2007 Results
In 2007 Martin Lake had poor water quality compared to other lakes in the North Central Hardwood Forest Ecoregion (NCHF), receiving a D letter grade. This eutrophic lake has chronically high total phosphorus and chlorophyll-a, and some of the poorest water quality in the county. 2007 had some of the worst water quality of all years monitored. Average total phosphorus (135 ug/L) was the highest of 9 years that it has been monitored and chlorophyll-a was the third worst. Secchi transparency was the second worst of 27 years that it has been monitored. Water quality was poor until late August, when it worsened. The conditions in Martin Lake were reflective of conditions in upstream Typo Lake, which drains into Martin Lake. Typo Lake has extremely severe water quality problems, and was especially bad in 2007, likely because of internal loading driven by low water conditions caused by drought.
ACD staff’s subjective perceptions of the lake’s physical characteristics and recreational suitability were that “high” algae made the lake unsuitable for swimming during the entire monitored period from May through September. In some other years, such as 2005, water quality was much better in spring and early summer.
Trend Analysis
Nine years of water quality data have been collected by the Minnesota Pollution Control Agency (1983), Metropolitan Council (1998), and ACD (1997, 1999-2001, 2003, 2005, 2007). Citizens monitored Secchi depths 17 other years. Anecdotal notes from DNR fisheries data indicate poor water quality back to at least 1954. A water quality change from 1983 to 2005 is detectable with statistical tests (repeated measures MANOVA with response variables TP, Cl-a, and Secchi depth; F2,6=5.69, p=0.04). However, further examination of the data a mixture of changes, some indicating improvement and other indicating deterioration. In the end, it is concluded that no true trend is present. This lake needs improvement regardless.
Discussion
Martin Lake, along with Typo Lake upstream, were the subject of an intensive TMDL study from 2001-03 by the Anoka Conservation District. This study documented the source of nutrients to the lake, the degree to which each is impacting the lake, and put forward lake rehabilitation strategies. The study report was completed in early 2006, however it is still waiting for review and approval by the MPCA. In the meantime, the ACD and Sunrise River WMO are pursuing some lake improvement strategies recommended in the report.