Crystal Lake IA 02-IOW-781

For the 2016 assessment/listing cycle, the Class A1 (primary contact recreation) uses of Crystal Lake are assessed (monitored) as "not supported" due to poor water transparency, aesthetically objectionable conditions caused by algae blooms and due to frequent violations of the state criterion for pH 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 67, 72, and 80 respectively for Crystal Lake. According to Carlson (1977) the Secchi depth, chlorophyll a, and total phosphorus values all place Crystal Lake in between the Eutrophic and the Hypereutrophic categories. These values suggest very high levels of chlorophyll a and suspended algae in the water, poor water transparency, and extremely high levels of phosphorus in the water column. The data show 5 violations of the Class A1 criterion for pH in 15 samples (33%).

The level of inorganic suspended solids was relatively low at Crystal Lake, and does not suggest water quality problems due to non-algal turbidity. The median level of inorganic suspended solids in Crystal Lake (2.5 mg/L) was ranked 39th among the 138 lakes by the ISU lake survey.

Data from the 2010-2014 ISU lake survey suggest a moderately large population of cyanobacteria exists at Crystal Lake. These data show that cyanobacteria comprised 95% of the phytoplankton wet mass at this lake. The median cyanobacteria wet mass (24.4 mg/L) was ranked 76th of the 138 lakes sampled.

The Class B(LW) (aquatic life) uses are assessed (evaluated) as “partially supported” based on results of a fish kill investigation in August 2009 and another in October of 2015.   The first kill occurred on or before August 28, 2009.   Thousands of dead minnows were found in the lake.   The kill was attributed to natural causes (=summer kill) due to an algae bloom and low dissolved oxygen.  The second kill occurred on or before July 9, 2015.  An estimated 1,000 fish were killed.  No estimates of the value of the fish killed or the cost of the Iowa DNR investigation were provided.  Similar to other recent kills, the cause of the kill was attributed to "summer kill/low DO".  The third kill occurred on or before October 22, 2015.   Thousands of fish of unknown types were found dead. The kill was also attributed to natural causes (=summer kill) due to an algae bloom die off resulting in low dissolved oxygen conditions. 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 (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. Thus, this assessment segment will remain in Category 3b of Iowa’s 2012 Integrated Report.

The Class B(LW) (aquatic life) uses are assessed (monitored) as "not supported" due to violations of the Class A1,B(LW) criterion for pH. Results of the ISU lake survey from 2010-2014 show there were no violations of the criterion for ammonia in 15 samples(0%), one violation of the criterion for dissolved oxygen in 15 samples(7%), and 5 violations of the criterion for pH in 15 samples(33%). Based on IDNR's assessment methodology these violations are significantly greater than 10% of the samples and therefore suggest impairment (not supported/monitored) of the Class B(LW) uses of Crystal Lake.

Fish consumption remain "not assessed" due to the lack of recent fish contaminant monitoring at this lake.

Note:  A TMDL for organic enrichment at Crystal Lake was prepared by IDNR and approved by EPA in 2002; thus, this waterbody was placed into IR Category 4a (TMDL approved) for the 2004 and 2006 assessment/listing cycles.    Because not all of the Section 303(d) impairments identified for the 2008 and 2010 assessment/listing cycle (indicator bacteria) were addressed by the TMDL, this waterbody was placed in IR category 5a (TMDL needed) for the 2008 and 2010 assessment/listing cycles.   Due to a decrease in indicator bacteria at Crystal Lake, the bacteria impairment was suggested for de-listing for the 2012 assessment/listing cycle, and thus Crystal Lake was moved back to IR Category 4a (TMDL approved).  It remains listed as Category 4a (TMDL approved) for the 20146 assessment/listing cycle.

Note: A hydraulic dredging project was completed in 2007 that should reduce suspended sediment and turbidity problems.   IDNR Fisheries staff also did a complete fisheries renovation in 2008 to remove common carp and black bullhead and create a desirable fishery.   This will also likely reduce sediment and turbidity problems.