Assessment Comments
Assessment is based on results of (1) IDNR/UHL beach monitoring in summers of 2002-04, (2) ISU lake survey from 2000-04, (3) surveys by IDNR Fisheries Bureau, and (4) ISU reports on lake plankton communities from 2000-05, and (5) results of U.S. EPA/IDNR fish tissue monitoring in 2003.
Basis for Assessment
SUMMARY: The Class A (primary contact recreation) uses are assessed (monitored) as "not supported" due to high levels of indicator bacteria at the beach of this lake. This is a new impairment for this lake. Additional impairments of the Class A uses are related to poor water transparency caused by algal blooms and by high levels of non-algal (inorganic) turbidity. The Class B(LW) aquatic life uses remain assessed (evaluated) as "partially supporting" due to nutrient loading to the water column that produces nuisance algal blooms. Fish consumption uses are assessed as “fully supported” based on fish contaminant monitoring in 2003. The sources of data for this assessment include (1) the results of the IDNR-UHL beach monitoring program in summers of 2002, 2003, and 2004, (2) results of the statewide survey of Iowa lakes conducted from 2000 through 2004 by Iowa State University (ISU), (3) information from the IDNR Fisheries Bureau, (4) information on plankton communities collected from 2000 through 2005 for the ISU lakes survey, and (5) results of U.S. EPA/IDNR fish tissue monitoring in 2003.
Note: A TMDL for organic enrichment at Lower Pine Lake was prepared by IDNR and approved by EPA in 2002; thus, this lake was placed into IR Category 4a (TMDL approved) for the 2004 assessment/listing cycle. Because the Section 303(d) impairments due to indicator bacteria (aka, "pathogens") was not addressed in the TMDL, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required) for the 2006 assessment/listing cycle.
EXPLANATION: Results of IDNR beach monitoring at Lower Pine Lake from 2002 through 2004 suggest that the Class A uses are "not supported." Levels of indicator bacteria were monitored once per week during the primary contact recreation seasons (May through September) of 2002 (29 samples), 2003 (29 samples), and 2004 (23 samples) as part of the IDNR beach monitoring program. According to IDNR’s assessment methodology, two conditions need to be met for results of beach monitoring to indicate “full support” of the Class A (primary contact recreation) uses: (1) all five-sample, thirty-day geometric means for the three-year assessment period are less than the state’s geometric mean criterion of 126 E. coli orgs/100 ml and (2) not more than 10 % of the samples during any one recreation season exceeds the state’s single-sample maximum value of 235 E. coli orgs/100 ml. If a 5-sample, 30-day geometric mean exceeds the state criterion of 126 orgs/100 ml during the three-year assessment period, the Class A uses should be assessed as “not supported”. Also, if more than 10% of the samples in any one of the three recreation seasons exceed Iowa’s single-sample maximum value of 235 E. coli orgs/100 ml, the Class A uses should be assessed as “partially supported”. This assessment approach is based on U.S. EPA guidelines (see pgs 3-33 to 3-35of U.S. EPA 1997b).
At Lower Pine Lake beach, the geometric means of 2 of the 25 thirty-day periods during the summer recreation seasons of 2004 exceeded the Iowa water quality standard of 126 E. coli orgs/100 ml. None of the geometric means exceeded this standard during the recreational seasons of 2002 (25 geometric means) or 2003 (19 geometric means). According to IDNR’s assessment methodology and U.S. EPA guidelines, these results suggest impairment (nonsupport) of the Class A (primary contact recreation) uses. Regardless of the impairment, the beach monitoring data from 2002-2004 suggest generally low levels of indicator bacteria at the Lower Pine Lake beach.
Results from the ISU statewide survey of Iowa lakes also suggest impairment of the Class A uses at Lower Pine Lake due to high levels of algal and non-algal turbidity. 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 72, 65, and 66, respectively. According to Carlson (1977), the index value for total phosphorus places this lake in the range of hyper-eutrophic lakes; the index values for chlorophyll-a and Secchi depth are in the middle range between eutrophic and hyper-eutrophic lakes. These index values suggest (1) very high levels of phosphorus in the water column, (2) somewhat elevated (but less than expected) production of suspended algae, and (3) moderately poor water transparency. The TSI values for both chlorophyll-a (65) and Secchi depth (66) suggest impairment of the designated uses.
According to Carlson (1991), the occurrence of a high TSI value for total phosphorus with relatively low values for chlorophyll-a and secchi depth indicate that some factor (e.g., nitrogen limitation, zooplankton grazing, or some other factor) other than phosphorus limits production of algae. The ISU lake data suggest that the moderately high levels of inorganic suspended sediment is likely the primary factor limiting algal production at Lower Pine Lake. 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 median level at Lower Pine Lake was 6.4 mg/l; this was the 53rd highest level of the 131 lakes sampled.
Other potential non-phosphorus limitation (nitrogen limitation and algal grazing) do not appear to limit algal production at this lake. Based on median values from ISU sampling from 2000 through 2004, the ratio of total nitrogen to total phosphorus for Lower Pine Lake is 45. This TN:TP ratio suggests that nitrogen availability does not limit algal production at this lake.
In terms of all Iowa lakes sampled, data from the ISU survey show relatively small populations of zooplankton species at this lake that graze on algae. Sampling from 2000 through 2005 showed that Cladoceran taxa (e.g., Daphnia) comprised only about 30% of the dry mass of the zooplankton community of this lake. The average per summer sample mass of Cladoceran taxa over the 2000-2005 period (39 mg/l) was the 18th lowest of the 131 lakes sampled. These results suggest little if any non-phosphorus limitation due to zooplankton grazing at Lower Pine Lake.
Thus, the relatively high TSI values for chlorophyll-a and secchi depth suggest impairments of the Class A (primary contact) uses due to poor water transparency caused by blooms of algae and by high levels of non-algal (inorganic) turbidity that violate Iowa’s narrative water quality standard protecting against aesthetically objectionable conditions.
The levels of nuisance (=noxious) algal species (i.e., bluegreen algae) at this lake do not suggest an impairment of Class A uses. While data from the ISU survey from 2000 through 2004 suggest that bluegreen algae (Cyanophyta) comprise a significant portion (approximately 60%) of this lake’s summertime phytoplankton community, sampling from 2000 through 2004 showed that the median per summer sample mass of bluegreen algae at Lower Pine Lake (25 mg/l) was the 37th highest of the 131 lakes sampled. This level is in the lowest 75% of the 131 Iowa lakes sampled. The presence of a moderately large population of bluegreen algae at this lake does not immediately suggest 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 less than the 75th percentile of this distribution (~29 mg/l) were arbitrarily considered by IDNR staff to not represent an impairment of the Class A uses of Iowa lakes. No criteria exist, however, upon which to base a more accurate identification of impairments due to bluegreen algae. Thus, while the ability to characterize the levels of bluegreen algae at this lake 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, of necessity, "evaluated" (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence).
Information from the DNR Fisheries Bureau suggests that the Class B(LW) aquatic life uses should remain assessed (evaluated) as "partially supported" due to high levels of nutrients in the water column that contribute to nuisance algal blooms. The ISU lake survey data also show generally good chemical water quality at this lake. Only one violation of the Class B(LW) criteria for dissolved oxygen occurred in the 14 samples collected (7%) during summers of 2000 through 2004. Two of 15 samples (13%) violated the Class A,B(LW) criterion for pH (maximum = 9.4; minimum = 7.0 pH units). Based on IDNR’s assessment methodology, these results do not suggest violation frequencies are significantly greater than 10% for either parameter and thus do not suggest impairment of either the Class A and Class B(LW) uses of Lower Pine Lake. The violations of the pH criterion likely reflect primary productivity at Lower Pine Lake and do not reflect the input of pollutants into this lake.
Fish consumption uses were assessed (monitored) as “fully supported” based on results of U.S.EPA/IDNR fish contaminant (RAFT) monitoring at Lower Pine Lake in 2003. The composite samples of fillets from channel catfish and largemouth bass had low levels of contaminants. Levels of primary contaminants in the composite sample of channel catfish fillets were as follows: mercury: <0.0181 ppm; total PCBs: 0.09 ppm; and technical chlordane: <0.03 ppm. Levels of primary contaminants in the composite sample of largemouth bass fillets were as follows: mercury: 0.048 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. 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 2003 RAFT sampling conducted at Lower Pine Lake: the levels of contaminants do not exceed any of the new (2006) advisory trigger levels, thus indicating no justification for issuance of a consumption advisory for this waterbody.
