Center Lake IA 06-LSR-1663

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 2008 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.

Basis for Assessment

SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “fully supported.”  The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported."  Fish consumption uses are “not assessed” due to a lack of fish contaminant monitoring at this lake.   Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2009-2012 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted in 2008 by University Hygienic Laboratory (UHL), and (3) information from the IDNR Fisheries Bureau.

EXPLANATION: For the 2014 reporting cycle, the Class A1 (primary contact recreation) uses for Center Lake are assessed as “fully supported."  Results from the ISU statewide survey of lakes and the UHL ambient lake monitoring program do not suggest impairment of the Class A1 uses at Center Lake.   Using the median values from these surveys from 2008 through 2012 (approximately 14 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 57, 55, and 68 respectively for Center Lake.   According to Carlson (1977) the Secchi depth and chlorophyll a values place Center Lake in the eutrophic category while the total phosphorus index values place Center Lake in the between the eutrophic and hypereutrophic categories.   These values suggest relatively low levels of chlorophyll a and suspended algae in the water, relatively good water transparency, and high levels of phosphorus in the water column.  

The levels of inorganic suspended solids at this lake were moderately high and do not suggest an impairment due to non-algal turbidity.   The median level of inorganic suspended solids in Center Lake (2.8 mg/L) and ranked 51st of the 134 lakes sampled by the ISU and UHL surveys.

Data from the 2008-2012 ISU and UHL surveys suggest that a moderately large population of cyanobacteria exists at Center Lake.   These data show that cyanobacteria comprised 95% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (29.9 mg/L) and ranked 97th of the 134 lakes sampled.  

The Class B(LW) (aquatic life) uses for Center Lake are assessed (monitored) as “fully supported."  The ISU and UHL lake surveys data from 2008-2012 show one violation of the Class B(LW) criterion for ammonia in 15 samples, one violation of the Class B(LW) criteria for pH in 15 samples, and one violation of the Class B(LW) criteria for dissolved oxygen in 15 samples.   These violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class B(LW) uses at Center Lake.  

Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.