Fatty acid trophic markers in the pelagic marine environment. Adv Mar Biol

University of Copenhagen, Danish Institute for Fisheries Research, Charlottenlund Castle, DK-2920 Charlottenlund, Denmark.
Advances in Marine Biology (Impact Factor: 3.48). 02/2003; 46:225-340. DOI: 10.1016/S0065-2881(03)46005-7
Source: PubMed


Fatty acids have been used as qualitative markers to trace or confirm predator-prey relationships in the marine environment for more than thirty years. More recently, they have also been used to identify key processes impacting the dynamics of some of the world's major ecosystems. The fatty acid trophic marker (FATM) concept is based on the observation that marine primary producers lay down certain fatty acid patterns that may be transferred conservatively to, and hence can be recognized in, primary consumers. To identify these fatty acid patterns the literature was surveyed and a partial least squares (PLS) regression analysis of the data was performed, validating the specificity of particular microalgal FATM. Microalgal group specific FATM have been traced in various primary consumers, particularly in herbivorous calanoid copepods, which accumulate large lipid reserves, and which dominate the zooplankton biomass in high latitude ecosystems. At higher trophic levels these markers of herbivory are obscured as the degree of carnivory increases, and as the fatty acids originate from a variety of dietary sources. Such differences are highlighted in a PLS regression analysis of fatty acid and fatty alcohol compositional data (the components of wax esters accumulated by many marine organisms) of key Arctic and Antarctic herbivorous, omnivorous and carnivorous copepod species. The analysis emphasizes how calanoid copepods separate from other copepods not only by their content of microalgal group specific FATM, but also by their large content of long-chain monounsaturated fatty acids and alcohols. These monounsaturates have been used to trace and resolve food web relationships in, for example, hyperiid amphipods, euphausiids and fish, which may consume large numbers of calanoid copepods. Results like these are extremely valuable for enabling the discrimination of specific prey species utilized by higher trophic level omnivores and carnivores without the employment of invasive techniques, and thereby for identifying the sources of energetic reserves. A conceptual model of the spatial and temporal dominance of group-specific primary producers, and hence the basic fatty acid patterns available to higher trophic levels is presented. The model is based on stratification, which acts on phytoplankton group dominance through the availability of light and nutrients. It predicts the seasonal and ecosystem specific contribution of diatom and flagellate/microbial loop FATM to food webs as a function of water column stability. Future prospects for the application of FATM in resolving dynamic ecosystem processes are assessed.

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    • "Lipid trophic biomarkers are compounds that provide signatures of a species, groups of organisms or environmental processes (Dalsgaard et al. 2003; Budge et al. 2006). Fatty acid (FA) biomarkers are normally synthesized at low trophic levels and correlate with various sources of primary production such as diatoms , bacteria, dinoflagellates and terrestrial runoff (Budge and Parrish 1998; Dalsgaard et al. 2003). These biomarkers are conservatively transferred throughout the food web and indicate dietary sources in both invertebrates and fish (St John and Lund 1996; Budge and Parrish 1999; Copeman et al. 2009; Kelly and Scheibling 2012). "
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    ABSTRACT: Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals, however, little is known about its early ecology and consequently how they might be affected by environmental changes. We aimed to characterize the mechanisms of spatial and ontogenetic variation in trophic biomarkers (lipid classes, fatty acids and bulk C and N stable isotopes) of saffron cod from the Western Arctic, Chukchi and Bering Seas. Size standardized analyses showed a significant difference in lipid condition metrics and trophic biomarkers as a function of survey location. Both ontogeny and sampling location played an important role in determining lipid stores with elevated levels in both small offshore juveniles (<55 mm) and larger inshore juveniles (>75 mm). Higher lipid storage in Arctic juveniles was associated with elevated levels of diatom fatty acid markers but not with near-shore carbon input. Increased lipids were found in age-1 juveniles from Prudhoe Bay in the Western Beaufort that fed at a lower trophic level then similarly sized age-0 juveniles from surface trawls in the Bering Sea. The use of otolith annuli reveal two discrete patterns of growth that help explain the trade-offs between energy storage and rapid growth that diverge between the Arctic and Bering Sea. Laboratory temperature-growth experiments confirmed that saffron cod have a eurythermal growth response and are able to store excess lipids at temperatures as high as 20 ºC.
    Polar Biology 10/2015; DOI:10.1007/s00300-015-1792-y · 1.59 Impact Factor
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    • "To test these questions we compared the fatty acid composition of two ubiquitous invertebrate groups (Trichoptera, Ephemeroptera ) collected from 16 streams arranged across a watershed geomorphic gradient in southwest Alaska, USA. Fatty acids are useful trophic markers because most of the fatty acids from an organism's diet are stored in its tissues without modification, and certain fatty acids are indicative of specific groups of primary producers or bacteria (Dalsgaard et al. 2003). Much of the relevant geomorphic variation in this system is strongly associated with mean watershed slope (Lisi et al. 2013); our primary hypothesis was that by constraining the accumulation rate of terrestrial OM, in the form of debris and organic soils, geomorphic conditions such as watershed slope would act as an ultimate control over the proximate processes that influence the carbon sources assimilated by stream consumers. "
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    ABSTRACT: Physical attributes of rivers control the quantity and quality of energy sources available to consumers, but it remains untested whether geomorphic conditions of whole watersheds affect the assimilation of different resources by stream organisms. We compared the fatty acid (FA) compositions of two invertebrate taxa (caddisflies, mayflies) collected from 16 streams in southwest Alaska, USA, to assess how assimilation of terrestrial organic matter (OM) and algae varied across a landscape gradient in watershed features. We found relatively higher assimilation of algae in high-gradient streams compared with low-gradient streams, and the opposite pattern for assimilation of terrestrial OM and microbes. The strength of these patterns was more pronounced for caddisflies than mayflies. Invertebrates from low-gradient watersheds had FA markers unique to methane-oxidizing bacteria and sulfate-reducing microbes, indicating a contribution of anaerobic pathways to primary consumers. Diversity of FA composition was highest in watersheds of intermediate slopes that contain both significant terrestrial inputs as well as high algal biomass. By controlling the accumulation rate and processing of terrestrial OM, watershed features influence the energetic base of food webs in boreal streams.
    Ecology 09/2015; 96(7):1775-82. DOI:10.1890/14-2247.1 · 4.66 Impact Factor
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    • "Fatty acids were quantified by integrating the peak areas using the CHROMQUEST 4.1 software and converting them into concentrations from the area vs. concentration of the internal standards. For fatty acid grouping into classes (total Saturated Fatty Acids, SAFA; Mono Unsaturated Fatty Acids, MUFA and Poly Unsaturated Fatty Acids, PUFA), only those with concentrations higher than 1% of the total fatty acids were considered (Dalsgaard et al., 2003). This methodology has already been applied in gorgonians (Gori et al., 2012b). "
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