Calcium content of crustacean zooplankton and its potential role in species distribution |
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Authors: | Svein B. Wæ rvå gen,Nina A. Rukke&dagger , Dag O. Hessen&dagger |
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Affiliation: | Department of Agriculture and Natural Science, Hedmark College, Blæstad, Ridabu, Norway;Department of Biology, University of Oslo, Blindern, Oslo, Norway |
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Abstract: | SUMMARY 1. The occurrence and species composition of crustacean zooplankton in Norwegian lakes was related to ambient Ca concentrations, pH, total phosphorus and chlorophyll a , and to the presence/absence of other zooplankters and a planktivorous fish (roach: Rutilus rutilus ). 2. Ambient Ca concentrations appeared to influence the distribution of Daphnia species: Daphnia longispina often occurred in Ca-rich lakes with low fish-predation pressure while the smaller Daphnia cristata often occurred in opposite conditions. 3. Body Ca contents were measured in zooplankters from a wide range of localities, to examine Ca requirements and thus the potential for Ca-limitation of common species. 4. All Daphnia species had relatively high specific Ca contents [ranging from 0.8 to 4.4% Ca dry weight (DW)−1] compared with other cladocerans and also copepods (ranging from 0.1 to 0.4% Ca DW−1). Within the Daphnia genus, the specific Ca content increased with increasing body size of the species, and thus the large-bodied species had especially high Ca demands. 5. Because of their high Ca demands, species of Daphnia could be competitively disadvantaged in softwater lakes relative to less Ca-demanding species. |
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Keywords: | calcium content crustacea Daphnia softwater zooplankton |
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