Fatty acid composition as an indicator of carnivory in Antarctic krill, Euphausia superba

In a previous study at South Georgia, carnivory was invoked as a cause of h igh polyunsaturated fatty acid (PUFA) content of Antarctic krill, Euphausia superba. To examine this, krill were sampled and fed for 16 days exclusive ly on the locally abundant copepod Drepanopus forcipatus. After 16 days, th e krill had increased their PUFA content from 28 to 54% of the total fatty acids. Concurrently, monounsaturated fatty acids (MUFAs) and saturated fatt y acids (SFAs) decreased from 41 to 27%. Thus, the krill appeared to accumu late PUFAs as reflected in their diet of D. forcipatus, which also had a re latively high PUFA content (50%). Overall, the results support omnivorous f eeding by krill at South Georgia during nonbloom periods. We propose that t he ratio of PUFA to SFA content may be used to detect carnivory in the rece nt feeding history of krill and suggest that this may be an index which cou ld be applied to other zooplankton.