Understanding the food selectivity of Euphausia pacifica in Yellow Sea: in-situ live feeding experiment with natural food assemblages

Abstract

Euphausia pacifica play a key role in the transfer of energy to higher trophic levels and maintain the function and structure of the Yellow Sea ecosystem because of their abundance and high biomass. Although understanding their feeding ecology is necessary to accurately elucidate the structure and function of the Yellow Sea ecosystem, very limited information is available on their feeding ecology and behavior through the season. Therefore, we conducted short-term live feeding experiments for adult E. pacifica with natural food assemblages at selected stations during spring and summer 2013. All live animals were collected and maintained in filtered seawater for ~ 6 hours before the experiments, to reduce their gut contents. Then 2~5 individuals were incubated in a glass jar (2 or 4 L) under dark and in-situ temperature conditions with or without natural food assemblages for 10~12 hours. At the end of the incubation, water samples for Chl-a, nutrients, POC, and microplankton assemblages were collected and analyzed to track any changes during incubations. The preliminary results suggest that adult E. pacifica seems to selectively feed on ciliates and heterotrophic dinoflagellates among natural diet assemblages during spring algal blooms even though a large amount of other food items (diatoms, autotrophic dinoflagellates, etc.) were available. However, no clear changes were detected in other measurements. Therefore, in-ogy is necessary to accurately elucidate the structure and function of the Yellow Sea ecosystem, very limited information is available on their feeding ecology and behavior through the season. Therefore, we conducted short-term live feeding experiments for adult E. pacifica with natural food assemblages at selected stations during spring and summer 2013. All live animals were collected and maintained in filtered seawater for ~ 6 hours before the experiments, to reduce their gut contents. Then 2~5 individuals were incubated in a glass jar (2 or 4 L) under dark and in-situ temperature conditions with or without natural food assemblages for 10~12 hours. At the end of the incubation, water samples for Chl-a, nutrients, POC, and microplankton assemblages were collected and analyzed to track any changes during incubations. The preliminary results suggest that adult E. pacifica seems to selectively feed on ciliates and heterotrophic dinoflagellates among natural diet assemblages during spring algal blooms even though a large amount of other food items (diatoms, autotrophic dinoflagellates, etc.) were available. However, no clear changes were detected in other measurements. Therefore, in-