Understanding the feeding ecology of Euphausia pacifica in the Yellow Sea using multiple approaches

Abstract

Euphausia pacifica, known as a key species in the Yellow Sea ecosystem, plays the roles to transfer the energy to higher trophic level and maintain the function and structure of the Yellow Sea ecosystem because of their abundance and high biomass. Although it is necessary to understand the feeding ecology of E. pacifica for elucidating the structure and function of the Yellow Sea ecosystem, it has not been sufficiently studied yet. Therefore, in order to trace the source of nutrient and diets of E. pacifica during spring and summer in the Yellow Sea, we applied multiple approaches (e.g., in-situ feeding experiments, gut contents, dietary fatty acid markers, stable isotope). According to the gut contents, dietary fatty acid markers, and stable isotope signatures, the diet sources of E. pacifica were seasonally shifted from algal-based (i.e., diatom) in spring to microbial-based particles (i.e., detritus, protozoa) in summer. Whereas their energy (carbon) source was highly variable and diverse in spring depending on the sampling location (inshore vs. offshore), it was relatively uniform and significantly contributed by in-situ production throughout the regions in summer due to the limitation of their foraging and feeding ground within the cold bottom water (≤10°C). In addition to, in-situ feeding experiments indicated that adult E. pacifica seems to preferentially feed on ciliates and heterotrophic dinoflagellates wiiomass. Although it is necessary to understand the feeding ecology of E. pacifica for elucidating the structure and function of the Yellow Sea ecosystem, it has not been sufficiently studied yet. Therefore, in order to trace the source of nutrient and diets of E. pacifica during spring and summer in the Yellow Sea, we applied multiple approaches (e.g., in-situ feeding experiments, gut contents, dietary fatty acid markers, stable isotope). According to the gut contents, dietary fatty acid markers, and stable isotope signatures, the diet sources of E. pacifica were seasonally shifted from algal-based (i.e., diatom) in spring to microbial-based particles (i.e., detritus, protozoa) in summer. Whereas their energy (carbon) source was highly variable and diverse in spring depending on the sampling location (inshore vs. offshore), it was relatively uniform and significantly contributed by in-situ production throughout the regions in summer due to the limitation of their foraging and feeding ground within the cold bottom water (≤10°C). In addition to, in-situ feeding experiments indicated that adult E. pacifica seems to preferentially feed on ciliates and heterotrophic dinoflagellates wi