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Microalgal Biomarkers: A Review of Recent Research Developments
Abstract
Microalgae are major sources of lipids in lacustrine and marine environments. This paper provides a review of some recent advances in our knowledge of the wide variety of lipid types that have been isolated from microalgae with an emphasis on those likely to be useful biomarkers for identifying sources of organic matter in sediments. Extensive data are now available on the fatty acids in all of the major classes of microalgae and some useful characteristic features have been observed in the abundance of particular polyunsaturated fatty acids. Despite several decades of study, it is now apparent that some of the biosynthetic steps leading to the formation of these unsaturated fatty acids are still not known with certainty as shown by the occurrence of C28 polyunsaturated fatty acids in some dinoflagellates and the likely involvement of chain-shortening reactions. Considerable data have also been obtained on the sterols in microalgae, but some classes of organisms are still not well documented (e.g. cryptomonads, eustigmatophytes, xanthophytes and raphidophytes). Diatoms show a great variety of sterol compositions and no sterol appears to be either unique or representative. However, 24-methylenecholesterol in sediments is probably derived in most cases from diatoms. High contents of C25 highly branched isoprenoid (HBI) alkenes have been identified in the diatom Haslea ostrearia and both C25 and C30 HBI alkenes have been found in diatom strains thought to be Rhizosolenia setigera. Genetic and environmental factors appear to be important controls on the relative abundances of the various homologues identified. Microalgae are also suspected to be a source of long-chain saturated fatty acids having an even carbon number predominance and of long-chain alkanes with no odd over even carbon number predominance, although the available data are not conclusive. An exciting development in recent years is the identification of highly aliphatic biopolymers (algaenans) in some species of marine and freshwater green algae and eustigmatophytes. This material persists in sediments and may be a source of the alkyl chains in ancient kerogens and crude oil constituents. Algaenans do not occur in all algal species and may be absent from some classes, such as diatoms. This implies that the organic matter preserved in sediments is strongly influenced by a subset of the microalgal contributors of organic matter. Although reasonable sources have been identified for many of the lipids in sediments, there are still many gaps in our knowledge and further studies are clearly required.
... For example, long-chain homologs (>C 24:0 ) are major constituents of leaf waxes of vascular plants and provide a signal of terrigenous input to marine and lacustrine sediments (e.g., see reviews by Diefendorf & Freimuth, 2017;Freimuth et al., 2021). Short-chain homologs are major constituents of vascular plants, but are also the dominant alkyl lipids produced by marine algae (e.g., Volkman et al., 1998), short-chain fatty acids, for example, make up the hydrophobic tails of the bacterial and eukaryotic membrane bilayer phospholipids (Meer et al., 2008). Mid-chain alkanes specifically are characteristic for submerged aquatic macrophytes (Ficken et al., 2000). ...
... Similarly, alkanols with chain lengths >C 22:0 and alkanoic acids with chain lengths >C 26:0 are generally assigned to have a predominately terrestrial origin (e.g., Fernades et al., 1999;Zheng et al., 2009). While the majority of alkanes is likely derived from autochthonous, terrigenous sources, short-chain alkanoic acids and alkanols (C 14:0 to C 18:0 ) are highly abundant in marine biomass and specifically in marine algae (e.g., Berg et al., 2020;Fernades et al., 1999;Volkman et al., 1998). Mixed marine and terrigenous sources of alkyl lipids within each compound class are therefore likely in Little Jason Lagoon, as reflected in the lower values of ACL alkanol (23.2 ± 0.8), ACL alkanoic acid , and FA terr (20.7 ± 1.8 and 0.35 ± 0.18, respectively) and the larger compositional variability within these compound classes compared to alkanes throughout the record (Figure 3). ...
... The CPI alkane is on average 6.2 ± 0.6 indicating that potential petrogenic sources of alkanes are masked by biogenic contributions, likely of terrigenous origin containing fresh vegetation, peat and soil. For the alkanoic acids, the ACL alkanoic acid and FA terr values are relatively low (18.7 ± 0.6 and 0.15 ± 0.05), as expected for marine OM, which is predominantly composed of short-chain alkanoic acids (e.g., Khotimchenko et al., 2002;Volkman et al., 1998). ...
Alkyl lipid distributions in terrestrial, lacustrine and marine sedimentary archives on sub‐Antarctic South Georgia are investigated to identify source endmembers and evaluate their variation in response to Holocene environmental changes. To understand organic matter exchange processes along the land‐ocean continuum, we combine lipid compositional data with compound‐specific ¹⁴C data in representative sedimentary records. These data provide additional source information and temporal constraints on exchange processes that operate at the landscape level. The alkane, alkanoic acid and alkanol distributions are distinct between terrestrial and marine sources, between vascular and primarily non‐vascular plants, and according to the level of degradation. Compound‐specific ¹⁴C ages of alkanes, alkanoic acids and alkanols reveal the complexity of the carbon pools associated with these carbon sources. We find that terrigenous compounds in lacustrine and marine sediments are generally older than those produced by aquatic sources, reflecting intermediate storage in peat/soil prior to deposition. Nonetheless, the pre‐depositional age of terrigenous alkyl lipids differs in the different settings although they are located in close proximity under the same climatic conditions. Overall, the ¹⁴C data reflect changes in the balance of accumulation and erosion of organic matter in the terrestrial catchments of the investigated sites in response to prevailing environmental conditions. Petrogenic OC ranges from 0% to 7% and 4%–37% in catchments with minor glacier presence and to up to 67%–76% in the large tidewater glacier catchment. Long‐term biospheric OC turnover seems to have been remarkably constant throughout most of the Holocene and higher than in analog settings in the northern hemisphere.
... Short-, middle-, and long-chain odd carbon n-alkanes were originated mainly from phytoplankton, submerged/floating macrophytes, and terrestrial plants, respectively, and their presence in sediments can thus indicate OM input from these sources (Ficken et al., 2000;Meyers, 2003;Lu and Meyers, 2009;Routh et al., 2007Routh et al., , 2009Zhang et al., 2016;Kim et al., 2018;Jiang et al., 2021;Ankit et al., 2022). Furthermore, some sterols were originated from specific phytoplankton and can indicate input of OM from these phytoplankton into sediments (Schubert et al., 1998;Zhang et al., 2019), with dinosterol and brassicasterol indicating the dinoflagellate and diatom inputs, respectively (Volkman et al., 1998). In addition, geologically configured 17(α), 21(β)-hopanes can reflect OM input from petroleum contamination or sedimentary rock erosion (Yunker et al., 2002;Rushdi et al., 2017;Bulbul et al., 2022;Lu et al., 2022;Zhu et al., 2023). ...
... compressum (Zhang et al., 2017). Brassicasterol is derived mainly from diatoms (Volkman, 1986), although other sources, such as the coccolithophore Emiliania huxleyi and Gephyrocapsa oceanica, cannot be excluded (Schubert et al., 1998;Volkman et al., 1998). Cholesterol is the dominant sterol in zooplankton (Jaffé et al., 2006), but it is also present in relatively low amounts in algae and cyanobacteria (Volkman, 1986;Pearson et al., 2007;Bet et al., 2015;Szymczak-Żyła and Lubecki, 2022). ...
... By comparing the abundance variation with brassicasterol and dinosterol, the sitosterol in ZW47, 51, 55, and 86 could be derived mainly from phytoplankton, while in ZW68, terrestrial plants were the major contributors (Fig. 7). In addition to the four sterols, pentacyclic triterpenols taraxerol and β-amyrin originated mainly from mangroves (Jaffé et al., 2001;Versteegh et al., 2004;Ranjan et al., 2015), while C 30 1,15 alkyl diol and long-chain n-alkanols were derived mainly from eustigmatophyceae (Volkman et al., 1998;Rampen et al., 2014) and terrestrial plants (Meyers, 1997;Pearson et al., 2007;Woszczyk et al., 2011), respectively. ...
... Most common polyunsaturated FAs in glycolipids from microalgae, particularly dinoflagellates, were identified as C18 compounds, but longer-chain fatty acids were also found in the corresponding metabolites [37,38]. Leblond and Chapman [39] developed a convenient procedure for the isolation of galactolipids from lipid mixtures by column chromatography with a gradual increase in the polarity of eluting systems. ...
... Blooms of the chloromonad Heterosigma carterae (formerly H. akashiwo) (Raphidophyceae) were observed in different areas of the World Ocean. The isolate 102R of this microalga was cultured in natural seawater, and four SQDGs (37)(38)(39)(40) from the extract of the obtained culture were partially purified and structurally identified using LC/MS/MS technique and NMR analysis. SQDG fractions were treated with BF 3 in methanol with liberation FA methyl esters and analyzed by the GC/MS technique. ...
... Arsenosugars 5-dimethylarsenoyl-β-D-Rib f [10][11][12][13] Arsenolipids 5-dimethylarsenoyl-β-D-Rib f , 5-dimethylarsenoyl-2-O-methyl-β-D-Rib f [15,[17][18][19] Galactolipids αand β-D-Gal p [29][30][31][32][33][34][35] Sulfoquinovosyl-containing glycolipids 6-sulfo-α-D-Gui p [37][38][39][40][41][42][43][44] Phosphoglycolipids β-D-Gal p [74] Steryl glycosides D-Glc p , 6-O-acyl-D-Glc p [4] Amphidinins α-D-Rib f [80] Prymnesins α-L-Xyl f , α-D-Rib f , α-D-Gal p , β-D-Gal f , α-L-Ara p [83,84,87] Mar. Drugs 2023, 21, 427 ...
Microalgae are abundant components of the biosphere rich in low molecular weight carbohydrate-containing natural products (glycoconjugates). Glycoconjugates take part in the processes of photosynthesis, provide producers with important biological molecules, influence other organisms and are known by their biological activities. Some of them, for example, glycosylated toxins and arsenicals, are detrimental and can be transferred via food chains into higher organisms, including humans. So far, the studies on a series of particular groups of microalgal glycoconjugates were not comprehensively discussed in special reviews. In this review, a special focus is given to glycoconjugates’ isolation, structure determination, properties and approaches to search for new bioactive metabolites. Analysis of literature data concerning structures, functions and biological activities of ribosylated arsenicals, galactosylated and sulfoquinovosylated lipids, phosphoglycolipids, glycoside derivatives of toxins, and other groups of glycoconjugates was carried out and discussed. Recent studies were fundamental in the discovery of a great variety of new carbohydrate-containing metabolites and their biological activities in defining the role of microalgal viral infections in regulating microalgal blooms as well as in the detection of glycoconjugates with potent immunomodulatory properties. Those discoveries support growing interest in these molecules.
... It is widely accepted that bacteria and phytoplankton/algae are characterized by shortchain n-alkanes (n-C 15 -n-C 20 ), aquatic macrophytes are the main producers of mid-chain n-alkanes (n-C 21 -n-C 25 ), and terrestrial plants are commonly characterized by long-chain n-alkanes (n-C 26 -n-C 35 ) (Eglinton and Hamilton, 1967;Cranwell et al., 1987;Meyers, 2003). n-Fatty acids are another lipid biomarker for organic matter (OM) source tracing in sediments, and evencarbon chain lengths can indicate biological origins (Volkman et al., 1998;Meyers, 2003). Lipid biomarkers are thus regarded as among the most effective indicators in lake sediments and are widely applied in paleoenvironmental investigations to distinguish between allochthonous (terrestrial plant-based) and autochthonous (phytoplankton-, algae-and macrophyte-based) sources of OM inputs, vegetation cover history in catchments (Schwark et al., 2002), and anthropogenic impacts on terrestrial and aquatic ecosystems (Lu and Meyers, 2009;Fang et al., 2017). ...
... In general, n-C 14 -n-C 18 fatty acids are reported to be the dominant lipid components of phytoplankton, algae and bacteria. For example, n-C 18 predominates in green algae, and n-C 16 is abundant in diatoms and cyanobacteria (Volkman et al., 1998). Therefore, these components were also closely associated with phytoplankton algae and bacteria. ...
Human activity and hydroclimate change greatly influence the environment in a lake and its catchment, particularly in areas with fragile ecosystems, such as arid Central Asia. In this study, lipid biomarkers (n-alkanes and n-fatty acids) were measured in a 210Pb- and 137Cs-dated sediment core from Lake Balkhash to determine their environmental significance and infer the history of environmental change over the last ~200 years. The terrestrial origin of long-chain n-alkanes and the aquatic origin of both n-fatty acids and mid-/short-chain n-alkanes were inferred from molecular distributions and diagnostic ratios. Three major environmental phases were identified over the past two centuries based on stratigraphic shifts in biomarker indicators. During 1800-1860 AD, the lake exhibited a high-water level with abundant submerged/floating macrophytes and limited phytoplankton, as suggested by multiple indicators, e.g., high proportions of aquatic macrophytes (Paq) and long-chain n-fatty acids (L-FAs). Overall, minor terrestrial inputs were revealed by low concentrations of long-chain n-alkanes (L-ALKs), suggesting dense vegetation cover in the catchment. The lake environment experienced a pronounced change in the subsequent phase from 1860–1930 AD, during which the cover of submerged/floating macrophytes gradually diminished, as revealed by the decreasing trend of aquatic proxies, e.g., L-FAs and Paq. In contrast, the number of emergent plants and terrestrial inputs increased, as suggested by the decreased Paq values. A great variation in water levels likely resulted in the shrinkage of the submerged/floating macrophyte cover. During 1930-2017 AD, anthropogenic impacts began to appear on the sediment profile. The highest terrestrial inputs, as revealed by the maximum L-ALK abundance on record, indicated intensive exploitation of the catchment during 1935-1959 AD. The lowest L-FA and Paq values suggested that submerged/floating macrophytes were at the lowest levels during this phase, possibly in response to the decreased water levels and increasing salinity. Increased human-induced nutrient loading coupled with elevated regional temperature prompted the lake to become an increasingly productive lake system, especially in more recent decades, as indicated by the highest levels of short-chain lipids. These results highlight the important role of hydrological variation and human activity in the environmental evolution of the Ili-Balkhash Basin.
... Pancost et al., 1998;Boudinot et al., 2020) and Canadian sites show high levels of anoxia independent of Tethyan water influence (Simons et al., 2003). Anomalously high concentrations of C 28 steranes, interpreted to indicate an abundance of prasinophytes (simple unicellular green algae, often present in abundance under stressed environmental conditions, although other sources for C 28 steranes such as chlorophyll c-containing algae are recognised: Volkman et al., 1994Volkman et al., , 1998, suggest generally inhospitable environmental conditions linked to anoxia at sites across the WIS (Curiale, 1994;French et al., 2019;Boudinot et al., 2020;Robinson et al., in prep). There remain unresolved questions in these organic geochemical datasets, relating to the heterogeneity of anoxia across the basin and the significance of high C 28 sterane concentrations, (Bralower and Bergen, 1998;Leckie et al., 1991;Kirkland, 1991), Gunnison Gorge (Noe, 2015), Rebecca Bounds core (Kennedy et al., 2005), Billings Landfill (Leckie and Leithold, unpublished) and Pratts Landing (Varban and Plint, 2008). ...
... C 28 steranes may derive from numerous chlorophyll a + c phytoplankton, such as Bacillariophyceae, Dinoflagellata, and Haptophyta (Falkowski et al., 2004;Volkman et al., 1998). Abundance of C 28 steranes has been particularly linked to prasinophyte abundance however, and are the dominant sterane within living prasinophyte species that have been studied (Volkman et al., 1994;Schwark and Empt, 2006). ...
... The proportional steranes can also provide some insights to indicate the OM origin of marine or lacustrine sediments (Seifert and Moldowan, 1978;Volkman, 1986;Volkman et al., 1998). Sterols will not completely catabolize or quickly degrade under a reducing environment and can be well preserved in sediments (Volkman, 1986;Volkman et al., 1998). ...
... The proportional steranes can also provide some insights to indicate the OM origin of marine or lacustrine sediments (Seifert and Moldowan, 1978;Volkman, 1986;Volkman et al., 1998). Sterols will not completely catabolize or quickly degrade under a reducing environment and can be well preserved in sediments (Volkman, 1986;Volkman et al., 1998). High C 29 steranes are usually considered to indicate typical terrestrial input, and C 28 steranes usually originate from phytoplankton containing chlorophyll-C, related to a limnic environment. ...
The organic matter (OM) enrichment mechanisms and depositional environment characteristics of lacustrine source rocks in western Bozhong Sag, Bohai Bay Basin (BBB) remain controversial. To address these issues, based on Rock‐Eval pyrolysis, kerogen macerals, H/C and O/C ratios, GC‐MS, major and trace elements, the Dongying Mbr 3 (E 3 d 3 ), the Shahejie Mbrs 1 and 2 (E 2 s 1+2 ), and the Shahejie Mbr 3 (E 2 s 3 ) source rocks in the western Bozhong Sag were studied. The above methods were used to reveal their geochemical properties, OM origins and depositional environments. The results indicate that the E 2 s 1+2 and E 2 s 3 are excellent source rocks, and the E 3 d 3 of the second good quality. E 3 d 3 source rocks were formed under a warm and humid climate, mainly belong to fluvial/delta facies, the E 3 d 3 sediments have formed under weakly oxidizing and freshwater conditions. Comparatively, the depositional environments of E 2 s 1+2 source rocks were arid and cold climate, representing saline or freshwater lacustrine facies, and the sediments of E 2 s 1+2 belong to anoxic or suboxic settings with large evaporation and salinity. During the period of E 2 s 3 , the climate became warm and humid, indicating the freshwater lacustrine facies, and E 2 s 3 was characterized by freshwater and abundant algae. Moreover, compared with other intervals, the OM origin of E 3 d 3 source rocks has noticeable terrestrial input. The OM origin of the E 2 s 1+2 and E 2 s 3 are mainly plankton and bacteria. Tectonic subsidence and climate change have affected the changes of the depositional environment in the western Bozhong Sag, thus controlling the source rocks distribution, the geochemical characteristics in the three intervals of lacustrine source rocks have distinct differences. Overall, it is effective to evaluate the paleoenvironmental characteristics of source rocks by biomarkers, major and trace elements. The established models may have positive implications for research of lacustrine source rocks in offshore areas with few drillings.
... The molecular biomarkers of phytoplankton, including brassicasterol, dinosterol and C 37 alkenones, are major cell membrane contents of diatoms, dinoflagellates and coccolithophores, respectively, and have been used as the indices of phytoplankton groups for studying variations in their biomass and community structure (Withers, 1987;Schubert et al., 1998;Zhao et al., 2006;Bai et al., 2010;Ding et al., 2019). These biomarkers are relatively stable with slow degradation and a long geological record (Volkman, 1998;Volkman, 1986;Volkman, 2006;Brassell et al., 1986;Prahl and Wakeham, 1987). The summed amounts of brassicasterol, dinosterol and C 37 alkenones can potentially reflect the primary production (Schubert et al., 1998;Seki et al., 2004). ...
... The synchronized rising of the SUM and cholesterol (R 2 =0.92, p <0.001), a good indicator of the abundance of zooplankton which are considered as the major consumers of the primary production, also suggests an increase of the primary productivity. These evidences from the core analysis match with the changes of the primary productivity from 1998-2006(Pabi et al., 2008 and an unprecedented jump of net primary production since 1998 (Lewis et al., 2020). The decadal variability of the primary production and the phytoplankton composition reconstructed from biomarkers in the core implies a rapid response of the Arctic ecosystem to the climate change. ...
We used molecular biomarkers (brassicasterol, dinosterol and C37 alkenones) measured from the surface sediments of the Bering Sea, the Chukchi Sea and the western Arctic Ocean in years of 1999 and 2010 to represent the groups of phytoplankton (diatoms, dinoflagellates and coccolithophores) and reconstruct the phytoplankton composition structure and biomass. The distribution of concentrations of three biomarkers were compatible to previous studies on measured phytoplankton, which showed that the phytoplankton biomass was most abundant in the Chukchi Sea, followed by the Bering Sea and the western Arctic Ocean, and diatoms were the dominant group. It suggests that molecular biomarkers are the suitable indicators of phytoplankton composition, structure and abundance. A record of biomarkers in a sediment core (NB01) collected at the Bering Sea in 2010 presented that the biomass of three phytoplankton groups increased in past 107 years, and their variation patterns were consistent. The synchronous increase of concentrations of phytoplankton biomarkers and cholesterol, a proxy of zooplankton biomass, implied that the primary production increased intensely in the last hundreds of years, corresponding to the trend of sea-ice melting as a result of global warming. Moreover, our results suggested that the combined effect of the anormal interannual changes of the El Niño-Southern Oscillation (ENSO) and the Arctic Oscillations (AO) played a key role in regulating the interannual and decadal variations of phytoplankton biomass and community composition, giving us an insight into the impact of atmospheric circulation on phytoplankton production and carbon flux in the Arctic seas.
... Some sterols are characteristic of various groups of organisms. For example, brassicasterol, 24-methylenecholesterol, and dinosterol are typical for phytoplankton (Barrett et al., 1995;Volkman et al., 1998). Cholesterol deposited in sediments is derived mainly from invertebrates, zooplankton and their faecal material. ...
... Analysis of percentages of single sterol compounds in ΣS-phyt allows for a more in-depth study of the origin of sedimentary organic matter in relation to the taxonomic composition of phytoplankton. At all locations examined, the distribution patterns of phytoplankton-derived sterols were dominated (range: 57-69% of ΣS-phyt) by brassicasterol, compound occurring mainly in diatoms, as well as in haptophytes and cryptophytes (Barrett et al., 1995;Volkman et al., 1998). However, the results of the principal component analysis (PCA) based on the occurrences of phytoplankton-derived sterols and specific carotenoids (data on carotenoids taken from Krajewska et al., 2020) indicate that haptophytes are an important source of brassicasterol in the studied fjords, due to a strong coupling between this sterol and haptophyte specific carotenoids (sum of 19′-hexanoyloxyfucoxanthin and 19′-hexanoyloxy-4-ketofucoxanthin) (Fig. 5a). ...
... Molecular geochemical parameters, e.g., the n-alkane distribution, can also be used to assess the origins of OM 43,44 . C 27 sterane is a marker of phytoplankton 45 , C 28 is expected to be derived from phytoplankton containing chlorophyll 46 , and C 29 sterane has various sources; in most cases, C 29 sterane is derived from terrigenous higher plants 47 , while some researchers argue that C 29 sterane may be derived from specific microalgae 48,49 . In this study, the ratio of steranes was used to characterize the OM source, e.g., a high (C 27 + C 28 )/C 29 sterane ratio indicates a high proportion of aquatic organisms accumulating OM. ...
The Lower Jurassic Ziliujing Formation in China’s Sichuan Basin is a significant shale target for exploration; however, the strong heterogeneity of the properties of organic matter (OM) in shale makes it challenging to identify the target area for exploration, and the mechanism of OM enrichment is still unclear. Furthermore, the mechanisms of the response of the Da’anzhai member to the Toarcian Oceanic Anoxic Event (T-OAE) are controversial. Previous studies have focused on sedimentary facies analysis based on mineralogy and elemental abundances and have provided minimal information about organic geochemistry, which adds to the challenge of deeply understanding the influence of the T-OAE on the molecular geochemical characteristics of the Da’anzhai member. In this study, the Da’anzhai member of the Lower Jurassic Ziliujing Formation in the Langzhong area, Sichuan Basin, is studied via X-ray diffraction, total organic carbon, gas chromatography–mass spectrometry, organic carbon isotope, organic petrographical and pyrolysis analyses. To accurately identify the trend of the paleosedimentary environmental proxies, the Mann‒Kendall test is utilized to identify the trend of the data. Our results show that the Da’anzhai shale was deposited in a dysoxic transitional environment to an intermittent reducing environment with freshwater to brackish conditions. The response to the T-OAE can be identified in the middle and upper parts of the middle submember and the bottom of the upper submember of the Da’anzhai member. The T-OAE influenced the redox conditions, salinity, and OM origins during deposition in the middle of the Da’anzhai member, which resulted in the enrichment of OM. The abnormally high C30 diahopane/C30 hopane (C30D/C30H) ratio can be considered a potential proxy for locating the section of strata that responded to the T-OAE in the Da’anzhai member. In the study area, the mechanism of the response of the Da’anzhai shale to the T-OAE manifested as an improvement in hydrological cycling rather than a marine incursion. Our study provides new information that deepens the understanding of the mechanisms of the response of lacustrine shales to oceanic anoxic events from the perspective of molecular organic geochemistry.
... In this regard, oxylipins may best serve as general biomarker for phytoplankton stress, as they are in the observations from the Mediterranean Sea [10]. Lastly, saturated long chain (C18-C20) and very long chain (C22-C26) free fatty acids are relatively rare fatty acids that are chemotaxonomic for cyanobacteria and eustigmatophytes [61] but were associated with CtenRNAV infection here (Figure 3b,c) and should be explored as a diagnostic tool in the future [57]. ...
Ecophysiological stress and the grazing of diatoms are known to elicit the production of chemical defense compounds called oxylipins, which are toxic to a wide range of marine organisms. Here we show that (1) the viral infection and lysis of diatoms resulted in oxylipin production; (2) the suite of compounds produced depended on the diatom host and the infecting virus; and (3) the virus-mediated oxylipidome was distinct, in both magnitude and diversity, from oxylipins produced due to stress associated with the growth phase. We used high-resolution accurate-mass mass spectrometry to observe changes in the dissolved lipidome of diatom cells infected with viruses over 3 to 4 days, compared to diatom cells in exponential, stationary, and decline phases of growth. Three host virus pairs were used as model systems: Chaetoceros tenuissimus infected with CtenDNAV; C. tenuissimus infected with CtenRNAV; and Chaetoceros socialis infected with CsfrRNAV. Several of the compounds that were significantly overproduced during viral infection are known to decrease the reproductive success of copepods and interfere with microzooplankton grazing. Specifically, oxylipins associated with allelopathy towards zooplankton from the 6-, 9-, 11-, and 15-lipogenase (LOX) pathways were significantly more abundant during viral lysis. 9-hydroperoxy hexadecatetraenoic acid was identified as the strongest biomarker for the infection of Chaetoceros diatoms. C. tenuissimus produced longer, more oxidized oxylipins when lysed by CtenRNAV compared to CtenDNAV. However, CtenDNAV caused a more statistically significant response in the lipidome, producing more oxylipins from known diatom LOX pathways than CtenRNAV. A smaller set of compounds was significantly more abundant in stationary and declining C. tenuissimus and C. socialis controls. Two allelopathic oxylipins in the 15-LOX pathway and essential fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) were more abundant in the stationary phase than during the lysis of C. socialis. The host–virus pair comparisons underscore the species-level differences in oxylipin production and the value of screening more host–virus systems. We propose that the viral infection of diatoms elicits chemical defense via oxylipins which deters grazing with downstream trophic and biogeochemical effects.
... Triaromatic dinosteroids (TDS) have specific biogenic significance (Zhang et al., 2000a). Dinosterol, the precursor of dinosteroids (dinosterane and triaromatic dinosteroids), is derived almost entirely from dinoflagellates (Volkman et al., 1990;Volkman, 1998), so dinosterane can almost be considered to be molecular biological fossils of dinoflagellates (Zhang et al., 2000b). ...
The Cambrian Yuertus Formation and Ordovician Saergan and Yingan formation source rocks, which TOC contents of 0.38%–4.30%, are well developed in the Keping area of the Tarim Basin. Reservoir bitumen had been found in the Cambrian Wusongger Formation and Shayilike Formation. In this study, the geochemical characteristics of the bitumen and source rocks were analyzed through biomarkers for oil-source correlation. The results show that the characteristics of the bitumen and Yuertus Formation source rocks are similar. Comparatively, the Yuertus Formation source rocks and bitumen have lower Pr/Ph values and higher C28/C29 regular steranes values. The maturity characteristics and depositional environment of the Cambrian source rocks in the Keping area and the platform basin areas are similar. Plots of Ph/n-C18 versus Pr/n-C17, Ts/(Ts+Tm) versus 4-/1-MDBT (methyl dibenzothiophene), and DBT/P (dibenzothiophene/phenanthrene) versus Pr/Ph distinguish the bitumen and source rocks well. As an original plot, we found that the Fla/Py (fluoranthene/pyrene) versus MP/P (methyl-phenanthrene/phenanthrene) intersection plot can be used to identify the possible sources of polycyclic aromatic hydrocarbons (PAHs) to a certain extent and can distinguish between the Cambrian and Ordovician source rocks in this study. Comprehensive analysis revealed that the bitumen samples most likely originated from the Yuertus Formation source rocks. It was also found that the biomarker characteristics such as the shape type of the C27-C28-C29 regular steranes, triarylosteranes, and triarylosteroids are not applicable to distinguishing the Cambrian and Ordovician source rocks in the Keping area. These research findings provide references for studying the Lower Paleozoic oil-source correlation in the platform in the Tarim Basin.
... Phytoplankton, bryophytes, and aquatic plants can all be associated with n-alkanes that are predominately mid-chain C 21 -C 25 homologues (Volkman et al. 1998). Although, the high abundances of long-chain C 27 homologues can be predominantly attributed to input from terrestrial plants (Zakrzewski et al. 2023). ...
Geochemical and biomarker characteristics of representative crude oil samples from selected fields in southern Nigeria were evaluated to determine the organic matter input, origin of biological material, depositional environment, thermal maturity, and genetic relationship between the oils. Four crude oil samples were obtained from various oil producing fields from Delta, Bayelsa and Abia state in southern Nigeria and labeled Kwale (KW), Kolo creek (KLC), Owaza (OWA1 and OWA2). The crude oil samples were fractionated into saturates, aromatic hydrocarbons and polar compounds using column chromatography on silica gel thereafter, analyzed using Gas chromatography-mass spectrometry (GC–MS). The calculated ratios of normal alkanes, acyclic isoprenoids, carbon preference index (CPI), hopanes, and steranes showed the following results: Pr/Ph (0.34 to 0.89); C29/C27 (0.78 to 1.25); 20S/(20S + 20R)C29sterane (0.28 to 0.66); 22S/(22S + 22R)C32 homohopane (0.17 to 0.23); CPI (0.96 to 0.98); Ts/Ts + Tm (0.46 to 0.50); and sterane/hopane (0.16 to 0.87). The results obtained were used to correlate the crude oils with respect to depositional environment, thermal maturity, and organic matter source. The Pr/Ph ratios of KW and KLC were less than one, and the cross-plot of Pr/nC17 versus Ph/nC18 of KW and KLC suggested that the oils were deposited under anoxic environments, whereas OWA1 and OWA2 indicated oxic conditions with no biodegradation. From the calculated ratios of 22S (22S + 22R)C32 homohopane and CPI, the oils were mature and had entered the generating window. Sample OWA1 is the most mature, while KLC is the least mature. The calculated ratios also showed that the four oil samples were from a shale source rock with both terrestrial and marine inputs.
... Δ 14 C LCFAs values along northern SCS shelf sediments are slightly higher than that of PR SPM and remained relatively constant over the ∼230 km transport pathway, despite the most distal site exhibiting a coarser mean grain size. Potential explanations include a partial origin of LCFAs from marine phytoplankton, zooplankton or microbially derived young carbon (Volkman et al., 1998;Wakeham & McNichol, 2014) or benthic microbial inputs (Gong & Hollander, 1997), or from eolian transport, with the latter potentially exhibiting a wide range of isotope values depending on source and provenance (δ 13 C 24-32FAs : 27.2 to 30.3‰; Δ 14 C 24-32FAs : 33 to 518‰, Matsumoto et al., 2001). Based on isotope mass balance calculations, a contribution of ∼70% marine-derived LCFAs (Δ 14 C = +32‰, assumed to mirror that of surface ocean dissolved inorganic carbon, Blattmann et al., 2018) is needed in order to explain the observed sedimentary Δ 14 C LCFAs values. ...
Plain Language Summary
Determining the factors driving degradation of terrestrial organic carbon (OCterr) is important for understanding the fate of OCterr in marginal seas and its impact on the global carbon cycle. In this study, we use bulk and molecular‐level carbon isotopic measurements as well as sedimentological data to investigate how OCterr characteristics evolve along the river‐estuary‐coastal ocean continuum for three different river systems discharging into the Chinese marginal seas. Marked decreases in the OCterr abundance and ¹⁴C contents reveal marked aging associated with degradation processes within estuaries over relatively short transport distances, likely due to degradation of younger and labile OCterr. Both aging and apparent “rejuvenation” of OCterr after estuarine transport was observed in different shelf systems, the latter likely resulting from inputs of fresh OCterr from proximal sources. Our findings suggest both sources and transport processes influence terrestrial OC and biomarker signatures in marginal sea sediments, highlighting the complexity of OCterr dynamics in coastal systems.
... The Mackenzie catchment is located in the Western Canada Sedimentary Basin and potential sources of OC petro are immature bitumen, coal and sedimentary rock such as shales from the Devonian Canol Formation 62,63 . The assessment of bulk soil TN:SOC ratios indicated a mixing of OC petro and biogenic organic carbon (OC biogenic ) in northern bulk SOC based on reported compositions of peat-derived OC in the Mackenzie River catchment and plant-derived long-chain fatty acids (C [28][29][30] ) extracted in this study ( Fig. 3a) 25,28,64 . Long-chain fatty acids with similar F 14 C (0.70-1.00; ...
Wildfires in the Arctic are producing pyrogenic carbon as product of incomplete biomass combustion. The storage and distribution of pyrogenic carbon in soils is poorly known, especially in carbon rich permafrost-affected mineral soils. Here, we extracted pyrogenic carbon in mineral soils from eleven forest sites across the North Canadian permafrost regions by hydrogen pyrolysis. We found pyrogenic carbon with millennial-scale ages that were older in continuous (1960–12,690 calibrated years before present) than in discontinuous (510–3560 calibrated years before present) permafrost-affected soils. In all cases, pyrogenic carbon showed longer residence times compared to bulk soil organic carbon. The proportions of pyrogenic carbon on total soil organic carbon were consistent at 6.9 ± 0.5% of total soil organic carbon. Thus, pyrogenic carbon forms a significant component of the total soil organic carbon and climatic as well as soil factors control the long residence times of pyrogenic carbon in vulnerable high-latitude forest mineral soils.
... For instance, a combination of Chlorella sp. and bio floc-based diet reported better free amino acids and fatty acid profile compared to single-food Chlorella sp. or microbial floc alone (Yao et al., 2018). Considerably higher levels of essential fatty acids such as n3, PUFA, and n3/n6 ratio in autotrophic and mixotrophic units compared with heterotrophic systems can be ascribed to the role of microalgae as the primary producers of PUFA (Volkman et al., 1998;Eryalçın, 2019.). A cocktail of microalgae was reported to improve the nutritional quality of Artemia sp. ...
... Sterols in microalgae have attracted much attention because the presence of these natural products in microalgae determines their nutritional value as food, and these compounds are highly useful biological indicators for identifying the source of organic matter in sediment. They are not only the main components of biofilm, but also the functional bodies of cell proliferation and signal transmission in microalgae, which can modulate the activity of membranerestriction enzymes [67,68]. The content and structure of Fig. 5 The typical structure of glycolipids [61] Content courtesy of Springer Nature, terms of use apply. ...
Microalgal lipids have been recognized as one of the crucial sources of liquid biofuels. In this review, composition and structure of microalgal lipids (lipidomics) have been reviewed. Lipidomics can play an essential role in liquid biofuel production via providing accurate structure information about microalgal lipids such as position of double bonds, length of carbon chains, and hetero-atom distribution. The total content (~ 5–50 wt.%) of microalgal lipids can be determined by gravimetric methods (mainly direct organic solvent extraction) and spectrometry. There are mainly eight categories of lipids including fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterol lipids, prenol lipids, saccharolipids, and polyketides. A scheme of isolation and structure analysis of microalgal lipids has been advised based on organic solvent extraction, saponification, and silica gel column chromatography. All carbon chains in these categories can be used in the production of alternative liquid biofuels with the necessary catalytic processes. Additionally, chlorophylls in microalgae also have an apparent effect on the characterization analysis of microalgal lipids and the application of lipids in catalytic conversion process. Therefore, the basic concept of microalgal lipids and how to determine their content in cells are firstly introduced in this review. Then, the detailed isolation procedure and structure information have been reviewed to guide the practical application of liquid biofuel production. Finally, the conclusions and future research suggestions have been recommended. This review provides the necessary guide for high-efficiency and low-cost cultivation of microalgae as via selected microalgae species with high content of lipids.
... Our SST records address the extent to which upwelled high latitude waters controlled EEP SST and productivity during the warmer Pliocene, predating the initiation of cyclic Northern Hemisphere glaciation (Bartoli et al., 2011). We also investigate east-west gradients in the accumulation of organic biomarkers, specifically alkenone concentrations, which are useful productivity proxies for phytoplankton abundance and activity (Raja & Rosell-Melé, 2021;Volkman et al., 1998), in addition to inorganic proxies related to ocean surface production. The ensemble of proxy estimates allows us to investigate the relative importance of upwelling in setting Pliocene SST gradients. ...
The modern eastern equatorial Pacific Ocean (EEP) exhibits strong upwelling, producing pronounced gradients in sea surface temperature (SST), nutrient concentration, and biological productivity between 80° and 140°W. During the globally warmer late Pliocene (3.0–3.6 Ma), the EEP may have experienced permanent El Niño‐like conditions, supported by a reduced SST gradient across the equatorial Pacific. However, the weakened east‐west SST gradient has been controversial, with disparate results depending on the proxy used to monitor Western Warm Pool SSTs. We present new Pliocene alkenone‐based SST and paleoproductivity records from four Ocean Drilling Program (ODP) cores spanning an east‐west transect across the EEP, which present an internally consistent picture of SST and productivity gradients in the modern cold tongue, resolved at orbital‐scale variability. Strong agreement between core top reconstructions and satellite estimates indicates that alkenone paleotemperature and paleoproductivity proxies are appropriate for reconstructing Pliocene EEP conditions. The average SST gradient between 90° and 120°W was reduced from the modern 1.8°C gradient to 0.9°C in the late Pliocene. Despite the weakened SST gradient, the surface productivity gradient was stronger during the late Pliocene compared to modern, based on calibrated X‐ray fluorescence biogenic opal and alkenone average accumulation rates. Contrary to modern El Niño SST and productivity patterns, reduced Pliocene surface productivity did not accompany the weakened SST gradient. Instead, strong Pliocene biogenic opal and alkenone concentration accumulation gradients in the eastern EEP suggest that subsurface tilting of the nutricline and thermocline persisted to supply vigorous upwelling of warm but nutrient‐rich subsurface waters in a warmer climate.
... In our samples the gammacerane/hopane ratios (Gam/H30, Table 2) show values of 0.24 and 0.34 for samples 1-SM and 2-PR, respectively. However, sample 3-CL shows the highest value (0.97), which could be related to hypersaline paleo-depositional environment (Ten Haven et al., 1987Volkman et al, 1998;Yangming et al., 2005) or stratification of the water column during deposition of the Chico Lomã sample. Furthermore, the sample 3-CL shows lower value to isoprenoids Pristane/Phytane ratio (Table 2), which could also be related to salinity of the paleoenvironment, according to Jiamo et al. (1986). ...
... Higher nutrient concentrations not only have a significant negative impact on the growth and development of seagrasses but also affect bacterial activity and alter microbial communities [67]. Nutrient concentrations can increase the input of unstable organic carbon into the sediment [68], leading to an increased microbial abundance in seagrass bed sediments and altering the composition of microbiomass carbon in SOC [69]. In this study, distance to aquaculture influenced the bacterial α diversity in the seagrass bed sediments, which demonstrated that eutrophication was one of the environmental stressors and had an impact on the bacterial diversity of the seagrass bed sediments. ...
Eutrophication due to aquaculture can cause the decline of seagrasses and impact their carbon storage capacity. This study explored the effects of aquaculture on the sediment organic carbon (SOC) in Thalassia testudinum seagrass beds using enzyme activity and microorganisms as indicators. Our results showed that the distance to aquaculture significantly increased the SOC and TN of sediments; the C/N ratio of sediments was reduced by the distance to aquaculture. Distance to aquaculture and seagrasses significantly impacted the δ13C of sediments, and their significant interactive effects on the δ13C of sediments were found. Distance to aquaculture and seagrasses had significantly interactive effects on the cellulase activity of sediments. Distance to aquaculture and seagrasses separately reduced the invertase activity of sediments. SOC in the seagrass bed was significantly positively impacted by cellulase activity and polyphenol oxidase activity in sediments. Firmicutes, Desulfobacterota and Chloroflexi were the dominant taxa in the S1 and S2 locations. From the S1 location to the S2 location, the relative abundances of Firmicutes and Desulfobacterota increased. The functional profiles of COG were relatively similar between the S1 and S2 locations. BugBase phenotype predictions indicated that the microbial phenotypes of all the seagrass sediment samples were dominated by anaerobic bacteria in terms of oxygen utilizing phenotypes. FAPROTAX functional predictions indicated that aquaculture affects functions associated with seagrass bed sediment bacteria, particularly those related to carbon and nitrogen cycling. This study can provide an important basis for understanding the response mechanism of global carbon sink changes to human activities such as aquaculture and supply more scientific data for promoting the conservation and management of seagrass beds.
... The source of organic matter in sediments and the primary productivity of lacustrine surface water can be expressed by biomarkers, in which the distribution of steroids can be effectively characterized (Volkman et al., 1998). The relative abundances of C 27 -C 29 regular steranes are good indicators for source organic matter input. ...
The organic-rich shale in the first member of the Qingshankou Formation, which is located in the southern Songliao Basin, is regarded as a high-quality source rock in East China. Geochemistry parameters were utilized to illustrate the formation and preservation conditions of the Qing1 Member in the Changling Sag, southern Songliao Basin. In the present study, from longitudinal continuity, the samples of organic geochemistry and elemental geochemistry were collected and systematically analyzed. This aims at determining the paleosalinity, paleoclimate, paleoredox conditions, and paleoproductivity and reconstructing its depositional paleoenvironment. According to total organic carbon (TOC) content, the Qing1 Member in the Changling Sag can be classified into two intervals, which are the lower part and the upper part, with high TOC content and low TOC content, respectively. It can be proved from the results of geochemical indicators that under warm and humid climatic conditions the relatively lower part was generated in the anoxic environment. Terrigenous input brought nutrients to the water body of the lake, made algae flourish, and had a relatively high paleoproductivity of the lake, which imposed a vigorous impact on the accumulation of organic matter. The upper part is mainly deposited under weakly oxidizing conditions, with gradually enhanced oxidation and reduced productivity. In contrast to the lower shale, the terrigenous inflow is relatively low. TOC content in the Qing1 Member has a positive relevance with the paleoredox conditions, as well as the paleosalinity conditions, indicating that good preservation is favorable for the accumulation of organic matter. A depositional model is proposed for the organic matter accumulation of this shale. The upper part was in a relatively hot and dry paleoclimate, with a low degree of organic matter enrichment, whereas the lower part had a warm and humid paleoclimate, with the input of terrestrial organic matter into the primary productivity of the lake basin and a high degree of organic matter enrichment.
... There are structural factors that might contribute to the high 4αM21ββ/4αM22ββ ratio. 4-Methylsterols with Δ 22 unsaturation are fairly common among microalgae (Volkman et al., 1998), and might be incorporated into kerogen via that double bond, which in turn might favour the formation of 4αM21ββ during catagenesis. Another consideration is the dinosterol contribution common in post-Paleozoic marine oils, to which can also be attributed their frequently abundant triaromatic dinosteroid content. ...
... This is likely not because of transport-induced degradation but because of low contents in the fluvial particles of Choshui River that are dominated by eroded ancient sedimentary rock OC. The summed OC-normalized contents of marine biomarkers of brassicasterol (B), dinosterol (D) and C 37 alkenones (A) are used to trace OC mar input in marine sediments (Volkman et al., 1998;Zhao et al., 2006;Xing et al., 2014). The ΣA + B + D contents showed an increasing Hou et al. (2021) and Kao et al. (2014). ...
... The homologous series of fatty acids (n-C 11:0 -n-C 32:0 ) are important biological constituents in terrestrial and aquatic organisms, such as bacteria, algae, and vascular land plants (e.g., Volkman et al., 1998). Therefore, fatty acids can be used to assess sedimentary organic carbon sources distinguishing between the degree of terrestrial-vs. ...
... Müller et al., 2009Müller et al., , 2011. These are produced by a variety of phytoplankton genera like dinoflagellates, diatoms and haptophytes (Boon et al., 1979;Robinson et al., 1984;Volkman et al., 1998). Alongside IP 25 , several other biomarkers are related to sea ice. ...
... Lipids are the most resistant biomolecules in the archaeological record, making them extremely useful proxies in many different contexts for paleoenvironmental and paleodietary research (Peters et al., 2007). Among the numerous lipid compounds preserved in organic-rich dung deposits, n-alkanes are the most resistant to microbial degradation (Volkman et al., 1998). Alkanes are hydrocarbon molecules that form linear chains of carbon atoms (nalkanes) and derive from epicuticular waxes of vascular plants (Eglinton & Hamilton, 1967). ...
The indigenous populations of La Palma (Canary Islands), who arrived on the island from Northwest Africa ca. 2000 years B.P., were predominantly pastoralists. Yet, many aspects of their subsistence economy such as the procurement, management, and use of wild plant resources remain largely unknown. To explore this, we studied the 600–1100‐year‐old archaeological site of Belmaco Cave, which comprises a stratified sedimentary deposit representative of a fumier . Here, we present a high‐resolution, multiproxy geoarchaeological study combining soil micromorphology, lipid biomarker analysis, X‐ray diffraction, μ‐X‐ray diffraction, μ‐X‐ray fluorescence, Fourier transform infrared spectroscopy, and μ‐Fourier transform infrared spectroscopy, to characterize formation processes and explore plant sources. Recurrent goat/sheep habitation and maintenance activities are represented by interstratified layers of unburned dung, charcoal‐rich sediment, and dung ash. Lipid biomarker data show a herd diet mainly composed of herbaceous plants, which is key to understanding the mobility of indigenous shepherds. Our results also revealed an unusual suite of authigenic minerals including hazenite, aragonite, and sylvite, possibly formed through diagenetic processes involving interaction between ash, dung, urine, volcanogenic components, and bacterial activity, coupled with arid and alkaline conditions. Our study shows the potential of a multiproxy approach to a fumier deposit in a volcanogenic sedimentary context.
... The similar distribution of fatty acids and n-alkanes indicates that the latter was likely derived from the decarboxylation of the former (Wang et al. 1995;Jiang, Tian, et al. 2021). In general, short-chain (<C 21 ) fatty acids are derived from phytoplankton and bacteria; medium-chain fatty acids (C 21 -C 25 ) are derived from aquatic macrophytes; long-chain (>C 25 ) fatty acids are derived from higher terrestrial plants (Duan et al. 1997;Volkman et al. 1998;Ficken et al. 2000;Tierney et al. 2011). Therefore, the predominance of short-to medium-chain fatty acids in these oils reflects a significant input of aquatic organic matter, which is consistent with their lacustrine source rocks (Fu et al. 2019;Ping et al. 2019;Jiang, Li, et al. 2021). ...
... The importance of bacterial relative to algal source organism inputs to marine sediments can be inferred by the relative abundance of hopanes vs. steranes preserved in sedimentary rocks. Hopanes are derived from bacteriohopanepolyols that are exclusively produced by bacteria, whereas steranes are primarily produced by eukaryotic sterols (Peters et al., 2005;Volkman et al., 1998 (Haddad et al., 2016;Martinez et al., 2018;Marynowski, Rakocinski, et al., 2011;Song et al., 2021). By contrast, much higher values were found in a Late Ordovician epeiric sea setting, where the average baseline was ~4.0-6.0 and excursions were up to ~12 (Rohrssen et al., 2013). ...
Studying the response and recovery of marine microbial communities during mass extinction events provides an evolutionary window through which to understand the adaptation and resilience of the marine ecosystem in the face of significant environmental disturbances. The goal of this study is to reconstruct changes in the marine microbial community structure through the Late Devonian Frasnian-Famennian (F-F) transition. We performed a multiproxy investigation on a drill core of the Upper Devonian New Albany Shale from the Illinois Basin (western Kentucky, USA). Aryl isoprenoids show green sulfur bacteria expansion and associated photic zone euxinia (PZE) enhancement during the F-F interval. These changes can be attributed to augmented terrigenous influxes, as recorded collectively by the long-chain/short-chain normal alkane ratio, carbon preference index, C30 moretane/C30 hopane, and diahopane index. Hopane/sterane ratios reveal a more pronounced dominance of eukaryotic over prokaryotic production during the mass extinction interval. Sterane distributions indicate that the microalgal community was primarily composed of green algae clades, with their dominance became more pronounced during the F-F interval and continued to rise in the subsequent periods. The 2α-methylhopane index values do not show an evident shift during the mass extinction interval, whereas the 3β-methylhopane index values record a greater abundance of methanotrophic bacteria during the extinction interval, suggesting enhanced methane cycling due to intensified oxygen depletion. Overall, the Illinois Basin during the F-F extinction experienced heightened algal productivity due to intensified terrigenous influxes, exhibiting similarities to contemporary coastal oceans that are currently undergoing globalized cultural eutrophication. The observed microbial community shifts associated with the F-F environmental disturbances were largely restricted to the extinction interval, which suggests a relatively stable, resilient marine microbial ecosystem during the Late Devonian.
... The analysed samples include abundant C 27-30 4-desmethyl steranes, with C 28 and C 29 steranes (and C 27 steranes in the extract sample from 3562.5 m) being more abundant in the Jarvis oil and in the Zechstein samples, respectively (Table 3). The regular sterane distribution is consistent with either marine algal organic matter (C 27 and C 28 ) or terrigenous (C 29 ) OM (Huang and Meinschein, 1979;Volkman, 1986;Volkman et al., 1998;Kodner et al., 2008); however C 29 steranes may indicate algal organic matter particularly in algal-dominated carbonate marine settings (Palacas et al., 1984;Walters and Cassa, 1985;Grantham, 1986). The sterane distribution in the Jarvis oil is similar to that of Kimmeridge Clay Formation source rocks and derived oils in the North Sea (Mackenzie, 1984;Hughes et al., 1985;Kubala et al., 2003;Petersen et al., 2016). ...
Oil in the Jarvis structure underlying the main Upper Jurassic reservoir at the Ettrick oilfield (Outer Moray Firth, UK northern North Sea) is present in Upper Permian (Zechstein) carbonates. The origin of this “Jarvis oil” is investigated in this paper using a multidisciplinary approach based on data from well‐logs and cores from wells 20/02‐2 and 20/02‐3. Reservoirs at the Jarvis structure consist of carbonates in the upper part of the Halibut Carbonate Formation (Ca2) and in the Carbonate Member of the Turbot Anhydrite Formation (Ca3). These carbonates are typical Zechstein dolomites composed of a range of facies from mudpackstones with storm beds deposited at moderate water depths to shoreface bioclastic‐oolitic packstones to shallow‐subtidal and intertidal microbial laminites. Interbedded anhydrites replace sabkha and lagoonal selenitic gypsum. Several shallowing‐upward units are recognised. Molecular analysis of the Jarvis oil, and comparisons with biomarker and other geochemical data from extracts of Zechstein cores and published data from different source rocks from the North Sea area, suggest that the oil was generated by marine, OM‐rich shales in the Upper Jurassic Kimmeridge Clay Formation. The oil was generated at peak oil window maturity and is characterised by high Pr/Ph, BNH/H and DBT/P ratios, and abundant C 28 steranes and C 28+29 monoaromatic and C 26 R + C 27 S triaromatic steroids. The molecular composition of organic material in extracts of core samples of Zechstein carbonates from wells in the Jarvis structure differs significantly from that of the Jarvis oil. Biomarkers such as BNH are absent in the core extracts, and there are different distributions and abundances of saturated and aromatic hydrocarbons, likely controlled by thermal maturity.
... strong predominance of even-carbon chain-lengths (Fig. 4B). Longer even-numbered C 24,26,28 and C 30 chain lengths are typical of aquatic and terrestrial inputs (Fig. 4B), and C 24 n-alcohol have been found in freshwater phytoplankton 81,82 . Microalgae produce long-chain alcohols, C 26 and C 28 n-alcohols are produced by freshwater Eustigmatophyceae 82 . ...
Among the outstanding questions about the emergence of human-controlled fire is the systematic recurrence between the geochemical remains of fire and its preservation in the archaeological record, as the use of fire is considered a technological landmark, especially for its importance in food cooking, defensive strategies, and heating. Here we report fossil lipid biomarkers associated with incomplete combustion of organic matter at the Valdocarros II site, one of the largest European Acheulean sites in Spain dated to marine isotopic stage (MIS) 8/7 (~ 245 kya) allowing a multiproxy analysis of human-controlled fire use. Our results reveal isolated cases of highly concentrated and diverse polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs (APAHs), along with diagnostic conifer-derived triterpenoids in two hearth-like archaeological structures. The presence of combustion byproducts suggests the presence of anthropogenic (controlled) fires at Valdocarros—one of the oldest evidence of fire use in Europe-in association with Acheulean tools and bones. Hominins possibly used fire for two main activities, as a means of defense against predators and cooking. Our results help to better delineate major gaps in our current knowledge of human-controlled fire in the context of the Middle-Pleistocene in Europe and suggest that human ancestors were able to control fire before at least 250 kya.
Nutrient reduction is an essential environmental policy for water quality remediation, but climate change can offset the ecological benefits of nutrient reduction and lead to the difficulty of environmental evaluation. Here, based on the records of three lipid microalgal biomarkers and stable isotopes of carbon and nitrogen in two sediment cores from the embayment of Perth, Australia, we reconstructed the microalgal biomasses (diatoms,
dinoflagellates and coccolithophores) over the past century and evaluated the ecological effects of nutrient
reduction on them, using Change Point Modeling (CPM) and redundancy analysis (RDA). The CPM result showed
that total microalgal biomarkers increased by 25% and 51% in deep and shallow areas, respectively, due to nutrient enrichment caused by industrial wastewater in the 1950s and the causeway construction in the 1970s, and dinoflagellates were beneficiaries of eutrophication. The nutrient reduction policy since the 1980s had not decreased total microalgal biomass, and diatoms were beneficiaries of this period. RDA based on time series of
sediment cores and water monitoring data revealed that the increase of sea-surface temperature and the decrease of rainfall since the 1980s may be important factors sustaining the high total microalgal biomass and increasing the degree of diatom dominance. The result also indicated that the variations of microalgal assemblages may better explain the effect of nutrient reduction rather than total microalgal biomass.
In the last 5 decades, paleontological research has exploded where fossils have enabled robust dating of rocks, improved understanding of origination/extinction rates or mass extinction events, biogeography, adaptive strategies, and many more. New molecular technologies have enabled intensive analyses of vertebrates and invertebrates, plant fossils, fossilized microbes, trace fossils, and fossil molecules, alike. Paleontological research has become interdisciplinary with inputs from geology, chemistry, biology, astronomy, and archaeology. Herein, we review the principles of promising molecular technologies and explore their applications and limitations vis-à-vis paleontological research. This review will attempt to provide a roadmap that can be used for future research directions. Advanced chemical imaging provides the ability to identify and quantify chemical characteristics to evaluate taphonomic damage, original biological structures, or fossils microbes. Molecular methods (e.g., molecular clock, DNA barcode, racemization dating, and biomarkers) offer a unique source of information and provide robust clues into the co-evolution of life in modern and past environments. Two main limitations are noted and include an exceptional preservation of the organic material, which is not always the case, and the complexity and cost of the instruments involved in the analyses. These difficulties are limiting the factual applications in paleontological analysis. Although very little research has been carried out on the aforementioned methods, they however, provide improved answers to highly debated and unsolved biological and climatic issues and a window to better understanding the origin of life. Biomarker proxies will be further developed and refined to answer emerging questions in the Quaternary Period.
In the search for life in our Solar System, Mars remains a promising target based on its proximity and similarity to Earth. When Mars transitioned from a warmer, wetter climate to its current dry and freezing conditions, any putative extant life probably retreated into habitable refugia such as the subsurface or the interior of rocks. Terrestrial cryptoendolithic microorganisms (i.e., those inhabiting rock interiors) thus represent possible modern-day Mars analogs, particularly those from the hyperarid McMurdo Dry Valleys in Antarctica. As DNA is a strong definitive biosignature, given that there is no known abiotic chemistry that can polymerize nucleobases, we investigated DNA detection with MinION sequencing in Antarctic cryptoendoliths after an ∼58-sol exposure in MARTE, a Mars environmental chamber capable of simulating martian temperature, pressure, humidity, ultraviolet (UV) radiation, and atmospheric composition, in conjunction with protein and lipid detection. The MARTE conditions resulted in changes in community composition and DNA, proteins, and cell membrane-derived lipids remained detectable postexposure. Of the multitude of extreme environmental conditions on Mars, UV radiation (specifically UVC) is the most destructive to both cells and DNA. As such, we further investigated if a UVC exposure corresponding to ∼278 martian years would impede DNA detection via MinION sequencing. The MinION was able to successfully detect and sequence DNA after this UVC radiation exposure, suggesting its utility for life detection in future astrobiology missions focused on finding relatively recently exposed biomarkers inside possible martian refugia.
Reef-building corals, recognized as cornerstone species in marine ecosystems, captivate with their unique duality as both symbiotic partners and autotrophic entities. Beyond their ecological prominence, these corals produce a diverse array of secondary metabolites, many of which are poised to revolutionize the domains of pharmacology and medicine. This exhaustive review delves deeply into the multifaceted world of coral-derived lipids, highlighting both ubiquitous and rare forms. Within this spectrum, we navigate through a myriad of fatty acids and their acyl derivatives, encompassing waxes, sterol esters, triacylglycerols, mono-akyl-diacylglycerols, and an array of polar lipids such as betaine lipids, glycolipids, sphingolipids, phospholipids, and phosphonolipids. We offer a comprehensive exploration of the intricate biochemical variety of these lipids, related fatty acids, prostaglandins, and both cyclic and acyclic oxilipins. Additionally, the review provides insights into the chemotaxonomy of these compounds, illuminating the fatty acid synthesis routes inherent in corals. Of particular interest is the symbiotic bond many coral species nurture with dinoflagellates from the Symbiodinium group; their lipid and fatty acid profiles are also detailed in this discourse. This exploration accentuates the vast potential and intricacy of coral lipids and underscores their profound relevance in scientific endeavors.
Recent exploration in the Nile Delta Basin has led to major oil and gas discoveries; however, source–reservoir relationships in the onshore part of the basin are still ambiguous. This work involves a comprehensive geochemical assessment of possible Oligocene–Pliocene source rocks, using TOC/Rock-Eval pyrolysis and gas chromatography–mass spectrometry. The aim is to investigate quantity, quality, thermal maturity, sources, and depositional paleoenvironment of the disseminated organic matter, and to correlate rock samples with hydrocarbons retrieved from the study area. Moreover, the chemical and isotopic compositions of gases were employed to examine origin, maturity, mixing and secondary alteration processes.
Results reveal fair to good organic richness (TOC ~1 wt%) for the Oligocene–Pliocene rocks, with the highest TOC content from the Oligocene Tineh Formation. The kerogen is generally gas-prone Type-III and to a lesser extent Type-IV and Type-II/III. Molecular and biomarker results indicate mixed source facies with variable contributions from higher plants, algae, bacteria, and plankton, deposited under suboxic to anoxic nearshore marine or lacustrine depositional settings. Significant biomarkers include elevated C26/C25 tricyclic terpane ratios (0.82–3.62), low C31 homohopane (22R)/C30 hopane ratios (0.17–0.63), and low oleanane and gammacerane contents. Maturity-related biomarkers, Rock-Eval Tmax and vitrinite reflectance values are consistent and suggest immature to early mature rock samples.
Molecular and isotopic compositions of mud gases indicate complex origins and mixing histories ranging from primary microbial to pure thermogenic, where thermogenic processes dominate the pre-Miocene intervals.
Chemometric analysis of 18 source-related biomarker ratios for rock extracts revealed four genetic families. Hierarchical cluster analysis (HCA) of biomarker data for rock extracts and condensate oils from the onshore Nile Delta indicates no correlation between Miocene–Pliocene rocks and condensates or oils in the area. Therefore, pre-Miocene source rocks are suggested to be the most probable candidates for hydrocarbons in the onshore Nile Delta.
Sediments deposited in the Indus Fan (Site 720) as well as Miocene sediments from the Owen Ridge (Sites 722 and 731) contain almost exclusively organic matter of terrigenous origin. The organic matter in sediments from the Oman Margin (Sites 723, 725, and 728) and in the Pliocene/Pleistocene sections from the Owen Ridge is mainly of a marine origin with variable admixtures of terrigenous material. -from Authors
Chain elongation and 2-hydroxylation pathways, which are specific for very long chain fatty acids (>C18), have been found in the yeast, Candida utilis. The chain elongation system acts specifically on fatty acids of chain length C20 to C24; there is no detectable elongation of C18 and only trace activity with C19. The product of the elongation enzyme or enzymes is C26 when C20, C22, or C24 is substrate and is a mixture of C25 and C27 when the substrates are C21 and C23. The 2-hydroxylation enzyme converts C26 acid, formed in situ by chain elongation, to 2-hydroxyhexacosanoic acid. The enzyme seems quite specific for the C26 chain length, although there may be some activity for chain lengths C24, C25, and C27.
In addition to the chain elongation and 2-hydroxylation systems, a relatively nonspecific system for the oxidative decarboxylation of 2-hydroxy acids has been studied in C. utilis. All 2-hydroxy fatty acids tested (C18 through C26 containing an even number of carbons) were converted, in part, to the unsubstituted acid containing 1 carbon less than the substrate. Decarboxylation was most efficient with 2-OH-C18 and least with 2-OH-C26 acids. Another product arising from the decarboxylation reaction was the aldehyde containing 1 carbon less than the 2-hydroxy acid substrate. The aldehydes were detected in trace amounts with the shorter chain substrates but were major products from the decarboxylation of 2-OH-C24 and 2-OH-C26. Presumably, the aldehyde is an intermediate between the 2-hydroxy acid substrate and the unsubstituted fatty acid which results as the final product in the oxidative decarboxylation process.
32. Volkman, J.K., Farrington, J.W., Gagosian, R.B. and Wakeham, S.G. (1983). Lipid composition of coastal marine sediments from the Peru upwelling region. In Advances in Organic Geochemistry, 1981. (eds Bjoroy M. et al.), pp. 228-240. Wiley, Chichester.
We report the distribution and quantitation of 21:6 hydrocarbon and 22:6 fatty acid within the major groups of algae in both marine and freshwater environments. The absence of 21:6 hydrocarbon in nonphotosynthetic dinoflagellates and diatoms suggested its localization within the chloroplasts. The hydrocarbon accounted for 2–15 per cent of the total lipid of diatoms, which have low (⪢ 1 per cent of total fatty acids) amounts of the 22:6 fatty acid. In comparison the dinoflagellates have major amounts of the 22:6 fatty acid (20–30 per cent) and small quantities of 21:6 hydrocarbon (less than 2 per cent of the lipid). The synthesis of 21:6 hydrocarbon by a specific 22:6 fatty acid decarboxylase appeared probable, and the activity of this enzyme appeared to vary in different groups of algae.
Suspended and sinking particulate matter from the water column and sediment and fecal pellets from Unit I sediments were collected
in the central basin of the Black Sea for organic geochemical investigations. The hydrocarbon compositions of these samples
proved informative for providing information on the sources for the particulate and sedimentary organic matter. Hydrocarbons
derived from planktonic, terrestrial, bacterial, and fossil sources can be distinguished. Plankton-derived hydrocarbons dominated
the Emiliania huxleyi), but an equal mix of planktonic and fossil hydrocarbons was present in the >53 µm particles. By contrast, 53 µm) particles in the anoxic zone contained equal amounts of hydrocarbons from all four sources. Fecal pellets and
sediments contained the greatest contribution of hydrocarbons of terrestrial origin (up to 56% of total hydrocarbons).
The highly branched isoprenoid (HBI) alkenes of three batch cultures of the diatom Haslea ostrearia have been examined and the occurrence of C25 tri-, tetra- and pentaenes confirmed. Growth of cultures outside at ambient temperature, under natural sunlight, in May (6days) and June (10days) 1995 and monitoring of HBI concentrations in samples collected daily and stored frozen, revealed that in May greater concentrations of HBIs (ca 6500fgcell−1) were produced than in June and at a much earlier stage of growth. Furthermore, in May the HBIs were more unsaturated (predominantly a tetraene rather than a triene). The reasons for these differences are at present unknown and future investigations of the effect of irradiance, temperature, salinity and other environmental variables are required. Such experiments may allow the various HBI distributions in the alga and in sediments to be better understood and, like some other polyunsaturated lipids, HBI alkenes may become useful environmental and palaeoenvironmental indicators. Two previously unreported alkenes, 2,6,10,14-tetramethyl-7-(3-methylpent-4-enyl)pentadec-2,5,9,13-ene (GC retention index, 2201DB-1) and 2,6,10,14-tetramethyl-7-(3-methylene pent-4-enyl)pentadec-2,5,9,13-ene (GC RI, 2248DB-1) from a batch culture of Haslea ostrearia grown in October/November 1993 and stored frozen for over a year, have also been isolated and characterised by 13C and 1H NMR, epoxide derivatisation and mass spectrometry. Such structural characterisation studies of HBI alkenes should also aid our understanding of the geochemical fate of these widely distributed hydrocarbons.
Conte, M.H., Volkman, J.K. and Eglinton, G. (1994). Lipid biomarkers of the Haptophyta. In The Haptophyte Algae (eds J.C. Green and B.S.C. Leadbeater), pp. 351-377. Clarendon Press, Oxford.
Three highly branched isoprenoid (HBI) polyenes have been isolated from the diatom Haslea ostrearia and characterised by nmr spectroscopy
Biological marker compounds provide useful tools for evaluating the depositional environments of Recent and ancient sediments and petroleums1, largely through established relationships between the organic matter of sediments and source organisms1,2. Such relationships are best tested and explored by investigating the lipid components of natural populations of autochthonous biota that can be clearly recognized as contributors to underlying bottom sediments. In this context we have studied the lipids of the freshwater dinoflagellate Peridinlum lomnickii Woloszynska (order Peridiniales, class Dinophyceae) collected from the waters of Priest Pot3, a eutrophic lake in the English Lake District. Its distributions of both 4alpha-methylsterols and 4alpha-methylstanones closely resemble those of the underlying bottom sediments, demonstrating that dinoflagellates are important contributors of these sedimentary compounds. The 4-methylsteroidal hydrocarbons found in ancient sediments and petroleums4-6 are presumably diagenetic products of such 4alpha-methylsteroids and therefore reflect dino flagellate inputs to the original depositional environments. Furthermore, the prominence of 5alpha(H)-cholestan-3beta-ol in P. lomnickii suggests that dinoflagellates may be the long sought, direct biological source of sedimentary 5alpha(H)-stanols.
The haptophyte algae (sometimes referred to as the prymnesiophyte algae) are cosmopolitan in their distribution and are particularly important in marine ecosystems. They form a significant component of the phytoplankon and may occasionally be the dominant organisms. In recent years there has been a marked increase in these algae, partly as a result of the occurence of a number of ichthyotoxic blooms in Scandinavian coastal waters, whose effects have been dramatic in terms of both the diversity of species affected and their economic impact. It is also now recognised that some members of the Haptophyta may affect our climate through the production of volatile sulphur compounds and through the effects that calcifying biomineralization may have on ocean/atmospheric carbon dioxide exchange. This is the first monograph on the Haptophyta, each chapter having been contributed by authors experienced in their subject. The topics covered include all major aspects of haptophyte biology, such as their structure, biochemistry, ecology, climatological and economic importance, fossil record, evolution and systematics.
Botryococcus braunii Kützing is a colonial Chlorophyceae (green microalga) characterized by an unusually high production of lipids and an original organization of colonies. This species is widely distributed on all continents, in freshwater, brackish and saline lakes, reservoirs or even small pools, situated in temperate, tropical and continental zones as well (1).The ability to develop spectacular blooms on the surface of unruffled waters which consist of a floating mass of colonies rich in oil is also a conspicuous feature of B. braunii. Thus during a survey of the 4000 ha Darwin River Reservoir in Australia, Wake and Hillen (2) estimated a bloom of B. braunii at 1500 tons and assaying at 30% oil.
It is generally accepted that the formation of kerogens is the result of the so-called depolymerization-recondensation pathway (Tissot and Welte, 1984; Durand, 1980), Thus, naturally occurring macromolecular substances such as polysaccharides and proteins are enzymatically depolymerized to oligo- and monomers, which for the most part are mineralized. However, a small part of them are thought to condense with other substances such as low-molecular-weight lipids in a random way (Fig. 1). During diagenesis, the “geopolymers” thus formed continuously undergo chemical transformations by which they become more and more insoluble and resistant. Kerogens are being formed, which—depending on the nature of the original organic matter contributions—can generate various amounts and sorts of oil under thermal stress.
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Thirteen species of algae covering an extensive range of classes were cultured and stable carbon isotopic compositions of their lipids were analysed in order to assess carbon isotopic fractionation effects during their biosynthesis. The fatty acids were found to have similar stable carbon isotopic compositions to each other in all the algae with the exceptions of the C28 fatty acid in Scenedesmus communis and the polyunsaturated fatty acids in Ampidinium sp. and Gymnodinium simplex which are 3.5 more depleted in 13C and up to 8 more enriched in 13C, compared to the C16 fatty acid, respectively. Phytol is consistently enriched in 13C by 2-5 compared with the C16 fatty acid in all algae. The sterols are, however, enriched in 13C by 0-8 compared to the C16 fatty acid, possibly due to a different pool of isopentenyl diphosphate in the cytosol. These large ranges in carbon isotopic compositions of compounds biosynthesized by the same eukaryotes can significantly complicate the interpretation of 13C values of sedimentary biomarkers.
A C20 isoprenoid alkane (1) reported to occur in several recent sediments, has been isolated from Rozel Point crude oil and its structure confirmed by synthesis.
The heterotrophic dinoflagellate Crypthecodinium cohnii contained the 4α-methyl sterols, dinosterol, dehydrodinosterol (4α,23,24-trimethylcholesta-5,22-dien-3β-ol) and the tentatively identified 4α,24-dimethyl-cholestan-3β-ol and 4α,24-dimethylcholest-5-en-3β-ol. The major 4-demethyl sterol was cholesta-5,7-dien-3β-ol which was accompanied by a smaller amount of cholesterol and traces of several other C27,C28 and C29 sterols. In addition, a 3-oxo-steroid fraction was isolated and the major component identified as dinosterone (4α,23,24-trimethylcholest-22-en-3-one). The possible biosynthetic relationships of these compounds are discussed.
About 30 species of algae, chosen from a wide range of algal classes and orders, have been examined to see whether the chlorosulpholipids are widely distributed in this division of the plant kingdom. Most of the fresh-water species examined contained chlorosulpholipids, although only Ochromonas danica and O. malhamensis contained large quantities. The chlorosulpholipids of O. malhamensis were predominantly of the tetracosane series, the parent compound of which was tetracosane-1, 14-diol disulphate. No chlorosulpholipids were detected in any of the marine species examined.
The steroidal derivatives, fatty acid alkyl esters and triacylglycerols have been identified in two cultured dinoflagellates, Woloszynskia coronata and Ceratium furcoides, and natural populations of two species, Peridinium lomnickii and P. cinctum. Within each species, the same sterol moieties occurred in free and esterified forms, but the species differed in the proportion of 4α-methyl and desmethyl sterols. Both groups occurred in the two Peridinium species, whereas W. coronata contained only 4α-methylsterols and C. furcoides, uniquely among dinoflagellates analysed to date, contained only desmethylsterols, although these were analogues of 4α-methylsterols present in the other species. 4α-Methyl steroidal ketones were present in P. lomnickii and W. coronata; cholest-4-en-3-one and 5α-cholestan-3-one were detected in C. furcoides, but no steroidal ketones were detected in P. cinctum. Methyl and ethyl esters of fatty acids (C12C18) were detected in three species, in P. cinctum the ethyl esters were dominant, while phytyl esters occurred only in the Peridinium spp. The molecular composition of triacylglycerols containing only saturated and monoenoic acyl groups was determined by GC-MS. Lower carbon number constituents from W. coronata contained a C4 acyl group, previously found only in animal milk fats.
Two new sterols, (24E)-24-n-propylidenecholesterol and 24ξ-npropylcholesterol, were isolated from a cultured marine Chrysophyte. Since most of the sterols found in marine invertebrates are unchanged or modified sterols of algal or symbiotic origin, the discovery of these two unusual sterols in a unicellular alga grown under well-defined conditions contributes to our knowledge of sterols in marine food chains and offers a potential substrate for biosynthetic labeling experiments.
Culture of the A race of Botryococcus braunii in the presence of SC 1058, a cinnolinyl acid derivative (1-N-benzyl-3-carboxy-4-ketocinnoline), was recently shown to result in marked inhibition of the resistant biopolymer (PRB A) in its outer walls and of the external pool of lipids, whereas the internal pool is strongly increased. These large effects were achieved with a SC 1058 concentration (5 x 10−3 M) which does not affect the primary metabolism of B. braunii. Examination of the influence of SC 1058 on various groups of external lipids indicated that (i) all the very long chain compounds identified in this pool are markedly inhibited (decrease of 50–80% relative to SC 1058-free controls), (ii) free fatty acids, comprising chiefly oleic acid, are sharply inhibited (ca 95%), and (iii) triacylglycerols (TAG) show a pronounced stimulation (+ 87%). However, the decrease observed for external free fatty acids cannot be entirely accounted for by the higher production of TAG.Study of the internal lipids revealed, in control cultures, large differences in distribution relative to external lipids; free fatty acids are still dominated by oleic acid but highly polar compounds are far more abundant. Culture with SC 1058 resulted in a pronounced increase in both internal TAG (ca × 7) and free fatty acids (ca × 4). Together these observations on internal and external lipids revealed that de novo synthesis of fatty acids is not affected by 5 x 10−1 M SC 1058, whereas transport of oleic acid from the internal to the external pool is markedly decreased. The parallel inhibition of external very long chain lipids and of PRB A confirms the occurrence of tight biosynthetic relationships between these compounds and the major role of oleic acid in their formation. In addition to oleic acid transport, SC 1058 would also inhibit the condensation step leading to high Mr lipids implicated as important intermediates in PRB A formation. Finally, as shown by FT IR spectra and pyrolysis product distributions, the very strong inhibition in PRB A formation obtained with SC 1058 is not associated with major changes in the bulk chemical features of the resistant biopolymer.
Cellular lipid concentrations of fatty acids, sterols, alcohols, hydrocarbons and 3-keto steroids were determined in laboratory cultures of the marine
The incorporation of sodium acetate-[1-14C] into the heterocyst glycolipids of Anabaena cylindrica cultures from 60–234 hr old is reported. Incorporation of radioactivity was maximal in 88 hr old cultures. In 60 hr and 88 hr cultures about 90 % of the radioactivity of the heterocyst glycolipids was found in the non-saponifiable glycolipid fraction, whereas in older cultures this fraction contained only 75 % of the radioactivity. Acid hydrolysis of non-saponifiable heterocyst glycolipid fractions showed that in 60 hr cultures, 81 % of the radioactivity occurs in the lipid moiety, whereas in older cultures a greater proportion (40–53 %) of the radioactivity was found in the sugar residue. The lipid fraction obtained by acid hydrolysis contained a mixture of labelled long chain mono-, di- and trihydric alcohols. In young (60 hr) cultures the primary alcohol fraction was most heavily labelled (57.3 % of the radioactivity in the non-saponifiable glycosides) with much smaller amounts in the diol and triol (8.4 and 15.1 % respectively), whereas in older cultures (234 hr) the primary alcohol (23.6 %) diol (22.5 %) and triol (18.9 %) fractions contained ca equal amounts of radioactivity.
C[sub 37]-C[sub 39] long-chain unsaturated ketones (alkenones) and alkenes were identified in samples of particulate organic matter obtained from surface waters spanning the temperature range [minus]0.7-12.2[degrees]C in the Southern Ocean south of Australia. The carbon number distribution indicates that these compounds are derived from the prymnesiophyte alga Emiliania huxleyi which is the predominant coccolithophorid in these waters. Values of U[sup k[prime]][sub 37] were calculated according to the definition U[sup k[prime]][sub 37] = [37:2]/([37:2] + [37:3]), where [37:[chi]] is the concentration of the C[sub 37] alkenone with [chi] double bonds, and plotted against sea surface temperature (SST). The data form a contiguous set with earlier compilations of data from warmer waters. Over much of the temperature range the relationship between U[sup k[prime]][sub 37] and temperature is remarkably linear, and is best fitted by the simple equation U[sup k[prime]][sub 37] = 0.0414T - 0.156 (for temperatures 4-25[degrees]C). This calibration of U[sup k[prime]][sub 37] with temperature for field samples is significantly different from that established from analyses of prymnesiophyte algae in culture, and it diverges especially at the colder temperatures. Data for temperatures below about 4-6[degrees]C show increased scatter and the calibration at these low temperatures may be better fitted by a nonlinear exponential function, but this requires further testing. Certainly, the predictive power of the linear calibration is severely constained at temperatures less than 5.0[degrees]C, but at temperatures above this the data establish the usefulness of U[sub k[prime]][sub 37] as an SST indicator for waters north of the polar front in the Southern Ocean and for several regions of the world ocean.
Comparative microscopical and chemical studies of recognizable entities in kerogen and their extant counterparts suggest a new and simple mechanism of kerogen formation which clarifies the interrelationships between extant biomass, kerogen, and fossil fuels.
C37–C39 long-chain unsaturated ketones (alkenones) and alkenes were identified in samples of particulate organic matter obtained from surface waters spanning the temperature range -0.7–12.2°C in the Southern Ocean south of Australia. The carbon number distribution indicates that these compounds are derived from the prymnesiophyte alga Emiliania huxleyi which is the predominant coccolithophorid in these waters. Values of Uk'37 were calculated according to the definition , where [37:x] is the concentration of the C37 alkenone with “x” double bonds, and plotted against sea surface temperature (SST). Our data form a contiguous set with earlier compilations of data from warmer waters. Over much of the temperature range the relationship between Uk'37 and temperature is remarkably linear, and is best fitted by the simple equation Uk'37 = 0.0414T — 0.156 (for temperatures 4–25°C). This calibration of Uk'37 with temperature for field samples is significantly different from that established from analyses of prymnesiophyte algae in culture, and it diverges especially at the colder temperatures. Data for temperatures below about 4–6°C show increased scatter and the calibration at these low temperatures may be better fitted by a nonlinear exponential function, but this requires further testing. Certainly, the predictive power of the linear calibration is severely constrained at temperatures less than 5.0°C, but at temperatures above this our data establish the usefulness of Uk'37 as an SST indicator for waters north of the polar front in the Southern Ocean and for several regions of the world ocean.
Organic molecules originating only from the in situ diagenesis of biogenic molecules are ideal geochemical fossils which may provide information essential for the characterization and reconstruction of depositional environments and subsequent chemical reactions during diagenesis. It is proposed herein that this is the case for the 5 -isomers of stanols and stanones produced during stenol hydrogenation in young aquatic sediments, if shown to be essentially free of any major anthropogenic pollution (particularly, sewage). In order to clarify the environmental factors controlling the production of the 5 -steroidal isomers from stenols in recent aquatic sediments, attempts were made to relate the occurrence of 5 -stanols to various environmental parameters. Positive correlations between elevated concentrations of 5 -stanols and the degree of autochthonous contribution to sedimentary organic matter were consistently found in various surface aquatic sediments from a wide variety of depositional environments and also in older sediments extending even to the late Pleistocene. According to this finding, it was concluded that the primary factor controlling the conversion of stenols to 5 -stanols through 5 -stanones in anaerobic aquatic sediments is probably the relative contribution of autochthonous organic matter suitable for microbial metabolism ( i.e. metabolizable organic matter) to the sediments. Consequently, it is proposed that the 5 -isomers of stanols and stanones, at least in immature aquatic (marine and non-marine) sediments, can serve as primary markers for defining the quality of sedimentary organic matter ( viz. the relative contribution of metabolizable organic materials to sedimentary organic matter) and as indicators for the types and rates of microbiological activities responsible for early diagenesis of organic matter in anaerobic sediments. It is also suggested that the combination of the 5 -steroidal isomers with organic source parameters will allow these compounds to assist in indicating oxic or anoxic depositional environments.
A detailed study has been made of the solvent extractable monocarboxylic, dicarboxylic and hydroxylated fatty acids and n-alkanes in a surface intertidal sediment, and the distributions compared to microorganisms cultured from the sediment. Diatoms are shown to contribute most of the monocarboxylic acids, particularly the significant amounts of polyunsaturated acids present, and a small proportion of the n-alkanes. Bacteria contribute between 11 and 14% of the monocarboxylic acids and markers for this, including trans-monounsaturated acids, are proposed. Detritus from the sea-grass Zostera muelleri is a major source of the α-hydroxy-, ω-hydroxy and α,ω-dicarboxylic acids in the sediment and a minor contributor of n-alkanes and long-chain fatty acids.
Batches of the cyanobacterium Aphanizomenon flos-aquae were cultured using different growth conditions to search for long-chain alkan-1,15-diols and alkan-15-one-1-ols expected to occur in these organisms based on a field sample study (Morris and Brassell, 1988). These compounds which are ubiquitous in Recent sediments were not present either free or bound in any of the cultures analysed, indicating that results of chemotaxonomical studied based on field samples should be interpreted with great caution. This statement is further supported by the absence of sterols in the cultured algae and their relatively high abundance in the field sample. A specific lipid, tentatively identified as (ω-1)-hydroxyhexacosanoic acid, was encountered in the cultured alga and has potential as a biomarker.
Total fatty acids from Heterosigma akashiwo contained 4.8–8.9 wt% of octadecapentaenoic acid (18:5n-3) through the growth cycle. This polyunsaturated fatty acid was preferentially located in monogalactosyldiacylglycerols and digalactosyldiacylglycerols (20.1% and 10.2% of fatty acids, respectively, at day 18) with 0.3% or less in sulphoquinovosylglycerol (SQDG)+phosphatidylglycerol (PG) and phosphatidylcholine. The SQDG+PG fraction contained six cis 16:1 isomers. These findings are discussed in relation to algal taxonomy.
Sterols and alcohols isolated from a collection of industrially important fresh-water green algaeChlorella kessleri, Scenedesmus acuminatus, S. acutus andS. acutus var.Tomasclli cultivated heterotrophically or autotrophically under pilot plant conditions, were identified and quantified by gas chromatography
— mass spectrometry. Previsously demonstrated sterols with double bonds in position 5 and 7 were detected. In addition, cholesta-5,7,22-trien-3
β-oI that had not yet been described in green algae was found inS. acutus. Alcohols were found only inC. kessleri cultivated under heterotrophic conditions. Some saturated and unsaturated alcohols were detected for the first time in green
algae.
The marine dinoflagellates Prorocentrum micans, Gonyaulax polyedra, Gymnodinium sp., and Alexandrium tamarense, collected from the Adriatic Sea during red-tide blooms, were cultured to investigate the 4-methyl sterol constituents. To ascertain a possible influence of cell age on the 4-methyl sterol content, for one strain (Gymnodinium sp.) we investigated the composition of these constituents at exponential and stationary growing phases. The lipid material extracted with acetone firm the lyophilized algal samples was fractionated by thin-layer chromatography. The 4-methyl sterols recovered from the layer were converted into the corresponding OTMS derivatives. Nine of 11 constituents were identified by gas chromatography and gas chromatography-mass spectrometry; only two minor constituents were characterized by their gas chromatographic parameters. All free methyl sterols identified in the algal samples had been detected previously in various dinoflagellates. The 4-methyl sterol fractions generally contained very few constituents. Except for the Gymnodinium sp. sample, collected at the exponential growing phase (GyD2 exp), which contains 4,24-dimethylcholestan 3-ol as a unique constituent, dinasterol was the major component. Moreover, 4,24-ethylcholestan-3-ol was also an important constituent of both Prorocentrum and Gonyaulax strains, whereas considerable amounts of dinostanol characterized all the Gymnodinium sp. strains. In addition, the latter contained several minor constituents such as 4-methylcholestan-3-ol, 4,24-dimethylcholesta 22-en-3-ol, and 4 methyl-24-ethylcholestan-3-ol. 4-Methyl-24-methylene-cholestan-3-ol was a constituent of the Gymnodinium sp. sample, collected at the stationary growing phase (GyD2 stat) only, whereas 4-methylgorgostanol was identified only in the Alexandrium tamarense Gt4 strain. Except for 4-methyl-24-ethylcholesta 8(14)-en-3-ol, all the methyl steol constituents from our algae show a saturated polynuclear system. The pathways by which side-chain modifications occur in dinoflagellate 4-methyl sterols are considered, and a map of the fragmentation pattern of the trimethyysilyl-4-methyl sterols under electronic impact is also reported.
The surface sediments and overlying water column from 3 Recent sedimentary environments-Walvis Bay off southwestern Africa, the Black Sea and the western North Atlantic-have been analyzed for stenols and their transformation products, stanols, sterenes, and steroid ketones. The steroid distributions in surface sediments are controlled by inputs from source organisms and from microbial or chemically mediated reactions occurring at the sediment-water interface or in the overlying water column. A general correlation was found to exist for various steroidal compounds in sediments from each area, suggesting related reaction sequences. Also, the steroid transformation products correlated with photoproduction in the overlying waters as well as with the oxic and anoxic conditions of the sedimentary environment.