Meyers Lake IA 02-CED-463

For the 2018 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Meyers 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 13 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 73, 69, and 74 respectively for Meyers Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Meyers Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, very poor water transparency, and very high levels of phosphorus in the water column. The data show no violations of the Class A1 criterion for pH in 13 samples.

The level of inorganic suspended solids was moderately high at Meyers Lake, and does suggest that non-algal turbidity may contribute to the impairment at this lake. The median level of inorganic suspended solids in Meyers Lake (4.4 mg/L) was ranked 88th among the 138 lakes by the ISU lake survey.

Data from the 2012-2016 ISU lake survey suggest a large population of cyanobacteria exists at Meyers Lake, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 77% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (41.1 mg/L) was ranked 111th of the 138 lakes sampled. This median is in the worst 25% of the 138 lakes sampled. The presence of a large population of cyanobacteria at this lake suggests a potential violation of Iowa's narrative water quality standard protecting against the occurrence of nuisance aquatic life. This assessment is based strictly on the distribution of the lake-specific median cyanobacteria values from 2012-2016. Median levels greater than the 75th percentile of this distribution were arbitrarily considered to represent potential impairment. No other criteria exist, however, upon which to base a more accurate identification of impairments due to cyanobacteria. Assessments based on level of cyanobacteria will be considered "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence) to account for this lower level of confidence.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” due to fish kills that occurred at Meyers Lake on March 22, 2007 and March 25, 2008. The first fish kill was attributed to natural conditions (winter kill) and affected 200 fish. The 2008 fish kill was also attributed to natural conditions (winter kill) and affected 2800 fish. According to DNR’s assessment/listing methodology, the occurrence of a single pollutant-caused fish kill, or a fish kill of unknown origin, on a waterbody or waterbody reach during the most recent assessment period (2009-2012) indicates a severe stress to the aquatic community and suggests that the aquatic life uses should be assessed as “impaired.” If a cause of the kill was not identified during the DNR investigation, or if the kill was attributed to non-pollutant causes (e.g., winterkill), the assessment type will be considered “evaluated.” Such assessments, although suitable for Section 305(b) reporting, lack the degree of confidence to support addition to the state Section 303(d) list of impaired waters (IR Category 5). Waterbodies affected by such fish kills will be placed in IR subcategories 2b or 3b and will be added to the state list of waters in need of further investigation.

Information from the DNR Fisheries Bureau supports that the Class B(LW) uses are "partially supported" due to the lake’s susceptibility to fish kills due to its shallow depth and nutrient concentrations.Results of the ISU lake survey from 2012-2016 show there were no violations of the criterion for ammonia in 13 samples(0%), no violations of the criterion for dissolved oxygen in 13 samples(0%), and no violations of the criterion for pH in 13 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 Meyers Lake.

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