Tracking seasonal dietary shift of Euphausia pacifica in the Yellow Sea using stomach contents and lipid biomarkers

Abstract

Krill Euphausia pacifica, known as one of major preys for various predators, is important species to understand their role for the energy transfer in the Yellow Sea ecosystem. Therefore, to determine the nutritional condition and seasonal diet shift of E. pacifica, they were collected using the conical type net during spring and summer 2010 in the Yellow Sea. Lipid and fatty acid (FA) were analyzed for adults. For some selected adults, stomach contents were also examined to provide a visual snapshot of eaten material and to compare with trophic FA markers. Total lipid contents in E. pacifica were higher in spring (7.4±1.5% of dry mass) than those in summer (5.2±2.3% of dry mass), with the major component of phospholipid (over half of total lipid). Overall major FAs composition showed seasonal differences (spring vs. summer). E. pacifica from spring contained higher concentration of polyunsaturated FAs (PUFAs) originating from algae than those from summer, whereas the relative abundance of branched FAs known to be of bacterial origin were significantly higher in E. pacifica from summer than those from spring. Actually, these results were also revealed through stomach contents, which consisted of more diatoms in spring and diverse and smaller-sized prey items (algae, protozoa, detritus, etc.) in summer. Thus, it suggests that E. pacifica mainly feeds on diatoms and flagellates in spring, but their diets can be resortiet shift of E. pacifica, they were collected using the conical type net during spring and summer 2010 in the Yellow Sea. Lipid and fatty acid (FA) were analyzed for adults. For some selected adults, stomach contents were also examined to provide a visual snapshot of eaten material and to compare with trophic FA markers. Total lipid contents in E. pacifica were higher in spring (7.4±1.5% of dry mass) than those in summer (5.2±2.3% of dry mass), with the major component of phospholipid (over half of total lipid). Overall major FAs composition showed seasonal differences (spring vs. summer). E. pacifica from spring contained higher concentration of polyunsaturated FAs (PUFAs) originating from algae than those from summer, whereas the relative abundance of branched FAs known to be of bacterial origin were significantly higher in E. pacifica from summer than those from spring. Actually, these results were also revealed through stomach contents, which consisted of more diatoms in spring and diverse and smaller-sized prey items (algae, protozoa, detritus, etc.) in summer. Thus, it suggests that E. pacifica mainly feeds on diatoms and flagellates in spring, but their diets can be resort