A view of physical mechanisms for transporting harmful algal blooms to Massachusetts Bay.

Physical dynamics of Harmful Algal Blooms in Massachusetts Bay in May 2005 and 2008 were examined by the simulated results. Reverse particle-tracking experiments suggest that the toxic phytoplankton mainly originated from the Bay of Fundy in 2005 and the western Maine coastal region and its local rivers in 2008. Mechanism studies suggest that the phytoplankton were advected by the Gulf of Maine Coastal Current (GMCC). In 2005, Nor'easters increased the cross-shelf surface elevation gradient over the northwestern shelf. This intensified the Eastern and Western MCC to form a strong along-shelf current from the Bay of Fundy to Massachusetts Bay. In 2008, both Eastern and Western MCC were established with a partial separation around Penobscot Bay before the outbreak of the bloom. The northeastward winds were too weak to cancel or reverse the cross-shelf sea surface gradient, so that the Western MCC carried the algae along the slope into Massachusetts Bay.