Lake Assessment Program - Turtle Lake, Itasca County

Turtle Lake is located in Itasca County, near the town of Marcell, Minnesota. With a surface area of about 2,018 acres, it is among the top five percent of lakes in the state in terms of size. Turtle Lake has a maximum depth of 150 feet and a mean depth of 33 feet, which is a typical depth for lakes of this region. The total watershed is very large at approximately twenty square miles (13,017 acres). Land use in the watershed is characterized primarily by forested (55 percent) and water/marsh (45 percent) uses. These values are very comparable to other lake watersheds in this region of the state – Northern Lakes and Forests (NLF) ecoregion. Turtle Lake was sampled during the summer of 2000 by the Minnesota Pollution Control Agency (MPCA) staff and citizens from the Turtle Lake Association (Association). Water quality data collected during the study reveal summer-mean total phosphorus (TP) concentration of 8.8 ?g/L, chlorophyll a of 2.8 ?g/L and Secchi transparency of 11.5 feet. All three measures are well within or better than the range of values exhibited by reference lakes in the NLF ecoregion. Total phosphorus, chlorophyll a and Secchi transparency help to characterize the trophic status of a lake. These measures indicate mesotrophic – conditions for Turtle Lake. Other water quality parameters measured are fairly typical of minimally-impacted lakes in the NLF ecoregion.