Island Lake
Beltrami County, MinnesotaOligotrophic
Island Lake sits at the top of the Minnesota PCA grading rubric with an A, a mark reached by the cleanest lakes in Minnesota. The three sub-grades — clarity, phosphorus, and chlorophyll-a — track close together, so no single parameter is dragging the average.
Trophically, Island Lake reads as oligotrophic — nutrient-poor, clear, and ecologically more sensitive to disturbance than richer lakes. 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. Within Beltrami County's 86 graded waters, Island Lake sits at rank 10, near the top of the local distribution.
No invasive species are currently listed at Island Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Island Lake, which usually reflects a lack of formal fisheries survey work rather than an empty 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.
Source: EPA Water Quality Portal sampling records, Minnesota DNR LakeFinder, last sampled 2025-09-23. Grade methodology: LakeGrade methodology.
Swimming Safety
Excellent for swimming, crystal clear water with minimal algae
Water Quality Grade: A, Excellent
Crystal clear, you can see 52.5 ft down. Phosphorus level: 10 µg/L. Trophic State Index: 29.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 52.5 ft | A |
| Phosphorus | 10 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 29 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Water Quality Trend: ↑ Improving
Based on 6 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | ↑ Improving | +0.4 m/yr | 6 |
| Phosphorus | ↑ Improving | -0.41 µg/L/yr | 6 |
Location
County Ranking
Ranked #10 of 86 lakes in Beltrami County
Nearby Lakes in Beltrami County
More Minnesota Lake Rankings
State Parks Near Island Lake
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Most recent sample: 2025-09-23
Monitoring stations: 1