Seasonal and growth stage changes in lipid and fatty acid composition in the multigeneration copepodDrepanopus pectinatusfrom Iles Kerguelen

Abstract

Changes in adult weight, lipid and fatty acid composition per lipid class were studied over a complete seasonal cycle in Drepanopus pectinatus Brady. This copepod displayed a strong seasonality in adult individual weight and total lipid content. Stages C3 to adult from a summer cohort were compared in terms of lipid and fatty acid structure. Changes in lipid content were related to wax esters and polar lipids (PL) while triacylglycerols (TAG) and cholesterol remained minor constituents except at the end of winter. Changes in fatty acid composition of different lipid classes showed that food limitation in winter was high enough to affect 22:6n-3 (DHA) content in PL, and provoke accumulation of maximal percentages of bacterial marker as branched acids. Composition of TAG followed closely the changes in trophic interactions as diatom and flagellate markers dominated in spring and summer while bacterial and detritus particle markers dominated in late winter. The composition of wax esters followed the same seasonal succession but with a lower level of turn over time and shifted characteristics (bacterial markers) from winter to spring individuals when compared to TAG. Ontogenetic changes showed high triacylglycerols content in younger C3 stages and increasing wax esters with increasing developmental stages. Fatty acid composition of PL showed low percentages of EPA and DHA in stage C3, and recovery of high levels of DHA for stage C4 or 20:5n-3 (EPA) at stage C5. The same trend was observed for 18:4n-3. The reverse pattern was noted for the n-6 polyunsaturated acids (PUFA) suggesting a greater requirement in younger stages. Fatty acid partitioning between neutral and PL suggested essential fatty acids selective incorporation from neutral classes into membrane lipids.

Biochemical composition and energy content of size-fractionated zooplankton east of the Kerguelen Islands

“…Wide spatial and temporal variations in the biochemical composition of zooplanktonic organisms are reported in the literature (Raymont et al 1971;Donnelly et al 1993;Nageswara Rao and Ratna Kumari 2002). Major variations are particularly observed in polar regions, where lipid storage is an important seasonal phenomenon (Percy and Fife 1981;Ward et al 1996;Lee et al 2006;Mayzaud et al 2011). Wide variations in the biochemical composition of size-fractionated zooplankton among stations were also recorded in Kerguelen waters during the onset of the spring bloom (Table 5).…”

“…Strong seasonality in total lipid content has been well studied in Arctic and Antarctic planktonic organisms, particularly in crustaceans, such as copepods, euphausiids and amphipods, that have to respond to food shortage and diapause for winter survival, then to reproduction and ontogeny during phytoplankton bloom (Percy and Fife 1981;Reinhard and van Vleet 1986;Mayzaud et al 2011). The energy content of planktonic organisms varies widely with season according to trophic resource variations and zooplankton growth (e.g.…”

“…However, most of them were performed either on bulk zooplankton without information on species and size composition (Bhat et al 1993;Nageswara Rao and Ratna Kumari 2002;Arun Kumar et al 2013), or on the dominant species (Percy and Fife 1981;Reinardt and van Vleet 1986;Torres et al 1994). Much information is available on lipid content, particularly for polar species (Ward et al 1996;Falk-Petersen et al 1999;Lee et al 2006;Mayzaud et al 2011), but less for proteins, carbohydrates or energy content (Donnelly et al 1993;Färber-Lorda et al 2009;Arun Kumar et al 2013).…”

Population dynamics of modern planktonic foraminifera in the western Barents Sea

“…Lipids in zooplankton organisms are very variable geographically, showing a latitudinal pattern with high percentages in polar areas and low percentages in warm tropical waters. Lipid percentages also display seasonal features, with higher values in summer than in winter (Falk-Petersen et al, 1999;Mayzaud et al, 2011;Kumar et al, 2013). It is thus possible that a part of the energy (biomass / C org ) of the PF collected along the south-tonorth transect shifts from being stocked as protein in warmer waters to being stocked as lipids in colder waters.…”

bg-2017-414 Authors response to Reviewer 1

“…Nematode fatty acid profiles are significantly enriched in C 16 : 1 (cis-9) and EPA, two major lipid compounds we have shown to be statistically associated with summer export events dominated by diatom resting spores. Resistance to grazing (Kuwata and Tsuda, 2005) and enhanced sinking velocities of resting spores compared to vegetative cells (McQuoid and Hobson, 1996) result in their effective transfer to the seafloor (Rembauville et al, 2016a), consistent with the fact they are a common feature of sediments underlying productive regimes (Crosta et al, 1997;Armand et al, 2008;Tsukazaki et al, 2013). The ecology of resting spore formation therefore acts as an efficient conduit for transferring energy-rich storage lipids to the sediment, and they may thus play a particularly important role in pelagic-benthic coupling.…”