Duluth Lake

On the scoring rubric Duluth Lake grades a D: clarity at 2.0 ft and 39 µg/L of phosphorus keep it in the lower bracket for St. Louis County. Clarity is the limiting factor — phosphorus is reasonable but suspended particles or algal cells keep water transparency below Minnesota norms.

At a TSI of 62, Duluth Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. The lake's maximum depth is not yet documented in state morphometric records — context for its physical structure remains limited. The lake's surface area is not consistently recorded across state datasets — physical context remains partial. Duluth Lake ranks 194 of 215 in St. Louis County — at the lower end of the locally monitored distribution.

Duluth Lake is on the Minnesota infested-waters list for zebra mussels — boaters should follow clean-drain-dry protocols when moving gear to or from the lake. The state fisheries records do not list documented species for Duluth Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. A documented public access point at Duluth Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. The grade is based on limited monitoring — fewer than three independent measurement years contribute, so future updates may shift the letter.