First Black Lake

First Black Lake earns a C — middle-of-the-pack water quality, with one or two parameters dragging the average down from a stronger grade. The lake's weakest score is on Secchi depth — the water looks more turbid than its phosphorus number alone would predict.

At a TSI of 58, First Black Lake reads as eutrophic — nutrient-rich enough that summer algal growth and reduced clarity are expected, not unusual. A maximum depth of 19 ft puts First Black Lake in the middle of Wisconsin's depth distribution. At 23 acres, First Black Lake sits below the Wisconsin median: a small water where shoreline activity has an outsized effect on water quality. Within the 33 graded lakes of Iron County, First Black Lake sits at rank 27, near the bottom of the county list.

No invasive species are currently listed at First Black Lake — the lake remains off the Wisconsin infested-waters roster. Walleye are documented at First Black Lake, one of 5 fish species on record for the lake. 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.