Little Spirit Lake IA 06-LSR-1659
Dickinson County S8T100NR36W 5 mi. NE of Montgomery.
- Cycle
- 2018
- Release Status
- Final
- Overall IR
- 4 - Water is impaired or threatened and a TMDL has been completed or is not needed.
- Trophic
- Hypereutrophic
- Trend
- Stable
- Created
- 4/9/2019 10:46:09 AM
- Updated
- 4/9/2019 10:48:57 AM
The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to poor water transparency caused by a combination of high levels of chlorophyll-a (suspended algae) and high levels of inorganic suspended solids. The Class B(LW) (aquatic life) uses are assessed (monitored) as “fully supported.” Fish consumption uses are considered “not assessed” (IR 3a) due to the age of the data upon which the previous assessment (“fully supported”) was based. Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes conducted from 2012 through 2016 by Iowa State University (ISU), (2) information from the IDNR Fisheries Bureau, and (3) results of U.S. EPA/IDNR fish contaminant monitoring in 2003.
For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Little Spirit Lake are assessed (monitored) as "not supported" due to poor water transparency and aesthetically objectionable conditions caused by algae blooms based on information from the ISU lake survey. Using the median values from these surveys from 2012-2016 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 70, 62, and 81 respectively for Little Spirit Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Little Spirit Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest moderately high levels of chlorophyll a and suspended algae in the water, very poor water transparency, and extremely high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 15 samples.Although the index value for Chlorophyll a is below the impairment trigger of 65 for this assessment cycle, Little Spirit Lake was listed as partially supporting its Class A1 uses due to aesthetically objectionable conditions. Based on DNR's methodology, the median TSI value for Chlorophyll a must be 63 or less for two consecutive assessment/listing cycles before a lake can be removed from the state's Section 303(d) list (IR Category 4a). Therefore, Little Spirit Lake will remain listed as "not supported" for the 2018 assessment/listing cycle. Note:A TMDL for turbidity and algae at Little Spirit Lake was prepared by DNR and approved by EPA in 2005. Because all Section 303(d) impairments identified for the 2016 assessment/listing cycle (algal growth and turbidity) are addressed by the TMDL, thiswaterbodyis placed in IR Category 4a (impaired; TMDL approved).
Data from the 2012-2016 ISU lake survey suggest a moderately large population of cyanobacteria exists at Little Spirit Lake. These data show that cyanobacteria comprised 92% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (17.8 mg/L) was ranked 73rd of the 138 lakes sampled.
The Class B(LW) (aquatic life) uses are assessed (monitored) as "fully supported." Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 15 samples(0%), no violations of the criterion for dissolved oxygen in 15 samples(0%), and no violations of the criterion for pH in 15 samples(0%). Based on DNR's assessment methodology these violations are not significantly greater than 10% of the samples and therefore suggest (fully supported/monitored) of the Class B(LW) uses of Little Spirit Lake.
The level of support of the Class HH-fish consumption uses is changed from “fully supporting” to “not assessed” due to the age of the data upon which the previous assessment was based. The previous assessment was based on results of U.S. EPA / DNR fish tissue (RAFT) monitoring at Little Spirit Lake in 2003. The composite samples of fillets from common carp and walleye had low levels of contaminants. Levels of primary contaminants in the composite sample of common carp fillets were as follows: mercury: 0.019 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of walleye fillets were as follows: mercury: 0.04 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). 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 2003 RAFT sampling conducted at this 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.