Shelfish such as Mussels and clams accumulate biotoxins produced by Alexandrium, which can cause paralytic shellfish poisoning in humans who ingest them.
NOAA Public Release
Researchers Issue Outlook for a Significant New England ‘Red Tide’ in 2010
Seed Population on Seafloor Points to a large ‘Red Tide’; Impacts will Depend on Ocean Conditions and Weather
Researchers at Gulf of Maine Toxicity project have issued an outlook for a significant regional bloom of a toxic alga that causes ‘red tides’ in the spring and summer of this year, potentially threatening the New England shellfish industry.
Microscopic image of Alexandrium fundyense cysts, the “seeds” that fall to the ocean bottom at the end of one season’s blooms. Under the right conditions, these cells can germinate the following year to initiate another season’s blooms. High resolution (Credit: Woods Hole Oceanographic Institution)
The outlook is based on a seafloor survey of the seed-like cysts of Alexandrium fundyense, an organism that causes harmful algal blooms, sometimes referred to as ‘red tides’. Cysts deposited in the fall hatch the following spring; last fall the abundance of cysts in the sediment was 60 percent higher than observed prior to the historic bloom of 2005, indicating that a large bloom is likely in the spring of 2010.
The cyst bed also appears to have expanded to the south, so the 2010 bloom may affect areas such as Massachusetts Bay and Georges Bank sooner than has been the case in past years.
Maps showing the concentration of Alexandrium cysts buried in Gulf of Maine seafloor sediments over four years. The cyst abundance in 2009 is higher than ever observed and the Alexandrium cyst “seedbed” extends further to the south than was ever observed before. High resolution (Credit: Woods Hole Oceanographic Institution)
Although the algae in the water pose no direct threat to human beings, toxins produced by Alexandrium can accumulate in filter-feeding organisms such as mussels and clams, which can cause paralytic shellfish poisoning in humans who consume them. In order to protect public health, shellfish beds are monitored by state agencies and closed when toxin concentrations rise above a quarantine level. There have been no illnesses from legally harvested shellfish in recent years despite some severe blooms.
“’Red tide’ is a chronic problem in the Gulf of Maine and states have limited resources to handle it,” said Darcie Couture, director of Biotoxin Monitoring for the Maine Department of Marine Resources. “When we get this information about the potential severity of a bloom season and the dynamics of the bloom once the season has started, then it gives us an advantage in staging our resources during an otherwise overwhelming environmental and economic crisis.”