Diarrhetic shellfish poisoning (DSP) has emerged as a significant and expanding seafood safety threat in coastal regions across the country and observations of intensifying blooms in TX, WA, NY, and New England may signal further expansion into new regions. Despite this immediate threat to human and ecosystem health, little is known of the environmental and biological drivers of Dinophysis growth and toxin production in the US, species or subpopulation (strain) variation, and the relative toxicity of the novel dihydro-DTX1. The objectives of this project Develop informative markers for species identification and investigate physiological responses among Dinophysis spp. to environmental and biological factors.