Calcium levels in Daphnia ephippia cannot provide a useful paleolimnological indicator of historical lakewater Ca concentrations |
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Authors: | Adam Jeziorski Andrew M. Paterson Norman D. Yan John P. Smol |
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Affiliation: | (1) Paleoecological Environmental Assessment and Research Lab (PEARL), Department of Biology, Queen’s University, Kingston, Ontario, Canada, K7L 3N6;(2) Ontario Ministry of the Environment, Dorset Environmental Science Centre, 1026 Bellwood Acres Road, Dorset, Ontario, Canada, P0A 1E0;(3) Department of Biology, York University, 4700 Keele Street, Toronto, Ontario, Canada, M3J 1P3;(4) Dorset Environmental Science Centre, 1026 Bellwood Acres Road, Dorset, Ontario, Canada, P0A 1E0 |
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Abstract: | Despite reductions in atmospheric sulphur emissions and the resulting decline in acidic deposition, many lakes on the Canadian Shield that have experienced acidification are either recovering at a rate slower than expected or not recovering at all. This lack of recovery is believed to be partly the consequence of the depletion of exchangeable base cations (principally calcium, Ca) from watershed soils. Although the implications of reduced Ca availability for biological communities remain poorly understood, the effects on crustacean zooplankton populations may be severe, as Ca is the primary structural component of the crustacean zooplankton exoskeleton. Because the daphniid resting egg is protected by a modified portion of the exoskeleton (ephippia) and because these ephippia are well preserved in lake sediments, we investigated whether inter-specific differences in Ca content are recoverable from Daphnia ephippia. However, using two methods, we did not find a recoverable Ca signal in the ephippia, indicating that future efforts should be focused upon sedimentary taxonomic assemblage differences, not differences in ephippial Ca levels. |
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Keywords: | Daphnia Calcium (Ca) Zooplankton Ephippia Acidification Cladocera |
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