Long Island Lake

The LakeGrade rubric puts Long Island Lake at a C: clarity at 8.0 ft, phosphorus readings still being added, and a TSI of 47 signal an intermediate trophic state.

Mesotrophic conditions dominate at Long Island Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. At 85 ft of maximum depth, Long Island Lake stratifies reliably through the summer — the hypolimnion stays cooler and clearer than the surface layer suggests. At 884 acres, Long Island Lake fits the Minnesota median for monitored lakes, with 23.4 miles of shoreline. Within Cook County's 128 graded lakes, Long Island Lake ranks 94 — below the local median, though not at the bottom.

Long Island Lake has no invasive species recorded in Minnesota state databases as of 2024, though prevention practices still apply at all access points. Bass fishing is part of the appeal: the species list runs to 6, anchored by largemouth and/or smallmouth bass. No formal public access is documented at Long Island Lake — most use is by shoreline residents and their guests. 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.