Post-Pollution: Characterizing Ecological Recovery in a Historically Nutrient Enriched Lake.

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Iain MacKenzie


An iconic story of recovery from nutrient pollution is the restoration of the heavily enriched Lake Washington in Seattle, Washington State. Originally an integral part of the municipal septic system, a diversion of wastewater in 1968 has allowed Lake Washington to return to what has been recently described as a natural and healthy state. Yet is it accurate to characterize a lake as “recovered” based purely on chemical measurements? Does a legacy of pollution linger on in the ecology of a lake system long after the lake has been given a clean bill of health?
Using paleolimological reconstructive techniques it is possible to compare pre-pollution and post-pollution communities of algae by looking at microfossils stored chronologically in the lake-bottom sediment. Use of this technique has afforded a test of the assumption that once pollution stress in a lake is alleviated, the algal communities quickly return to the pre-pollution state. Work on Lake Washington indicates that this does not always hold true. Instead, it suggests that a legacy of pollution persists in the algae and ecological community of the lake long after the nutrient levels have returned to normal.

Article Details

Session II: Ecology
Author Biography

Iain MacKenzie, Dept. of Biology

Moderator: Ms. Anne Johnson, Robert M. Buchan Department of Mining

Faculty Supporter: Dr. Brian Cumming