Assessment Comments
Assessment is based on: (1) results of the statewide survey of Iowa lakes conducted from 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of a fish kill investigation in May 2005.
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 a fish kill that occurred in May 2005. 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 2002 through 2006 by Iowa State University (ISU), (2) results of the statewide ambient lake monitoring program conducted from 2005 through 2006 by University Hygienic Laboratory (UHL), (3) information from the IDNR Fisheries Bureau, and (4) results of a fish kill investigation in May 2005.
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 2002 through 2006 (approximately 23 samples), Carlson’s (1977) trophic state indices for Secchi depth, chlorophyll a, and total phosphorus were 62, 67, and 67 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 moderately high 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 4.3 mg/L, which was the 64th highest of the 132 monitored lakes.
Data from the 2002-2006 ISU and UHL surveys suggest a relatively small population of cyanobacteria exists at Upper Pine Lake. These data show that cyanobacteria comprised 52% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (10.7 mg/L) was the 38th lowest of the 132 lakes sampled.
The Class B(WW-1) (aquatic life) uses are assessed (evaluated) as “partially supported” due to a fish kill that occurred in May of 2005. This 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. According to the IDNR 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 (2004-2007) 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.
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 2002-2006 there was one violation of the Class B(WW-1) criterion for ammonia in 16 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 23 samples and 2 violations of the pH criterion in 23 samples (9%). These violations are not significantly greater than 10% of the samples and therefore do not suggest an impairment of the Class B(WW-1) uses at Upper Pine Lake.
Fish consumption uses remain "not assessed" due to the lack of fish contaminant monitoring in this lake.
