Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of fish kill investigations in May 2005 and April 2009.
Basis for Assessment
SUMMARY: The Class A1 (primary contact recreation) uses are assessed (monitored) as “partially supported” due to elevated levels of chlorophyll a (algae) that cause aesthetically objectionable conditions. The Class B(WW-1) aquatic life uses are assessed (evaluated) as “partially supported” due to fish kills that occurred in May 2005 and April 2009. Nutrient loading to the water column and siltation also remain water quality concerns at this lake. Fish consumption uses remain “not assessed” due to the lack of fish contaminant monitoring at this lake. Sources of data for this assessment include: (1) results of the statewide survey of Iowa lakes conducted from 2006 through 2010 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2006 through 2008 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of fish kill investigations in May 2005 and April 2009.
Note: A TMDL for siltation at Upper Pine Lake was prepared by IDNR and approved by EPA; thus, this lake was placed into IR Category 4a (TMDL approved). Because not all impairments at this lake are addressed by the TMDL, this waterbody was moved from IR Category 4a to Category 5a (impaired; TMDL required).
EXPLANATION: Results from the ISU and UHL lake surveys suggest that the Class A1 (primary contact recreation) uses at Upper Pine Lake are “partially supported” due to elevated chlorophyll a (algae) levels. Using the median values from these surveys from 2006 through 2010 (approximately 22 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 63, 65, and 69 respectively for Upper Pine Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Upper Pine Lake in between the eutrophic and hypereutrophic categories. These values suggest high levels of chlorophyll a and suspended algae in the water, moderately poor water transparency, and high levels of phosphorus in the water column.
The level of inorganic suspended solids is moderate at Upper Pine Lake and suggests that non-algal turbidity may occasionally cause water quality problems, but does not suggest an impairment at this lake. The median inorganic suspended solids concentration at Upper Pine Lake was 3.5 mg/L, which was the 63rd lowest of the 134 monitored lakes.
Data from the 2006-2010 ISU and UHL surveys suggest a moderate population of cyanobacteria exists at Upper Pine Lake. These data show that cyanobacteria comprised 81% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (21.8 mg/L) was the 61st highest of the 134 lakes sampled.
The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to a fish kills that occurred in May of 2005 and April of 2009. The 2005 kill was attributed to natural causes (spawning stress). The kill affected bluegill and crappie; no estimates were made of the number of dead fish. The kill was believed due to fluctuating water temperatures that contributed to spawning stress. The 2009 kill was also attributed to natural causes (fluctuating water temperatures). The 2009 kill affected approximately 2500 fish; mostly bluegill and crappie. No estimate of the value of these fish was made. According to IDNR’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 (2008-2011) 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 IDNR 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 IDNR Fisheries Bureau suggests that nuisance algae blooms are a concern at this lake. Data from the ISU and UHL lake surveys, however, suggest Upper Pine Lake has relatively good chemical water quality. Data from these surveys show that during 2006-2010 there was one violation of the Class B(WW-1) criterion for ammonia in 21 samples. Based on IDNR’s assessment methodology, a single violation of the ammonia criterion does not suggest impairment of the Class B(WW-1) uses. There were no violations of the Class B(WW-1) criterion for dissolved oxygen in 22 samples and no violations of the pH criterion in 22 samples. These results suggest that the Class B(WW-1) uses are "fully supported."
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.
