Stormwater Microarray Study Completed

The Clean Water Act's objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters. For more than forty years, efforts to achieve this objective have focused on controlling municipal and industrial wastewater discharges. Discharge monitoring has driven the implementation of these controls. However, discharge monitoring does not assess the integrity of a water body. Discharge monitoring only provides a rough estimate of potential environmental effects based upon limited information on pollutant concentrations over time in relationship to variable receiving stream chemistry and flow. Storm water discharge monitoring will generate information that is certain to be inadequate for evaluating urban stream health given the large number of storm water outfalls discharging highly variable volumes containing rapidly changing pollutant concentrations. Regularly monitoring all storm water outfalls for every potential pollutant would be very expensive and generate information of limited usefulness. In addition, the detection of unknown or illegal discharges is too often left to chance resulting in a possibly serious information gap when considering stream health.

An alternative to point source measurements taken at specific times is the characterization of aquatic organism responses in streams experiencing both point and non-point sources. For example, test organisms placed in a stream would both experience a realistic environmental exposure and be able to respond to a broad spectrum of toxic chemicals. Measuring test organism responses at the molecular level using DNA transcriptional responses derived from microarray techniques would enhance knowledge of the effects on the in situ test organisms of any chemicals detected and could provide an alert if any chemicals need to be added to the analysis list. Gene microarrays applied to test organisms have the potential for an economy of scale if used routinely.

In spring 2010, the USGS will demonstrate the use of cDNA microarray techniques performed on larval trout both in the field and a laboratory setting as a method for assessing the suitability of streams for supporting salmon early lifestages. Gene microarray analysis measures the expression of hundreds or thousands of genes from an organism exposed to chemical pollutants. Microarrays for assessing environmental contaminants evolved from microarrays used to study developmental processes or basic physiology. Microarrays note when genes are turned on and when they are turned off. A gene might turn on to resist toxicity or turn off because of interference from a chemical. Scientists have discovered patterns of microarray response that are diagnostic of some chemicals. The manufacture and reading of microarrays have been automated. Some tissue preparation is needed prior to microarray exposure.

In the spring/early summer of 2010, Washinton State Department of Ecology will provide the USGS with a minimum of 40 larval rainbow trout that have been exposed to natural stream flow found in Indian Creek in the Olympia area. The fish will be equally distributed from two sites (upstream and downstream) with varying levels of suspected contamination on Indian Creek. The USGS will assess transcriptional responses on whole larval fish using a custom made low density targeted rainbow trout cDNA microarray. The USGS will provide microarray results from the upstream site and from the downstream site. A laboratory study will also be performed using larval rainbow trout. In the laboratory study, Ecology will expose a minimum of 170 larval rainbow trout to contaminated waters of know source and condition. At the end of the exposure period, Ecology will extract the livers out of a minimum of 150 fish. The livers will be preserved on dry ice or other preservative provide by the USGS in three evenly disturbed groups. Each group of 50 livers needs to equal 50mg. Ecology will provide the USGS with the remaining fish from this laboratory study as well. The USGS will perform microarray analyses on the liver samples and 3 analysis on the whole fish. During the laboratory study, Ecology will also expose a minimum of 20 larval rainbow trout to clean water. The USGS will perform 3 microarray analyses on the 20 fish exposed to the clean laboratory water. Ecology will also provide the USGS with ancillary chemistry data from the Indian Creek sites and laboratory exposures to be used in the USGS's report. A brief USGS report will be published online.