Carbon Budgets for Overwintering Larval Euphausia superba

K.L. Daly, J. Torres, and S. Gallager

The overwintering behavior of larval krill (Euphausia superba) was investigated along the Western Antarctic Peninsula to better understand the effects of environmental variability on krill survival and recruitment. Recruitment has been linked to annual sea ice formation and extent, as sea ice may provide an overwintering food source (i.e., sea ice biota). Ingestion, assimilation efficiencies, respiration, and egestion rates of larvae were measured during autumn and winter 2001. Although larval krill were observed under sea ice, results suggest that sea ice formed late in the year at high latitudes may not allow sufficient growth of sea ice communities to provide a significant food source for overwintering krill. Assimilation efficiencies of larvae decreased between autumn and winter, reflecting the decreased quality of food. Concomitantly, carbon egestion almost doubled. Larval respiration and growth rates also decreased between fall and winter. Mass balance calculations indicate that on average C ingestion about equaled C losses. Larvae likely supported metabolic processes during winter by ingesting microzooplankton and detritus in the water column and from the undersurface of sea ice and by body combustion. Despite the late sea ice formation, a significant recruitment to the juvenile stage occurred following winter.

STATUS UPDATE:

Title, abstract, and author list received on 06/15/05.