Mary Lake

On the scoring rubric Mary Lake grades a D: clarity at 5.5 ft and phosphorus readings still being added keep it in the lower bracket for Wright 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.

Eutrophic conditions are the baseline here: clarity drops noticeably in late summer, and dissolved oxygen near the bottom can become a concern. Mary Lake is unusually deep for Minnesota at 102 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 196 acres, Mary Lake fits the Minnesota median for monitored lakes, with 2.4 miles of shoreline. Within Wright County's 64 graded lakes, Mary Lake ranks 42 — below the local median, though not at the bottom.

Eurasian watermilfoil is established at Mary Lake, which can dampen recreational access and pressure the native plant community. Walleye are documented at Mary Lake, one of 13 fish species on record for the lake. Public access is available — the lake is on the Minnesota PCA public-access list. The lake has a partial ice record — 5 observed ice-outs, centered near Apr 4. 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.