Evidence of diarrhetic shellfish poisoning along the coast of Maine

Following the occurrence of several unexplained incidents of shellfish-rela ted gastroenteritis, field studies were conducted to determine if diarrheti c shellfish poisoning (DSP) toxins are present in Maine coastal waters. A p rotein phosphatase inhibition assay for DSP toxins revealed the presence of low levels of okadaic acid-like activity in blue mussels (Mytilus edulis) at sampling sites in the Frenchman Bay-Eastern Bay region. All other sires along the Maine coast were negative. Phytoplankton populations from this ar ea were dominated by Dinophysis norvegica, a known toxic species. Two addit ional known toxic species of Dinophysis were also found: Dinophysis acumina ta and D. rotunda. However, all plankton samples were negative for okadaic acid-like activity. Examination of the epiphytic communities from areas whe re mussels showed okadaic acid-like activity revealed the presence of the t oxic dinoflagellate Prorocentrum lima in association with the brown alga, E ctocarpus sp. Epiphytic samples rich in P. lima were active in the phosphat ase inhibition assay; Subsequent analysis of these samples using LC-MS/MS i dentified the presence of dinophysis toxin-l (DTX-1). Empty P. lima thecae identified in the digestive tract of mussels from these areas indicate that P. lima is consumed by mussels. This is the first confirmation of P. lima in northern United States coastal waters and identifies DSP as a potential public health issue.