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GLIN==> SEMINAR OCT 15 - ANN ARBOR



Title:
NOAA GREAT LAKES SEMINAR SERIES
http://www.glerl.noaa.gov/news/seminars/

Date:
Wednesday, October 15, 2003

Time:
10:30 a.m.

Title:
"HISTORICAL RESPONSE OF ZOOPLANKTON COMMUNITIES TO ECOLOGICAL CHANGE IN LAKE VICTORIA (EAST AFRICA)"

Speaker:
Dr. Thomas Bridgeman
Research Assistant Professor
University of Toledo, Lake Erie Center


Where:
GLERL Main Conference Room
2205 Commonwealth Blvd.
Ann Arbor, MI 48105
For directions:

    http://www.glerl.noaa.gov/facil/triptik.html

Abstract
The introduction of a large predator, the Nile perch (Lates niloticus), caused devastating losses in the fish community of Lake Victoria between 1960-1990, with an accompanying loss of zooplankton and phytoplankton species diversity.  Climate change and anthropogenic influences have also been implicated in these losses, 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-year record of changes in the plankton community.  The most dramatic changes occurred in the 1980s when several cladoceran species were extirpated from nearshore zooplankton assemblages.  These losses corresponded to a rapid shift in the diatom community from dominance by Aulacoseira sp. to Nitszchia sp., and to increasing populations of Chaoborus and the cyprinid planktivore Rastrineobola argentea 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.  An additional example of the importance of stratification and hypoxia in structuring invertebrate communities is given from current research on western Lake Erie mayfly (Hexagenia sp.) recruitment.

For more information, contact:
Dr. David Reid
734-764-2019

david.reid@noaa.gov

-- 
David F. Reid, Ph.D.
U.S. Department of Commerce
National Oceanic and Atmospheric Administration
Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI  48105-2945
Voice:	734-741-2019
FAX:	743-741-2055
GLERL home page:
   http://www.glerl.noaa.gov

-- 
David F. Reid, Ph.D.
U.S. Department of Commerce
National Oceanic and Atmospheric Administration
Great Lakes Environmental Research Laboratory
2205 Commonwealth Blvd.
Ann Arbor, MI  48105-2945
Voice:	734-741-2019
FAX:	743-741-2055
GLERL home page:
   http://www.glerl.noaa.gov