Lake Sugema IA 04-LDM-1029

Assessment Comments

Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau.

Basis for Assessment

SUMMARY: This lake is not designated for Class A1 (primary contact recreation) uses in the Iowa water quality standards.   The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.”  Fish consumption uses remain “not assessed.”  Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau.

EXPLANATION: For the 2008 assessment/listing cycle, results from the ISU and UHL lake surveys and information from the IDNR fisheries bureau indicate that the Class B(LW) (aquatic life) uses are (monitored) “fully supported.”  Using the median values from the ISU and UHL surveys from 2002 through 2006 (approximately 20 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 60, 63, and 60 respectively for Lake Sugema.   According to Carlson (1977) the Secchi depth, and total phosphorus values place Lake Sugema at the upper end of the eutrophic category, while the chlorophyll a score places Lake Sugema in between the eutrophic and hypereutrophic categories.   These values suggest moderately high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and moderately high levels of phosphorus in the water column.  

Based on data from the ISU and UHL lake surveys, the level of inorganic suspended solids was relatively low at this lake and does not suggest impairment due to high non-algal turbidity.   The median inorganic suspended solids concentration at Lake Sugema was 2.1 mg/L, which was the 24th lowest of the 132 monitored lakes.

Data from the 2002-2006 ISU and UHL surveys suggest a moderate population of cyanobacteria exists at Lake Sugema.   These data show that cyanobacteria comprised 89% of the phytoplankton wet mass at this lake.   The median cyanobacteria wet mass (17.0 mg/L) was the 64th lowest of the 132 lakes sampled.   These results suggest full support of the Class B(LW) uses at Lake Sugema.  

Results of the ISU and UHL lake surveys from 2002 through 2006 show no violations of the Class B(LW) criterion for ammonia in 14 samples, one violation of the Class B(LW) criterion for dissolved oxygen in 19 samples (5%), and 2 violations of the Class B(LW) criterion for pH in 18 samples (11%).   Based on IDNR’s assessment methodology, however, these violations are not significantly greater than 10% of the samples and therefore do not suggest impairment of the Class B(LW) uses of Lake Sugema.

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