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Science 19 January 1990:
Vol. 247. no. 4940, pp. 312 - 315
DOI: 10.1126/science.247.4940.312
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Articles

Effects of Fish and Plankton and Lake Temperature and Mixing Depth

A. Mazumder 1, W. D. Taylor 1, D. J. McQueen 2, and D. R.S. Lean 3

1 Department of Biology, University of Waterloo, Waterloo, Ontario, N2L 3G1 Canada
2 Department of Biology, York University, North York, Ontario, M3J 1P3 Canada
3 National Water Research Institute, Post Office Bos 5050, Burlington, Ontario, L7R 4A6 Canada

A comparative study of small temperate lakes (<20 square kilometers) indicates that the mixing depth or epilimnion is directly related to light penetration measured as Secchi depth. Clearer lakes have deeper mixing depths. This relation is the result of greater penetration of incident solar radiation in lakes and enclosures with high water clarity. Data show that light penetration is largely a function of size distribution and biomass of algae as indicated by a relation between the index of plankton size distribution (slope) and Secchi depth. Larger or steeper slopes (indicative of communities dominated by small plankton) are associated with shallower Secchi depth. In lakes with high abundances of planktivorous fish, water clarity or light penetration is reduced because large zooplankton, which feed on small algae, are reduced by fish predation. The net effect is a shallower mixing depth, lower metalimnetic temperature and lower heat content in the water column. Consequently, the biomass and size distribution of plankton can change the thermal structure and heat content of small lakes by modifying light penetration.

Submitted on July 31, 1989
Accepted on November 13, 1989


THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES:
Environmental factors controlling the vertical distribution of phytoplankton in lakes.
M. L. Longhi and B. E. Beisner (2009)
J. Plankton Res. 31, 1195-1207
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