Coastal waters of the northeastern U.S. are subject to recurrent outbreaks of paralytic shellfish poisoning (PSP) caused by the toxic dinoflagellate Alexandrium fundyense. Similarly, a new toxin syndrome caused by spirolide toxins originating with a related species called Alexandrium ostenfeldii now threatens public health in the region. Little is known about the extent of spirolide toxicity in the Gulf of Maine, but it is nevertheless clear that both spirolide and PSP toxicity are not uniform across the region. This results from Alexandrium growth and toxin accumulation in several separate habitats defined by coastal circulation patterns and the discontinuous distribution of the dinoflagellates as well as underlying toxin variability among isolates of both species. Overall, this variability in PSP and spirolide toxicity represents a significant challenge from public health and fisheries management perspectives. To date, research and monitoring programs have recognized neither the extent to which genetically distinct sub-populations of A. fundyense and A. ostenfeldii co-exist and compete for dominance nor the effects these population differences can have on shellfish toxicity. Based upon hydrographic data and laboratory and field observations, we hypothesize that: Alexandrium fundyense and A. ostenfeldii blooms in the Gulf of Maine are not single, homogeneous populations, but are comprised of distinct sub-populations, each with it's own physiological characteristics, toxicity, and genetic history. The nature of these distinct populations, the extent of genetic mixing and recombination, and selection pressures imposed by environmental forcings all influence Alexandrium population structure and contribute to the ultimate toxicity threat to humans. The proposed project has the following specific aims: 1. Identify a genetic marker capable of distinguishing different genotypes within Alexandrium spp. populations; 2. Determine the extent of natural genetic diversity ofAlexandrium spp. in the Gulf of Maine; 3. Characterize the relationships between toxicity, physiological variability and genotype in Alexandrium spp. from the Gulf of Maine; 4. Track changes in the relative abundance of Alexandrium genotypes in Bay of Fundy source population through time; 5. Track temporal changes in the genotypic diversity of Alexandrium populations within the Gulf of Maine; 6. Investigate the relationship between Alexandrium population structure and the quantity and composition of toxins in the plankton.
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