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(R) WHOI researcher Bruce Keafer preparing a corer to collect sediment samples. (Photo: Amy Lloyd-Rippe)
Researchers expect moderate red tide for Gulf of Maine
(UNITED STATES, 4/10/2012)
New England is expected to experience a "moderate" regional "red tide" this spring and summer, report National Oceanic and Atmospheric Administration (NOAA) funded scientists working in the Gulf of Maine to study the toxic algae that causes the bloom. The algae in the water pose no direct threat to human beings, however, the toxins they produce can accumulate in filter-feeding organisms such as mussels and clams— which can cause paralytic shellfish poisoning (PSP) in humans who consume them.
Under a newly developed rating system, a moderate bloom could cause the closure of shellfish beds along an estimated 126–250 mi of coastline.
The 2012 outlook is based on the quantities of the algae Alexandrium fundyense in its dormant – or cyst – state detected in Gulf of Maine sediments last fall. These data are combined with computer simulations that model a complex range of meteorological and oceanographic conditions -- winds, sunlight, rainfall, tides, and currents -- that impact the size of the bloom.
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| Cysts of Alexandrium fundyense algae. (Photo: Don Anderson, Woods Hole Oceanographic Institution) |
"Our goal over the last 10 years has been to develop a system to help the shellfish industry and environmental managers better plan for the annual bloom," said Woods Hole Oceanographic Institution (WHOI) biologist Don Anderson, who has worked with WHOI colleague Dennis McGillicuddy and North Carolina State University (NCSU) Prof Ruoying He to develop the computer model to help predict the intensity and location of blooms.
The scientists use the computer model to produce a range of bloom scenarios – or an "ensemble forecast" – tracking variables like wind direction and water characteristics based on previous years' conditions. This is similar to the system used to forecast hurricanes.
"The surveys of cyst abundance gives us an indication of the potential extent of the bloom, but whether or not that potential is realized depends on the growing conditions," said McGillicuddy. "In 2010 we forecast a large bloom but we got it wrong. That spring, an unusual mass of warm, fresh water that was low in nutrients changed the growing conditions."
Wind direction imposes another uncertainty to the forecast.
"Each year, we add another set of environmental conditions to our archive of model runs. In the future, a winter that is warmer and drier than normal can be represented by 2012, but right now, we have no similar year in that archive," said Anderson.
The economic impacts of PSP toxicity are significant in the region. Direct and indirect costs of the extensive Alexandrium bloom in 2005 were estimated at nearly USD 50 million for Massachusetts and USD 23 million for Maine.
As part of that work, Judy Kleindinst, a member of Anderson's team, analyzed records of harvesting closures due to PSP extending back 35 years, and identified three categories of bloom severity.
The categories -- "limited, "moderate", and "extensive" – are equivalent to closures over 0 - 125, 126 – 250, and 251 – 375 mi of coastline.
When combined, the forecast terminology, the annual cyst surveys and the continual improvements and additions to the computer model have developed into a useful management tool.
editorial@fis.com
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