Lipids as markers of nutritional condition and diet
in the Antarctic krill Euphausia superba
and Euphausia crystallorophias during
austral winter
Se-Jong Ju and H. Rodger Harvey
To
understand the nutritional condition and feeding history of Antarctic krill
during winter, two species of krill, Euphausia superba and E.
crystallorophias, were collected by MOCNESS during July-August 2001 in Marguerite
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 collected from the water column and
representing potential diets were also quantified and compared to krill. Stomach contents of adult krill were also
examined in select animals to provide a visual snapshot of ingested material
and allow 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). Results for lipid classes and individual
lipids suggest that E. superba is less dependent on stored lipid for
overwintering than E. crystallorophias.
Individual lipid profiles and stomach content of furcilia and adult E.
superba find that animals vary their diets over time, with copepods
representing a significant dietary source for adult animals in winter. Furciliae appears to feed largely on detritus
and diatom dominated ice algae with lower levels of lipid storage.