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), (3) information from the IDNR Fisheries Bureau, and (4) IDNR fish contaminant monitoring in 2012.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “not supported” due to aesthetically objectionable conditions caused by poor water transparency due to both non-algal turbidity and algae. The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.” Fish consumption uses are assessed as "fully supported." 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 2007 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) IDNR fish contaminant monitoring.
Note: A TMDL for algae and turbidity at Five Island Lake was prepared by IDNR and approved by EPA in 2006. Because all Section 303(d) impairments identified for the 2008, 2010, 2012 and current (2014) assessment/listing cycle (algal growth and turbidity) are addressed by the TMDL, this waterbody remains in IR Category 4a (impaired; TMDL approved).
EXPLANATION: For the 2014 reporting cycle, the Class A1 (primary contact recreation) uses for Five Island Lake are assessed (monitored) as “not supported” based on results from the ISU statewide survey of lakes and the UHL ambient lake monitoring program. Using the median values from these surveys from 2008-2012 (approximately 14 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 70, 67, and 67 respectively for Five Island Lake. According to Carlson (1977) the Secchi depth value places Five Island Lake in the hypereutrophic category, while the chlorophyll a and total phosphorus values place Five Island Lake in between the eutrophic and the hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, extremely poor water transparency, and high levels of phosphorus in the water column.
The levels of inorganic suspended solids at this lake were high and suggest that non-algal turbidity contributes to the impairment at this lake. The median level of inorganic suspended solids in Five Island Lake (11.4 mg/L) and ranked 120th of the 134 lakes sampled by the ISU and UHL programs.
Data from the 2008-2012 ISU and UHL surveys suggest a large population of cyanobacteria exists at Five Island Lake, which contributes to the aesthetically objectionable conditions at this lake. These data show that cyanobacteria comprised 96% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (47.0 mg/L) was ranked 117th of the 134 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed as “fully supported” based on information from the IDNR Fisheries Bureau, and results of the ISU and UHL lake surveys. The ISU and UHL lake surveys data from 2008-2012 show no violations of the Class B(LW) criteria for ammonia in 14 samples, no violations of the Class B(LW) criterion for dissolved oxygen in 14 samples, and no violations of the Class A1,B(LW) criterion for pH in 14 samples. Based on IDNR’s assessment methodology these results suggest full support of the Class B(LW) uses at Five Island Lake. According to the IDNR Fisheries Bureau water quality has improved at Five Island Lake due to a lake dredging project.
Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S. EPA/IDNR fish contaminant (RAFT) monitoring at Five Island Lake in 2012. The composite samples of fillets from walleye and channel catfish had low levels of contaminants. Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.037 ppm. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: 0.0219 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. The existence of, or potential for, a fish consumption advisory is the basis for Section 305(b) assessments of the degree to which Iowa’s lakes and rivers support their fish consumption uses. The fish contaminant data generated from the 2012 RAFT sampling conducted at this Five Island Lake show that the levels of contaminants do not exceed any of the advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
