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Blue crab in netChronic blue-green algal blooms in the James River are releasing a toxin that is common not only in the waters of this Chesapeake Bay tributary, but also in the bodies of blue crabs, according to a Virginia Commonwealth University professor.

“In crab muscle tissue in certain times of the year, the toxins build up to levels that the World Health Organization considers unsafe for consumption,” Ecologist Paul Bukaveckas told The Richmond Times Dispatch.

Toxins from blue-green algae (also known as cyanobacteria) was detected in 104 of 105 water samples taken in the fresh water portion of the James River from May to October of 2012, and in 254 of 379 (67 percent) of fish and shellfish examined over the same period of time, according to data from Bukaveckas’ research posted on the Virginia Department of Environmental Quality website.  He also found the toxin this summer, but at levels that were not as high.

"Toxin levels in the water peaked in August at ~0.6 ug/L which is lower than the peaks we observed in 2012 (1.0 ug/L) and 2011 (4.5 ug/L)," Bukaveckas wrote in an email to Bay Daily. "Therefore I am expecting concentrations in crabs and fish to be lower than last year."

High levels of toxins from blue-green algae can cause rashes, nausea, vomiting, and potentially liver disease if they are ingested, according to the U.S. Centers for Disease Control.  However, the Virginia Department of Health and Virginia Marine Resources Commission said the concentrations in the James River and in crabs caught from the waterway do not pose a threat to people, according to the Richmond Times Dispatch.

There are still unresolved questions.  But one thing that is clear is the cause of the algal blooms. Excessive amounts if phosphorus and nitrogen pollution, from lawns, farms, sewage plants, and runoff from urban areas, is feeding excessive growth of algae not only in the James River, but across the Chesapeake Bay watershed.  This blooms become more intense in the hottest times of summer.

Virginia, Maryland, Pennsylvania and the other Chesapeake region states must reduce this phosphorus and nitrogen to meet EPA pollution limits and state cleanup plans in the Chesapeake Clean Water Blueprint.  Investments in runoff pollution control systems will help to meet these goals, as will upgrades to sewage treatment plants and keeping farm fertilizer away from streams.

All this will make not only a healthier Bay, but also a healthier environment for the blue crabs we all love to eat.

By Tom Pelton

Chesapeake Bay Foundation


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