Polly Lake

On the LakeGrade scale Polly Lake grades a B, with clarity at 11.0 ft and phosphorus readings still being added placing it above the Minnesota median. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

Mesotrophic conditions dominate at Polly Lake: enough nutrients for a healthy fishery, not so much that algal blooms become a chronic problem. Polly Lake is unusually deep for Minnesota at 95 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 122 acres, Polly Lake fits the Minnesota median for monitored lakes, with 4.5 miles of shoreline. Among the 142 graded lakes in Lake County, Polly Lake sits at rank 58, above the county median.

No invasive species are currently listed at Polly Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Polly Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Polly 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.