Marion Lake

On the scoring rubric Marion Lake grades a D: clarity readings still being added and 71 µg/L of phosphorus keep it in the lower bracket for McLeod County. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.

A TSI in the eutrophic range signals a lake doing what nutrient-loaded waters do — supporting an active algal community at the cost of clear water. The lake bottoms out at 15 ft — a moderate depth that supports a warm-water fishery without the year-round cold refuge a deeper basin provides. The lake's 520 acres and 6.7 miles of shoreline put it in the mid-range bucket — large enough for varied use, small enough that watershed inputs reach the whole basin. Among the 5 graded lakes in McLeod County, Marion Lake ranks 1 — in the top quartile locally.

Marion Lake has no invasive species recorded in Minnesota state databases as of 2021, though prevention practices still apply at all access points. The fishery includes walleye alongside the lake's other 13 documented species — a notable draw for Minnesota anglers. A documented public access point at Marion Lake makes the lake usable for shore fishing, paddle craft, and trailered boats. 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.