Foss Lake

Foss Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. Foss Lake is a shallow lake at 6 ft maximum depth, which means it warms quickly, mixes constantly, and amplifies nutrient inputs. Foss Lake is small — 36 acres alongside 1.1 miles of shoreline — which makes it sensitive to even modest changes in watershed runoff or recreational pressure. Foss Lake ranks 198 of 215 in St. Louis County — at the lower end of the locally monitored distribution.

No invasive species are currently listed at Foss Lake — the lake remains off the Minnesota infested-waters roster. 3 fish species are on record, with panfish making up the recreational core. The lake lacks a documented public access point, so visitor use is limited. Monitoring depth is thin here: the LakeGrade rubric is applied to a small number of sample years, and the grade will be revised as more data accumulates.