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. Sub-grades cluster within a single letter of each other, which usually means the lake is in stable trophic balance rather than fighting one specific stressor.

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. Long Island Lake covers 884 acres alongside 23.4 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. 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. 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.