SS3.01 Landscape Control of High Latitude Lake and River Ecosystems
Date: Thursday, June 13, 2002
Time: 12:00:00 PM
Location: Carson A
 
RiedelAJ, Simon Fraser University, Burnaby, Canada, ajriedel@sfu.ca
Lesack, L, F, Simon Fraser University, Burnaby, Canada, Lance_Lesack@sfu.ca
 
ZOOPLANKTON COMPOSITION AND CONTROL OF HETEROTROPHIC FLAGELLATES AMONG LAKES OF THE MACKENZIE DELTA
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Frequency and duration of river flooding may substantially influence food webs among the 25,000 lakes in the Mackenzie River Delta. Food web configurations may change as the river flooding regime is altered via climatic warming. To model links among the flooding regime, autotrophic production, and DOC-fueled heterotrophic production, zooplankton community composition was assessed for 15 lakes across the flood-frequency gradient of the delta, and the weekly dynamics in 3 lakes were tracked over an open-water season. The potential for zooplankton groups to consume heterotrophic flagellates was assessed by isolating (microcosms) communities from lakes with 3 differing flood-frequencies into 3 planktonic size fractions in a lab incubator and measuring the clearance of flagellates. Lakes of intermediate flooding-frequency had the highest total zooplankton densities. Rotifers and small-bodied zooplankton dominated in frequently-flooded lakes, while Copepods and large-bodied zooplankton dominated in infrequently-flooded lakes. In the experimental manipulations, the greatest clearance of flagellates occurred when the community was dominated by Cladocerans. However, control of flagellates and bacteria among these lakes may not be a direct result of zooplankton consumption.