SS1.03 Zooplankton Response to Climate Variability
Date: Monday, June 10, 2002
Time: 3:00:00 PM
Location: Lecture Theatre
 
LevineSN, Univ. Vermont, Burlington, USA, slevine@zoo.uvm.edu
Zehrer, R, F, Univ. Otago, Dunedin, New Zealand, reglindiszehrer@yahoo.de
Burns, C, W, Univ. Otago, Dunedin, New Zealand, carolynburns@stonebow.otago.ac.nz
 
IMPACT OF RESUSPENDED SEDIMENTS ON ZOOPLANKTON FEEDING IN A SHALLOW LAKE
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Wind-driven mixing frequently resuspends sediments in shallow exposed lakes. Consequences include reduced light penetration, elevated nutrient and organic matter concentrations, and interference with zooplankton and fish feeding. We assessed the impact of suspended sediments on Daphnia carinata and Boeckella hamata feeding in shallow Lake Waihola, New Zealand, by incubating animals in bottles amended with surface sediments and turned on a plankton wheel. A turbidity increase of from 2.5 to 10 NTU reduced Daphnia clearance rates on all important prey items. Phytoplankton harvesting declined by 75%, while filtration of ciliates, amoeba, heterotrophic flagellates and attached bacteria declined by 30-100% (free bacteria were not eaten). Further inhibition occurred at 30, 60 and 100 NTU. Boeckella feeding was assessed only at 2.5 and 100 NTU. This increase reduced grazing on rotifers by 56% (phytoplankton were not consumed). Given that Lake Waihola’s turbidity exceeds 10 NTU more than 50% of the time, suspended sediments likely play an important role in structuring the lake’s food web.