Thresholds of Toxicity in Urban Streams
Project Number: BQY23
Project Chief: Steven R. Corsi
Project Topics: xxxc
Cooperators: Wisconsin Department of Natural Resources
Period of Project: July 2001–September 2006
The state of Wisconsin has recently implemented a federally mandated program that requires cities with populations greater than 10,000 to develop stormwater-management plans. The intent is to eventually regulate stormwater as a point source of pollution by setting limits on the quantity and quality of runoff entering receiving waters.
The critical problem that needs to be addressed is the degree to which toxicants found in urban runoff need to be regulated in order to protect the biological integrity of receiving streams. One question that needs to be addressed: is there a threshold level of watershed imperviousness below which regulation of toxicants in stormwater runoff is not needed? Another question that needs to be answered is: at what field concentration of potential toxicants do we see adverse effects in stream-dwelling organisms? This will permit regulatory effort to be more effectively focused on problem areas and problem chemicals.
The Wisconsin Department of Natural Resources would use this information to identify areas where regulation of toxicants in runoff is necessary to protect, enhance, or restore aquatic communities. Municipalities will need this information to most economically and effectively comply with these impending regulations.
The purpose of this study is to examine the relation of watershed imperviousness in urban river systems to measures of toxicity in aquatic organisms. More specifically, the objective is to determine the toxicity of urban river systems to P. promelas as measured in 21-day spawning tests using in-situ caged fish.
In-stream fish exposures involve the following details: (1) in-stream fathead minnow exposures consist of tests at 3 to 7 streams per time period with 1 test chamber per stream and one control chamber in the laboratory; (2) chambers consist of 6 cartridges with a pair of adult fathead minnows (one female and one male) per cartridge; (3) each stream tested fits into a matrix of different urban influences; and (4) Site visits are made each day to check on the condition of the minnows, and collect data. (Placement of chambers coincides with the NAWQA EUSE topical study.)
The overall goal is to conduct this test for 21 days at each of 30 different sites with varying degrees of urbanization. Toxic response as measured by spawning success will be compared to the degree of urbanization.
Data analysis was conducted on the results from 11 stream tests from the summer of 2005. Preliminary results indicate that dissolved oxygen in the stream correlates with egg count. Egg count also had correlations with several biotic indices computed from EUSE test results.
Fourteen sites will be monitored during the summer of 2006 and data analysis will be conducted during the fall of 2006. The final group of sites will be monitored during the summer of 2007 with final data analysis and reporting conducted from October 2007 through September 2008.
Publications and Reports
A final report will be written after the summer of 2007 and submitted to an appropriate journal.