Grazing rates of a calanoid copepod (Paralabidocera antarctica) in a continental Antarctic lake

The presence of crustaceans in some Antarctic lakes adds a level of complex ity to the food webs of these environments. The grazing pressure of the cru staceans on phytoplankton and other protists, and the role they play in con trolling food web structure, has not yet been examined in any detail. This paper presents the first data on grazing pressure of crustacean zooplankton in continental Antarctic lakes. In this study the grazing rates of Paralab idocera antarctica in saline Ace Lake, Vestfold Hills, were assessed using a radio-tracer method. Clearance rates ranged from approximately 1 to 8 ml ind.(-1) day(-1), depending on developmental stage. Due to their high abund ance, nauplii exhibited the highest daily carbon ingestion rates. The popul ation cleared about 3% of the water column per day, accounting for a signif icant fraction of primary production. P. antarctica has a considerable impa ct on the carbon cycle in Ace Lake and, by inference, in the other lakes in which it occurs.