Meadow Lake IA 04-LDM-1089

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Meadow 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 2010-2014 (approximately 15 samples), Carlson 's (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 70, 71, and 70 respectively for Meadow Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Meadow Lake in the Hypereutrophic category. These values suggest very 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 15 samples.

The level of inorganic suspended solids was moderately high at Meadow Lake, and does suggest that non-algal turbidity may contribute to the impairment at this lake. The median level of inorganic suspended solids in Meadow Lake (3 mg/L) was ranked 71st among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a large population of cyanobacteria exists at Meadow Lake, which suggests the potential for an impairment due to nuisance aquatic life These data show that cyanobacteria comprised 97% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (72.7 mg/L) was ranked 126th 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 2010-2014. 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” based on information from the IDNR Fisheries Bureau and results from the ISU lake surveys due to a large population of cyanobacteria.   Nutrient loading to the water column, moderately high levels of algal turbidity, and siltation in the lake, however, remain water quality concerns at this lake that may affect support of the Class B(LW) uses. Additionally grass carp eliminate almost all aquatic vegetation in the lake which promotes nuisance algae blooms during the summer. These potential impairments are not appropriate for Iowa’s Section 303(d) list of impaired waters (Integrated Report Category 5) but are appropriate for IR Category 3b of Iowa’s Integrated Report and Iowa’s list of waters in need of further investigation. Results of the ISU lake survey from 2010-2014, however, 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 IDNR'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 Meadow Lake.

NOTE: Meadow Lake was drawn down in the winter of 2008-2009 and sediment and nutrient retention structures were built in the watershed in 2010.  

Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.   EPA/IDNR turtle contaminant (RAFT) monitoring at Meadow Lake in 2010.  The shoulder samples from snapping turtle had low levels of contaminants.   Levels of primary contaminants in the shoulder sample of snapping turtle were as follows: mercury: 0.119 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 turtle contaminant data generated from the 2010 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.

Fish contaminant monitoring conducted in 2013 sugggests "full support" of fish consumption uses at Meadow Lake  The composite samples of fillets from channel catfish had low levels of contaminants.    Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: <0.05 ppm; total PCBs: <0.6 ppm; and technical chlordane: <0.2 ppm.    Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.576 ppm; which exceeds the 1 meal per week advisory trigger.  According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.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 2013 RAFT sampling conducted at this lake show that the levels of mercury justify the need for follow-up monitoring.

Additional followup fish contaminant monitoring conducted in 2014 sugggests "full support" of fish consumption uses at Meadow Lake. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: < 0.05 ppm; which does not exceeds the 1 meal per week advisory trigger.  According to IDNR’s assessment methodology, the single occurrence of contaminant above an advisory trigger level neither warrants issuance of an advisory nor indicates impairment of the fish consumption uses: two consecutive samplings that show contaminant levels are above the trigger level in fillet samples are needed to justify issuance of an advisory.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 level of mercury in the sample of largemouth bass fillets ( < 0.05  ppm) is below the IDPH/IDNR advisory trigger level and therefore suggests that the fish consumption uses be assessed (monitored) as "fully supported."