Since 2004, MERI has conducted Red Tide Monitoring in Blue Hill Bay in partnership with the Maine Department of Marine Resources (DMR).  From April through October MERI samples sites onshore and in Blue Hill Bay weekly for the presence of Alexandrium, the species of marine algae responsible for paralytic shellfish poisoning (PSP).  In 2008, a bloom of Alexandrium was responsible for sickening a family of six in Jonesboro, underscoring the importance of this monitoring program

A ‘red tide’ occurs when toxic algal species multiply to the point of producing toxin levels that can cause human and marine animal health effects. The algae increase in numbers and darkens the color of the water. From 2005 to 2009, record-breaking Alexandrium blooms occurred, resulting in extensive closures of shellfish beds for harvest and millions of dollars in lost revenue for area fishermen as well as impacts on local tourism.  

Shellfish are filter feeders and, as such, accumulate saxitoxin, a toxin produced by Alexandrium that is more deadly than cyanide. Approximately 9 µg/kg of saxitoxin is considered a toxic dose.  Symptoms of PSP begin within 30 minutes following ingestion of a contaminated meal with a tingling sensation of the lips and tongue leading to respiratory paralysis. With no known antidote, PSP can be fatal if respiratory therapy is not given. If an individual survives more than 24 hours, recovery is usually complete with no lasting effects.

Scientists believe that red tide events are caused by a combination of factors including high Alexandrium cyst abundance in the western Gulf of Maine, high spring rainfall and snowmelt which add nitrogen to coastal waters, and heavy easterly winds in spring which push the cysts on shore where shellfish beds absorb them.  High cyst abundance seems to be a critical factor. The Bay of Fundy is a cell retention zone with a secondary seed bed in the western Gulf.  Maturing cysts are carried along the Eastern Maine Coastal Current (EMCC) and are usually turned offshore due to the physics of the Gulf system. However, easterly winds, increasingly common in spring, can push the cells onto shore where they bloom. 

MERI and the Maine DMR Partner to Intensify Red Tide Monitoring in Blue Hill Bay

Starting in 2010, MERI is partnering with the DMR scientists to intensify phytoplankton monitoring in Blue Hill Bay. The data to be collected will help the DMR determine where to draw shell fish closure lines throughout this area. 2009 is on record as the worst red tide season in history. This increase in toxicity made evident the need for more intensive monitoring in the Bay in order to deliver precise warnings to the public about the presence of red tide.

MERI researchers will set out buoys containing live mussels at three sites within the triangle between Pond Island, Tinker Island and East Barge Islands. Mussel samples will be collected from these sentinel buoys during the peak summer months and tested for the presence of the biotoxin which causes PSP. In addition, MERI researchers will continue to collect phytoplankton samples from four offshore sites and four onshore sites within the bay. This effort will produce new information about red tide that presently does not exist. The data will provide more certainty to decisions regarding shellfish closure lines, and in some cases, will possibly result in increased access to these areas or fishermen and visitors alike.