CS39B Zooplankton - Community Dynamics
Date: Wednesday, June 12, 2002
Time: 11:15:00 AM
Location: Sidney
 
LarsonGL, USGS Forest and Rangeland Ecosystem Science Center, Corvallis, USA, gary_l._larson@usgs.gov
Hoffman, R, L, College of Oceanic and Atmospheric Science, Oregan State University, Corvallis, USA, 
McIntire, C, D, Department of Botany and Plant Pathology, Oregan State University, Corvallis, USA, 
 
PERSISTENCE OF AN UNUSUAL PELAGIC ZOOPLANKTON ASSEMBLAGE IN A CLEAR, MOUNTAIN LAKE
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The planktonic zooplankton assemblage in Mowich Lake, Mount Rainier National Park (MORA), was composed almost entirely of rotifers in 1966 and 1967. Adult pelagic crustacean taxa were rare. The paucity was attributed to predation by kokanee salmon (Oncorhynchus nerka), which had been stocked in 1961. During a park-wide survey of 24 lakes in 1988, Mowich Lake was the only one that did not contain at least one planktonic crustacean species. The Mowich Lake zooplankton assemblages in 1988-1999 were consistent with those in 1966 and 1967. Crustacean taxa were extremely rare, but they included most of the primary taxa collected from 23 MORA lakes surveyed in 1988. Nonetheless, the 1988 collections showed that the September rotifer assemblage in Mowich Lake was similar to 10 of the 24 lakes sampled. Seven of the 10 lakes were dominated by cladocerans, primarily Daphnia rosea and Holopedium gibberum. Therefore, it appeared that either one or both of these species may have numerically dominated the crustacean zooplankton assemblage in th elake prior to 1961.