CS17 Invasive Species
Date: Thursday, June 13, 2002
Location: Poster Session - VCC
 
BrownME, University of Minnesota, Duluth, USA, smit1483@d.umn.edu
Branstrator, D, K, Univeristy of Minnesota Duluth, Duluth, USA, dbranstr@d.umn.edu
 
COMPOSITION AND ABUNDANCE OF ZOOPLANKTON IN THE WESTERN ARM OF LAKE SUPERIOR SINCE THE ARRIVAL OF BYTHOTREPHES
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Comprehensive surveys of zooplankton on Lake Superior were last conducted in 1973. Since then the lake has experienced a number of noteworthy changes to its biota including the invasion of the zooplankter Bythotrephes. We surveyed zooplankton in the western arm of the lake between Duluth, MN, and Silver Bay, MN, during May and August 2001. In August, Bythotrephes were widespread throughout the western arm, ranging in density from 40 to 285 individuals per square meter. We report declines in Bosmina and increases in Holopedium abundance since 1973. Seasonal patterns in plankton development are consistent with historical patterns in Lake Superior in that across all taxa the abundance and species richness at nearshore stations are greater in August compared to May. In August, abundance is higher at shallower stations compared to deeper stations.