Lipids as markers of nutritional condition and diet in the Antarctic krill Euphausia superba and Euphausia crystallorophias during austral winter

Abstract

To understand the nutritionalcondition and feeding history of Antarctic kril lduring winter, Euphausia superba and E. crystallorophias were collected by MOCNESS during July–August 2001 in Maguerite Bay southeast of Adelaide Island. Total lipid, lipid classes, fatty acids, fatty alcohols and sterols were analyzed in animals among several life stages. Lipids in seston and major copepods representing potential diets were collected from the water column and quantified to compare with krill. Stomach contents also were examined in selected adult krill to provide a visual snapshot of ingested material and comparison with lipid biomarkers. Total lipids in adult E. crystallorophias were significantly higher than adult E. superba (30.0% and 20.2% of dry weight, respectively). Wax esters were the major storage lipid in E. crystallorophias, accounting for over half (mean of 55.9%) of the total lipid in adult animals. In contrast, E. superba contained triacylglycerols as the dominant storage lipid in adults (mean of 45.5% of total lipid). Fatty acid and sterol distributions in krill showed minor differences between species and life stages. Larval krill, however, contained higher polyunsaturated fatty acids (PUFA) than sub- and adult krill. While only trace amounts of fatty alcohols were found in E. superba, significant amounts were found in E. crystallorophias, particularly 14:0 and 16:0, which were major components of wax esters. Results for lipid classes, individual lipids, and stomach content suggest that E. superba is less dependent on stored lipid for overwintering than E. crystallorophias. E. superba are omnivorous, with copepods representing a significant dietary source for adults in winter. Furciliae of both species contain lower levels of lipid storage in winter and feed largely on detritus or organisms associated with ice. r 2004 Elsevier Ltd. All rights reserved.