Mary Lake

Mary Lake earns an A — water clarity, phosphorus, and chlorophyll-a all rate among the best monitored waters in Marinette County. 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.

The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. A maximum depth of 38 ft puts Mary Lake in the middle of Wisconsin's depth distribution. At 186 acres, Mary Lake fits the Wisconsin median for monitored lakes, with partial shoreline records. Among the 22 graded lakes in Marinette County, Mary Lake ranks 5 — in the top quartile locally.

Eurasian watermilfoil has been documented at Mary Lake, requiring shoreline management to keep dense mats from crowding native vegetation. Bass fishing is part of the appeal: the species list runs to 3, anchored by largemouth and/or smallmouth bass. A documented public access point at Mary Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.