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.

At a TSI of 55, Marble Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. Marble Lake reaches 20 ft at its deepest point — typical for Minnesota mid-sized lakes, with seasonal stratification but limited cold-water refuge. The lake's 160 acres and 2.9 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. 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. The lake lacks a documented public access point, so visitor use is limited. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.