Starkweather Creek Sediment Toxicity Study 2017

Purpose

This report summarizes findings of toxicity tests conducted on stream sediment samples collected at seven sites throughout the Starkweather Creek Watershed in Madison, Wisconsin in May 2017. Study results indicate that stream sediment collected from 5 of the 7 sample sites in the Starkweather Creek watershed were either toxic to invertebrate test organisms that live in streambed sediment or at the sediment – water column interface.

Objective

The Friends of Starkweather Creek (FSC) is a citizen - led advocacy group dedicated to the enhancement of the Starkweather Creek Watershed’s environmental quality. Their primary goals are to raise public awareness and appreciation of the creek through education of and outreach to watershed residents. FSC members contacted department staff in December 2016 seeking support to better understand the environmental quality of the stream and potential sources of degradation, beyond the routine monitoring of water quality and macroinvertebrates, regularly currently done by FSC (annually? ). The State Laboratory of Hygiene (SLH) had capacity in Spring 2017 to test the toxicity of sediment samples through contract services with the Department of Natural Resources (DNR). City of Madison engineering staff mapped seven pore points in the Starkweather Creek Watershed that reflect relatively discrete areas of stormwater drainage to the stream in this highly urbanized watershed (Figure 1). In May 2017, sediment grab samples (reference the procedures used) of sediment were collected by department staff and FSC immediately downstream of these seven pour points. The goals of this study were to assess whether the sediment in Starkweather Creek may be toxic to aquatic life, and, if so, whether there are geographic differences in sediment toxicity in the watershed. This study was not designed to provide evidence of specific pollutants that may impact the stream, the sources of pollutants, or guidance on management actions. Various studies cited in this report provide information on pollutants found in the water of Starkweather Creek, likely sources of environmental contamination, and management goals and recommendations.

Outcome

Survival of laboratory test organisms (amphipoda: Hyalella azteca adults, and dipteran: Chironomus dilutus larvae) did not appear to be affected by exposure to Starkweather Creek sediment during standard 10 - day animal survivorship tests. The sediment samples did appear to reduce the growth rates of the test organisms at five of the seven sample sites, indicating sediment pollutants are toxic to aquatic life in the stream.

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2017
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Starkweather Creek Toxicity Study