Turtle Lake
Itasca County, MinnesotaOligotrophic
On the LakeGrade rubric, Turtle Lake pulls an A: clarity at 17.1 ft and 8 µg/L of phosphorus put it in the top bracket for Minnesota. Clarity, phosphorus, and chlorophyll-a all rate similarly, so there is no obvious single lever to pull on watershed management.
The lake's low TSI puts it in oligotrophic territory — the cleanest of the four trophic classes, but also the most vulnerable to nutrient-driven shifts. Turtle Lake is unusually deep for Minnesota at 54 ft, which buffers the lake against summer warming and helps the deep water stay oxygenated. At 120 acres, Turtle Lake fits the Minnesota median for monitored lakes, with 3.2 miles of shoreline. Among the 141 graded lakes in Itasca County, Turtle Lake ranks 10 — in the top quartile locally.
No invasive species are currently listed at Turtle Lake — the lake remains off the Minnesota infested-waters roster. The state fisheries records do not list documented species for Turtle Lake, which usually reflects a lack of formal fisheries survey work rather than an empty lake. No formal public access is documented at Turtle Lake — most use is by shoreline residents and their guests. 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 2024-09-03. 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 17.1 ft down. Phosphorus level: 8 µg/L. Trophic State Index: 35.
| Metric | Value | Grade |
|---|---|---|
| Water Clarity (Secchi Depth) | 17.1 ft | A |
| Phosphorus | 8 µg/L | A |
| Chlorophyll-a (Algae) | No data | |
| Trophic State Index (TSI) | 35 | Oligotrophic |
Low nutrients, clear water, excellent for swimming
Lake Details
| Characteristic | Value |
|---|---|
| Maximum Depth | 54 ft |
| Surface Area | 119.55 acres |
| Shoreline Length | 3.2 mi |
| Littoral Zone | 82% |
| Public Access | No |
Water Quality Trend: → Stable
Based on 5 years of monitoring data (2020-2025).
| Metric | Trend | Change/Year | Years |
|---|---|---|---|
| Water Clarity | → Stable | +0.04 m/yr | 5 |
| Phosphorus | → Stable | +0.05 µg/L/yr | 5 |
Location
County Ranking
Ranked #10 of 141 lakes in Itasca County
Nearby Lakes in Itasca County
More Minnesota Lake Rankings
State Parks Near Turtle Lake
Other Grade A Lakes in Minnesota
Oligotrophic Lakes in Minnesota
DNR Fisheries Survey Summary
2 surveys on file from MN DNR Fisheries. Most recent: 1989-07-17 (Standard Survey).
Top Species by Catch Rate
| Species | Avg CPUE | Avg Weight |
|---|---|---|
| Bluegill | 9.63 | 0.35 lb |
| Northern Pike | 5.27 | 1.57 lb |
| Pumpkinseed | 2.75 | 0.35 lb |
| Yellow Perch | 1.96 | 0.17 lb |
| Black Crappie | 1.88 | 0.53 lb |
| Walleye | 0.86 | 1.97 lb |
CPUE = catch per unit effort, averaged across surveys (excludes juvenile shoreline seining). Higher CPUE = more abundant in standardized sampling.
From the 1989-07-17 survey
WALLEYES, ALTHOUGH NEVER STOCKED IN GRASS LAKE, HAVE BEEN SAMPLED IN BOTH THE 1978 SURVEY AND THIS ASSESSMENT. YOUNG-OF-THE-YEAR LARGEMOUTH BASS WERE CAPTURED IN THE MINNOW TRAPS BUT NONE WERE CAUGHT IN THE NETS. NORTHERN PIKE ABUNDANCE, AS INDICATED BY GILLNET CATCH, IS WELL ABOVE STATE AND LOCAL MEDIANS.
DNR Reports & Resources
Minnesota DNR LakeFinder publishes lake survey, fish stocking, water access, and aquatic plant data for Turtle Lake. 2 reports on file.
- —Fisheries Lake Survey — GrassFisheries Lake Survey · MN DNR LakeFinder
- —Aquatic Plant Report — Grass (0708)Aquatic Plant Report · MN DNR LakeFinder
Data Sources
Water quality data from the EPA Water Quality Portal
Grading methodology based on Metropolitan Council standards
Lake details from Minnesota DNR LakeFinder
Most recent sample: 2024-09-03
Monitoring stations: 2