Marble Lake

On the scoring rubric Marble Lake grades a D: clarity at 4.5 ft and phosphorus readings still being added keep it in the lower bracket for Lake County. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.

At a TSI of 55, Marble Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 20 ft puts Marble Lake in the middle of Minnesota's depth distribution. Marble Lake covers 160 acres alongside 2.9 miles of shoreline — a mid-sized water that supports a working fishery without being so large that conditions diverge between basins. Marble Lake ranks 123 of 142 in Lake County — at the lower end of the locally monitored distribution.

Marble Lake has no invasive species recorded in Minnesota state databases as of 2020, though prevention practices still apply at all access points. The state fisheries records do not list documented species for Marble Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Marble Lake — most use is by shoreline residents and their guests. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.