Grass Island Lake

Grass Island Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI value of 36 puts Grass Island Lake in the oligotrophic range, where biological productivity stays low and the water column remains clear. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Among the 86 graded lakes in Beltrami County, Grass Island Lake sits at rank 30, above the county median.

No invasive species are currently listed at Grass Island Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Grass Island Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.