CS16 Harmful Algal Blooms
Date: Wednesday, June 12, 2002
Time: 4:30:00 PM
Location: Sidney
 
ColinSP, University of Connecticut, Groton, USA, sean.colin@uconn.edu
Dam, H, G, University of Connecticut, Groton, USA, hans.dam@uconn.edu
 
ADAPTATION OF THE COPEPOD ACARTIA HUDSONICA TO THE TOXIC DINOFLAGELLATE ALEXANDRIUM SP.
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Harmful algal blooms (HABs) appear to be spreading geographically and their effects on coastal ecosystems are not understood, i.e. how grazers respond to them. We report on adapted resistance of natural copepod populations to the spreading toxic dinoflagellate Alexandrium sp. In transplant experiments, we show that the calanoid copepod Acartia hudsonica from regions frequently exposed to the toxic Alexandrium blooms exhibit higher ingestion rates and fitness parameters than A. hudsonica from populations na´ve to these blooms. Measurements of short-term changes in the na´ve copepods’ ingestion rates (3 hour intervals) revealed that the copepods were initially ingesting toxic Alexandrium at high rates. However, their ingestion rates decreased to near zero within twelve hours. These decreases in the ingestion rates of na´ve A. hudsonica were accompanied by significant decreases in metabolic rates (i.e. oxygen consumption). The ingestion and metabolic rate changes suggest that toxic Alexandrium physiologically incapacitate the na´ve copepods. Genetic differentiation among A. hudsonica populations has occurred and suggests a strong selective pressure by the toxic dinoflagellate.