Environmental scientists found high levels of a toxin produced by freshwater blue green algae in mussels from San Francisco Bay, according to reports.
The finding is significant because although shellfish harvested from California’s coastal waters are routinely monitored for marine algae, they are not regularly tested for the said freshwater toxin, called microcystin.
The toxin causes liver damage and is produced by algae that thrive in warm, nutrient rich water conditions.
“We found that this freshwater toxin accumulates in shellfish, both mussels and oysters, and that in San Francisco Bay, the toxin levels in some mussels exceed the recommended guidelines for consumption by quite a bit,” explained Raphael Kudela, the
Lynn Professor of Ocean Health at University of California Santa Cruz.
“There is monitoring of shellfish for marine-derived toxins, but because this is a freshwater toxin no one has been looking for it. Now it seems microsystin is something we should be monitoring as well,” added Corinne Gibble, an environmental scientist at the California Department of Fish and Wildlife.
While tests have shown that the contamination levels are still below the recommended limits for human consumption, Kudela warned that it could have a great impact on marine mammals in the area. Among others, sea otters are at great risk because they consume large amounts of the shellfish. In 2010, scientists reported that microsystin poisoning killed several sea otters in Monterey Bay.
“This really highlights the connectivity between what people do on land and what happens in the ocean. A lot of shellfish farms are downstream from freshwater sources, so we want to raise awareness of this issue,” Kudela concluded.
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