2005 Results:
In 2005 Round Lake had very good water quality compared to other lakes in this region (NCHF Ecoregion), receiving an overall B letter grade. This is slightly worse the other four years that have been monitored, with the exception of 1998. The lake is mesotrophic. Water quality did deteriorate slightly in late summer, including increases in phosphorus and algae, but was still quite good. Water clarity was about 12 feet in spring and about 6 feet in late summer. Dissolved oxygen was consistently within the range needed by fish and other aquatic life.
Trend Analysis:
Five years of water quality monitoring have been conducted by the Anoka Conservation District (1998-2000, 2003, and 2005). This is not enough data for a powerful statistical test of trend analysis. Generally, within this record, water quality was poorest in 1998, better in 1999-2003, and poorer again in 2005. The magnitude of differences among years seems to be with the range of variation that would be expected naturally. In all years it would be considered very good.
Discussion:
Round Lake is one of the four clearest lakes in Anoka County . Shallow lakes like Round seldom have such a clear water condition. The two primary factors causing this are 1. the small watershed with relatively few surface water or storm water inputs and 2. the abundant macrophytes (large, aquatic plants). While nutrient inputs are p rob ably few, the plants in the lake consume nutrients that are present, preventing algae blooms. Chara is common in this lake and forms carpets that stabilize bottom sediements. Macrophytes also foster zooplankton (microscopic animals that eat algae) communities by providing refuges from fish predators.