1,720,995 research outputs found
Stoichiometric theory extended to micronutrients: comparison of the roles of essential fatty acids, carbon, and nitrogen in the nutrition of marine copepods
No full textConventional stoichiometric theory, which is used to study the limitation of zooplankton production by C, N, and other elements, is extended to include the essential polyunsaturated fatty acids (PUFAs) 20:5(n-3) and 22:6(n-3). Using typical biochemical compositions of consumer (Calanus helgolandicus) and algal food (hypothetical diatom-dinoflagellate mixtures), the analysis shows that PUFAs or macronutrients can be important in limiting zooplankton production, depending on the biochemical compositions of consumer and food and the efficiencies with which dietary components are used. Predicted limitation by fatty acids is strongest when zooplankton use a monospecific diet, indicating that such limitation may be of particular significance in laboratory zooplankton, which are often fed phytoplankton monocultures. The analysis illustrates several factors that operate to minimize the limiting potential of fatty acids to the extent that limitation by C or N could occur: selective grazing to obtain a nutritionally balanced diet, plasticity in consumer biochemical composition, and high C requirements for respiration. The possibility of macronutrient limitation is increased further if zooplankton are able to actively synthesize essential PUFAs, although this is not thought to be the case in most aquatic systems. The work highlights the need for complete data sets incorporating fatty acids and bulk elemental properties of consumers and prey, as well as an improved understanding of the roles and cycling of essential fatty acids, if we are to be able to provide a unified view of zooplankton nutrition
An experiment to determine if the foraminiferan Haynesina germanica consumes sewage-derived organic matter, using fatty acid and sterol (corpostanol) biomarkers
No full textFeeding of benthic foraminifera on diatoms and sewage-derived organic matter: an experimental application of lipid biomarker techniques
No full textForaminiferal ecology at sewage outfalls has been investigated in numerous field studies over the last 30 years. Foraminifera have been frequently used as biomonitors of sewage pollution since they are both abundant and ubiquitous. Sewage outfalls have been demonstrated to have both positive and negative effects on adjacent foraminiferal populations, but it has never been shown conclusively why sewage affects foraminifera in these ways. Such information on the impact mechanisms of sewage pollution is essential if foraminifera are to be used as sewage pollution biomonitors, and also to understand the ecology of these important protists. One possible cause of a positive effect is the direct consumption of sewage-derived particulate organic matter (POM) by the foraminifera themselves. However this hypothesis has never been tested experimentally. Here, lipid (fatty acid and sterol) biomarker techniques were applied to study the ingestion of two potential food items by the foraminiferan Haynesina germanica in the laboratory. An experiment was conducted to confirm that the laboratory conditions were conducive to the survival and feeding of the foraminifera. In this experiment, foraminifera were provided with the pennate diatom Phaeodactylum tricornutum, which was considered to be a suitable food source. After 2 weeks, a four-fold increase in the levels of the diatom fatty acid biomarker, 20:5(n-3), in the foraminifera suggested that they had fed actively on the diatoms and survived under the experimental conditions. These experimental conditions were used in the main experiment, where foraminifera were fed the POM from sewage. Lipid biomarker analysis indicated that H. germanica did not consume secondary treated sewage-derived POM. Neither fatty acid profiles in the sewage nor coprostanol, the diagnostic human faecal sterol, were detected in foraminifera after exposure to the potential sewage food source. However, foraminifera may have consumed bacteria associated with the sewage in the experiment. The findings are discussed in terms of current EU legislation on sewage treatment that has affected the composition of sewage discharges, and therefore possibly reduced the nutritive value of sewage to the marine benthos
Ecology and nutrition of the large agglutinated foraminiferan Bathysiphon capillare in the bathyal NE Atlantic: distribution within the sediment profile and lipid biomarker composition
No full textThe large agglutinated foraminiferan Bathysiphon capillare de Folin (Protista) was an important component of the macrofauna in box core samples recovered at a 950 m site on the southern flank of the Wyville-Thomson Ridge, northern Rockall Trough. The long, narrow, very smooth, flexible tubes of B. capillare reached a maximum length of almost 10 cm. Densities ranged from 100 to 172 ind. m-2, a figure that represents at least 5 to 9% of metazoan macrofaunal densities. This infaunal species usually adopted a more or less horizontal orientation within the upper 5 cm layer of brownish sandy silt. Its cytoplasm yielded a diverse spectrum of fatty acids. These included various monounsaturated fatty acids (39% of total), mainly 18:1(n-7), 20:1(n-9) and 22:1(n-7), the polyunsaturated fatty acids (PUFA) 20:4(n-6), 20.5(n-3) and 22.6(n-3), and non-methylene diene-interrupted fatty acids (NMIDS), particularly 22:2[delta]7,13 and 22:2[delta]7,15. The spectrum of PUFAs is consistent with the ingestion by B. capillare of phytodetrital material. However, the presence of NMIDS, reported here for the first time in a protist, provides evidence for a substantial bacterial component in the diet. Viewed by scanning electron microscopy (SEM), the cytoplasm occupied a narrow space between the inner organic test lining and an inner core of detritus around which it formed a sheath. The core material included numerous spherical structures (2 to 10 µm diameter) that we interpret as stercomata (waste pellets composed largely of mineral grains). Taken together, our observations suggest that B. capillare is a deposit feeder, consuming sediment, detritus and associated bacteria. Other deep infaunal foraminiferans probably have a similar diet, leading us to speculate that these protists, which are often abundant in dysoxic settings, may contribute significantly to carbon cycling in the deep sea. Since B. capillare and similar large Bathysiphon species can be recovered in good condition from bathyal depths, they may prove to be ideal experimental subjects for addressing some fundamental issues in the lipid biochemistry of deep-sea benthic organisms
Sewage effects on the food sources and diet of benthic foraminifera living in oxic sediment: a microcosm experiment
No full textA microcosm experiment was conducted to investigate the effects of sewage-derived particulate organic matter (POM) on the food sources and diets of two species of intertidal benthic foraminifera, Ammonia beccarii and Haynesina germanica, using lipid biomarkers to determine trophic relationships. The lipid content of the sediment and associated micro-organisms was a guide to potential food sources while that of the foraminifera was a guide to what they had actually eaten. Six microcosm tanks were established, with constant salinity, temperature and oxygen content, and each with a thin layer of sediment containing living foraminifera. Three microcosms were used as controls and three were treatments to which the POM from secondary treated sewage was added. Each microcosm was treated as a single replicate (to avoid pseudoreplication). The experiment was run for 38 days. The results showed that the food sources (from the sediment) and the diet of the foraminifera did not significantly differ in the controls or the treatments, but quantities of fatty acids decreased in both the sediment system and the foraminifera over the duration of the experiment. It is concluded that sewage-POM (secondary treatment) does not have a direct effect on the food sources of the foraminifera or their diet. The foraminifera did not feed directly on the sewage-derived POM, nor did the addition of sewage stimulate growth of micro-organisms associated with the sediment system. However, recent field data collected by the authors provides evidence that season plays an important role in foraminiferal response to organic pollution (OP), and microcosm sediment might have been unknowingly collected at a time when foraminifera are now known not to respond to OP, i.e. in summer
Selective feeding by benthic foraminifera on labile phytodetritus on the western Antarctic Peninsula shelf (500m water depth): evidence from fatty acid biomarker analysis
No full textFeeding ecology of deep-sea seastars (Echinodermata: Asteroidea): a fatty-acid biomarker approach
No full textFatty-acid biomarkers and stomach content analysis were used to investigate the diets of 9 species of deep-sea seastar. Polyunsaturated fatty acids were the most abundant categories of fatty acid contained in the total lipids of all species. They were dominated by 20:5 (n-3) and 20:4 (n 6), with 22:6 (n-3) present in much lower proportions. Monounsaturated fatty acids were also abundant, particularly 20:1 (n-13) and (n-9). Odd-numbered, branched-chain fatty acids and non-methylene interrupted dienes (NMIDs) were present in relatively high levels in all species. Cluster and multi-dimensional scaling (MDS) analyses of the fatty acid composition separated the seastar species into 3 trophic groups; suspension feeders, predators/scavengers, and mud ingesters. Suspension feeders showed greatest reliance on photosynthetic carbon as indicated by the abundance of fatty-acid biomarkers characteristic of photosynthetic microplankton. By contrast, mud ingesters were found to rely heavily on heterotrophic bacterial carbon, containing high percentages of 18:1 (n-7) and NMIDs. Predator/scavengers occupied a trophic position between the suspension feeders and mud ingesters. Zoroaster longicauda, an asteroid of unknown diet, had a similar fatty acid composition to the 3 suspension feeders, Freyella elegans, Brisingella coronata and Brisinga endecacnemos. While the suspension feeders are specialists on benthopelagic copepods, the preferred prey of Z. longicauda is unknown, but is likely to be very similar to that of the suspension feeders. Stomach content analysis revealed the diet of Z. longicauda also includes benthic echinoderms and crustaceans
Changes in Emiliania huxleyi fatty acid profiles during infection with E. huxleyi virus 86: physiological and ecological implications
Full text linkFatty acids profiles of Emiliania huxleyi strain CCMP1516 were determined in a virus-induced culture crash with E. huxleyi virus 86 (EhV-86). As cell numbers declined in the infected cultures due to virus lysis, a concomitant decrease in fatty acids was observed in the particulate fraction. The composition of fatty acids within infected E. huxleyi cells was restructured, with a shift from polyunsaturated to monounsaturated and saturated fatty acids (respective distributions changing from 70:10:20% at the start of the experiment to 44:24:32% at the final time point). In particular, decreases were seen in the major fatty acid 22:6(n-3) and in 18:5(n-3), whereas greatest increases were seen in 18:1(n-9) and 22:0. The increase in the amount and restructuring of the fatty acid pool in E. huxleyi was indicative of a combination of specific and non-specific effects of virus infection. Specific effects primarily included induction of metabolic pathways such as the synthesis of components involved in virus replication, the production of virions and signal transduction via sphingolipid biosynthesis. Non-specific effects due to stress were likely mediated by reactive oxygen species. Changes in the composition of virus-infected E. huxleyi are of significance to the food web since grazing on virus-infected blooms will decrease the amount of essential polyunsaturated fatty acids passed on to higher trophic levels. Consequently, this could decrease the overall productivity of marine ecosystems
Selective feeding by benthic foraminifera on phytodetritus on the western Antarctic Peninsula shelf: evidence from fatty acid biomarker analysis
Full text linkThis study presents the first direct evidence, based on biochemical analysis of fresh material, that certain benthic foraminifera feed selectively on specific components of seasonally deposited phytodetritus in their natural environment. Three abundant species of benthic foraminifera, the calcareous species Globocassidulina subglobosa and Quinqueloculina seminula and the agglutinated species Thurammina albicans, collected after the deposition of phytoplankton bloom material at a shelf site (560 m water depth) west of the Antarctic Peninsula in March 2001, showed significant differences in their fatty acid profiles compared to the surrounding phytodetritus. Furthermore, the 2 calcareous species contained significantly higher amounts of polyunsaturated fatty acids (PUFAs) than were found in their presumptive phytodetrital food source, indicating that the foraminifera discriminate between, and selectively feed on, the different components of the deposited material. Possible implications for the benthic food web are discussed
Application of liposome and stable isotope tracer techniques to study polyunsaturated fatty acid biosynthesis in marine zooplankton
No full textWe investigated the ability of four species of marine zooplankton to synthesize polyunsaturated fatty acids (PUFAs) during pulse-chase tracer experiments. Liposomes containing a deuterium labelled precursor fatty acid, D5-18:3n-3, were fed to female Calanus finmarchicus, Calanoides acutus, Drepanopus forcipatus and calyptopus larvae of Euphausia superba during ship-board experiments. Although all species of zooplankton readily ingested the liposomes and incorporated the D5-18:3n-3 tracer into their somatic lipid pool, only negligible products of elongation and desaturation; D5-18:4n-3, D5-20:5n-3 and D5-22:6n-3 were detected after 96 h incubations. We conclude that the four species of marine zooplankton examined here are unable to synthesize PUFA at ecologically significant rates and certainly not in amounts sufficient to support growth and reproductive processes
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