2008 a potential red tide season, computer models reveal.

The end of April usually brings the first signs of harmful algae in New England waters, and this year, researchers participating in the Gulf of Maine Toxicity (GOMTOX) study—led by Woods Hole Oceanographic Institution (WHOI)--are preparing for a potentially big bloom. A combination of abundant beds of algal seeds and excess winter precipitation have set the stage for a harmful algal bloom similar to the historic “red tide” of 2005, according to WHOI biologist Don Anderson, principal investigator of the GOMTOX program. The 2005 bloom shut down shellfish beds from the Bay of Fundy to Martha’s Vineyard for several months and caused an estimated $50 million in losses to the Massachusetts shellfish industry alone. Weather patterns and ocean conditions over the next few months will determine whether this year’s algal growth approaches the troubles of 2005. Oceanographers Dennis McGillicuddy (WHOI) and Ruoying He (North Carolina State University) are several years along in the development of a computer model to predict the intensity and location of blooms of the toxic algae Alexandrium fundyense in the Gulf of Maine.


Though the scientists are reluctant to make an official “forecast” (because bloom outcomes are dependent on weather events that cannot be predicted months in advance), colleagues in coastal management and fisheries believe that even rough seasonal forecasting can be useful in preparing for contingencies. "With advance warning of a potentially troublesome year for algae, shellfish farmers and fishermen might shift the timing of their harvest or postpone plans for expansion of aquaculture beds,” said Anderson, a WHOI senior scientist in the Biology Department and director of the Coastal Ocean Institute. “Restaurants might make contingency plans for supplies of seafood during the summer," Anderson added, "and state agencies can ensure they have adequate staff for the significant monitoring efforts that might be required to protect public health and the shellfish industry.”

Seeds or “cysts” of A. fundyense naturally germinate and turn into cells that swim up from the seafloor around April 1 of each year. By the end of April, cells usually begin to appear in large numbers in the waters off coastal Maine. The algae are notorious for producing a toxin that accumulates in clams, mussels, and other shellfish and can cause paralytic shellfish poisoning (PSP) in humans who consume them. According to a seafloor survey conducted in the fall of 2007 by Anderson’s team, the number of Alexandrium cysts—the dormant, seed-like stage of the algae’s life-cycle—is more than 30 percent higher than what was observed in the sediments prior to the historic bloom of 2005. The seed beds were especially rich in mid-coast Maine, origin of many of the cells that affect western Maine, New Hampshire, and Massachusetts.

Other environmental factors then determine the extent to which the blooms spread down the New England coast. Much of the Northeastern United States was hit with record- or above-average rain and snowfall this winter, which will likely provide a larger than normal pulse of fresh water and nutrients into coastal waters this spring. The blend of nutrients and fresh water into salty sea water can improve growing conditions for algae.

"Our hypothesis is that cyst abundance is an indicator of the magnitude of the bloom,” said McGillicuddy, a senior scientist in the WHOI Department of Applied Ocean Physics and Engineering. “If there is a large bloom offshore, then wind patterns and ocean currents in the next few weeks will determine whether it will be transported onshore and have an effect on coastal shellfish resources.” The research team has run its computer model through 4 scenarios, using the predominant wind patterns and ocean conditions from each year since 2004. Toxicity levels during those years have ranged from relatively low in 2004 and 2007 to high levels in 2005 and 2006. Coastal exposure to the blooms is worst for scenarios in which the spring weather was dominated by strong northeast winds, which tend to drive Alexandrium cells toward the southern New England coast. When southwesterlies dominated, the algae stay offshore. Even when there are a lot of cells and toxicity, the effect can be confined to offshore waters. Biologists and oceanographers were surprised by the substantial scale and persistence of Alexandrium blooms observed on Georges Bank last year. via WHOI.edu

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