms, the key species were largely able to cover both energy pools, yet a tendency of lipid reduction was observed in surface animals. Omni‐ and carnivory feeding modes, FA trophic makers, and δ13C patterns in essential compounds emphasized that cyanobacterial FAs and AAs have been incorporated into mesozooplankton mainly via feeding on mixo‐ and heterotrophic (dino‐) flagellates and detrital complexes during summer. Foraging for essential highly unsaturated FAs from (dino‐) flagellates may have caused night migration of Pseudo‐/Paracalanus spp. from the deep subhalocline waters into the upper waters. Only in the hot summer (SST>19.0°C) was T. longicornis submerged in the colder subthermocline water (~4°C). Thus, the continuous warming trend and simultaneous feeding can eventually lead to competition on the preferred diet by key copepod species below the thermocline in stratified systems. A comparison of δ13C patterns of essential AAs in surface mesozooplankton across sub‐basins of low and high cyanobacterial biomasses revealed the potential of δ13C‐AA isoscapes for studies of commercial fish feeding trails across the Baltic Sea food webs. To our knowledge, this is the first study that concomitantly evaluates δ13C values of individual FAs and AAs in aquatic organisms, which provides new insights into the powerful but still novel application of compound‐specific δ13C patterns in marine systems. In this study, we unravel the foraging strategies and reconstruct a dietary baseline of mesozooplankton for the supply of dietary fatty acids and amino acids during unpalatable, lipid‐poor cyanobacteria blooms. This study emphasizes that combined analyses of novel compound‐specific δ13C patterns with conventional trophic marker approach answer different but complementary questions.
Fisheries in Brazil, the country with most territory in South America, is
not comprehensive at all. The lack of precise historical data is the main concern
faced by perspectives of fishery management. The majority of data are simplistic
records of extrapolated biomass published by federal entities regardless the habitat
from where fish resources were harvested, how they were captured and lengths of
capture. Little attention was given to the social, economic and cultural aspects of
traditional communities and their livelihood. Worst is the case of estuarine systems
of the Western Atlantic, where artisanal fishery rules the landings and the absence
of proper monitoring, control and surveillance leads to poor managerial actions. As
a result, fishery studies conclude that most fish stocks of Western Atlantic estuaries
show signs of over-exploitation. Palliative measures such as closed periods for cap�[
ture of common resources has emerged as urgent option aiming to reduce the
impacts of overfishing. Bycatch reduction devices are examples of emerging
ishery management of Brazilian estuaries urges accelerated actions: intro�
duce rights and duties-based fishery management to guarantee the declaration of
every fisherman activities; enable fishers to organize themselves through the idea of
ecological sustainability and economic efficiency; and acquiring daily reports of
fish landings through stakeholder approach and co-management. Fishery pressure is not the unique responsible for reduced estuarine production. Bycatch due to smallmesh nets, oxygen-consuming effluents, emerging pollutants, solid wastes, deforestation of mangrove forest for human purposes and human-driven changes in river flow and estuarine morphology are rapidly changing the nature of a nursery environment. Co-management, long-term data and daily reports on production can help to design stock assessment models, understand variations in biomass over time, detect problems of uncontrolled fishing effort, point periods of seasonal habits for each fishery resource, and, most importantly, guarantee that enough juveniles of each living resource can be recruited to adult stocks. The compliance of ecological data and biological research, robust data for landing stats and the social profile of the fishery community seems to be the ideal approach to build proper rules of comanagement in Western Atlantic estuaries
jats:p>Fish, whales, and seabirds along the productive west coast of Vancouver Island (WCVI), NE Pacific, rely on copepod prey that are assumed to be rich in lipid. However, the total lipid (TL) and fatty acid content of most copepod species and other mesozooplankton in this region have not been measured. To assess the diets and quality of zooplankton prey off the WCVI, we investigated differences in lipid content and composition of mesozooplankton according to their taxonomic versus functional group identities. Copepods, chaetognaths, euphausiids, and amphipods, belonging to 3 different functional groups, were sampled on the WCVI during pre-, mid-, and post-bloom conditions. Compared to taxonomic classifications, the functional group approach was superior in its ability to discern statistical differences in TL among zooplankton and between seasons. Furthermore, multivariate analyses using zooplankton fatty acid composition from all oceanographic regimes produced 3 to 4 statistically different clusters of species that corroborated functional group designations. However, some trophic flexibility was observed in several copepod species, particularly Calanus marshallae , that may relate to food scarcity or the presence of potentially noxious prey. The omnivorous-herbivorous functional group frequently contained higher amounts of TL and masses of essential fatty acids than the carnivorous group. Euphausiids and C. marshallae contributed the most lipid (mg m -3 ) to the pelagic ‘lipid pool’, due to very high lipid content and high abundance, respectively. However, on the continental slope and shelf break, chaetognaths and Neocalanus spp. copepods contributed substantially to the lipid pool.</jats:p
The marine pelagic primary production is an important energy source for most Arctic ecosystems, both marine and terrestrial. Single‐celled algae in the water column and in sea ice are at the base of the food web. There are two main drift patterns for sea ice and the upper polar mixed layer in the Arctic Ocean: the Beaufort Gyre (BG) and the Transpolar Drift (TPD). The TPD and the interconnected current systems in the Nordic seas and the Arctic Ocean form the trans‐Arctic highways, transporting zooplankton and ice fauna species over long distances. Regardless of how a continued warming of the Arctic may affect the productivity of the system, there are two key areas where climate change is likely to have an effect on the Arctic pelagic ecosystem: the timing of key life history events; and extension of boreal species northwards.
Albacore tuna (Thunnus alalunga) is a highly economically important species in the western Indian Ocean. However, knowledge of its ecological and nutritional characteristics, essential for proper management of the species, is lacking in the region. The trophodynamics of the Indian Ocean albacore was thus examined using known fatty acid trophic markers (FATMs) of primary producers, nutritional condition indices (NCIs) (omega-3/omega-6 ratio and total fatty acid content (TFA)), and baseline and lipid corrected stable isotope of carbon (δ13Ccorr) and nitrogen (δ15Ncorr), measured in the muscle tissue. We applied generalized additive mixed models to understand the spatiotemporal patterns and drivers of these tracers, taking into consideration several intrinsic and extrinsic variables: fish size, fishing position, month, chlorophyll-a and sea surface temperature (SST). Both chlorophyll-a and SST were significant as single explanatory variables for all tracers with SST being the best predictor for docosahexaenoic acid/eicosapentaenoic acid ratio, the omega-6 protists FATM, omega-3/omega-6 ratio, δ13Ccorr and δ15Ncorr. TFA was best predicted by fish size only. Higher primary productivity, as inferred by high δ13Ccorr values and diatom contribution, nutritional condition and trophic position, as inferred by high δ15Ncorr values, were observed in albacore from the temperate southern waters than in the northern tropical regions. Relationships between environmental variables and corrected stable isotopes, FATMs confirm that ocean warming and changes in primary productivity will impact nutrient flow and energy transfer in the marine food web which may have negative nutritional outcomes for albacore. This knowledge is particularly crucial in areas where oceanographic conditions and seawater temperatures are changing at a fast rate and should also be taken into consideration by fisheries managers.
The trophic ecology of albacore tuna in the western Indian Ocean and adjacent Atlantic waters based on stomach content analysis, using a reconstituted length and weight of prey approach, was studied. From a total of 686 non-empty stomachs, collected between 2001 and 2015 across three biogeographic provinces, we described the diet composition of albacore tuna, analysed its feeding habits, and investigated the structure and diversity of mid-trophic level communities. Epipelagic fish were found to be the principal prey by number and reconstituted weight; cephalopods were the second important prey group. Small organisms prevailed in the diet of albacore tuna, with commonplace predation on juvenile fish. Albacore tuna exhibits a flexible, opportunistic feeding strategy, from ram-filter feeding on abundant schooling prey to visual predation on large individuals. Prey-species richness varied highly across the region. Oligotrophic conditions within the subtropical gyre of the Indian Ocean generated the most diverse mid-trophic level communities, with less diverse communities occurring in productive areas. Albacore tuna occupies a similar trophic niche throughout the global ocean, foraging on the same prey families and even species. This study indicates overall temporal stability of the Indian Ocean and south-east Atlantic ecosystems where principal prey species remain unchanged over decades.
Swarms of Themisto abyssorum and one of Themisto libellula (Hyperiidea, Hyperiidae) were observed during four dives of Mir deep-sea manned submersibles in the Norwegian and Greenland Seas at depths of about 1000 m. Concentrations of the amphipods in the most dense swarm were as high as high as 25–38 individuals per cubic meter in the layer 100–5 m above the bottom. However, such swarming does not seem to be obligatory for Themisto. The animals picked up (food?) particles directly from the seabed.
The feeding dynamics and predation impact of the hyperiid amphipod Themisto gaudichaudi on mesozooplankton were studied in the vicinity of South Georgia, Southern Ocean, during austral summer 1994. Data show that T. gaudichaudi is a visual opportunistic predator, consuming primarily the most abundant species of copepods, euphausiids and pteropods. In situ estimated daily rations were equivalent to 6.3% of body dry weight, and similar to the value of 7.1% of body dry weight derived using an energy budget approach which takes into account the total daily energy requirements. In vitro estimates produced daily rations higher than these, ranging from 8.5 to 21.8% of body dry weight, increasing with prey density. The predation impact of T. gaudichaudi adults, averaged over a 0 to 200 or 0 to 100 m layer, never exceeded 2.1% of mesozooplankton standing stock per day but accounted for up to 70% of the daily secondary production. This suggests that in the vicinity of South Georgia T. gaudichaudi adults are able to control the local mesozooplankton community and may contribute significantly to the downward flux of biogenic carbon.
Proximate (protein, lipid, carbohydrate and chitin) and elemental (carbon and nitrogen) composition were determined for 18 species of Antarctic micronektonic Crustacea, representing the majority of species found in the Antarctic water column. Individuals used in the analyses were captured during fall and winter; for 8 species data were collected in both seasons. Seven of the 8 species showed some evidence that combustion of body stores were an aid to surviving the winter months; comparison with data from other investigators suggests that most of the species inhabiting shallow and mid-depths exhibit some degree of combustion of body stores during winter. Three types of overwintering strategies are proposed for Antarctic zooplankton and micronekton. Type 1, exhibited by some calanoid copepods, is characterized by accumulation of large lipid deposits and a true dormancy, or diapause, during winter. Type 2, exhibited by euphausiids and hyperiid amphipods, is characterized by a marked reduction in metabolic rate, combustion of body substance, opportunistic feeding, but no true dormancy. Type 3, 'business as usual' is exhibited by decapods and gammarid amphipods; it is characterized by an absence of a winter reduction in metabolic rate, combustion of body stores in some species but a lack of combustion or accumulation of energy in others, and opportunistic feeding. Over-wintering scenarios computed for Euphausia superba suggest that the impact of the winter season is most severe in the smaller size classes.
Oxygen comsumption rates were determined on 21 species of crustaceans typical of the Southern Ocean micronektonic crustacean assemblage during spring (November), fall (March), and winter (June-August). Specimens were collected in the Scotia-Weddell Sea region in the vicinity of 60-degrees-S, 40-degrees-W in the upper 1000 m of the water column. Respiration (y, mul O2mg-1 wet mass h-1) declined with depth of occurrence (x, m) according to the equation y = 0.125 x-0.172 +/- 0.052 (p < 0.05) despite the isothermal character of the water column, suggesting that lower metabolic rates are a temperature-independent adaptation to life in the deep sea. Three species of Crustacea showed a lowered metabolism during the winter season: the krill Euphausia superba and the 2 hyperiid amphipods Cyllopus lucasii and Vibilia stebbingi. Critical oxygen partial pressure (Pc) varied between 29 and 52 mm Hg, well below the lowest PO2 found in the water column. It is suggested that the long nights of the Antarctic winter decrease the effectiveness of visual predation in the epipelagic zone, allowing lowered metabolic rates to be a viable overwintering strategy for some species.
Antarctic hyperiid (Themisto gaudichaudi, Hyperia macrocephalus, and Primno macropa) and gammarid amphipods (Eusirus perdentatus and Orchomene rossi) were collected near Elephant Island, located in the South Shetland Islands, during January and February 1997 and 1998. Polar lipid (PL) was the major lipid class in all amphipods (58–88% of total lipid), except for T. gaudichaudi in which triacylglycerol (TAG) was dominant (62%). Cholesterol was the major sterol in the gammarid amphipods (89–91% of total sterols), and the hyperiid P. macropa (70%). The hyperiids T. gaudichaudi and H. macrocephalus had a more diverse sterol composition including trans-dehydrocholesterol, desmosterol, 24-nordehydrocholesterol, 24-methylcholest-5,22E-dien-3β-ol, 24-methylenecholesterol, and stanols (mostly cholestanol). Eicosapentaenoic acid [EPA, 20:5(n−3)] and docosahexaenoic acid [DHA, 22:6(n−3)] were the major polyunsaturated fatty acids (PUFA) in all amphipods. The PUFA octadecapentaenoic acid [18:5(n−3)] was not detected in 1997 samples, but comprised 0.3–1.2% in all 1998 samples. The PUFA 18:4(n−3) comprised 0.2–4.2% in all samples from both years. Very long chain PUFA (VLC-PUFA) (C24 and C26) were not detected in the one 1997 sample but comprised 0.6–2.8% of total fatty acids in almost all 1998 amphipods. Monounsaturated fatty acids included 18:1(n−9)c, 18:1(n−7)c, and 16:1(n−7)c. Principal saturated fatty acids in all amphipods were 16:0, 14:0, and 18:0. Examination of biomarker lipids has helped clarify trophic interactions for these Antarctic amphipods, and revealed annual differences in their food sources.
Variations in total lipid content (g of lipid, and as % of wet and dry body weights) of the prawn Pandalus borealis, ranging from eggs to 52 mo old adults, indicate that lipid growth exhibits marked seasonal oscillations while growth in carapace length shows only comparatively weak seasonality. Positive (anabolic) lipid growth occurs from about April to September inclusive (with up to 40 % of dry body weight as lipid), the major production season for both phytoplankton and herbivorous zoo-plankton. Negative (catabolic) lipid growth (with lipid being reduced to about 10 % of dry weight) is prominent during the winter. Correspondence analysis involving the relative body-content of total lipid, total protein, ash and water indicates that both 'age' and 'seasonally' related trends are visible; lipid tends to play an increasingly important role with age but lipid levels oscillate between peaks in late summer (August/September) and troughs in late winter (February/March). Qualitative investigations of gut contents and analyses of lipid-class composition and fatty acid food-chain markers of selected sizes and ages of prawn indicate that lipid-rich zooplankton (mainly copepods and krill) form the bulk of the food of prawns from 1 to 4 yr old. Although benthic polychaetes and detrital material tend to increase in relative importance with increasing size and age of prawn, they are of secondary importance compared to pelagic organisms. The older prawns frequently contained substantial numbers of capelin scales, probably from feeding on discarded fish from prawn trawling. This study thus reveals that P. borealis in north Norwegian fjords is linked trophically to the highly seasonal pelagic production cycle. The lipid percentage of P. borealis is, however, less than that of herbivorous zooplankton but substantially greater than that of the lipid-deficient benthos.
The notion of a barren central Arctic Ocean has been accepted since English's pioneering work[1] on drifting ice-islands. The year-round presence of ice, a short photosynthetic season and low temperatures were thought to severely limit biological production1,2, although the paucity of data was often noted. Because primary production appeared to be low[1,2], subsequent studies assumed that most organic carbon was either derived from river inputs or imported from adjacent continental-shelf regions3,4. Here we present shipboard measurements of biological produc-tion, biomass and organic carbon standing-stocks made during a cruise through the ice covering the central Arctic Ocean. Our results indicate that the central Arctic region is not a biological desert. Although it is less productive than oligotrophic ocean regions not covered by ice, it supports an active biological community which contributes to the cycling of organic carbon through dissolved and particulate pools.
Samples of ice algae from the Marginal Ice Zone in the Barents Sea could be divided into two categories: one dominated by
assemblages of Melosira arctica, and the other dominated by Nitzschia frigida and associated diatoms. Total lipid from the Melosira assemblages consisted of approximately equal amounts of polar lipids and triacylglycerols. Total lipid from the Nitzschia assemblages contained more triacylglycerols than polar lipids. Total lipid from the Melosira assemblages had higher percentages of C16 PUFA, especially 16:4(n-1) and 20:5(n-3), than that from the Nitzschia assemblages, this reflecting the higher percentages of both C16 PUFA and 20:5(n-3) in polar lipids than in triacylglycerols.
Phytoplankton from the pelagic zone were␣richer in flagellates and contained less C16 PUFA and 20:5(n-3) but more C18 PUFA
and 22:6(n-3). The dominance of diatoms in the ice-algae assemblages in the Marginal Ice Zone and their high nutritional value
as a source of 20:5(n-3) for higher trophic levels are emphasised.
Antarctic salps (Salpa thompsoni and Ihlea racovitzai) and their commensal hyperiid amphipods (Vibilia antarctica, Cyllopus lucasii and C. magellanicus) were collected near Elephant Island, in the South Shetland Islands, during 1997 and the salp-rich year 1998. The sterol
composition of aggregate S. thompsoni and I. racovitzai (mostly 24-methyl-5,22E-dien-3β-ol, 24-nordehydrocholesterol, cholesterol and trans-dehydrocholesterol) was reflected in the sterol composition of the commensal amphipods and was consistent with a herbivorous
planktonic diet. This was not the case for solitary S. thompsoni, with 24-methylenecholesterol as the major sterol. There was a greater abundance of aggregate salp stanols in 1997 (11.7%
total sterols) than 1998 (5.2%) and these different stanol levels were reflected in the commensal amphipods. Eicosapentaenoic
acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] were the major polyunsaturated fatty acids (PUFA) in all organisms. Octadecapentaenoic acid [18:5(n-3)] comprised 0.4–5.8% (of total fatty acids) in all 1998 salps and amphipods, but was absent in 1997 samples. This suggests
a greater presence of dinoflagellates or other species rich in 18:5(n-3) in the “salp year” 1998. Very long chain PUFA (C24, C26, C28) were also only detected in 1998 samples (up to 5.3%), reflecting commensalism and greater presence of dinoflagellates or
species containing very long chain PUFA. Examination of the biomarker lipids has provided an indication of trophic interactions
for these Antarctic salps and their commensal hyperiid amphipods.
Summer food of the little auks nesting on Bjornoya consisted of large copepods, decapod larvae and pelagic amphipods. Food
items of 4–6 mm constituted the most common prey size fraction. This prey size range appears to be optimal (most profitable)
with regard to the balance between mean individual mass and density of items in the surface layers of the sea. Little auks
from Bjørnøya only sporadically take the abundant copepod Calanus finmarchicus (2–3.5 mm in length) but select the much less abundant and larger Calanus glacialis (3–6 mm).RID=""ID="" Acknowledgements The authors would like to thank Dr. Monika Normant from the University of
Gdansk for her assistance with caloric measurments, and Lech Illiszko and Adam Wajrak for their help with the fieldwork on
Bjørnøya.RID=""ID="" Correspondence to J. M. We¸sławski
Seasonal changes in the lipid class composition and fatty acid and fatty alcohol composition of neutral lipids were determined for Calanus finmarchicus, Metridia longa and Sagitta sp. in Balsfjord, northern Norway. Similar analyses were obtained for C. hyperboreus and Parathemisto abyssorum in an adjacent fjord, Ullsfjord, in spring. C. finmarchicus, C. hyperboreus, M. longa, and Parathemisto abyssorum all contained large amounts of wax esters whereas Sagitta sp. contained small amounts of triacylglycerols and traces of wax esters. the levels of wax ester in C. finmarchicus and M. longa were highest in late autumn (respectively 88% and 84% of total lipid) and lowest in early spring (respectively 85% and 27% of total lipid). The accumulation of these neutral lipids in spring and summer is related to the feeding activity during the primary production period, while their decline in late winter is associated with the mobilisation of metabolic energy for production of gonads. The major fatty alcohols in the wax esters of C. finmarchicus and C. hyperboreus and Parathemisto abyssorum were 20:1 and 22:1 while those in the wax esters of M. longa were 14:0 and 16:0. The traces of wax esters in Saqitta were rich in 20:1 and 22:1 fatty alcohols. These analyses are consistent with C. finmarchicus and C. hyperboreus being strictly herbivorous, M. longa being more carnivorous and both Sagitta sp. and Parathemisto being highly carnivorous, probably ingesting substantial amounts of calanoid copepods.
Mesozooplankton collected during five summer expeditions to the Arctic Ocean between 1987 and 1991 was analysed for regional
patterns in biomass and species distribution, distinguishing between an epipelagic (0–100 m) and a deeper (0–500 m) layer.
A total of 58 stations was sampled mainly in the Nansen, Amundsen and Makarov Basins of the central Arctic Ocean and in areas
of the Greenland Sea, West Spitsbergen Current and Barents Sea. Results from the different expeditions were combined to create
a transect extending from the Fram Strait across the Eurasian Basin into the Makarov Basin. Mesozooplankton dry mass in the
upper 500 m decreased from 8.4 g m−2 in the West Spitsbergen Current to less than 2 g m−2 in the high-Arctic deep-sea basins. In the central Arctic Ocean, biomass was concentrated in the upper 100 m and was dominated
by the large copepods Calanus hyperboreus and C. glacialis. In contrast, the mesozooplankton in the West Spitsbergen Current was more evenly distributed throughout the upper 500 m,
with C. finmarchicus as the prevailing species. The distribution of abundant mesopelagic species reflected the hydrographic regime: the calanoid
copepod Gaetanus tenuispinus and the hyperiid amphipod Themisto abyssorum were most abundant in the Atlantic inflow, while Scaphocalanus magnus was a typical component of the high-Arctic fauna. The relatively high mesozooplankton biomass and the occurrence of boreal-Atlantic
species in the central Arctic Ocean are indicators for the import of organic material from allochthonous sources, especially
from the northern North Atlantic. Hence, in spite of its enclosure by land masses, the Arctic Ocean is characterized by an
exchange of water masses and organisms with the North Atlantic, and advection processes strongly influence the distribution
of plankton species in this high-latitude ecosystem.
To verify the potential of fatty acids as trophic markers, feeding experiments were carried out with the dominant herbivorous copepods Calanus finmarchicus, C. hyperboreus and C. glacialis from the Greenland Sea during two Arctic expeditions in June/July 1991. Depending on the fatty acid composition of these copepods, the diatom Thalassiosira antarctica or the dinoflagellate Amphidinium carterae were offered as food to induce deviating fatty acid compositions. Since the copepodite Stages CV of C. finmarchicus had very low amounts of the 16:1(n−7) fatty acid but high amounts of 18:4(n−3), the specimens were fed on T. antarctica rich in 16:1(n−7) over a period of up to 42 days. At the end of the feeding experiment the portion of the 16:l(n-7) fatty acid had strongly increased by 11%, while the 18:4(n−3) fatty acid was almost depleted. In contrast, high amounts of the 16:1(n−7) fatty acid in C. hyperboreus (CV) suggested feeding on diatoms, therefore its diet was changed to A. carterae dominated by high amounts of the 18:4(n−3) fatty acid. After 47 days the portion of 18:4(n−3) increased by 8%, whereas 16:1(n−7) decreased by 3 %. In female C. glacialis the changes in the fatty acid composition after feeding with A. carterae were less pronounced as compared to the other species, due to a severe lipid loss during the experiment. The feeding experiments document the incorporation and turnover of dietary fatty acids under controlled laboratory conditions and provide clear evidence for the potential of specific fatty acids as trophic marker lipids.
The abducted juvenile pteropod Spongiobranchaea australis had less triacylglycerol (10.9% of total lipid) than free-living S. australis (34.7%), and they lack glyceryl ethers. Ratios of eicosapentaenoic acid [20:5(n-3)] to docosahexaenoic acid [22:6(n-3)] were also less (0.5) for abducted than free-living S. australis (1.4). The polyunsaturated fatty acid 14:3 was detected for the first time in both abducted and free S. australis. A number of odd chain fatty acids were also detected, particularly 17:1 (up to 3.6% of total fatty acids) and also 15:0, 17:0, i17:0, and i19:0. The major sterols in the amphipod host, Hyperiella dilatata, included cholesterol (52–55% of total sterols) and trans-dehydrocholesterol (33–38%), whereas in S. australis (both free and abducted) the major sterols included trans-dehydrocholesterol (23–37%), brassicasterol (14–27%), and cholesterol (13–19%). The sterol profile of H. dilatata is consistent with a carnivorous diet, whereas that of S. australis is more representative of an herbivorous diet. This finding is consistent with the major prey of S. australis being the herbivore Clio pyramidata.
Ringed seals Phoca hispida and harp seals P. groenlandica were collected for diet analysis along the ice edge in the Barents Sea to investigate possible niche overlap between these 2 seal species. The diet analysis is based on contents from stomachs and intestines. A resource availability survey was conducted concurrently based on an echo survey combined with demersal and pelagic trawling. This survey showed that the potential prey biomass was dominated by pelagic crustaceans (99 % of total biomass) - principally Themisto libellula and Thyssanoessa spp. Despite the prevalence of these crustaceans both seal species showed a strong preference for fish of various species, which constituted only 1 % of the biomass in the area. The most common fish in their diet was polar cod Boreogadus saida, which had a Manly's prey preference index of 0.87 for ringed seals and 0.42 for harp seals. Pianka's niche overlap index for the 2 seal species in this area was 0.985, indicating an almost complete niche overlap. However, harp seals prey on significantly larger polar cod than ringed seals, and the larger cod were distributed in deeper water than smaller cod. Thus it appears that the 2 seal species exploit different fractions of the same resource.
The effects of physical mixing processes on phytoplankton production in the marine environment are well established. However, the effects of these processes on growth and condition of zooplankton and larval fish are at present poorly understood. In this study, we utilized phytoplankton group-specific fatty acid content to trace the phytoplankton group and mixing regime contributing to the condition of individual juvenile North Sea cod. In order to establish a relationship between lipid tracer content and algal utilization, post yolk-sac larval North Sea cod were reared in the laboratory on food chains based on monocultures of either the diatom Skeletonema costatum or the dinoflagellate Heterocapsa triquetra (algae dominating in the mixed and stratified regions of the North Sea). In the laboratory, these algae were fed to cultures of adult Acartia tonsa, the copepod eggs were collected, hatched and the N1 nauplii from these different feeding regimes fed to post yolk-sac larval North Sea cod. Post yolk-sac larval cod required 8 d on either a Heterocapsa- or Skeletonema-based food chain before tracer Lipid signals (the ratio of the lipids 16:1 omega 7 to 16:0) in the larvae began to change from their original values to those similar to the algae at the base of their respective food chains. The cod larvae displayed a lipid tracer content similar to that of their algal food source after 13 d on their respective feeding regimes. During a cruise in May 1992 to examine the distribution of larval and juvenile North Sea cod, a subsample of 100 juvenile cod from the stratified, mixed and frontal regimes of the northeastern North Sea were examined for their content of lipid biomarkers and condition (as determined by the ratio of total lipid content to total length). Juvenile cod displaying a lipid tracer content indicating utilization of diatom-basea food webs (found in proximity to regions of frontal mixing) were observed to be in significantly better condition (p less than or equal to 0.05) than those containing a lipid signal indicative of utilization of flagellate-based food webs (found in stratified regions of the North Sea).
1.1. A number of 56 different fatty acids and 7 sterols was found and identified in Themisto gaudichaudii.2.2. 20:5(n−3), 22:6(n−3), 16:0, 18:1(n−9), 16:1(n−7) and 18:1(n−7) were the dominating fatty acids in total lipids, phospholipids and triacylglycerols.3.3. T. gaudichaudii contains an extremely high content of 20:5(n−3) (21.1%) and 22:6(n−3) (15.9%) in total fatty acids.4.4. The sterol fraction contained cholesterol, desmosterol and 22-dehydrocholesterol as main components.
Zooplankton were collected by trawl from the Elephant Island region of the Antarctic Peninsula and from East Antarctica near 63–65°S and 139–150°W. Most zooplankton had low percentages of wax esters (0–8%, as percent of total lipid). High triacylglycerol levels were found in the hyperiid amphipod Themisto gaudichaudii (68%, as percent of total lipid), the krill (Euphausiacea) Euphausia tricantha (44–54% triacylglycerol) and Euphausia frigida (27% triacylglycerol) and the scyphomedusan Periphylla periphylla (42–48% triacylglycerol). Polyunsaturated fatty acids (PUFA) comprised 23–60% of the total fatty acids, with the omega-3 fatty acids eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] being most abundant. P. periphylla was an exception with 12–19% docosapentaenoic acid [22:5 (n-3)] being the major PUFA. The major euphausiid sterols included cholesterol (75–92%, as percent of total sterols) and desmosterol (6–22%). The major sterols of other zooplankton were more diverse and included trans-dehydrocholesterol, 24-methylenecholesterol, brassicasterol and 24-nordehydrocholesterol. The benthic ascidian, Distaplia cylindrica, had 45% stanols, as percent of total sterols, whereas the pelagic ascidian Salpa thompsonii had only 8–11% stanols. Lipid, fatty acid and sterol data are used to examine trophodynamic interactions and provide an ability to distinguish herbivorous and carnivorous diets and determine survival and reproductive strategies.
Plusieurs Parathemisto gracilipes Norman (Amphipoda, Hyperiidea) ont été maintenus en vie dans des réservoirs spéciaux à température constante. Les observations ont porté sur leur alimentation, ainsi que sur leur processus de mue, lequel a été comparé à celui d'Amphipodes Gammarides littoraux. La différence d'habitat peut expliquer les différences que présentent ces processus.
Previous (workers who have examined the gut contents of members of the genus Parathemisto , and who have kept and fed specimens in laboratory conditions, have concluded that they are chiefly carnivorous in habit, feeding largely on zooplankton, and to a lesser extent on phytoplankton (Conover, 1960; Baker, 1963; Kane, 1967).
The gut of P. gaudichaudi has been found to contain almost intact copepods, especially Calanus and occasionally Temora (Bigelow, 1926 – Gulf of Maine); young specimens of Euphausia superba (Hardy & Gunther, 1935 – Antarctic); and copepods (Nemoto & Yoo, 1970). Siegfried (1965 – west coast of S. Africa) found P. gaudichaudi to be a rather indiscriminate feeder, its gut contents reflecting the composition of the plankton.
The pattern and characteristics of diving in two female macaroni penguins Eudyptes chrysolophus was studied, during the brooding period, using continuous-recording time-depth recorders, for a total of I8 days (15 consecutive days) during which the depth, duration and timing of 4876 dives were recorded. Diving in the first 11 days was exclusively diurnal, averaging 244 dives on trips lasting 12 hours. Near the end of the brooding period trips were longer and included diving at night. About half of all trips (except those involving continuous night-time diving) was spent in diving and dive rate averaged 14–25 dives per hour (42 per hour at night). The duration of day time dives varied between trips, and averaged 1.4–1.7 min, with a subsequent surface interval of 0.5–0.9 min. Dive duration was significantly directly related to depth, the latter accounting for 53% of the variation. The average depths of daytime dives were 20–35 m (maximum depth 11 5 m). Dives at night were shorter (average duration 0.9 min) and much shallower (maximum 11 m); depth accounted for only 6% of the variation in duration. Estimates of potential prey capture rates (3–5 krill per dive; one krill every 17–20 s) are made. Daily weight changes in chicks were directly related to number of dives, but not to foraging trip duration nor time spent diving. Of the other species at the same site which live by diving to catch krill, gentoo penguins forage exclusively diurnally, making longer. deeper dives; Antarctic fur seals, which dive to similar depths as macaroni penguins, do so mainly at night.
Total lipids, hydrocarbons, wax esters, triacylglycerols, and phospholipids were determined for 22 major biomass species of zooplankton and fish in an Antarctic mesopelagic community that were collected in 1982 and 1983. Lipid levels were similar to levels in more temperate mesopelagic species. Total lipid concentration was depth related, with all lipid-rich species being collected at depths greater than 230 m. Wax ester content in copepods (60 to 70% of the total lipid) was generally higher than in subtropical species. Lipids indicated three predator-prey relationships (Parandania boecki-Atolla wyvillei, Thysanoessa macrura-Calanoides acutus andEurythenes gryllus-Atolla wyvillei). These were confirmed by gut content analyses. The mesopelagic fishBathylagus antarcticus, Pleuragramma antarcticum, andProtomyctophum bolini stored most lipid intramuscularly, whereasElectrona antarctica andGymnoscopelus nicholsi contained extensive stores in subcutaneous lipid sacs. The intramuscular lipids inP. antarcticum and the subcutaneous lipid sacs ofE. antarctica were primarily wax esters, possibly used for increased buoyancy or long-term energy storage. Unlike the odd-carbon preference of aliphatic hydrocarbons which typifies terrestrial plants and temperate marine organisms, even-carbon chain-length paraffins predominate in 80% of the Antarctic species analyzed. Although the source of these even-carbon n-alkanes cannot be determined from our data, their dominance in the species analyzed suggests that an unusual biochemical pathway may be responsible for their synthesis in this ecosystem.
All stages from egg to adult of the North Pacific copepod,Euchaeta japonica contained wax esters in their lipid stores, while triglycerides were important only in the eggs, early naupliar stages, and
adults. The large lipid reserves of the eggs were wax esters and triglycerides (58% and 19% of the lipid, respectively), both
of which were used rapidly during the early stages of development. Wax esters continued to decrease after triglycerides had
been utilized completely for energy. The slow metabolism of lipid during starvation indicated that lipid stores in adult females
may be conserved for egg production. The dominant alcohols of the wax esters of all stages were tetradecanol (24–42% of the
total) and hexadecanol (25–65%). Only minor amounts of polyunsaturated alcohols were observed. There was, however, a high
proportion of polyunsaturation in the wax ester fatty acids, even though octadecenoic was generally predominant (16–46% of
the total wax ester fatty acids). The polyunsaturation of the wax esters fatty acids and the presence of 21∶6 hydrocarbon
suggest phytoplankton in the diet of adults and in the younger stages. Cholesterol was the main sterol, but there were minor
amounts of desmosterol (1–12% of the total sterols) present. The latter sterol has not been found previously in copepods,
although reported from Cirripedia and Decapoda.
The diet of the diving petrels Pelecanoides georgicus and P. urinatrix was studied during 1986 (P. georgicus) and 1987 (both species) by lavaging adults as they returned to feed chicks on Bird Island, South Georgia. The diet of both
species was dominated by crustaceans, in particular euphausiids (mainly Euphausia superba and some Thysanoessa), which contributed 47–76% of the biomass of crustaceans in the diet of P. georgicus, and copepods, which contributed 71% of the biomass of crustaceans in the diet of P. urinatrix. Calanoides acutus was the most numerous copepod in the diet of both species; however, Rhincalanus gigas was more common in P. urinatrix than in P. georgicus. The dominant amphipod in the diet of P. georgicus, Primno macropa, was absent from the diet of Pelecanoides urinatrix, in which Themisto gaudichaudii (rare in Pelecanoides georgicus) dominated. Dietary differences were maintained in the period (2 weeks of a total of 10 weeks) when both species were simultaneously
rearing chicks. Knowledge of the prey species and of the diving abilities and foraging habits of diving petrels suggests that
at South Georgia Pelecanoides urinatrix feeds closer inshore and dives deeper than Pelecarnoides georgicus.
Collection of live planktonic animals by divers has confirmed that hyperiid amphipods in the genera Vibilia and Lycaea are specific and obligate symbionts of salps. Species in the genera Brachyscelus, Parathemisto, Oxycephalus and Phronima are also sometimes associated with salps. Vibilia feed preferentially on the particulate food collected by the salp, whilst Lycaea consume the salp tissue directly. There are further differences in the distribution and life cycle of the two genera on their hosts. Our collections indicate specific host-parasite relationships exist in at least two species of Lycaea.
A method is described whereby a complete analysis of individual neutral lipid and phospholipid classes in marine animal total lipid can be achieved using an latroscan TLC-FID analyser. The method involves separate analyses of two samples of total lipid in solvents designed to separate neutral and polar lipid classes, together with calibration by a composite standard similar in composition to the sample under analysis. The method does not depend on the degree of unsaturation of the fatty acids present, is rapid and compares well in accuracy with conventional combined gravimetric, colouritnetric, and densitometric procedures.
Key factors governing polar ocean ecosystems are low temperatures and a pronounced seasonal variability of ice cover, light regime and primary production. Depending on their ecological niche and trophic position, zooplankton species at high latitudes have developed a variety of reproductive strategies and energetic adaptations to cope with these extreme environmental conditions. Life-cycle strategies of the herbivorous copepods and euphausiids, which make up the major portion of polar zooplankton biomass, include seasonal vertical migration, dormancy (diapause, quiescence) and the accumulation of energy reserves. These lipid stores help to buffer the pulsed seasonal food supply, and they play an important role in fueling reproduction independent of phytoplankton. Only a smaller fraction of the lipid reserves accumulated during spring and summer are usually catabolized for metabolic maintenance during the food-limited dark season. These deposits are retained until the end of winter and allow early egg production and spawning prior to—or coinciding with—the onset of vernal primary production. It enables the new generation to make full use of the short productive season for growth and development to reach viable overwintering stages. The Antarctic krill Euphausia superba is an exception since it uses its depot lipids for metabolic maintenance during the dark season. It therefore relies on external resources (Primary production) for reproductive processes, resulting in a later spawning period as compared to the other euphausiids. Another important component of the herbivorous Antarctic zooplankton, the salps, have developed a very different reproductive strategy. They are able to switch from sexual reproduction to asexual budding (metagenesis), which allows extreme multiplication rates under favourable feeding conditions. Due to these successful adaptations, herbivores are able to build up huge stocks, in spite of the short productive period. Omnivorous and carnivorous zooplankton species, e.g., amphipods or chaetognaths, are not much constrained by the seasonality problem, but experience a more constant food supply. They show a tendency towards K strategies with a prolonged reproductive period, reduced egg numbers and increasing parental care. However, they do not exhibit such typical “polar adaptations” as developed by the herbivorous species.
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