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Rx for Action

A blog devoted to helping people find local medicine take-back programs and highlighting current research findings and pending legislation.

Living in the chemical brew: smallmouth bass in the Potomac River

Smallmouth bass in the historically polluted Potomac River have been demonstrating disturbingly high rates of lesions on their bodies and intersex conditions. Since fish symptoms pointed to chemical pollution interfering with smallmouth bass's natural hormone signaling systems, Dana Kolpin and colleagues from USGS set out to explore what kinds of compounds were around these baby fish. Six sample sites in the Potomac River Watershed and a reference site in the Gualey River Watershed were established to survey the background chemical concentrations near smallmouth bass nesting sites.

In a bid to address a lingering question in emerging contaminate research–just what happens to fish exposed to a complex brew of chemicals over their lifetimes–researchers used an innovative mix of sampling techniques. Besides traditional methods of onetime water collections, sediment was also gathered from within nesting sites, and passive water samplers (think termite traps, but for chemicals) were installed near nests for 30 days. Fish analysis was carried on simultaneously, but was recorded in a different publication.

The research team reported that in general, more chemicals were found at "sites where adverse biological effects on fish were observed." While this study wasn't designed to pinpoint a single cause of fish disorders, adoption of the additional sampling techniques did show just how many chemicals juvenile fish are exposed to. Of 283 chemicals tested, 135 showed up in some form around nesting sites. The fact that many of these chemicals only showed up in the passive water and sediment samples showed that young fish are exposed to a far more complex array of contaminates than one-time samples could capture.

These contaminates included everything from caffeine to pharmaceuticals to herbicides, and some of these substances are known for causing hormonal disruption in wildlife. In particular, the presence of veterinary antibiotics and some herbicides was highly correlated with intersex conditions in the fish. Consequently, researchers suggested that multiple human activities might be responsible for many of these chemicals and should be studied further to discover just why Potomac male smallmouth bass are exhibiting intersex conditions.

Kolpin, D. W., V. S. Blazer, J. L. Gray, M. J. Focazio, J. A. Young, D. A. Alvarez, L. R. Iwanowicz, W. T. Foreman, E. T. Furlong, G. K. Speiran, S. D. Zaugg, L. E. Hubbard, M. T. Meyer, M. W. Sandstrom, L. B. Barber. Chemical contaminants in water and sediment near fish nesting sites in the Potomac River basin: Determining potential exposures to smallmouth bass (Micropterus dolomieu). Science of the Total Environment2013;443:700-716.

Written by Corrie Layfield

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Posted by Laura Kammin at 8:00AM on 5/6/2013
Categories: Latest Research