Stable isotope labeling reveals patterns in essential fatty acid growth efficiency in a lipid-poor coastal calanoid copepod

Autor: Suzanne M. Budge, Catherine Johnson, Laura Helenius
Rok vydání: 2020
Předmět:
Zdroj: Marine Biology. 167
ISSN: 1432-1793
0025-3162
DOI: 10.1007/s00227-020-03794-8
Popis: Copepods are an important link in marine food webs, transferring crucial nutrients such as essential fatty acids (EFA) from primary producers to higher consumers. Yet data on lipid dynamics in marine ecosystems associated with small lipid-poor copepods are scarce. In this study, we used the coastal calanoid copepod Eurytemora herdmani, which is an opportunistic generalist feeder, to assess EFA-specific gross growth efficiency (GGEEFA), defined as the fraction of ingested EFA retained in copepod tissue. We conducted two eight-day feeding experiments with 13C-labeled phytoplankton to quantify incorporation and GGEEFA of eicosapentaenoic acid (20:5n-3; EPA) and docosahexaenoic acid (22:6n-3; DHA) in stage CV E. herdmani copepodites consuming either the EPA-replete diatom Thalassiosira weissflogii or the DHA-replete mixotrophic dinoflagellate Heterocapsa triquetra. EFA incorporation was quantified using gas chromatography. We recorded rapid shifts (within 48 h) in copepod tissue fatty acid (FA) composition following diet change, but not directly mirroring dietary algal FA. We also found high GGEEFA, with maxima of 46% and 61% for EPA and DHA, respectively, in copepods ingesting T. weissflogii and 39% and 87%, respectively, in copepods ingesting H. triquetra. GGEDHA remained higher than GGEEPA throughout the experiments regardless of dietary algae. GGEEFA decreased overall when copepods matured and produced nauplii, indicating EFA allocation for reproductive purposes. GGEDHA values in non-reproducing E. herdmani copepodites were high, suggesting that under predicted shifts in copepod community size structure, trophic transfer by small copepods could help compensate for DHA reductions resulting from lower abundances of large, lipid-rich species.
Databáze: OpenAIRE
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