Response of Headwater Lakes to Varying Atmospheric Deposition in North-Central Ontario, 1979–85

Publisher Website
Google Scholar
Abstract
Between 1976 and 1985, loadings of SO42− to the Algoma district (north-central Ontario) varied from a low of 47 (1980) to a high of 84 meq∙m−2 (1978) and was low in years of low annual precipitation. The mean and median lake concentrations of H+ and SO42− in 54 lakes declined between 1979 and 1982 following the period of lowest annual deposition and declined further between 1982 and 1985. Overall, mean lake pH increased 0.35 unit between 1979 and 1982 and an additional 0.07 unit over the next 3 yr. Lake concentrations in the Turkey Lakes watershed exhibited a similar trend. Two lakes without fish in 1979 and with pH's < 5.5 developed white sucker (Catostomus commersoni) populations by 1986 with ages indicating that survival began after 1980. This apparent invasion from downstream populations probably occurred when lake pH's neared 5.5. Although a direct link has not been established, these lakes appear to be extremely responsive to changes in atmospheric deposition. The "recovery" of water quality clearly extends beyond that locally documented at Sudbury, Ontario, yet it remains to be determined to what degree the responses relate to differences in continental deposition and/or responses within the watershed.