Acidification of the La Cloche Mountain Lakes, Ontario, and Resulting Fish Mortalities

Abstract

The loss of populations of lake trout (Salvelinus namaycush), lake herring (Coregonus artedii), white suckers (Catostomus commersoni), and other fishes in Lumsden Lake was attributed to increasing levels of acidity within the lake. An absence of fishes was also observed in nearby lakes. In some lakes, acid levels have increased more than one hundredfold in the last decade. The increases in acidity appear to result from acid fallout in rain and snow. The largest single source of this acid was considered to be the sulfur dioxide emitted by the metal smelters of Sudbury, Ont.In 1971, pH measurements were taken from 150 lakes in the general study area 65 km southwest of Sudbury. Some 33 of these lakes showed a pH of less than 4.5 and were described as "critically acidic." An additional 37 lakes had a pH in the range of 4.5–5.5 and were termed "endangered" lakes.