The Water Quality of North Lake Leelanau: A Shoreline Algal Survey

Abstract

The Shoreline algal (cladophora) survey identified 53 cladophora . growths, the majority of which we suspect are related to leaching septic systems or excessive lawn fertilization. Most growths were small, indicating a small nutrient source although we did identify several larger problems. Also, lakeshore dumping of leaves and grass clippings which caused several cladophora growths was more frequent on North take Leelanau than any other lakes we have surveyed. Our theoretical analysis of the sources of phosphorus entering North take Leelanau shows .the major phosphorus sources to the lake to be watershed runoff (70%) and precipitation/dry fallout (25%). Overall the contribution from septic systems (3%) and lawn fertilization (2%) is small. Despite this relatively small phosphorus contribution, septic and lawn fertilization problems are more controllable than either watershed runoff or precipitation/dry fallout so therefore we support efforts to minimize them to the maximum extent possible.