Chasing ecological change in large lake ecosystems: The Lake Ontario story

摘要

An era of accelerated ecological change for Lake Ontario commenced with the establishment of the first European settlement near Kingston (Ontario, Canada) in the late I 600s. As the basin's human population grew, ecosystem stressors such as overfishing, cultural eutrophication, colonization by nonindigenous species, and contaminant discharge led to degradation in water quality, loss of habitat, and the decline of native fish communities. By 1970, Lake Ontario's major native fish stocks had been pushed to near extinction (CHRISTIE 1972). Large phosphorus inputs from the watershed during the 1950-1970s produced dense beds of Cladophora in coastal Lake Ontario signaling continued environmental degradation. The 1972 Great Lakes Water Quality Agreement (GLWQA; INTERNATIONAL JOINT COMMISSION 1988) between the United States and Canada sought to reverse eutrophication by establishing permissible phosphorus loadings to each of the Great Lakes, marking a new era of ecosystem management and rehabilitation. Phosphorus concentrations declined more quickly than anticipated, and by the mid-1980s, the target level of 10 μg/L for offshore Lake Ontario had been achieved (MILLARD et al. 2003). The GLWQA marked the beginning of an ecosystem approach to resource management, an integrative style in which environmental, social, and economic factors were addressed along ecosystem rather than political boundaries.