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A semi-automated digital microphotographic approach to measure meiofaunal biomass: Measurement of meiofaunal biomass
Limnology and Oceanography: Methods
Abstract
Meiofauna studies often investigate community structure and function where biomass estimates and taxo- nomic analysis are required. Nondestructive methods of biomass estimation are necessary to preserve specimens for subsequent taxonomic analysis. A semi-automated protocol to estimate meiofaunal biomass was developed to meet this need. The method improves upon previous indirect biomass techniques by using digital micropho- tography and analytical graphics software to obtain better estimates of biovolume. The technique is not fully automated because the digital images require some manipulation. Dry mass and carbon mass were estimated for two dominant components of marine benthic meiofauna (Nematoda and Harpacticoida) as the product of conversion factors and body volumes. The technique was validated by comparing indirect dry and carbon mass estimates to direct measurements using an analytical balance and carbon-hydrogen-nitrogen (CHN) elemental analyzer. No significant difference was found between the semi-automated method and direct measurements for harpacticoid dry or carbon mass (P = 0.68 and P = 0.74, respectively), or nematode dry mass (P = 0.28) or carbon content (P = 0.17). The semi-automated indirect method was used to estimate the biomass of meiofau- na (13,279 harpacticoids and 12,288 nematodes) collected from the deep-sea Gulf of Mexico. Estimated average wet mass was compared to direct analytical balance measurements from an earlier, independent study in the same area. Wet mass estimates generated by the indirect method (2.67 ± 0.86 µg/harpacticoid and 0.85 ± 4.78 µg/ nematode) were similar to direct measurements in the earlier study (2.80 µg/harpacticoid and 0.85 µg/nema- tode). The semi-automated indirect method is about three times faster than traditional microscope methods to measure body volume, estimates biomass comparably to direct methods, and conserves samples and images of samples for other analyses.
... Nematode biovolume was assessed on the basis of automatic measurements (by procedures in the Image Analysis module) and calculated using two different equations. The first equation is for the volume of a cylinder—a widely used equation for nematode biovolume estimations (e.g., McCulloch and Gems 2003; Baguley et al. 2004; Jung et al. 2012): where r [lm] is the radius (width/2) and L [lm] is the nematode length. The second equation is for the volume of rectangular cuboid corrected for a circular body shape using the conversion factor C cf according to Warwick and Price (1979): ...
... The described semi-automated method gave similar estimates of the total nematode biomass as the traditional manual measurements and was much less time-consuming and more objective in making certain required measurements (i.e., individual width). The method described here also has some obvious advantages over the semi-automated method proposed by Baguley et al. (2004). The latter method required that a group of nematodes was placed on slides—a preparatory step that was both quite time consuming and required a high level of precision and experience by the analyst . ...
... The major difference between the two semi-automatic methods is actually in the measurements that are to be collected. In our method, software measures the length and width of the animal, while in the approach used by Baguley et al. (2004) the area covered by an animal on the picture was measured automatically; however, the mid-body width (maximum width) was measured by a computer, but in a location that needed to be indicated manually. As we have shown, the manual selection of the point of maximum width is very subjective and can produce statistically significant differences between the measurements performed by different analysts. ...
Meiofaunal biomass, despite its ecological importance, is rarely assessed in marine ecological studies due to time-consuming and costly indirect procedures or inaccurate direct methods. Here, we present a semi-automated image analysis method for obtaining the widths and lengths of photographed nematodes that employs the Leica LAS Image Analysis module and is used to estimate Nematoda (a dominant marine meiofaunal taxon) biomass. Samples of 100 individual nematodes from 10 replicate samples representing two different environments (muddy fjord bottom and seagrass-vegetated sands) were used for the analyses, which were performed manually and semi-automatically. Manual measurements were taken by three independent analysts to check for individual differences. The automated measurements were collected almost two times faster than the manual ones. The three analysts and the computer did not differ in their assessments of nematode length, but significant differences existed among the measurements of maximum width by the three analysts (due to different designations of the point of nematode maximum width required by the manual method). For estimating individual nematode biomass, a formula using the equation for the volume of cylinder (one of the three tested in the study) is recommended. The total nematode biomass values obtained with this method were comparable to those reported from similar habitats. This semi-automated method seems to be less biased and more time and cost effective compared with standard manual protocols. The wider application of this method should facilitate the more frequent inclusion of meiofaunal biomass assessments in marine benthic surveys.
... size spectrum evaluation (Baguley, Hude, & Montagna, 2004;Broun et al., 2001;Vanaverbeke, Steyaert, Vanreusel, & Vincx, 2003;Vanreusel et al., 1995;Vanreusel, Vincx, Vangansbeke, & Gijselinck, 1992). In addition, a sieving method was used sometimes: sample was passed through a series of sieves and then the number of organisms retained by each sieve was counted and multiplied by the (previously estimated) mean weight of the given size fraction (Shirayama, 1984;Widbom, 1984). ...
... The values obtained by gravimetry were 2-fold higher than those from the volumetric method. In their recent study, Baguley et al. (2004) also obtained that mean weights for nematodes, determined gravimetrically, were 1.5 to 2-fold higher than those calculated volumetrically, depending on the details of the biovolume calculations. Another source for such difference may be the low estimate of specific weight used for converting volume to wet weight (1.13 for marine nematodes, Wieser, 1960). ...
... The formalin solution binds to substances, especially proteins, in the body of the preserved animal, resulting in the formation of non-volatile compounds that increase the dry weight (Jones, 1976;Landahl & Nagell, 1978). There is considerable variability in published conversion factors of linear dimensions/volume, dry/wet mass, carbon/dry mass, and specific gravity for nematodes and other meiobenthos that may lead to noticeable biases in calculations (Baguley et al., 2004). This discouraging result evidently points out that caution is necessary when data obtained by different methods are compared. ...
Relationships between nematode size and water depth were studied using 309 values of mean nematode individual weight (MNW) from 120 worldwide locations in the depth range from 0 to 8260 m. Neither the type of sampling device (tubes, box corer or multiple corer) nor sample size influence MNW, while the weight evaluation technique does: MNW values obtained by gravimetric measurements were twice as high as those obtained from comparable depth ranges by a volumetric method. For the whole depth range, MNW was negatively correlated with depth, mainly due to the significant (on average 3-fold) drop in nematode size across the top of the continental rise (usually at 500+ m) and deeper. This overall depth-related trend was clearly defined only in oligotrophic waters, in eutrophic regions the regressions were not significant. Multiple regression analysis showed that sediment composition and trophic conditions (pigment concentration or estimated POM flux) explained together from 40% to 60% of overall variations in MNW, while the effect of depth was not significant. Mean particle size determined a considerable part of total MNW variation in relatively shallow zones (continental shelf and upper slope) only. At depths of 200 m and deeper, where the heterogeneity of the sediments drops sharply, the influence of trophic factors increased 10-fold, yet the effect of sediments remained significant up to 2000 m. Under shallow waters down to 1000 m (except for the highly productive region of Peruvian upwelling), neither trophic factors nor depth had any effect, while the sediment properties were the only significant ones. Deeper, the effect of trophic factor is much more prominent in oligotrophic areas.
... However, meiofauna trophic interactions as well as community respiration in the deep sea are poorly understood. Rates of meiofauna grazing (Montagna, 1984Montagna, , 1993Montagna, , 1995) as well as accurate biomass measurements (Baguley et al., 2004) are necessary to validate deep-sea trophic structure models and gain understanding of meiofauna community function. Prior to the 1980s little was known of meiofauna trophic interactions with the microflora (i.e. ...
... Meiofauna biomass was calculated using a newly developed digital microphotographic approach (Baguley et al., 2004) for all samples at all DGoMB stations (Fig. 1). Briefly, all harpacticoids and a sub-sample of 30 nematodes were digitally photographed using a compound microscope. ...
... Briefly, all harpacticoids and a sub-sample of 30 nematodes were digitally photographed using a compound microscope. Area and width measurements were calculated using Sigma Scan Pro 4.0, analytical graphics software (Baguley et al., 2004). Nematode biovolume (V, in nl units) was estimated (sensu Baguley et al., 2004) by assuming nematode body shape is approximately cylindrical: ...
Metazoan meiofauna are ubiquitous in marine soft sediments and play a pivotal role in diagenesis of particulate organic matter. However, the relative importance of meiofauna to the function of deep-sea benthic boundary layer communities has not been resolved. Here, meiofauna biomass, respiration, and grazing on aerobic heterotrophic bacteria were estimated and compared to standing stocks and fluxes of other benthic components (e.g., bacteria and macrofauna). Biomass and respiration declined with depth. Highest biomass and respiration occurred in the proximity of the Mississippi River on the upper continental slope of the central Gulf of Mexico. Meiofauna required 7% of their biomass per day to meet their metabolic energy budget, compared to approximately 24% day−1 in shallow water. Respiration accounted for 8–22% of whole sediment community respiration (SCOC), reflecting the importance of meiofauna in diagenesis, deep-sea carbon budgets, and global biogeochemical cycles.
... The standing stocks were determined for each of the sampling sites, based on standard methods for quantitative assessments for each category within the community: bacteria, meiofauna (metazoans and Foraminifera), macrofauna, megafauna, and fishes. The chemical and physical properties of the sediments, bacterial stocks and biomass, and the metazoan meiofauna were estimated from subcores mounted within GOMEX box cores (Morse and Beazley, 2008;Deming and Carpenter, 2008;Baguley et al., 2004Baguley et al., , 2005Baguley et al., , 2008. The bacteria counts per wet sediment volume were based on epifluorescent staining (DAPI and Acridine Orange); the total biomass of bacteria was calculated from the sizes of the stained cells (Deming and Carpenter, 2008). ...
... ATP concentrations were converted to organic carbon using established conversions (DeLaca, 1986). The metazoan meiofauna standing stocks were based on ludox density separation, followed by sieving through 45 mm sieve, of the top 3 cm of subcores mounted within the box cores at all sites (Baguley et al., 2004). The macrofauna were sampled by sieving (4300 mm) the top 15 cm of the GOMEX box cores, with five replicates per site, aboard ship. ...
... The biomass of the meiofauna and the macrofauna were estimated from measurements of animal dimensions using an ocular micrometer and assuming a specific gravity of 1.2. This ''wet preserved weight'' was converted to carbon equivalents following conversion factors for macrofauna (Rowe, 1983) and meiofauna (see Baguley et al., 2004). The ''meiofauna'' category includes both the protists and the metazoans lumped together, in this analysis. ...
A budget of the standing stocks and cycling of organic carbon associated with the sea floor has been generated for seven sites across a 3-km depth gradient in the NE Gulf of Mexico, based on a series of reports by co-authors on specific biotic groups or processes. The standing stocks measured at each site were bacteria, Foraminifera, metazoan meiofauna, macrofauna, invertebrate megafauna, and demersal fishes. Sediment community oxygen consumption (SCOC) by the sediment-dwelling organisms was measured at each site using a remotely deployed benthic lander, profiles of oxygen concentration in the sediment pore water of recovered cores and ship-board core incubations. The long-term incorporation and burial of organic carbon into the sediments has been estimated using profiles of a combination of stable and radiocarbon isotopes. The total stock estimates, carbon burial, and the SCOC allowed estimates of living and detrital carbon residence time within the sediments, illustrating that the total biota turns over on time scales of months on the upper continental slope but this is extended to years on the abyssal plain at 3.6 km depth. The detrital carbon turnover is many times longer, however, over the same depths. A composite carbon budget illustrates that total carbon biomass and associated fluxes declined precipitously with increasing depth. Imbalances in the carbon budgets suggest that organic detritus is exported from the upper continental slope to greater depths offshore.
... The general workflow of the process in Zoo/PhytoImage, from the raw images to final descriptive statistics at the sample level, is presented in Fig 2. It can be split into three main stages: (1) image analysis and importation of data and metadata in R, (2) elaboration of training set(s) and classifier(s) coupled with their associated calibration and performance analysis and (3) their use for automatic classification of unknown samples 3 . Zoo/PhytoImage can analyze almost any kind of digital images. ...
... Calculation of the biomasses involves the use of an empirically-defined conversion function to convert from the area of the particles as measured in the digital images into the dry weight of the organisms, or their carbon content [1,3,14]. Providing you have such relationships available, processSample() is also able to calculate plankton biomasses. ...
This chapter illustrates supervised classification of objects based on features measured on digital images, as it works in R using the zooimage and mlearning packages. It focuses mainly on plankton images, but it is also usable in different but similar contexts. Plankton is a diverse community of organisms that live in aquatic environments far away from hard substrate. Its diversity and the patchiness in its distribution, both in time and space, make it difficult to sample and to study. Automated classification of plankton digital images with machine learning algorithms in R has been used for the past few years to speed up the process of the large amounts of samples typically encountered in oceanographic campaign. Through the analysis of a sample dataset of tropical zooplankton from Madagascar, we show how the zooimage R package, and the Zoo/PhytoImage software, contributed to the adoption of R for such a task. More particularly, we insist on the integration of data mining tools inside a larger workflow, from the processing of raw images to the calculation of derived statistics usable by the ecologist. Challenges and difficulties associated with this complex multiclass supervised classification application are also discussed.
... Photographic techniques have already been used in a variety of benthic studies (e.g., Gutt et al. 1999;Gutt et al. 1996;Jørgensen and Gulliksen 2001;Pech et al. 2004;Piepenburg and Schmid 1997) where the main goal of image analysis was to extract information about covered areas or counting data of classified features in the picture. Volume and biomass estimations have also been conducted using photo images (Abdo et al. 2006;Baguley et al. 2004). Techniques involving color, edge contrast, or sharpness correction of the whole image or parts of it have been applied to improve data extraction and reduce processing time (Andresen 2003;Dahab et al. 2004;Taylor 2003b). ...
... The key here was to automate as many of the recurring tasks as possible, especially when large numbers of pictures should be analyzed (Taylor 2003a). One strategy was the automatic recognition of surfaces (Baguley et al. 2004) or landscape patterns (Teixido et al. 2002) that can be related to species or community characteristics. Another approach was the application of point-sampling methods by superimposing grids on the image and subsequent quantification of objects at the intersections of the gridlines (Gatlin et al. 1993;Roberts et al. 1994). ...
Benthic rocky bottom studies often investigate community structure and function where estimates of percentage cover and abundance of epibenthic organisms are required. Nondestructive photographic methods have the advantage of preserving benthic communities for repeated sampling. There is a need to accelerate image processing to make sample analysis more cost efficient and to make the data available in a timely manner. A semiautomated procedure to estimate epibenthic cover and abundance using Adobe Photoshop and the image analysis plug-in Fovea Pro was developed to meet this need. The method improves upon previous techniques by using color-based automated selection tools and a species-coding system. The technique required some manual processing because some species were less suitable for color recognition and the photographs were of inconsistent quality. The semiautomated selection of colony-forming organisms was validated by comparing it to a strictly manual approach using a data set from Balsfjord/northern Norway. Constrained ordination and Procrustes analyses showed that the automatic and manual methods were equally effective at documenting variation in the species/abundance data along the driving ecological gradient of depth. The minor deviations in species abundance estimation between the two methods (mostly <20%) were unrelated to the depth gradient and thus had negligible influence on the main ecological conclusions of the study. The semiautomated method is up to four times faster than the manual approach, has clear advantages over former benthic image analysis methods, and is well suited for detection of systematic biological patterns like ecological gradients.
... On the other hand, there are non-destructive estimates of biomass based on a combination of independent factors including counts, biovolume determined from measures of individual body size (length and width), conversion factors determined from body shape and chemical measurements. Biovolume estimates and conversion factors required by indirect methods increase opportunities for error, because error associated with multiple independent factors can be propagated at each stage of calculation (Baguley et al., 2004). However, these procedures preserve the samples and allow further taxonomical and ecological studies. ...
... Despite the growing worldwide interest in the application of this software (Benfield et al., 2007;Gislason and Silva, 2009), few studies to date have used it to estimate copepod biomass (Zarautz et al., 2008). Image analysis though, has long been used for biovolume estimation of copepods and zooplankton (Alcaraz et al., 2003;Baguley et al., 2004;Billones et al., 1999;Clark et al., 2001). ...
... This decline is partially explained by the decrease in average metazoan size with water depth [8]. The size of individual nematodes has also been noted to decrease with depth in the deep sea [9,10] and has been attributed to the typically decreasing availability of food and decreasing sediment grain size. Studies on the functional diversity of nematodes as determined by buccal morphology show that with increasing water depth deposit feeders predominate while predators were less dominant [10]. ...
... The meiobenthic samples were two of the seven subsamples with the box, each with a 5.5 cm inner diameter and a circular surface area of 22.9 cm 2 . The meiofauna were extracted by sieving through a 45 mm mesh sieve and centrifugation with Ludox [9]. Macrobenthos from the Arctic deep-sea Canada Basin were collected from a total of 22 quantitative box corer casts at a total of 8 stations at depths of 640–3961 m (Figure 1). ...
Nematodes occur regularly in macrobenthic samples but are rarely identified from them and are thus considered exclusively a part of the meiobenthos. Our study compares the generic composition of nematode communities and their individual body weight trends with water depth in macrobenthic (>250/300 µm) samples from the deep Arctic (Canada Basin), Gulf of Mexico (GOM) and the Bermuda slope with meiobenthic samples (<45 µm) from GOM. The dry weight per individual (µg) of all macrobenthic nematodes combined showed an increasing trend with increasing water depth, while the dry weight per individual of the meiobenthic GOM nematodes showed a trend to decrease with increasing depth. Multivariate analyses showed that the macrobenthic nematode community in the GOM was more similar to the macrobenthic nematodes of the Canada Basin than to the GOM meiobenthic nematodes. In particular, the genera Enoploides, Crenopharynx, Micoletzkyia, Phanodermella were dominant in the macrobenthos and accounted for most of the difference. Relative abundance of non-selective deposit feeders (1B) significantly decreased with depth in macrobenthos but remained dominant in the meiobenthic community. The occurrence of a distinct assemblage of bigger nematodes of high dry weight per individual in the macrobenthos suggests the need to include nematodes in macrobenthic studies.
... CC BY 4.0 License. 12% for meiofauna (Baguley et al., 2004) and 4.3% for macrofauna (Rowe, 1983). Finally, all the OC stock of fauna was divided by the sampling area and then converted to the unit of mg C m -2 . ...
The Gaoping Submarine Canyon (GPSC) off Southwest Taiwan has been extensively studied due to its unique geology, the role of transferring terrestrial material to the deep sea, and diverse biological communities. However, there is a lack of understanding of carbon cycling across the sediment–water interface in the canyon. This study aims to fill the gap by utilizing the field data collected between 2014 and 2020 and the Linear Inverse Model (LIM) to reconstruct the benthic food web (i.e., carbon flows through different stocks) in the head of GPSC and the upper Gaoping slope (GS). The biotic and abiotic organic carbon (OC) stocks were significantly higher on the slope than in the canyon, except for the bacteria stock. The sediment oxygen utilization was similar between the two habitats, but the magnitude and distribution of the OC flow in the food web were distinctively different. Despite a significant input flux of ~1400 mg C m−2 d−1 in the canyon, 85 % of the carbon flux exited the system, while 14 % was buried. On the slope, 75 % of the OC input (~105 mg C m−2 d−1) was buried, and only 11 % exited the system. Bacteria processes play a major role in the carbon fluxes within the canyon. In contrast, the food web in the upper slope exhibited stronger interactions among metazoans, indicated by higher fluxes between meiofauna and macrofauna compartments. Network indices based on the LIM outputs showed that the canyon head had higher total system throughput (T..) and total system through flow (TST), indicating greater energy flowing through the system. In contrast, the slope had a significantly higher Finn cycling Index (FCI), average mutual information (AMI), and longer OC turnover time, suggesting a relatively more stable ecosystem with higher energy recycling. Due to sampling limitations, the present study only represents the benthic food web during the “dry” season. By integrating the field data into a food web model, this study provides valuable insight into the fates of OC cycling in an active submarine canyon, focusing on the often overlooked benthic communities. Future studies should include “wet” season sampling to reveal the effects of typhoons and monsoon rainfalls on OC cycling.
... Detection of jellyfish in situ has been achieved by the establishment of a jellyfish camera system by Graham et al. (2003). A semi-automated digital microphotographic approach was developed to measure meiofaunal biomass by Baguley et al. (2004). Furthermore, using acoustic techniques for jellyfish monitoring has been reported. ...
The Liaoning Hongyan River Nuclear Power Plant is located on the east coast of Liaodong Bay in the Bohai Sea, China, and the safety of the cooling water is often threatened by large-scale jellyfish outbreaks. Thus, monitoring jellyfish growth, migration, and disappearance is essential to the safety of the nuclear power plant. In this study, high-throughput sequencing was used to analyze the community characteristics of mesoplankton in the sea area at the inlet and outlet from April to September 2019. At the same time, the micro-individuals of jellyfish (including oosperm, planula, polyps, or ephyra of jellyfish) in the water were detected by real-time fluorescent quantitative PCR (qPCR). Both the maximum abundance of Aurelia coerulea and Nemopilema nomurai in July were detected by high-throughput sequencing and qPCR. Only three common taxa of plankton (Paracalanus, Calanoida, and Poaceae) were found in the waters near the inlet and outlet, and the beta diversity of plankton in the waters near the inlet and outlet was low in the same period. Based on the plankton community composition in the sea water near the inlet, it could be speculated that jellyfish outbreaks would have a significant impact on the plankton via the predation effect. The maximum mt-16S rDNA copy numbers of A. coerulea and N. nomurai in the samples from the waters of Liaodong Bay were detected in June 2019, and that of N. nomurai showed an increasing trend from north to south, with the jellyfish tending to move to the seawaters near the plant. The results indicate that the optimum monitoring period for jellyfish outbreaks in Liaodong Bay is from the end of May to the end of July.
... For small-sized prey, such as prodissoconch bivalves (~ 0.2 mm), halacarids, ostracods (< 1 mm) and copepods (< 1 mm) the wet mass was estimated as average value calculated on a larger sample of specimens. Wet mass of nematods was derived from published data (Baguley et al. 2004) because of a small total number of specimens found in the diet of material examined. Wet mass of the entire gut content (W GC ) was calculated as the total weight of all prey items and unidentifiable remains (Kovačić 2007). ...
... Thus, the nematode individual wet weight (μg) that was calculated using Andrássy's formula (1956) was converted into dry weight applying a dry/wet weight ratio of 0.25 (Wieser, 1960). Next, nematode ash free dry weight (AFDW) was calculated by multiplying the dry weight with a factor of 0.51 (Baguley et al., 2004), and was converted into grams (g). The weight values were expressed as energy units using a conversion factor given by Peters (1983), where 1 g (AFDW) = 5.3 kcal (Ceccherelli and Mistri, 1991). ...
Knowledge regarding the benthic community structure (macro- and meiofauna) and its production is crucial for understanding the consequences of ongoing climate change, yet it is still limited, particularly concerning springtime. This is the first study to provide information on the community characteristics and secondary production of macro- and meiofauna collected in the European sector of the Arctic Ocean, along a depth gradient, from shallow Svalbard fjords, the Barents Sea shelf and slope, to the deep Nansen Basin and the Yermak Plateau north off Svalbard. Our results show significant differences in benthic fauna community structure and productivity among fjords, shelf and northern deep stations. Density, biomass, and secondary production decreased significantly with depth, following the decrease in quantity and quality of organic matter reaching the sea floor. Macrofauna was dominated by polychaetes and bivalves, and meiofauna by nematodes. Nematode production was higher than that of macrofauna in areas where no or very limited fresh organic matter was available. We conclude that nematode production in the deep-sea sediments of the Arctic Ocean can be an important component of the benthic communities, and thus carbon cycling, but this relation will likely be influenced by ongoing climate change and related sea ice retreat and, therefore, changes in primary production patterns.
... The estimation of mass from a single measured dimension (SL) relies on a consistent relationship between the measured dimension and the two unmeasured dimensions, whereas the volumetric approach measures two dimensions, with the second-dimension measurement (ECD) subjectively modified to be representative of the third unmeasured dimension. Further, as previously discussed, the mass of an individual of a given standard length may be, for example, substantially influenced by its life stage, physical condition, feeding success, health, season, and geographic location (e.g.Meyer 1989;Primavera et al. 1998; Kimmerer et al. 2005;Méthot et al. 2012;Mahé et al. 2016;Zilli et al. 2017).The volumetric assessment of individual biomass is frequently used in the study of microscopic and small-bodied organisms(Baguley et al. 2004;Mustard and Anderson 2005; Novack-Gootshall 2008;Mazurkiewicz et al. 2016). Studies of macro-and megafaunal marine organism biovolume have previously been used as an indicator of relative biomass, or the physical space occupied by individuals(McClain 2004;Jones et al. 2007;McClain and Boyer 2009 ...
This study attempts to advance the quantitative ecology of the megabenthos by (i) adopting and developing the use of mass seabed photography, and by(ii) extending body-size-based ecosystem assessment to this group. The metabolic theory of ecology (MTE) builds from simple bio-energetic assumptions of individual metabolism to make predictions about ecological processes from individual structure and functioning, to community and ecosystem dynamics. Under the ‘energetic equivalence rule’, or Damuth’s rule, the population density of living organisms is related to a -3/4 power of body mass, indicating equal resource acquisition across body-size classes. In the marine environment, meio- to macrobenthic assemblages have be usefully modelled as a notional single trophic level, suggesting energetic equivalence throughout the two fractions. That concept is tested here by extension to the megabenthos. The body-size structure of benthic assemblages was examined in four contrasting settings: two shelf-sea sites in the Celtic Sea (Greater Haig Fras marine conservation zone; Shelf-Sea Biogeochemistry area), and two deep sea sites (Porcupine Abyssal Plain sustained observatory, PAP-SO, northeast Atlantic; Clarion-Clipperton Zone, CCZ, northeast Pacific). Imagery data were collected using autonomous underwater vehicles, allowing consistent assessment of the megabenthos in the form of individual-based body-size spectral analyses, over landscape-scale areas encompassing multiple habitat types. For the well-known Celtic Shelf and PAP-SO assemblages, species specific length-weight relationships were used to derive individual biomass data. However, that was not possible for the poorly studied CCZ fauna, prompting the development of a generalised volumetric method for individual body-mass estimation. The MTE framework was used to investigate the effects of seafloor temperature and resource supply on the stocks and flows of mass and energy at these sites. The results of this study demonstrate the practical advantage of mass seabed photography in the quantitative ecological assessment of the megabenthos. The volumetric methodology developed overcomes the taxonomic, temporal, and spatial, dependencies known to impact length-weight relationships. The megabenthos body-size distributions produced were broadly consistent across sites, and generally conformed to the MTE expectations, i.e. controlled by both seafloor temperature and resource supply. These results suggest a much greater ecological significance of the megabenthos than has generally been assumed, i.e. at the PAP-SO site they account for 93% of the total metabolically active standing stock carbon biomass, and 27% of total benthic carbon respiration. Individual-based body-size spectral analyses, coupled with the MTE framework, provide a robust baseline for assessing ecological patterns, and for monitoring change.
... Biovolume estimates and conversion factors required by indirect methods increase opportunities for error because the error associated with multiple independent factors can be propagated at each stage of calculation [38,39]. ...
LifeWatch Italy, the Italian node of LifeWatch ERIC, has promoted and stimulated the debate on the use of semantics in biodiversity data management. Actually, biodiversity and ecosystems data are very heterogeneous and need to be better managed to improve the actual scientific knowledge extracted, as well as to address the urgent societal challenges concerning environmental issues. LifeWatch Italy has realized the Phytoplankton Virtual Research Environment (hereafter Phytoplankton VRE), a collaborative working environment supporting researchers to address basic and applied studies on phytoplankton ecology. The Phytoplankton VRE provides the IT infrastructure to enable researchers to obtain, share and analyse phytoplankton data at a level of resolution from individual cells to whole assemblages. A semantic approach has been used to address data harmonisation, integration and discovery: an interdisciplinary team has developed a thesaurus on phytoplankton functional traits and linked its concepts to other existing conceptual schemas related to the specific domain.
... Individual nematode length [excluding filiform tail tips; L (µm)] and maximum body width [W (µm)] was measured under the compound microscope (Olympus BX-50) with Olympus CellˆD software, and body volume estimated by applying Andrassy's formula (wet weight; Andrassy, 1956;Wieser, 1960). A ratio of a 0.124 was assumed to convert nematode wet weight into carbon weight (µgC; Baguley et al., 2004). ...
Understanding the effects of bottom-trawling induced changes in benthic community structure, diversity and ecosystem functioning across different benthic-size components is imperative to determine the future sustainability of bottom-trawling fisheries in deep-sea regions. In this study, we combined field sampling observations with a pulse-chase experiment on sediments obtained from two stations of interest along the West Iberian Margin (WIM) distinguished by different trawling pressures. We compared these two stations in terms of meio-and macrofauna (infauna) standing stocks, biodiversity and several ecosystem function proxies. These proxies included: (i) 13 C uptake by bacterial communities, (ii) infauna respiration rates, (iii) penetration of 13 C in the sediment, and (iv) sediment pore-water nutrient concentrations. The pulse-chase experimental results were complemented with a larger biological dataset partially compiled from previous studies in the area, to investigate structural and functional diversity ecosystem functioning (respiration) patterns across the WIM. Our observations indicated that different regimes of trawling pressure influenced both macrofaunal respiration rates with disturbed sediments predominantly composed of deposit-/detritus-feeding smaller-sized macrofauna species. Moreover, sediment biogeochemical functioning (ammonium profiles) and 13 C bacterial uptake showed differences among the two disturbance regimes. On the contrary, the biomass of small-sized biota, including bacteria and meiofauna, did not show marked differences between stations. The general depletion in macrofauna species richness across impacted areas of the study region was also correlated with a reduction in total biomass and respiration, suggesting that the long history of trawling disturbance at the WIM may affect regulatory ecosystem functions. These preliminary findings alert for the impacts of trawling on crucial functions of benthic ecosystems that may be imperceptible to the current tools used in monitoring programs.
... Individual nematode length [excluding filiform tail tips; L (µm)] and maximum body width [W (µm)] was measured under the compound microscope (Olympus BX-50) with Olympus CellˆD software, and body volume estimated by applying Andrassy's formula (wet weight; Andrassy, 1956;Wieser, 1960). A ratio of a 0.124 was assumed to convert nematode wet weight into carbon weight (µgC; Baguley et al., 2004). ...
Understanding the effects of bottom-trawling induced changes in benthic community structure, diversity and ecosystem functioning across different benthic-size components is imperative to determine the future sustainability of bottom-trawling fisheries in deep-sea regions. In this study, we combined field sampling observations with a pulse-chase experiment on sediments obtained from two stations of interest along the West Iberian Margin (WIM) distinguished by different trawling pressures. We compared these two stations in terms of meio- and macrofauna (infauna) standing stocks, biodiversity and several ecosystem function proxies. These proxies included: (i) ¹³C uptake by bacterial communities, (ii) infauna respiration rates, (iii) penetration of ¹³C in the sediment, and (iv) sediment pore-water nutrient concentrations. The pulse-chase experimental results were complemented with a larger biological dataset partially compiled from previous studies in the area, to investigate structural and functional diversity ecosystem functioning (respiration) patterns across the WIM. Our observations indicated that different regimes of trawling pressure influenced both macrofaunal respiration rates with disturbed sediments predominantly composed of deposit-/detritus-feeding smaller-sized macrofauna species. Moreover, sediment biogeochemical functioning (ammonium profiles) and ¹³C bacterial uptake showed differences among the two disturbance regimes. On the contrary, the biomass of small-sized biota, including bacteria and meiofauna, did not show marked differences between stations. The general depletion in macrofauna species richness across impacted areas of the study region was also correlated with a reduction in total biomass and respiration, suggesting that the long history of trawling disturbance at the WIM may affect regulatory ecosystem functions. These preliminary findings alert for the impacts of trawling on crucial functions of benthic ecosystems that may be imperceptible to the current tools used in monitoring programs.
... The volumetric assessment of individual biomass is frequently used in the study of microscopic and small-bodied organisms (Baguley et al. 2004;Mustard and Anderson 2005;Novack-Gottshall 2008;Mazurkiewicz et al. 2016). Studies of macro-and megafaunal marine organism biovolume have previously been used as an indicator of relative biomass, or the physical space occupied by individuals (McClain 2004(McClain , 2009Jones et al. 2007). ...
Biomass is a key variable for understanding the stocks and flows of carbon and energy in the environment. The quantification of megabenthos biomass (body size ≥ 1 cm) has been limited by their relatively low abundance and the difficulties associated with quantitative sampling. Developments in robotic technology, particularly autonomous underwater vehicles, offer an enhanced opportunity for the quantitative photographic assessment of the megabenthos. Photographic estimation of biomass has typically been undertaken using taxon-specific length-weight relationships (LWRs) derived from physical specimens. This is problematic where little or no physical sampling has occurred and/or where key taxa are not easily sampled. We present a generalised volumetric method (GVM) for the estimation of biovolume as a predictor of biomass. We validated the method using fresh trawl-caught specimens from the Porcupine Abyssal Plain Sustained Observatory (northeast Atlantic), and we demonstrated that the GVM has a higher predictive capability and a lower standard error of estimation than the LWR method. GVM and LWR approaches were tested in parallel on a photographic survey in the Celtic Sea. Among the 75% of taxa for which LWR estimation was possible, highly comparable biomass values and distribution patterns were determined by both methods. The biovolume of the remaining 25% of taxa increased the total estimated standing stock by a factor of 1.6. Additionally, we tested inter-operator variability in the application of the GVM, and we detected no statistically significant bias. We recommend the use of the GVM where LWRs are not available, and more generally given its improved predictive capability and its independence from the taxonomic, temporal, and spatial, dependencies known to impact LWRs.
... Count data from zooplankton tow and fish gut samples were transformed to biomass using estimates of carbon content (μg C animal −1 ) for each prey group (Table 1). Biomass estimates for similar taxa were obtained from the literature and adjusted for discrepancies in the body size of animals sampled from fish guts in Moorea relative to the size of the reference organisms (Yúfera et al. 1999;Satapoomin 1999;Logerwell and Ohman 1999;Baguley et al. 2004;Alldredge and King 2009;Almeda et al. 2010). The environmental zooplankton samples from each collection location were used to calculate expected dietary evenness and percent contribution of oceanic and reef-associated taxa to fish diet under random feeding. ...
Combining gut content analysis and sampling of ambient zooplankton, we examine departures from random feeding in a planktivorous coral reef fish and explore the effects of apparent non-random feeding behavior on the relative contribution of oceanic versus reef-associated zooplankton to fish diet. The planktivorous damselfish Dascyllus flavicaudus appears to exhibit strong positive electivity for oceanic copepods including Candacia spp. and copepods from the families Oncaeidae and Corycaeidae and consistent negative electivity for cyclopoid copepods (Oithonidae). In total, prey taxa categorized as oceanic in origin contributed 10–76 % of total zooplankton biomass in fish guts. The summed contribution of oceanic prey taxa to fish diet was significantly higher than expected under a model of random feeding based on the availability of oceanic versus reef-associated prey as sampled by zooplankton net tows. The feeding behavior of D. flavicaudus appears to be visibility-selective rather than or in addition to size-selective, as electivity across prey taxa could not be explained by differences in prey size alone.
... Nonetheless, empirical determinations have suggested a dry mass to carbon conversion factor of 51.4% is more appropriate (Baguley et al., 2004). This would tend to increase the figure calculated for carbon biomass of nematodes within the lagoon. ...
... While in the holding container, twenty individuals from each taxon were selected to determine mean dry weight biomass (mg) (EPA Great Lakes National Program Office, 2003). In order to preserve specimens for subsequent analysis, nondestructive indirect biomass estimation techniques were utilized (Baguley et al., 2004). Digital photos were taken of each individual in the chamber using a Dino-Lite AM-2011 Digital Microscope, and individuals were measured (mm) using ImageJ 1.45s software (Schneider et al., 2012). ...
Biotic interactions between herbivores and primary producers are believed to play a major role in determining community composition of many ecological communities. How differences in herbivore abundance alter the relative importance of these interactions is not well understood, especially in seasonal wetland systems. This study investigated the effects of varying Pseudacris regilla (pacific chorus frog) larval densities on California vernal pool aquatic communities. It was hypothesized that with increasing tadpole density, macrophyte abundance, percent cover, biomass and richness would decrease; while algae and zooplankton abundance, biomass and richness increase. The experimental mesocosm design consisted of five tadpole density treatments, and was arranged in a 5 × 5 randomized block design. Each density treatment was replicated five times. Macrophytes, algae and invertebrates were identified to the lowest possible taxonomic unit, and the biomasses of each community were quantified. Treatment effects were determined using both multivariate and univariate analysis of variance techniques. To detect differences in community composition, multivariate ordination analyses (ANOSIM, SIMPER, nMDS) were conducted. Increasing densities of P. regilla tadpoles had a large impact on the vernal pool macrophyte community. Plant abundance, diversity, biomass, percent cover and species richness were all negatively impacted by increasing tadpole densities. Macrophyte community structure was also found to be significantly different in the presence of tadpoles due to the fact that D. bicornuta, R. aquatilis, and G. ebracteata were predominately isolated to mesocosms were P. regilla was absent. In addition, periphyton biomass was shown to be facilitated by increasing tadpole densities in the lower treatment ranges. Aquatic macroinvertebrates and phytoplankton communities, on the other hand, were not significantly affected by increasing tadpole densities. This study demonstrates the impact of P. regilla larvae on the primary producers within California vernal pool systems. Understanding the impact of these abundant consumers, and the mechanisms that drive the importance of their direct and indirect effects are essential for the conservation of vernal pools and the threatened species associated with them.
... No sedimento, os Nematoda geralmente são mais abundantes, representando 60-90% da fauna total e os Copepoda vêm geralmente em segundo lugar com 10-40% (COULL, 1999). No entanto, com o aumento da profundidade, a biomassa média dos Nematoda tende a diminuir enquanto que a dos Copepoda Harpacticoida aumenta (BAGULEY et al., 2004). ...
Meiofauna is an ecologically heterogeneous group that occupies a variety of benthic habitats in marine environments. Meiofauna is defined in terms of size and habitat. Meiofauna communities are characterized by high taxonomic diversity compared to macrofauna and microfauna. In the process of colonization and succession of meiofauna on substrates recently made available, the first phases are moving fast and then slow further as niches are being filled. Due to its rapid response to changes in environment, meiofauna is indicated as a useful tool in studies of environmental quality.
... For copepods we used the regional relationship established by . For appendicularians, ctenophores, chaetognaths, and other gelatinous organisms, we used the conversion factors of Lehette and Hernandez-Leon (2009) assuming a 30 % carbon content in the DW of appendicularians and medusae (Deibel, 1986;Larson, 1986) and a 50 % carbon content in the DW of chaetognaths (Baguley et al., 2004). For protozoans we used the mean conversion factor for foraminifers and radiolarians of Michaels et al. (1995). ...
A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here we combine mooring times series, ship-based measurements and remote sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their determinants in summer. Flux data were obtained with sediment traps moored around 125 m and via a regional empirical algorithm applied to particle size distributions (17 classes from 0.08–4.2 mm) measured by an Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy particles) derived from the algorithm (1.26 ± 0.34) and the dominance (~ 77%) of rapidly sinking small aggregates (< 0.5 mm) in total fluxes suggested that settling material was the product of recent aggregation processes between marine detritus, gel-like substances, and ballast minerals. Modeled settling velocity of small and large aggregates was, respectively, higher and lower than in previous studies within which a high fractal dimension (i.e., more compact particles) was consequential of deep-trap collection (~400–1300 m). Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e., principal coordinates of neighbor matrices, PCNM) were conducted to partition the variation of the 17 POC flux size classes. Flux variability was explained at 69.5% by the addition of a temporal trend, 7 significant PCNM, and 9 biophysical variables. The first PCNM canonical axis (44.5% of spatial variance) reflected the total magnitude of POC fluxes through a shelf-basin gradient controlled by bottom depth and sea ice concentration (p < 0.01). The second most important spatial structure (5.0%) corresponded to areas where shelf break upwelling is known to occur under easterlies and where phytoplankton was dominated by diatoms. Among biophysical parameters, bacterial production and northeasterly wind (upwelling-favorable) were the two strongest corollaries of POC fluxes (r2 cum. = 0.37). Bacteria were correlated with small aggregates, while northeasterly wind was associated with large size classes (> 1 mm ESD), but these two factors were weakly related with each other. Copepod biomass was overall negatively correlated (p < 0.05) with vertical POC fluxes, implying that metazoans acted as regulators of export fluxes, even if their role was minor given that our study spanned the onset of diapause. Our results demonstrate that on interior Arctic shelves where productivity is low in mid-summer, localized upwelling zones (nutrient enrichment) may result in the formation of large filamentous phytoaggregates that are not substantially retained by copepod and bacterial communities.
... For small-sized prey, such as prodissoconch bivalves (~ 0.2 mm), halacarids, ostracods (< 1 mm) and copepods (< 1 mm) the wet mass was estimated as average value calculated on a larger sample of specimens. Wet mass of nematods was derived from published data (Baguley et al. 2004) because of a small total number of specimens found in the diet of material examined. Wet mass of the entire gut content (W GC ) was calculated as the total weight of all prey items and unidentifiable remains (Kovačić 2007). ...
... These techniques often involve the use of color, edge contrast, or sharpness correction of the entirety, or subsections , of a collected image (Diaz et al. 2003; Dahab et al. 2004; Beuchel et al. 2010). Another method that has been used is automatic recognition of individuals (Baguley et al. 2004) or landscape patterns (Teixido et al. 2002) that can be generalized to community characteristics. An alternative method to traditional platforms (e.g., divers, moored cameras, etc.) for benthic image collection is the use of small autonomous underwater vehicles (AUVs; Singh et al. 2004). ...
The establishment, spread, and impact of the invasive bivalve Corbicula fluminea (C. fluminea), in Lake Tahoe
threatens native species distribution in the lake and, potentially, has long-term implications for water clarity. In
2009, UBC-Gavia, an Autonomous Underwater Vehicle (AUV), was used as a platform to collect georeferenced
imagery of the benthic regions of Lake Tahoe to determine the lake-wide distribution of C. fluminea. Images
were collected in water depths less than 10 m at an approximately constant height above the bottom of 2 m.
Images were processed using a semi-automated procedure to determine the ratio of the lakebed covered by
exposed C. fluminea shells. A visual review was conducted on a subset of the images to determine presence of
filamentous algae that has been observed in association with C. fluminea. Nearly 100 km of shoreline was covered
over a 7-d period, and C. fluminea presence was reconfirmed in 4 regions and additional 10 regions identified.
In regions where the presence of C. fluminea was confirmed, C. fluminea depth distribution was validated
by comparing image detection counts and results from a benthic sediment grab sample survey. Three regions
around the lake were identified to have filamentous green algae or charophyte species. It was impossible to identify
species of the known filamentous algal taxa (Cladophora glomerata, Spirogyra spp., and Zygnema spp.). The
collected imagery provides a synoptic view on species distribution within the lake that can be used for efficient
monitoring of invasive species in freshwater and saltwater bodies.
... Nematodes were grouped into 3 size categories, with the average dimensions based on measurements of 5 to 20 individuals at each location. Individual dimensions were used to calculate biovolume and, in turn, the biomass of protists (Putt & Stoecker 1989, Wetzel & Likens 1991 and nematodes (Baguley et al. 2004). ...
We examined benthic microbial communities in 3 contrasting subtidal salt marsh sediments over the course of a year to investigate the relationship between environmental conditions and benthic microbial community structure. Samples were collected monthly from a high-energy sandy beach, a tidal creek bed, and a Spartina alterniflora marsh border. The oncentrations and biomasses of benthic microalgae (BMA), total and potentially active bacteria (measured by an enzyme-activated fluorogenic compound), heterotrophic protists, and metazoan meiofauna were measured at each location. Sediment grain size and porewater pH explained most of the variability in biomass distributions; variations in benthic biomass did not correlate well with temperature. There was a seasonal shift from a BMA-dominated community in the spring and summer months to bacteria-dominated communities in autumn at all locations, when inactive bacteria were most abundant. When normalized to sediment porewater volume, benthic protists concentrations were not significantly related to sediment porosity. Benthic protist porewater concentrations (mean: 3.4 × 10 3, range: 0.1 to 9.3 × 103 protists ml-1) were comparable to protist concentrations in the water column. In contrast, bacteria were several orders of magnitude more concentrated in the sediments (mean: 4.2 × 109; range: 0.6 to 16 × 109 bacteria ml-1) than the water column. Low abundances of protists relative to bacteria appear to contribute to long bacterial turnover times, especially in fine-grained sediments. We hypothesize that both grazing by meiofauna and low anaerobic growth efficiency lead to relatively low biomass of bacterivorous protists.
... Nematodes were grouped into 4 size categories with the average dimensions based upon 60 individuals. Individual dimensions were used to calculate biovolume and biomass of protists (Putt & Stoecker 1989, Wetzel & Likens 1991 and nematodes (Baguley et al. 2004). ...
We examined 8 sediment samples collected at 3 h intervals at Dean Creek (Sapelo Island, Georgia) to assess the impact of protist bacterivory on the standing crops of benthic bacterial biomass. The combined biomass of the benthic microalgae (BMA), bacteria, heterotrophic protists, and meiofauna ranged from 0.41 to 0.57 mg C g–1 wet sediment (gws) in the samples examined. BMA represented >80% of total biomass and remained relatively stable throughout the study period. Bacterial biomass ranged from 28 to 91 µg C gws–1 (5 to 16% of total biomass) in the samples. Heterotrophic protists (mainly ciliates, flagellates, and testate amoeba) and meiofauna (mainly nematodes) each contributed small (<1% each) amounts to the total biomass. Protist grazing accounted for the loss of <1.1 and <4.7% h–1 of the total and enzymatically active bacterial standing stock, respectively. Grazing rates were highest in the morning samples, concurrent with the highest portion of potentially active bacteria. However, there was no statistically significant change in grazing impact throughout the day and in most cases bacterivory would not reduce the standing bacterial biomass. Food web simulations demonstrate that the confluence of protist loss factors (such as meiofaunal predation) and reduced grazing at low bacterial concentrations can limit the production of bacterivorous protists and, in turn, their use of the large store of benthic bacterial biomass.
... Their biovolumes were calculated from length and width measurements and converted to wet weight. The wet weight was converted to dry weight and carbon content (Feller and Warwick 1988;Baguley et al. 2004). ...
The benthic microbial food web can be responsible for a large proportion of benthic carbon cycling yet there are few data
on the trophic interactions between this food web and macrobenthos. A large-scale field experiment was conducted to investigate
effects of eliminating the polychaete Arenicola marina on benthic microbes (prokaryotes, heterotrophic and autotrophic protists) and metazoan meiofauna in a marine intertidal flat
of the North Sea, Germany. Over a period of 2 years, quantity and composition of micro- and meiobenthos from unmanipulated
sites were compared to those from sites deplete of lugworms. These grazer treatments were cross-classified with different
sediment characteristics (low- and mid-intertidal areas). Lugworm removal resulted in an initial increase in abundance of
prokaryotes and nanoflagellates, which became less pronounced in the second year. Ciliates were not affected quantitatively,
but in the absence of lugworms, diversity and the proportion of carnivorous forms increased. Meiobenthos (nematodes, ostracods
and copepods) were affected only moderately. The observed changes are probably due to a combination of release from grazing/predation
pressure, changes in the species composition of higher trophic levels (namely large polychaetes) and altered environmental
conditions (such as depth of the oxygenated layer and sediment grain size). Spatial differences between sites of different
tidal exposure/grain size appeared to be as large as temporal differences during the 2 years following the manipulation of
the system. We conclude that in intertidal sediments, indirect effects due to habitat transformation are as important as direct
biological interactions (grazing pressure and competition) for the dynamics of the benthic microbial food web.
... Also, SHA detection cannot differentiate between living individuals and their remnants in the gut contents or feces of planktonic predators. Calibration curves might be improved through quantification of target biomass rather than individual numbers (Baguley et al., 2004). To assess their precision, calibration curves for specific targets should be re-investigated in mixed cultures involving a more natural diversity of zooplankton taxa. ...
... Narcotizing meiofauna is necessary to minimize body shape distortion during the preservation process. Preventing animal distortion was critical for biomass calculations and taxonomic identifications (see Baguley et al., 2004;Baguley et al., 2006 in revision). Samples were then preserved in an equal volume of 10% buffered formalin (yielding a final concentration of 5% formalin) (Hulings and Gray, 1971). ...
In order to more fully understand the distribution of meiofauna and how they respond to topographic, geochemical and physical forcing in the northern Gulf of Mexico, meiofauna abundance and environmental variables were analyzed in a hypothesis-based univariate and multivariate design. Meiofauna abundance was significantly related to water depth, but also exhibited significant longitudinal differences resulting from proximity to Mississippi River outflow. Canyon features in proximity of Mississippi River outflow were found to greatly enhance meiofauna abundance. The Florida Escarpment interacts with Mississippi River outflow and the Loop Current to enhance meiofauna abundance at stations lying directly above and below the escarpment. Multivariate comparisons of meiofauna abundance with environmental variables revealed a strong Mississippi River influence. River outflow alters local sediment characteristics, and interacts with loop current eddies and dynamic slope topography to increase particulate organic matter flux in the northeastern region, thus creating areas of higher than normal meiofauna abundance.
... Previous work on nematode population samples resort to intensity thresholding followed by filling, drawing and measuring operations in a semi-automatic fashion [8] and specimens are carefully placed apart from each other to prevent occlusion. Applying image processing techniques when dealing with several biological specimens that despite of belonging to the same class differ in shape and appearance makes parameter setting a complicated issue [9] and narrows the scope of possible applications. ...
In this paper we present an approach to perform automated analysis of nematodes in population images. Occlusion, shape variability and structural noise make reliable recognition of individuals a task difficult. Our approach relies on shape and geometrical statistical data obtained from samples of segmented lines. We study how shape similarity in the objects of interest, is encoded in active contour energy component values and exploit them to define shape features. Without having to build a specific model or making explicit assumptions on the interaction of overlapping objects, our results show that a considerable number of individual can be extracted even in highly cluttered regions when shape information is consistent with the patterns found in a given sample set. Espol
... In [8] nematode population analysis relies on well-known image processing techniques namely intensity thresholding followed by filling, drawing and measuring operations in a semi-automatic fashion. However sample preparation was carefully done to place specimens apart from each other to prevent overlapping. ...
In this paper we study how shape information encoded in contour energy components values can be used for detection of microscopic organisms in population images. We proposed features based on shape and geometrical statistical data obtained from samples of optimized contour lines integrated in the framework of Bayesian inference for recognition of individual specimens. Compared with common geometric features the results show that patterns present in the image allow better detection of a considerable amount of individuals even in cluttered regions when sufficient shape information is retained. Therefore providing an alternative to building a specific shape model or imposing specific constrains on the interaction of overlapping objects. Department of telecommunication and information processing, Ghent University, St-Pieters Nieuwstraat 41, B-9000, Ghent, Belgium Centro de Vision y Robotica, Facultad de Ingenieria en Electricidad y Computación, ESPOL University, Km 30.5 via perimetral, 09015863, Guayaquil, Ecuador
... We hypothesize that most authors who work in the field of marine sciences do not know this technique and use other better-known methods to measure total nitrogen. In marine sciences, there are many studies performed with CHN elemental composition (Lourenço et al. 2002;Anger and Moreira 2004;Baguley et al. 2004;Langenbuch and Pörtner 2004;Rotllant et al. 2004;Barbarino and Lourenço 2005;Galley et al. 2005;Parrish et al. 2005, among others) and Kjeldahl method (Yang and Hodgkiss 2004;Gao et al. 2005;Shin et al. 2006;Hjalmarsson et al. 2007;Khodabux et al. 2007, among others). Comparative studies that test the quality and accuracy of the Hach method can demonstrate its usefulness to the scientific community of marine sciences. ...
The quantification of total nitrogen in biological samples has wide applications in marine sciences. Different methods are currently used to quantify nitrogen content, but their accuracies have not been extensively tested with samples of marine origin. In this study, we compared results for total nitrogen analysis generated by the Hach method, a relatively new and low-cost technique, with CHN elemental analysis, a widely accepted and costly technique. Sixty aquatic organisms were tested covering substantial biological diversity, including algae, invertebrates, fishes, mangrove plants, salt marsh plants, and seagrasses. Two pure protein standards (bovine serum albumin and bovine milk casein) were also tested. All materials were tested using freeze-dried samples. Fishes showed the highest concentrations of nitrogen, with values always higher than 14%, whereas leaves of mangrove plants showed the poorest N content among all species (<2.0%). In general, animals showed higher values for total nitrogen than algae and spermatophytes. Results obtained with CHN analysis and the Hach method were compared for each species based on triplicate analyses for each method. Comparisons for each species showed no statistical differences between the techniques, which yielded virtually identical nitrogen measurements. In addition, results obtained with both CHN analysis and the Hach method for the two pure protein standards were similar to data provided by the manufacturer. The set of results indicates that the Hach method is suitable for nitrogen analysis of marine organisms and should be considered as an inexpensive and accurate alternative for nitrogen quantification.
... Meiofaunal counts comprise two categories: temporary meiofauna (i.e., those juveniles of the macrofauna that will eventually grow into larger organisms) and permanent meiofauna (i.e., those groups where adults are <300 µm in length; e.g., Nematoda, Harpacticoida, Gastrotricha, Turbellaria, Acari, Gnathostomulida, Kinorhyncha, Tardigrada, Ostracoda, and some Nemertinea, Oligochaeta, Polychaeta; Higgins and Thiel, 1988; Giere, 1993). Biomass was calculated for nematodes and harpacticoid copepods, the two dominant components of Gulf of Mexico deep-sea meiofauna community biomass, using a newly-developed digital microphotographic approach (Baguley et al. 2004, Baguley, 2004). Foraminiferal and metazoan biomass differences were compared using a paired t-test. ...
Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 2617-2626, doi:10.1016/j.dsr2.2008.07.011. Benthic foraminiferal biomass, density, and species composition were determined at ten sites in the Gulf of Mexico. During June 2001 and June 2002, sediment samples were collected with a GoMex boxcorer. A 7.5-cm diameter subcore was taken from a box core collected at each site and sliced into 1-cm or 2-cm sections to a depth of 2 or 3 cm; the >63-mm fraction was examined shipboard for benthic foraminifera. Individual foraminifers were extracted for adenosine triphosphate (ATP) using a luciferin-luciferase assay, which indicated the total ATP content per specimen; that data was converted to organic carbon. Foraminiferal biomass and density varied substantially (~2-53 mg C m-2; ~3,600-44,500 individuals m-2, respectively) and inconsistently with water depth. For example, although two ~1000-m deep sites were geographically separated by only ~75 km, the foraminiferal biomass at one site was relatively low (~9 mg C m-2) while the other site had the highest foraminiferal biomass (~53 mg C m-2). Although most samples from Sigsbee Plain (>3000 m) had low biomass, one Sigsbee site had >20 mg foraminiferal C m-2. The foraminiferal community from all sites (i.e., bathyal and abyssal locales) was dominated by agglutinated, rather than calcareous or tectinous, species. Foraminiferal density never exceeded that of metazoan meiofauna at any site. Foraminiferal biomass, however, exceeded metazoan meiofaunal biomass at five of the ten sites, indicating that foraminifera constitute a major component of the Gulf’s deep-water meiofaunal biomass. Funded by Minerals Management Service contract 1435-01-99-CT-30991 to G.T. Rowe (Texas A&M University).
The Gaoping Submarine Canyon (GPSC) off southwest Taiwan has been extensively studied due to its unique geology, its role in transferring terrestrial material to the deep sea, and its diverse biological communities. However, there is a lack of understanding of carbon cycling across the sediment–water interface in the canyon. This study aims to fill the gap by utilizing the field data collected between 2014 and 2020 and a linear inverse model (LIM) to reconstruct the benthic food web (i.e., carbon flows through different stocks) in the head of GPSC and the upper Gaoping slope (GS). The biotic and abiotic organic carbon (OC) stocks were significantly higher on the slope than in the canyon, except for the bacteria stock. The sediment oxygen utilization was similar between the two habitats, but the magnitude and distribution of the OC flow in the food web were distinctively different. Despite a significant input flux of ∼ 2020 mg C m−2 d−1 in the canyon, 84 % of the carbon flux exited the system, while 12 % was buried. On the slope, 84 % of the OC input (∼ 109 mg C m−2 d−1) was buried, and only 7 % exited the system. Bacteria processes play a major role in the carbon fluxes within the canyon. In contrast, the food web in the upper slope exhibited stronger interactions among metazoans, indicated by higher fluxes between meiofauna and macrofauna compartments. Network indices based on the LIM outputs showed that the canyon head had higher total system throughput (T..) and total system throughflow (TST), indicating greater energy flowing through the system. In contrast, the slope had a significantly higher Finn cycling index (FCI), average mutual information (AMI), and longer OC turnover time, suggesting a relatively more stable ecosystem with higher energy recycling. Due to sampling limitations, the present study only represents the benthic food web during the “dry” period. By integrating the field data into a food web model, this study provides valuable insight into the fates of OC cycling in an active submarine canyon, focusing on the often overlooked benthic communities. Future studies should include “wet” period sampling to reveal the effects of typhoons and monsoon rainfalls on OC cycling.
This open access book summarises the latest developments on data management in the EU H2020 ENVRIplus project, which brought together more than 20 environmental and Earth science research infrastructures into a single community. It provides readers with a systematic overview of the common challenges faced by research infrastructures and how a ‘reference model guided’ engineering approach can be used to achieve greater interoperability among such infrastructures in the environmental and Earth sciences.
The 20 contributions in this book are structured in 5 parts on the design, development, deployment, operation and use of research infrastructures. Part one provides an overview of the state of the art of research infrastructure and relevant e-Infrastructure technologies, part two discusses the reference model guided engineering approach, the third part presents the software and tools developed for common data management challenges, the fourth part demonstrates the software via several use cases, and the last part discusses the sustainability and future directions.
Benthic fauna refers to all fauna that live in or on the seafloor, which researchers typically divide into size classes meiobenthos (32/64 µm–0.5/1 mm), macrobenthos (250 µm–1 cm), and megabenthos (>1 cm). Benthic fauna play important roles in bioturbation activity, mineralization of organic matter, and in marine food webs. Evaluating their role in these ecosystem functions requires knowledge of their global distribution and biomass. We therefore established the BenBioDen database, the largest open-access database for marine benthic biomass and density data compiled so far. In total, it includes 11,792 georeferenced benthic biomass and 51,559 benthic density records from 384 and 600 studies, respectively. We selected all references following the procedure for systematic reviews and meta-analyses, and report biomass records as grams of wet mass, dry mass, or ash-free dry mass, or carbon per m² and as abundance records as individuals per m². This database provides a point of reference for future studies on the distribution and biomass of benthic fauna.
The feeding ecology of De Buen's goby Buenia affinis was studied on a population collected in the north-eastern Adriatic Sea (Kvarner area). The sampling was carried out by SCUBA diving from May 2003 to April. 2004. The stomach contents analysis revealed that this epibenthic gobiid is a carnivorous and generalist feeder. B. affinis fed mostly on organisms that live on the bottom, or close to it, belonging to both meiofauna and macrofauna. Despite the small size of B. affinis, it relied on a wide size range of prey, from copepods and prodissoconch bivalve to fish, larger crustaceans and polychaetes. The diet composition of B. affinis was significantly different among seasons and between small-sized and large-sized individuals.
In this work, we discuss the problems of automatic segmentation of Arabidopsis thaliana epidermal cell patterning in images captured using a Differential Interference Contrast (DIC) microscope. These images are difficult to analyze due to the non-linear nature of DIC optics. The border of objects appear as a combination of bright and dark shadows with variable thickens and contrast levels. Our segmentation approach exploits prior knowledge on the optical properties of A. thaliana cell walls. A set of matching filters and a scale space line detector are used to generate an enhanced image that shows a single response at the location of cellular walls. To reduce the uncertainty in low contrast cellular walls several images are captured at different orientations. After image fusion, we obtain a single image that can be segmented using well established algorithms. Experiments on a manually annotated DIC image data set demonstrated the effectiveness of the proposed scheme.
A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here we combine mooring times series, ship-based measurements and remote sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their determinants in summer. Flux data were obtained with sediment traps moored around 125 m and via a regional empirical algorithm applied to particle size distributions (17 classes from 0.08–4.2 mm) measured by an Underwater Vision Profiler 5. The low fractal dimension (i.e., porous, fluffy particles) derived from the algorithm (1.26 ± 0.34) and the dominance (~ 77%) of rapidly sinking small aggregates ( 1 mm ESD), but these two factors were weakly related with each other. Copepod biomass was overall negatively correlated (p
A better understanding of how environmental changes affect organic matter fluxes in
Arctic marine ecosystems is sorely needed. Here, we combine mooring times-series,
ship-based measurements and remote-sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their biophysical determinants in summer. Flux data were obtained with sediment traps and via a regional empirical algorithm applied to particle size-distributions (17 classes from 0.08–4.2 mm) measured by an Underwater Vision Profiler 5. Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e. principal coordinates of neighbor matrices, PCNM), were conducted to partition the variation of POC flux size-classes. Flux variability
was explained at 69.5% by the addition of a linear temporal trend, 7 significant PCNM and 9 biophysical variables. The interaction of all these factors explained 27.8% of the variability. The first PCNM canonical axis (44.4% of spatial variance) reflected a shelf-basin gradient controlled by bottom depth and ice concentration (p < 0.01), but a complex assemblage of fine-to-broad scale patterns was also identified. Among biophysical
parameters, bacterial production and northeasterly wind (upwelling-favorable) were the two strongest explanatory variables (r2 cum. = 0.37), suggesting that bacteria were associated with sinking material, which was itself partly linked to upwellinginduced productivity. The second most important spatial structure corresponded actually to the two areas where shelf break upwelling is known to occur under easterlies.
Copepod biomass was negatively correlated (p < 0.05) with vertical POC fluxes, implying that metazoans played a significant role in the regulation of export fluxes. The low fractal dimension of settling particles (1.26) and the high contribution (� 94%) of fast-sinking small aggregates (< 1mm; 20–30md−1) to the mass fluxes suggested that settling material across the region was overall fluffy, porous, and likely resulting from the aggregation of marine detritus, gel-like substances and ballast minerals. Our study demonstrates that vertical POC fluxes in Arctic shelf systems are spatially complex, sensitive to environmental forcings, and determined by both physicochemical mechanisms and food web functioning. In conclusion, we hypothesize that the incorporation of terrestrial matter into the Beaufort Sea food web could be catalyzed by bacteria via the incorporation of dissolved terrestrial carbon liberated through the photo-cleavage and/or hydrolysis of land-derived POC interweaved with marine aggregates.
A better understanding of how environmental changes affect organic matter fluxes in Arctic marine ecosystems is sorely needed. Here, we combine mooring times-series, ship-based measurements and remote-sensing to assess the variability and forcing factors of vertical fluxes of particulate organic carbon (POC) across the Mackenzie Shelf in 2009. We developed a geospatial model of these fluxes to proceed to an integrative analysis of their biophysical determinants in summer. Flux data were obtained with sediment traps and via a regional empirical algorithm applied to particle size-distributions (17 classes from 0.08–4.2 mm) measured by an Underwater Vision Profiler 5. Redundancy analyses and forward selection of abiotic/biotic parameters, linear trends, and spatial structures (i.e. principal coordinates of neighbor matrices, PCNM), were conducted to partition the variation of POC flux size-classes. Flux variability was explained at 69.5 % by the addition of a linear temporal trend, 7 significant PCNM and 9 biophysical variables. The interaction of all these factors explained 27.8 % of the variability. The first PCNM canonical axis (44.4 % of spatial variance) reflected a shelf-basin gradient controlled by bottom depth and ice concentration (p
Nematode morphometrics were compared at 11 fine-sand and three muddy-sediment sites on the Louisiana, USA continental shelf to explore nematode-sediment relationships. Over 1800 nematodes were measured, and morphometric profiles through 4 cm were examined. The mean length of nematodes did not differ between muds and sands, although nematode diameter was greater in muds below 2 cm in sediment depth. Sand-dwelling nematodes, which slide through interstitial pore spaces, were longer relative to their diameter compared to nematodes that burrow through muddy sediments lacking interstices. Nematode diameter increased with both increasing particle size and particle heterogeneity among sandy stations. In muds, nematode length, diameter and biovolume increased with sediment depth, although length:width ratio did not vary with depth in the sediment. In sands, nematode length and length:width ratio increased with increasing sediment depth, but neither diameter nor biovolume varied with depth in the sediment. These results suggest that nematode body size and shape are related both to variation in sediment pore spaces and to vertical gradients within sediments. Within sands, body size variation attributable to granulometry was greater than variation associated with vertical gradients, while within muds variation in body size with sediment depth was greater than variation associated with particle size. Variation in body shape was similar along the vertical sediment profile and with variation in particle size in both sands and muds. We conclude that nematodes are excellent test organisms with which to test hypotheses regarding the confounded effects of sediment granulometry and chemical gradients in benthic ecosystems.
Studies designed to describe the structure of soft bottom meiobenthic communities have used diverse sorting methods, thus making the comparison of results difficult. This study compared sorting specimens using the manual and centrifuge density gradient sorting methods, for two deep-sea depth zones [continental slope (1630–1860 m) and abyssal plain (3720–3830 m)] in the southwestern Gulf of Mexico. The manual sorting method produced more taxonomic groups and higher abundance and biomass values, compared to the differential density Ludox-centrifuge sorting method. The results obtained from the two sorting methods suggest that distribution patterns of deep-sea meiofaunal samples can be an artefacts of the sorting.
We present a new method for detection and separation of individual nematode worms in a still image. After pre-processing stage,
which includes image binarization, filling the small holes, obtaining the skeleton of the new image and pruning the extra
branches of skeleton, we split a skeleton into several branches by eliminating the connection pixels (pixels with more than
2 neighbors). Then we compute angles of all branches and compare the angles of the neighboring branches. The neighbor branches
with angle differences less than a threshold are connected. Our method has been applied to a database of 54 overlap worms
and results in 82% accuracy as automatic and 89% as semi-automatic with some limited user interaction.
Nowadays an increasing research interest in the field of biotechnology has been drawn to achieve reliable information from model organisms. C. Elegans nematode worm is one of the major animals. Machine vision analysis of this animal needs to solve many important problems, e.g. detection of each individual in population images, movement patterns of isolated and overlapped worms and so on. In this paper, we describe our recently proposed method with an analysis to show the impact of two major parameters on the method efficiency. Based on our analysis on 255 isolated and overlapped worms, we find that our method prepares the best correct detection (TAR=83%) for thetas<sub>Th</sub> and N<sub>Th</sub> between 15 and 20 pixels.
Experiments on model organisms are used to extend the understanding of complex biological processes. In Caenorhabditis elegans studies, populations of specimens are sampled to measure certain morphological properties and a population is characterized based on statistics extracted from such samples. Automatic detection of C. elegans in such culture images is a difficult problem. The images are affected by clutter, overlap and image degradations. In this paper, we exploit shape and appearance differences between C. elegans and non-C. elegans segmentations. Shape information is captured by optimizing a parametric open contour model on training data. Features derived from the contour energies are proposed as shape descriptors and integrated in a probabilistic framework. These descriptors are evaluated for C. elegans detection in culture images. Our experiments show that measurements extracted from these samples correlate well with ground truth data. These positive results indicate that the proposed approach can be used for quantitative analysis of complex nematode images.
This thesis aimed at achieving a deeper understanding of the dynamics and structure of microbenthic communities with a focus on protists. The most important discovery concerning protozoa in recent years is the fact that they play a much more important role in for example carbon and energy flow in nature than previously believed. In this thesis several studies were presented which focus on the seasonal dynamics and the spatial distribution of components of the small benthic community in marine and freshwater environments in temperate and arctic climates and which aim at establishing a generalised model of relationships and controlling factors in small benthic food webs. Samples of the upper 3 mm of the surface of soft sediment were collected in coastal freshwater and marine sites in Germany, USA and North East Greenland. The abundance and biomass of bacteria, cyanobacteria, diatoms and nanoflagellates (phototrophic and heterotrophic) were enumerated by means of epifluorescence microscopy. Ciliate species and meiofauna were enumerated with the help of light microscopy after QPS (quantitative protagol staining). Environmental data, such as temperature, salinity, sediment water content, grain size distribution, total and organic carbon- and nitrogen content as well as chlorophyll-a values were determined in order to study their influence on the community structures and total biomass. The investigation of a habitat in a mudflat in Dorum (Germany) revealed that the benthic microbial food web varied with the season with a primacy of bottom-up control during winter and spring, an increasing influence of top-down forces mainly by meiofauna grazing towards summer, decreasing again towards autumn, accompanied by a recovery of microphytobenthos.Investigations of soft sediment communities in different climate and geographic positions of freshwater and marine sites in Germany, North America (USA; Pennsylvania, New Jersey) and in North East Greenland were carried out. The results revealed considerable differences in the biomass of the small benthic components as well as in ciliate species composition and richness. The study of the ciliate species composition also exhibited a high variability of feeding types between the investigated sites, but the herbivorous feeding type seemed to be dominant in all sediments. Differences in total microbenthic biomass, abundance and ciliate species richness could not be attributed to the differences measured in carbon content, salinity or climatic parameters. The amount of chlorophyll-a was the only factor influencing the small benthic biomass. The sources of chlorophyll-a remained unclear. The hypothesis of Manini et al. (2003) stating that the composition of available carbon has a strong influence on the structure and biomass of microbial communities in shallow sediments seemed to hold true for the investigated sites. In a series of laboratory experiments the influence of the absence of all macrograzers as well as the presence of a single common abundant small macrograzer such as Hydrobia ulvae, Corophium sp. as well as Chironomid larvae and polychaets on the components of the microbenthic communities in sediments from all study sites were investigated. The structuring influence of Arenicola marina on components of the small food web was investigated in a long term field experiment on the island of Sylt. The results of the laboratory experiments and those of the field study revealed that the small macrofauna tended to have positive stimulating effects on the microbial community by bioengineering, rather than negative ones by grazing. The exclusion of Arenicola marina in a long term experiment revealed the fact that the role of this grazer was adopted by other grazers.The results of this thesis and literature data led to the conclusion that in small communities of soft sediments the trophic levels are blurred and most species rather feed opportunistically on what is most available. The dominance of the omnivourous feeding type, detritus feeding, stimulating bioengineering effects and feed back mechanisms compose a highly networked food web. The fundamental attributes of microbes such as large absolute population sizes, short generation times and high dispersal capabilities, form a system with rapid changes in species composition.The outcome of this thesis verified the model of Fretwell (1977) for benthic microbial food webs in coastal regions, predicting that top-down forces form the trophic structure, but the bottom-up attributes of the ecosystems, such as nutrients availability, temperature and light, determine the fundament of the community as total biomass, abundance and production.
In connexion with the high species richness of deep-sea sediments the question arises which spatial processes influence the species composition, abundance and biomass of the communities. Which processes produce and maintain diversity in the deep sea and at what spatial scales do they operate?The background of the study is the concept that biogenic structures create at a small scale a heterogeneous environment that influences the structure of the communities and the dynamics of the populations of benthic meiofauna organisms. As an example for biogenic structures, the influence of deep-sea sponges on small-scale distribution pattern of benthic deep-sea nematodes was investigated.Overall the nematode community from the sponge samples show a higher functional divergence and thus a high degree of niche differentiation.Within the nematode community from the sponge cores a stronger interaction between the species and a higher functional diversity seems to allow a larger extend of resource utilisation.
Meiofaunal samples were collected from intertidal mudflats in the lower, middle and upper reaches of the Tamar estuary, South West England in April and October, 1982. Species abundance and biomass patterns of nematodes and copepods did not follow the expected trends in relation to salinity: the lowest species diversity (below neutral model predictions), the steepest ranked species abundance curves and the greatest departure from the theoretical lognormal distribution of numbers and biomass of individuals among species were found at the middle rather than the upper site. Huston's (1979) dynamic equilibrium hypothesis is invoked to explain these phenomena, but the hypothesis remains to be tested. Intense macrofaunal predation and disturbance, together with more pronounced environmental fluctuations, may eliminate competitive exclusion at the upper site resulting in a relatively high species diversity. The absence of such population reduction mechanisms at the middle site results in competitive exclusion and lowered diversity. The major nematode species at the upper site have certain opportunistic characteristics, and at the middle site conservative characteristics, which support the contention that these are respectively successional and climax communities. The lower site may represent an intermediate successional stage with the highest diversity. The apparent correlation between the abundances of 3 copepod and 1 nematode species with changes in salinity at the middle and upper sites between April and October is thought to result from passive suspension and transport of these species upstream during the summer: there is a distinct fine-scale vertical stratification of species in the sediment at the middle site, with the species in question having an extreme surficial distribution.
Changes in the cephalothorax length and dry weight of Formalin‐preserved copepodite and adult Acartia clausi were followed from 12 March–1 June 1976 and naupliar weights and lengths determined for one sample. Preservation in Formalin caused a significant loss of dry weight, carbon, and nitrogen in adult females, mostly during the first 24 h, but did not significantly affect the C:N ratio or the cephalothorax length of the animals.
Length and weight were inversely related to seawater temperature at the time of sampling. As the animals became older this relationship was increasingly affected by their past temperature history. Separate linear relationships between log length and log weight were observed for the nauplii, the CIs, the CII–CVs, and the adults, making it possible to estimate the weight of individual stages from measurements of length.
Animals collected on the same day from different stations sometimes showed significant differences in weight for a given length. Such differences could be more clearly expressed by calculation of a condition factor relating weight to the cube of cephalothorax length. The differences in the condition factor appeared to be related to food availability and such differences may be even more apparent when weights of live animals are examined.
Statistical methods for analysing changes in community structure fall under the three general headings of univariate, graphical/distributional and multivariate. These methods are applied to a variety of benthic community data (macrobenthos, meiobenthos, corals, demersal fish), from a variety of localities (intertidal/subtidal, temperate/tropical) and over both spatial and temporal scales. Four general conclusions emerge from this comparative study:
(1) The similarity between sites or times based on their univariate or graphical/distributional properties is usually different from their clustering in multivariate analyses.
(2) Species dependent (multivariate) methods are much more sensitive than species independent (univariate and graphical/distributional) methods in discriminating between sites or times.
(3) In examples where more than one component of the fauna has been studied, univariate and graphical/distributional methods may give different results for different components, whereas multivariate methods tend to give the same results.
(4) By matching multivariate ordinations from subsets of environmental data to an ordination of faunistic data, the key environmental variables responsible for community change may be identified.
Wet and dry weight, total carbon, nitrogen, hydrogen, and ash contents were determined on 33 species of zooplankton distributed predominantly in the open sea region of the North Pacific. Sampling covered the waters from 44N to the equator. Average percentage of dry weight to wet weight was about 19% of all samples from the whole area. Percentage dry weight of carbon in copepods was on an average 51.5%. The highest value, 66.6%, was obtained in eggs of the copepod Pareuchaeta sarsi. Mixed zooplankton was assumed to contain carbon comprising about 35 to 45% of the dry weight. Carbon contained in the zooplankton biomass existing in the upper 200 m in the western parts of the northern North Pacific and Bering Sea during spring and summer was estimated to range from 20 to 85 mg C/m3. Nitrogen content varied considerably with localities. Average ratio of carbon to nitrogen was 8.5 in subarctic copepods, and 4.1 in subtropic-tropic copepods. This ratio also varied with season. In the copepod Calanus cristatus the ratio was highest (10.0) in May, immediately after the spring bloom of phytoplankton, when the animals contained much fat. The ratio fell to 5.1 in December. There seemed to be a large seasonal variation in boreal zooplankton due to great fluctuations of environmental conditions, especially the amount of food available; in tropical species the range was small because of environmental uniformity. Average hydrogen content was about 6 to 10%. The percentage of ash to dry weight amounted to 39.3% in pteropods and 3.4% in copepods.
In the general depth range of 300-3000, nematodes, harpacticoid copepods, nauplii, polychaetes, ostracods, and kinorynchs were numerically dominant, in that order in the meiofauna; together, these groups made up 98% of the fauna. The macrofauna was dominated by polychaetes, ostracods, bivalves, tanaids, bryozoans, and isopods, in that order; together these made up 86% of the fauna. Between depths of 300 m and 3000 m there was a 3-fold decrease in meiofaunal and a 2-fold decrease in macrofaunal density. On the slope off Louisiana and E Texas, at 400-900 m, dense biological communities were encountered at c40 locations aggregated around oil and gas seeps; organisms include clusters of large tube worms (vestimentiferans), vesicomyid clams, mussels, galatheid crabs, bresiliid shrimps, neogastropods, limpets, and fishes. This community is trophically dependent upon chemoautotrophic bacteria (which utilize hydrogen sulfide), although some mussels directly utilize methane as a carbon source. The megafauna of the N and E Gulf of Mexico falls into the following depth distribution pattern: Shelf/Slope Transition Zone (118-475 m), Archibenthal Zone-Horizon A (500-775 m), Archibenthal Zone-Horizon B (800-975 m), Upper Abyssal Zone (1000-2275 m), Mesoabyssal Zone (2300-3225 m), and Lower Abyssal Zone (3250-3850 m). -from Authors
A new isopycnic separation technique was developed to minimize the effect of sediment granulometry on extraction efficiency of benthic meiofauna. The method uses colloidal silica Ludox((R)) (DuPont) HS 40 as a high density solution to extract meiofaunal organisms from sediment. Previous protocols using silica sols have had problems with physical interactions between the sediment and the specimens, causing large variations in extraction efficiencies between sediment types. The procedure presented herein reduces this problem by the addition of a 5 min period of fluidization of the sediment. The time used to complete the method is minimized with a final centrifugation step, which accelerates the settling rate of the fine sediment, resulting in a total time required for separation of approximately 20 min. Forty-eight samples were processed, with sediments ranging from sand to silty clay. The average extraction efficiency was 96.8 +/- 3.9% for the total meiofaunal abundance. Extraction efficiency was independent of sediment granulometry over the range of sediments tested.
The size distribution of benthic nematodes was investigated along different gradients of food availability in various regions of the north-eastern Atlantic: I, across the continental margin and II, with increasing distance from the continental rise. An overall trend for miniaturization with increasing distance from the food source was found. Moreover, our results indicate that seasonally varying food supply or a periodically pulsed input of organic matter to the sea floor affects nematode size spectra. The hypothesis is proposed that the life cycle of deep-sea nematode species and hence the size structure of their populations are related to seasonal energy availability. This dependence might result in one year life spans of deep-sea nematodes and probably other meiofauna.
The GOMEX box corer has been used extensively for over a decade in the Gulf of Mexico, but the details of its construction and use have heretofore not been published. The advantages of the GOMEX corer accrue from its tripping and closing mechanisms, as well as its modest weight and size. It is comparatively easy to use, safe in rough seas, and modest in cost compared to the cumbersome but widely accepted USNEL spade corer. Comparison of macrofaunal densities in the Norwegian and the Greenland Seas, with data from the same areas with the USNEL corer, suggests that GOMEX sample quality surpasses other quantitative samplers now in use by deep‐sea biologists. Success frequencies appeared to be related to the depth to which the sediment could be penetrated—a function of sediment water content (porosity) and grain size—rather than water depth or sea state.
The sediment-inhabiting meiofauna is a major component of benthic ecosystems, parti-cularly in the deep sea. Knowledge on the deep-sea meiobenthos has increased considerably during recent decades, and attempts have been made to relate standing stocks with various environmental factors. The flux of organic matter from surface productivity to the seafloor has been proven to exert considerable control on benthic standing stocks. The energy content of sedimentating organic matter generally decreases with water depth because of degradation processes within the water column. Consequently, benthic standing stocks decrease with increasing water depth. Generally enhanced densities of benthic animals are to be expected in areas of increased surface production and subsequently enhanced flux of organic matter to the seafloor. Thus, meiobenthic densities and biomasses should show perceptible differences not only with water depth, but also between areas with different primary productivity in surface layers. The objective of this paper is to condense current information focusing on the abun-dance of metazoan meiofauna along continental margins, and to compare meiofauna stocks from various climatic regions of the world, representing areas of diverse productivity in the water column. Results clearly demonstrate regional differences on global scale: richer com-munities were generally found in areas with increased productivity and enhanced input of organic matter to the seafloor.
Oxygen uptake, ammonia excretion and phosphate excretion were measured in 14 Antarctic zooplankton species, including various size classes of krill (Euphausia superba), during a cruise to the Antarctic Ocean adjacent to Wilkes Land in the summer of 1980. Elemental composition (C, N and P) was also determined on the specimens used in these metabolic rate measurements. The values obtained for C, N and P were 4.7 to 47.5%, 1.2 to 12.5% and 0.09 to 1.23% of dry weight, respectively. Regression analyses of metabolic rates on different measures of body weight (fresh, dry, C, N and P) were made on krill, salps and other zooplankton as arbitrarily defined groups and also on the combined groups to determine the best measure of body weight for intra- and interspecific comparison of metabolic rates. The correlations were highly significant in all regressions, although no common measure of body weight provided the best correlation for the three groups of animals. Except for the regression of ammonia excretion on C and N weight, all other regressions of metabolic rates and body weights were significantly different within these three groups. In the combined group, oxygen uptake and ammonia excretion were better correlated to C and N weights than to dry and P weights. For phosphate excretion in the combined groups, dry weight gave the best correlation. Despite these results, the choice of a particular measure of body weight was shown to be important in a comparison of the rates between krill and salps because of their widely different chemical compositions. Our results of rate measurements are compared with those of previous workers for some Antarctic zooplankton, particularly krill. Some of the previous data are in good agreement with ours, while others are not. Possible contributing factors are considered in the latter case. The ratios between the rates (O:N, N:P and O:P) fell within the general ranges reported for zooplankton from different seas. The O:N ratio was consistently low (7.0 to 19.8, by atoms) in all species, suggesting the importance of protein in their metabolic substrates. Protein-oriented metabolism was also supported by the results of C and N analyses which indicated no large deposition of lipid in these animals. From the results of metabolic rate measurements and elemental analyses, daily losses in bodily C, N and P for Antarctic zooplankton in summer were estimated as 0.4 to 2.8%, 0.6 to 2.5% and 1.3 to 19.4%, respectively. These values are approximately one order of magnitude lower than those reported for subtropical and tropical zooplankton.
Individual dry weights and ash-free dry weights for different meiofauna taxa from two soft bottom localities (31 and 117 m depth) in Gullmar Fjord on the Swedish west coast were determined. Samples from August 1980 and February 1981 of about 100 to 600 formalin-preserved specimens of each of the different taxa from each of four sieve fractions were weighed on a microbalance. Individual dry weights ranging from 0.12 g (nematodes in the 0.040-mm fraction) to 172 g (polythalamous, arenaceous Foraminifera in the 0.500-mm fraction) and ash-free dry weights ranging from 0.10 g (nematodes in the 0.040-mm fraction) to 37 g (polychaetes in the 0.500-mm fraction) were obtained. Great similarities were noted between corresponding values from the two stations as well as between summer and winter values. The percentage of organic matter, determined by ashing, in the body weight differed greatly among taxa. Some standard individual dry weight and ash-free dry weight values, to be used for re-calculation of abundance values into biomass, are presented.
Nematodes from a mud-flat in the river Lynher estuary, Cornwall, U.K., have a population density ranging between 8 and 9 × 106 m−2 in the winter months, corresponding to a dry weight of 1·4 and 1·6 g m−2. They reach a peak abundance of 22·86 × 106 m−2 (3·4 g) in May. About 40 species are present, and the species composition remained seasonally stable over the period of study. Analysis of age-structure suggests that the major species have continuous asynchronous reproduction.Respiration rates of 16 species have been determined at 20 °C using Cartesian diver respirometry. For five species, respiration/body size regressions were obtained in the form log10R = log10a+b log10V, where R = respiration in nl O2 ind−1 h−1 and V = body volume in nl: Mesotheristus setosus (log10a = −0·04,b = 0·74), Sphaerolaimus hirsutus (log10a = 0·11, b = 0·68), Axonolaimus paraspinosus (log10a = 0·00, b = 0·79), Metachromadora vivipara (log10a = −0·59, b = 1·07), Praeacanthonchus punctatus (log10a = 0·00, b = 0·55). For the remaining 11 species, several animals were used in each diver and, by assuming b = 0·75, log10a′ values were calculated: Viscosia viscosa (log10a′ = 0·188), Innocuonema tentabundum (−0·012), Ptycholaimellus ponticus (−0·081), Odontophora setosa (−0·092), Sphaerolaimus balticus (−0·112), Dichromadora cephalata (−0·133), Atrochromadora microlaima (−0·142), Cylindrotheristus normandicus (−0·150), Terschellingialongicaudata (−0·170), Sabatieria pulchra (−0·197), Terschellingia communis (−0·277). These values are compared with recalculated values for other species from the literature.Annual respiration of the nematode community is 28·01 O2 m−2, equivalent to 11·2 g carbon metabolised. Community respiration is compared with figures from N. American saltmarshes. At 20 °C, a respiration of about 61 O2 m−2 year−1 g−1 wet weight of nematodes appears to be typical. Annual production is estimated to be 6·6 g C m−2. The correlation between feeding-group, body-size, habitat and the repiration rate of individual species is discussed.
Quantitative information on the abundance and biomass of metazoan meiofauna was obtained from samples collected at 15 deep-sea stations in the Eastern Mediterranean Sea (533–2400m). Meiofaunal abundance was compared to bacterial biomass and other environmental factors such as the total sedimentary organic matter content, the concentrations of the main biochemical classes of organic compounds (i.e. proteins, carbohydrates and lipids) and to ATP. To estimate the sedimentation potential of primary organic matter, sediment bound chloroplastic pigment equivalents (CPE) were assayed. Meiofaunal density was very low ranging from 4 ind.10cm−2 (Station A4, 1658m depth) to 290 ind.10cm−2 (Station A12, 636m depth). Nematodes were the numerically dominant taxon (68% of total meiofauna) and were usually confined to the top 6cm of the sediments. Total meiofaunal biomass ranged from 2.78μgC 10cm−2 (Station A4) to 598.34μgC 10cm−2 (Station 15A). There was a significant decrease in the density of metazoan meiofauna with water depth. Bacterial biomass largely dominated the total biomass (as the sum of bacterial and meiofaunal biomass) with an average of 73.2% and accounted for 35.8% of the living biomass (as ATP carbon) whereas meiofaunal biomass accounted only for 6.56%. Bacterial biomass was significantly related to the DNA concentrations of the sediment. A significant correlation between ATP concentration and CPE content was also found. No correlations were found between meiofauna, ATP and CPE, or between meiofauna and bacterial parameters. The significant relationship between meiofaunal density and the ratio of labile organic matter/total organic matter indicates that deep-sea meiofauna inhabiting an extremely oligotrophic environment (such as the Eastern Mediterranean) may be more nutritionally dependent upon the quality than on the quantity of sedimentary organic matter.
Studies on the soil microfauna-II
- Overgaard Nielsen
Overgaard Nielsen, C. 1949. Studies on the soil microfauna-II. Nat. Jutl. 2:1-131
Meiofauna techniques
- A D Mcintyre
- R M Warwick
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