Comparative lipid dynamics of euphausiids from the Antarctic and Northeast Pacific Oceans
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To better understand the feeding and reproductive ecology of euphausiids (krill) in different ocean environments, lipid classes and individual lipid components of four different species of euphausiids from Northeast Pacific (temperate species) and Southern Ocean (Antarctic species) were analyzed in animals from multiple life stages and seasons. The dominant krill species in the Northeast Pacific Euphausia pacifica and Thysanoessa spinifera, were compared to the two major Antarctic species, Euphausia superba and E. crystallorophias. Analysis comprised total lipid and lipid classes together with individual fatty acid and sterol composition in adults, juveniles, and larvae. Antarctic krill had much higher lipid content than their temperate relatives (10–50 and 5–20% of dry mass for Antarctic and temperate species, respectively) with significant seasonal variations observed. Phospholipids were the dominant lipid class in both temperate krill species, while neutral storage lipids (wax esters and triacylglycerols for E. crystallorophias and E. superba, respectively) were the major lipid class in Antarctic krill and accounted for up to 40% of the total lipid content. Important fatty acids, specifically 16:0, 18:1ω9, 20:5ω3, and 22:6ω3, were detected in all four krill species, with minor differences between species and seasons. Detailed lipid profiles suggest that krill alter their lipid composition with life stage and season. In particular, larval Antarctic krill appear to utilize alternate food resources (i.e., sea-ice associated organisms) during austral winter in contrast to juveniles and adults (i.e., seston and copepods). Lipid dynamics in krill among krill in both systems appear closely linked to their life cycle and environmental conditions including food availability, and can provide a more complete comparative ecology of euphausiids in these environmentally distinct systems.
KeywordsLipid Class Fatty Alcohol Total Lipid Content Temperate Species Antarctic Krill
We thank William Peterson, Tracy Shaw, Leah Feinberg, Rachael Dyda, Steve McGuire and Susan Klosterhaus for their assistance in the collection of euphausiids. This work was supported by the NSF through the Southern Ocean GLOBEC program (OPP-9910043 to HRH) and NOAA through the Northeast Pacific GLOBEC program (OCE-0000732 to HRH through NSF). S.-J. Ju was also partially supported by KORDI projects (PP00720 and PE9830V) and the industrial and academic outstanding researcher invitation program sponsored by KORP. This manuscript is contribution No. 4269 of The University of Maryland Center for Environmental Science and contribution No. 630 of USGLOBEC program.
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