By Julia Robins, Staff Writer
No one is sure how Alexandrium monilatum got into the Chesapeake Bay. A favorite theory is that it was brought in by a foreign ship. But scientists can agree that since it was spotted in 2007, blooms of the toxic algae in the Bay have increased almost every year.
Sarah Pease, a Virginia Sea Grant graduate research fellow at Virginia Institute of Marine Science, is assessing the health impacts of this toxic algae.
“We know it’s toxic, but what’s the timing?” asks Pease. “How long do oysters need to be exposed to show signs of impaired health? Which life stage is most susceptible? And how much toxin is in the water when we start seeing issues?” According to Pease, there’s no single answer—a combination of factors determines when, and if, A. monilatum will become a problem.
To find some answers, she is performing bioassays: raising the toxic algae in a lab, growing it into a dense culture, and diluting it to various concentrations to see how much algae it takes to have a toxic effect on adult oysters.
“The hope is that the data we collect in the lab will give us an idea of what might be happening to oysters out in the wild actually experiencing this,” says Pease. So far, she has performed one run of bioassays and begun mapping cyst beds in the Bay—zones in which cells of A. monilatum that are in a “resting” stage fall and collect in the sediments. “We’ve found that there are cysts almost everywhere that we looked,” says Pease. She hopes the cyst beds will aid in tracking A. monilatum blooms.
What is likely the most important part of her research, says Pease, is finding out whether A. monilatum poses a health risk to humans. If it is a risk, people could be affected by A. monilatum toxin through consuming shellfish. That’s because shellfish are likely to contain higher concentrations of the toxin than the surrounding water if they’ve been filtering water containing toxic algae.
In order to determine if there is a health risk, Pease will feed meat from the oysters, which she exposed to A. monilatum in her first experiment, to striped bass. Then, she will look for behavioral or health changes in the bass that suggest they are affected by the toxin. She will also take tissue samples from the bass and try to quantify how much toxin is in their bodies, a potential indication of whether the toxin can be transferred by eating oysters that have been exposed to it.
“That would give us an idea as to how this might relate to humans,” says Pease.
During her research, Pease is working with the Virginia Department of Health and the shellfish industry. The two groups hope that her findings can be turned into a scientific publication that will help with human health and shellfish management.
Pease still has some work to do before she can form any conclusions. She is tracking A. monilatum blooms in the Bay in addition to taking samples of the algae throughout the year, which she will use to perform additional bioassays and research over the next year and a half.
“This is kind of uncharted territory,” says Pease. “There’s a lot we don’t know and, to me, that’s what makes it exciting and interesting.”
