Distribution and abundance of zooplankton populations
in Crater Lake,Oregon |
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Authors: | Gary L Larson C David McIntire Mark W Buktenica Scott F Girdner Robert E Truitt |
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Institution: | (1) U. S. Geological Survey, Forest and Rangeland Ecosystem Science Center, 3200 SW Jefferson Way, Corvallis, OR 97331, USA;(2) Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA;(3) Crater Lake National Park, Crater Lake, OR 97604, USA;(4) College of Forestry, Oregon State University, Corvallis, OR 97331, USA |
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Abstract: | The zooplankton assemblages in Crater Lake exhibited consistency in species richness and general taxonomic composition, but
varied in density and biomass during the period between 1988 and 2000. Collectively, the assemblages included 2 cladoceran
taxa and 10 rotifer taxa (excluding rare taxa). Vertical habitat partitioning of the water column to a depth of 200 m was
observed for most species with similar food habits and/or feeding mechanisms. No congeneric replacement was observed. The
dominant species in the assemblages were variable, switching primarily between periods of dominance of Polyarthra-Keratella cochlearis and Daphnia. The unexpected occurrence and dominance of Asplanchna in 1991 and 1992 resulted in a major change in this typical temporal shift between Polyarthra-K. cochlearis and Daphnia. Following a collapse of the zooplankton biomass in 1993 that was probably caused by predation from Asplanchna, Kellicottia dominated the zooplankton assemblage biomass between 1994 and 1997. The decline in biomass of Kellicottia by 1998 coincided with a dramatic increase in Daphnia biomass. When Daphnia biomass declined by 2000, Keratella biomass increased again. Thus, by 1998 the assemblage returned to the typical shift between Keratella-Polyarthra and Daphnia. Although these observations provided considerable insight about the interannual variability of the zooplankton assemblages
in Crater Lake, little was discovered about mechanisms behind the variability. When abundant, kokanee salmon may have played
an important role in the disappearance of Daphnia in 1990 and 2000 either through predation, inducing diapause, or both.
Electronic supplementary material Electronic supplementary material is available for this article at
and accessible for authorised users. |
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Keywords: | Zooplankton Rotifer Cladoceran Caldera lake Crater Lake |
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