Lotts Creek IA 04-EDM-1836

The assessment of the presumptive Class B(WW1) aquatic life uses is partly based on biological data collected in 2002 as part of the DNR/SHL stream REMAP project. A series of biological metrics which reflect stream water quality and habitat integrity were calculated from the biological sampling data. The biological metrics are based on the numbers and types of benthic macroinvertebrate taxa and fish species that were collected in the stream sampling reach. The biological metrics were combined to make a fish community index of biotic integrity (FIBI) and a benthic macroinvertebrate index (BMIBI). The indexes rank the biological integrity of a stream sampling reach on a rising scale from 0 (minimum) to 100 (maximum). The 2002 FIBI score was 48 (fair) and the BMIBI score was 48 (fair). The aquatic life use support was assessed as partially supporting (=PS), based on a comparison of the FIBI and BMIBI scores with biological impairment criteria (BIC) established from a statistical analysis of data collected at stream ecoregion reference sites from 1994-2008. The non-riffle habitat FIBI BIC for this ecoregion is 32 and the BMIBI BIC for this ecoregion is 62. This segment passed the FIBI BIC and failed the BMIBI BIC in 2002.

This assessment is considered "evaluated" because there were not two or more samples collected in multiple years from 2012-2016. Also, because these data are now considered too old (greater than five years) to accurately characterize current water quality conditions, the assessment category is considered “evaluated” (indicating an assessment with relatively lower confidence) as opposed to "monitored" (indicating an assessment with relatively higher confidence). According to DNR’s assessment/listing methodology, impairments based on “evaluated” assessments are of lesser confidence and are thus not appropriate for Section 303(d) listing (Category 5 of the Integrated Report). DNR does, however, consider these impairments as appropriate for listing under either Category 2b or 3b of the Integrated Report (waters potentially impaired and in need of further investigation).

As part of the REMAP project, diurnal dissolved oxygen/temperature monitoring conducted during July-August 2002 found substantial fluctuation of d.o. levels, including nighttime sags (<3 mg/L), associated with very high estimated levels of community respiration and primary production. Levels of BMIBI metrics that are sensitive to organic enrichment suggest a nutrient enrichment/algal growth-related water quality problem. Habitat modification that has resulted in a wide and shallow stream channel with high solar input may contribute to algal growth. Additional sampling data are needed to evaluate the extent, causes and sources of this water quality problem.

The previous IR Category 5b impairment of the presumptive Class B(WW1) aquatic life uses due to a fish kill in September 2008 was de-listed for the 2016 IR cycle. The kill occurred along two miles of Lotts Creek south of Whittemore. At the time of the investigation DNR observed a blue-gray color in the water near the B44 bridge, and dead fish at the 180th and 190th St. bridges. No live fish were observed. No counts of the dead fish were done and no estimate of the value of the fish was calculated. The cause of the kill was not identified, but was suspected to be human caused.

According to DNR’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 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 is identified, and the cause is either known, or suspected, to be a “pollutant”, the assessment type is considered “monitored” and the affected waterbody is a candidate for Section 303(d) listing. Fish kills attributed to a pollutant, but where a source of the pollutant was not identified and/or where enforcement actions were not taken against the responsible party, will be placed into Integrated Report subcategory 5b. Thus, this impairment was added to Iowa’s 2010 list of Section 303(d) impaired waters.

This stream segment’s fish community was sampled on October 8, 2014, as part of the DNR Watershed Improvement and Water Monitoring sections’ fishkill follow up monitoring program. Sampling methods described in DNR’s fish kill follow-up protocol (Attachment 5 of Iowa’s assessment/listing methodology) were followed. Approximately 690 feet of stream were sampled using a single pass with two backpack electro fishing units. Results of this sampling show that this stream supports approximately 2,740 fish per mile compared to the Level IV ecoregion 47f REMAP average of approximately 2,310 fish per mile; 91% of the expected fish taxa for this ecoregion were sampled compared to the assessment threshold of 50% of the expected fish species. The results from this follow-up sampling and comparison of these results to ecoregion averages suggest that the fish community of this stream segment is similar to or better than non-fishkill impacted streams. Although the results of the fishkill follow-up sampling lack the scientific rigor to determine whether the designated aquatic life uses are “fully supported,” the results do indicate that the stream has recovered from the September 2008 fish kill event. Thus, the previous IR Category 5b fish kill impairment was de-listed and was moved to Category 3a (designated use not assessed) of Iowa's 2016 Integrated Report.