TITLE:    Krill as Consumers: The Importance of Phytoplankton
	  Community Composition to Krill Diet

AUTHORS:  KL Haberman, RM Ross and LB Quetin (presented by KLH)

MEETING:  American Society of Limnology and Oceanography

DATE:     June 12-15, 1995


ABSTRACT: Antarctic krill, Euphausia superba, are key consumers of 
phytoplankton in the Antarctic marine ecosystem.  This study focuses 
upon the importance of phytoplankton community composition to the krill.  
In particular, the suitability of the prymnesiophyte Phaeocystis sp. 
as food for krill is compared to diatoms, based on ingestion rates, 
assimulation efficiency, growth and condition of the krill.
   Ingestion rates by krill on Phaeocystis sp. ranging from single 
cells to large colonies were compared to rates on the diatoms 
Thalassiosira sp. and Nitzschia sp.  Algal monocultures, mixtures of 
mconocultures, and natural phytoplankton assemblages were used as 
phytoplankton sources.  Ingestion rates and selectivity were measured 
based upon disappearance of chlorophyll and key pigments from the water.  
Carbon and nitrogen ingestion rates were calculated based on CHN 
analysis.  Carbon and nitrogen ingestion were approximately equal for 
Thalassiosira and Phaeocystis colonies but lower for single cell Phaeocystis, 
at initial chlorophyll concentrations of 5 micrograms per liter.
     Experiments in progress include measurement of assimilation efficiency by
krill for different phytoplankton types, and comparison of growth and
condition factor for krill fed Phaeocystis vs. diatoms.