PARENT SESSION
Oral Session #27: Aquatic Ecology: Lake structure and function. Presiding: L.A. Hansson.
Tuesday, August 7, 2001. 8:00 AM to 11:30 AM. Hall of Ideas I.
Lake eutrophication along the urban fringe.
MOORE, JONATHAN1, SCHINDLER, DANIEL1, SCHEUERELL, MARK1, SMITH, DANIELLE1, FRODGE, JONATHAN2, 1 2
ABSTRACT- Nutrient pollution and subsequent eutrophication of freshwaters threatens both human use and the ecological properties of lakes. We examined how human residential development influences the level of eutrophication of lakes in the Seattle (WA) region. We surveyed 29 lakes and measured indicators of eutrophication: chlorophyll-a, phosphorus, and the proportion of large, ungrazable algae. There were three classes of lakes based on waste treatment of shoreline homes: septic lakes, sewer lakes, and undeveloped lakes. Septic lakes occurred in rapidly developing areas along the urban fringe while sewer lakes occurred in urban centers. Septic lakes appeared more eutrophic than sewer lakes as indicated by higher levels of phosphorus and chlorophyll-a. Both classes of developed lakes (septic and sewer) were more eutrophic than the undeveloped reference lakes, as indicated by higher levels of chlorophyll-a, phosphorus, and ungrazable algae. Septic lakes were more likely to be eutrophic than sewer and undeveloped lakes based on the level of phosphorus or chlorophyll-a. These results suggest that septic systems contribute to the high levels of eutrophication that occur in lakes along the urban fringe. The urban fringe represents a major opportunity for proactive management to protect surface waters from eutrophication.
KEY WORDS: eutrophication, phosphorus, urban, lake