The Mysterious Case of the Missing Mussel

Submitted by: Joe Bartoszek, Ph.D., Resource Contaminant Specialist (USFWS)

This is the 3rd installment of this story. To learn more, read "Mussels in a Desert?!" and “What Happened to Pearlshell Mussels in the Hanford Reach?”

The western pearlshell, once abundant in the Hanford Reach of the Columbia River in southeastern Washington, can no longer be found. Although the cause for their disappearance is not known, the long-lived mussel (some individuals have been aged at more than 100 years) may have suffered from releases of contaminants from the Hanford Department of Energy site.

      Pearlshell mussel collected from the Eel River, CA. Photo credit: Dr. Chris Barnhart    

The Hanford Natural Resource Trustees would like to understand what happened to mussels in the river by testing potential sensitivity to contaminants released from the site, particularly hexavalent chromium (the contaminant made famous in the Erin Brockovich movie). 

On an expedition to the Eel River in Northern California, Dr. Jeanette Howard of The Nature Conservancy collected and sent some western pearlshell mussels to Dr. Chris Barnhart at Missouri State University for rearing. With knowledge gained last year, Dr. Barnhart will be able to supply the USGS testing laboratory in Columbia, MO with juvenile western pearlshell mussels for toxicity tests. 

In preliminary tests last year, the western pearlshell was found to be slightly less sensitive to hexavalent chromium than the commonly tested freshwater mussel, the fatmucket. The western pearlshell sensitivity to hexavalent chromium seemed to increase at higher temperatures. We hope to learn more details this year in our testing. 

Doctors Chris Ingersoll and Ning Wang at the USGS lab in Columbia are recognized experts in mussel toxicity tests and wrote the ASTM standard used for mussel toxicity testing. They will soon be receiving the juvenile mussels at their lab. The glochidia that Dr. Barnhart has raised this year can be seen in the video below.

(Video of glochidia under a microscope - courtesy of Dr. Chris Barnhart.) 

The glochidia are the parasitic life cycle stage of these fresh water mussels and live for a short time on the gills of fish such as trout and salmon. They then drop off (this is one method they use to move over greater distances than they might otherwise be able to) and begin life as juvenile mussels.

Juvenile mussels from this year - Photo credit: Dr. Chris Barnhart

With what we will learn from these tests, we hope to discover the reason the mussels are no longer found in the Hanford Reach and restore them to their former habitat.

To learn more about this project please visit: (link) http://www.fws.gov/wafwo/studies_new.html.

To learn more about Hanford Reach visit: http://science-ed.pnnl.gov/pals/resource/cards/reach.stm and http://www.fws.gov/refuge/Hanford_Reach/.