Lipids and trophodynamics of Antarctic zooplankton

Abstract

Zooplankton were collected by trawl from the Elephant Island region of the Antarctic Peninsula and from East Antarctica near 63–65°S and 139–150°W. Most zooplankton had low percentages of wax esters (0–8%, as percent of total lipid). High triacylglycerol levels were found in the hyperiid amphipod Themisto gaudichaudii (68%, as percent of total lipid), the krill (Euphausiacea) Euphausia tricantha (44–54% triacylglycerol) and Euphausia frigida (27% triacylglycerol) and the scyphomedusan Periphylla periphylla (42–48% triacylglycerol). Polyunsaturated fatty acids (PUFA) comprised 23–60% of the total fatty acids, with the omega-3 fatty acids eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] being most abundant. P. periphylla was an exception with 12–19% docosapentaenoic acid [22:5 (n-3)] being the major PUFA. The major euphausiid sterols included cholesterol (75–92%, as percent of total sterols) and desmosterol (6–22%). The major sterols of other zooplankton were more diverse and included trans-dehydrocholesterol, 24-methylenecholesterol, brassicasterol and 24-nordehydrocholesterol. The benthic ascidian, Distaplia cylindrica, had 45% stanols, as percent of total sterols, whereas the pelagic ascidian Salpa thompsonii had only 8–11% stanols. Lipid, fatty acid and sterol data are used to examine trophodynamic interactions and provide an ability to distinguish herbivorous and carnivorous diets and determine survival and reproductive strategies.