Island Lake

The LakeGrade rubric puts Island Lake at a C: clarity at 6.4 ft, 30 µg/L of phosphorus, and a TSI of 52 signal an intermediate trophic state. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. A maximum depth of 43 ft puts Island Lake in the middle of Minnesota's depth distribution. At 616 acres, Island Lake fits the Minnesota median for monitored lakes, with 9.4 miles of shoreline. Island Lake ranks 13 of 16 in Mahnomen County — at the lower end of the locally monitored distribution.

Island Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. The fishery includes walleye alongside the lake's other 11 documented species — a notable draw for Minnesota anglers. Public access is available — the lake is on the Minnesota PCA public-access list. 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.