SS1.03 Zooplankton Response to Climate Variability
Date: Monday, June 10, 2002
Time: 11:15:00 AM
Location: Lecture Theatre
 
BridgemanTB, University of Michigan, Ann Arbor, USA, thomas.bridgeman@utoledo.edu
 
HISTORICAL RESPONSE OF ZOOPLANKTON COMMUNITIES TO ECOLOGICAL CHANGE IN LAKE VICTORIA (EAST AFRICA)
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In recent decades, profound changes in the Lake Victoria ecosystem have been accompanied by changes in zooplankton and phytoplankton communities. Climate change and anthropogenic influences have been implicated, but analysis has been confounded by a scarcity of historical records, creating difficulties in determining the timing of changes in zooplankton, phytoplankton, and fish communities in relation to each other. In this study fossil remains of diatoms, zooplankton (Bosmina, chydorids), and an invertebrate predator (Chaoborus) in sediment cores were analyzed to assemble a 50-100 year record of changes in the plankton community. The most dramatic changes occurred in the 1980s, when chydorids and Bosmina declined precipitously, nearly disappearing from nearshore areas (Bosmina persist offshore). The loss of cladocerans from the nearshore plankton corresponded to a shift in the diatom community from dominance by Aulacoseira sp. to Nitszchia sp., and to increasing populations of Chaoborus and a cyprinid planktivore in nearshore areas. The results suggest that the demise of cladoceran zooplankton resulted from increasing predator densities combined with environmental changes that led to increased hypoxia of bottom waters.