Marlu Lake

Marlu Lake pulls a D on the LakeGrade rubric — phosphorus loading and limited clarity hold it below the Minnesota average.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. Marlu Lake covers 320 acres alongside partial shoreline records — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Within Pope County's 25 graded lakes, Marlu Lake ranks 17 — below the local median, though not at the bottom.

Zebra mussels have been documented at Marlu Lake, which alters the filter-feeding balance and can paradoxically increase water clarity while disrupting the food web. The state fisheries records do not list documented species for Marlu Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. The lake lacks a documented public access point, so visitor use is limited. Ice-out has been recorded 15 times at Marlu Lake, with a median around Apr 10. 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.