Pearl Lake is a shallow, medium-sized lake located south of Rockville, Minnesota. The lakeshore is heavily developed by residential properties and the watershed is large relative to its surface area with a 25:1 watershed to lake area ratio. Land use is dominated by agriculture, including both row cropping and pasture lands. Recent trends in water quality indicate the lake is becoming increasingly eutrophic (nutrient rich) and Pearl Lake is subject to occasional summer algal blooms, with average summer water clarity around a meter.
In addition to lake eutrophication, Pearl Lake has seen the increasing abundance of the non-native curly-leaf pondweed. Curly-leaf pondweed thrives in nutrient-rich conditions, and at some threshold of nutrient levels (exact quantity unknown), can become a self-sustaining internal driver of poor water quality conditions.
The fish community of Pearl Lake is dominated by Centrarchids including Bluegill, Black Crappie, and Largemouth Bass. The Walleye population is maintained via stocking and Yellow Perch are present though their numbers have been declining in recent years, similar to many other Minnesota lakes. Pearl Lake does contain a diverse non-game fish community with four species (Blackchin and Blacknose Shiner, Banded Killifish, and Iowa Darter) intolerant of excessive nutrient loading. These species have disappeared from many of the Metro area lakes to the east after nutrient loading increased following lakeshore and watershed development.
Pearl Lake is a good example of a central Minnesota Lake threatened by increasing nutrient levels and invasive species.