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DECLINE IN LAKE ONTARIO POPULATIONS OF BENTHIC MACROINVERTEBRATES
Citation:
Lozano, S J., J. V. Scharold, AND T. F. Nalepa. DECLINE IN LAKE ONTARIO POPULATIONS OF BENTHIC MACROINVERTEBRATES. JOURNAL OF FISHERIES AND RESEARCH BOARD OF CANADA 58(3):518-529, (2001).
Description:
Surveys of benthic macroinvertebrates conducted in Lake Ontario during 1994 and 1997 revealed declines in populations of three major groups of organisms: oligochaetes, sphariids, and Diporeia spp. (Amphipoda), with the most drastic reductions occurring in the latter. Based on physical and chemical characteristics of the sediments, the lake could be divided into three zones: an erosional zone around the edge of the lake, a depositional zone located central in the lake, and a transitional zone. Mean densities of Diporeia were greatest in the transitional zone, with densities of 3368 m -2 in 1994 to 1997. Mean densities of Oligochaeta and Sphaeriidae were greatest in the erosional zone. Abundance of all three major taxa declined within all three sediment classes from 1994 to 1997. The largest reductions in abundance occurred in the erosional zone where populations of Diporeia declined from 2918 . m -2 to 341 . m -2, and oligochaete abundance fell from 2262 . m -2 to 969 . m -2.