Abstract

The Leelanau Conservancy is home to seven lake basins, all of which Leelanau County relies on as tourist and recreational attractions. Since nutrient content is a key metric in understanding water quality, the Leelanau Conservancy has been monitoring phosphorous, nitrogen, and chlorophyll-a levels in each lake for the past 25 years. Measurements were taken at the surface, bottom, and intermediate depths of each lake during different seasons throughout each year. With 25 years of data collected from four depths in seven lakes, multivariate statistical techniques were needed to identify long-term trends in water quality. A Principal Components Analysis was performed on the data using Program R. The resulting biplots showed evident seasonal changes in five lakes, a decrease in nutrients from 1990-2015 in all lakes, and lower levels of nitrogen in three lakes after zebra mussels invaded. These results will be communicated to the Leelanau Conservancy for use in managing their lake basins.