2006 Results
In 2006 Lake Netta had very good water quality for this region of the state (NCHF Ecoregion), receiving an overall B+ letter grade. The lake is slightly eutrophic. Total phosphorus, chlorophyll-a, and secchi depths were all similar to past years and were a testament to the clear water and healthy vegetation in the lake. Secchi transparency was the best seen in all years monitored. ACD staff’s subjective observations of the lake’s physical characteristics and recreational suitability were that there was little or “some” algae present, with the exception of a moderate amount of large, globular, neon green algae during the first half of July. This same algae was noted at the same time in 2004. Overall, clear water conditions were common and conditions were excellent for swimming and boating.
Trend Analysis
Seven years of water quality data have been collected by the Anoka Conservation District (1997-99, 2001, 2003-04, 2006), along with Secchi measurements by citizens five other years. Lake water quality has fluctuated between “A” and “B” grades. There is no significant long-term trend (repeated measures MANOVA with response variables TP, Cl-a, and Secchi depth, F2,4=0.81, p>0.05). However, this analysis excludes secchi depths taken in the early 1990’s by volunteers. Some longer-term trend may be occurring; annual average secchi depth before 1998 was 1.5 to 2.5 m, but have been 2.5 to 3m since 1998 indicating better water clarity in recent years.
Discussion
This lake has excellent water quality. It is a macrophyte (large plant) dominated lake, as opposed to algae dominated. These plants are essential to maintaining good water quality. The plants consume nutrients in the water, making them unavailable to algae. They also minimize sediment disturbance by wind or boats and provide refuges for zooplankton, which eat algae. Other reasons for good water quality in this lake include that it has a small watershed and receives little direct runoff. No streams of any consequence enter this lake. Maintaining good water quality in this lake will be, in large part, dependent upon protecting the in-lake aquatic vegetation, as well maintenance of vegetated buffers near the water’s edge by property owners.