Assessing stable isotope dynamics of diapausing Calanus finmarchicus and C. hyperboreus during the overwintering period: a laboratory experiment

• Published in: Journal of Plankton Research
• Main Authors: Perrin, G., DiBacco, C., Plourde, S., Winkler, G.
• Format: Text
• Language: English
• Published: Oxford University Press 2012
• Subjects: Article; Canada; Calanus finmarchicus; Subarctic; Copepods
• Online Access: http://plankt.oxfordjournals.org/cgi/content/short/fbs042v1; https://doi.org/10.1093/plankt/fbs042

This study aimed at describing changes in the stable isotopic composition of late copepodite stage V (CV) subarctic marine copepods ( Calanus finmarchicus and C. hyperboreus ) during overwintering non-feeding periods. Diapausing stage CVs sampled in deep waters of the Lower St. Lawrence Estuary (Québec, Canada) in late-September 2009 were monitored for 4 months under controlled laboratory conditions. CVs and newly moulted adults were analyzed for δ 13C and δ 15N signatures as well as lipid, carbon and nitrogen content. Lipids were extracted in half of the samples to compare δ 13C of individuals with and without lipids and to evaluate the accuracy of mass balance correction models for δ 13C under lipid influence. Lipid content generally decreased with time for both species, which was reflected in an increase of δ 13C values of CVs but a constant δ 13C in newly moulted adults. Accordingly, lipid extraction resulted in an increase of δ 13C in CVs and adults. The mean δ 13C signature of lipid-extracted individuals remained constant through the time for CVs of both species and for C. finmarchicus adults. δ 15N signatures of individuals increased after lipid extraction, but this did not result in a constant value over time, suggesting that several endogenous metabolic processes affected nitrogen isotopic content. The accuracy of the mass balance model differed between species and stages, suggesting that lipid extraction should always be performed prior to applying mathematical corrections.