Assessment Comments
Assessment is based on results of (1) ISU lake survey from 2000-04, (2) surveys by IDNR Fisheries Bureau, (3) ISU reports on lake plankton communities, 2000-05, and (4) results of U.S. EPA/IDNR fish tissue monitoring in 1999.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation uses) are assessed (monitored) as "not supported" due primarily to inorganic turbidity, aesthetically objectionable algal blooms, and high levels of pH and secondarily due to presence of excessive growth of nuisance aquatic life (bluegreen algae). The Class B(LW) aquatic life uses are assessed (monitored) as "partially supported" due to high levels of pH that violate state criteria and to algal blooms and siltation impacts at the lake. Fish consumption uses remain assessed (monitored) as "fully supported." Sources of data for this assessment include (1) results of the statewide survey of Iowa lakes sponsored by IDNR and conducted by Iowa State University (ISU) from 2000 through 2004, (2) information from the IDNR Fisheries Bureau, (3) information on plankton communities collected at Iowa lakes from 2000 through 2005 as part of the ISU lake survey, and (4) U.S. EPA/IDNR fish tissue monitoring in 1999.
Note: A TMDL for siltation and nutrients at Badger Creek Lake was prepared by IDNR and approved by EPA in 2003; thus, this waterbody was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because all Section 303(d) impairments identified for the 2006 assessment/listing cycle (algal growth [inlcuding nuisance growth of cyanobacteria] and pH) are addressed by the TMDL, this waterbody remains in IR Category 4a.
EXPLANATION: The level of support of the Class A (primary contact recreation) uses are assessed as "not supported" based on results from the ISU statewide survey of Iowa lake. Using the median values from this survey from 2000 through 2004 (approximately 15 samples), Carlson's (1977) trophic state indices for total phosphorus, chlorophyll-a, and Secchi depth are 86, 64, and 71, respectively, for Badger Creek Lake [these TSI values are nearly identical to those calculated for the 2000-2002 period for the previous (2004) 305(b) cycle: 86, 64, and 70, respectively]. According to Carlson (1977), the index value for total phosphorus places this lake in the upper range of hyper-eutrophic lakes; the index value for chlorophyll-a is in the middle range between eutrophic and hyper-eutrophic lakes, and the index value for secchi depth is in the lower range of hyper-eutrophic lakes. These index values suggest extremely high levels of phosphorus in the water column, moderately high levels of chlorophyll-a (suspended algae), and very poor water transparency.
According to Carlson (1991), the occurrence of a high TSI value for total phosphorus with relatively lower values for chlorophyll-a and secchi depth indicate that some factor (e.g., nitrogen limitation, zooplankton grazing, or some other factor) limits production of algae. The ISU lake data suggest that algal production at Badger Creek Lake is limited by nitrogen availability, zooplankton grazing, and by inorganic turbidity. Based on median values from ISU sampling from 2000-04, the ratio of total nitrogen to total phosphorus for Badger Creek Lake is 6; this ratio suggests that algal production at this lake is limited by nitrogen availability.
Data from the ISU survey also show only moderately large populations of zooplankton species at Badger Creek Lake that graze on algae. Sampling from 2000 through 2005 showed that Cladoceran taxa (e.g., Daphnia) comprised approximately 54% of the dry mass of the zooplankton; this lake, however, only had the 74th highest per summer sample mass of Cladoceran grazers (77.3 mg/l) of the 131 lakes sampled.
The levels of inorganic suspended solids at this lake are moderately high and suggest potential problems with high levels of inorganic turbidity. The median level of inorganic suspended solids in the 131 lakes sampled for the ISU lake survey from 2000 through 2004 was 5.2 mg/l. The corresponding median level of inorganic suspended solids at Badger Creek Lake was somewhat greater than this median at 8.4 mg/l, thus suggesting a potential contribution to limiting algal production through turbidity and light limitation. These conditions indicate impairments to the Class A (primary contact) uses through presence of aesthetically objectionable blooms of algae and due to inorganic turbidity.
The presence of nuisance aquatic (algal) species (i.e., bluegreen algae) may also contribute to impairment at this lake. Data from the ISU survey from 2000 through 2004 suggest that bluegreen algae (Cyanophyta) comprise a significant portion of this lake’s summertime phytoplankton community. Sampling from 2000 through 2004 showed that the percent wet mass of bluegreen algae in the phytoplankton community of this lake in summers of the 2000-2004 period was approximately 84%. Also, the average per summer sample mass of bluegreen algae at this lake (35.2 mg/l) was the 27th highest of the 131 lakes sampled. This median is in the worst 25% of the 131 Iowa lakes sampled. The presence of a large population of bluegreen algae at this lake suggests a potential violation of Iowa’s narrative water quality standard protecting against occurrence of nuisance aquatic life. This assessment, however, is based strictly on a distribution of the lake-specific median bluegreen algae values for the 2000-2004 monitoring period. Median levels greater than the 75th percentile of this distribution were arbitrarily considered to represent “potential impairment: partially supported.” No other criteria exist, however, upon which to base a more accurate identification of impairments due to bluegreen algae. Thus, while the accuracy of this (2006) assessment has improved over that of the previous (2004) assessment due to collection of additional data, the assessment category for assessments based on level of bluegreen algae nonetheless remains "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
The hyper-eutrophic conditions at this lake, along with information from the IDNR Fisheries Bureau, suggest that the Class B(LW) aquatic life uses are "partially supported" due to nuisance blooms of algae and siltation impacts in the lake. Despite these apparent impacts, Badger Creek Lake continues to support a quality recreational fishery. The ISU lake survey data suggest an impairment due to high levels of pH at this lake. Three of 14 samples violated the Class B(LW) criteria for dissolved oxygen during summers of 2000 through 2004. Based on IDNR’s assessment methodology, the occurrence of 3violation in the 14 samples collected at this station does not suggest an impairment of aquatic life uses at this lake. Five of 14 samples, however, violated the Class A,B(LW) criterion for pH (maximum = 9.8; minimum = 8.0 pH units). Based on IDNR’s assessment methodology, these results suggest that significantly more than 10 percent of the samples exceed Iowa’s pH criteria. Thus, these results suggest an impairment (partial support/monitored) of the Class A and Class B(LW) uses of this. These violations, however, likely reflect primary productivity at Badger Creek Lake and do not reflect the input of pollutants into this lake.
Fish consumption uses are assessed as "fully supported" based on results of U.S. EPA/IDNR fish tissue (RAFT) monitoring in 1999. Fish consumption uses are assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Badger Creek Lake in 1999. The composite samples of fillets from channel catfish and black crappie had low levels of contaminants. 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. Prior to 2006, IDNR used action levels published by the U.S Food and Drug Administration to determine whether consumption advisories should be issued for fish caught as part of recreational fishing in Iowa. In an effort to make Iowa’s consumption more compatible with the various protocols used by adjacent states, the Iowa Department of Public Health, in cooperation with Iowa DNR, developed a risk-based advisory protocol. This protocol went into effect in January 2006 (see http://www.iowadnr.gov/fish/news/consump.html for more information on Iowa’s revised fish consumption advisory protocol). Because the revised (2006) protocol is more restrictive than the previous protocol based on FDA action levels; fish contaminant data that previously suggested “full support” may now suggest either a threat to, or impairment of, fish consumption uses. This scenario, however, does not apply to the fish contaminant data generated from the 1999 RAFT sampling conducted in this lake: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus suggesting no justification for issuance of a consumption advisory for this waterbody.
