Progress Toward Understanding HAB Climate Response Through Intensive In Situ Observation of Alexandrium catenella

Globally, Alexandrium catenella is the most widespread harmful algal bloom (HAB) species responsible for outbreaks of paralytic shellfish poisoning (PSP), a potentially life-threatening seafood poisoning syndrome. Like many other HAB dinoflagellates, A. catenella exist as resting cysts for much of their lifetime and bloom phenology is largely driven by entry and exit from this benthic stage of its life cycle. A long history of laboratory investigations have described temperature-dependence in the behavior and physiology of both benthic and planktonic life cycle stages of this species. However, recent intensive in situ investigations through the Woods Hole Center for Oceans and Human Health (WHCOHH) have revealed substantially higher rates of growth, swimming, toxin production and sexual induction than was previously understood. WHCOHH studies have also described new temperature dependent mechanisms controlling dormancy cycling within resting cysts. Understanding temperature controls in natural populations is critical for improved monitoring and prediction of blooms, especially in the face of rapid change within coastal ecosystems. Results also point to a need to better understand the factors stimulating higher activity in natural populations than is observed in culture. New insights have been made possible through development of new field-based approaches that leverage continuous in situ cell imaging, adaptive field collections, and new analytical methods to characterize the physiological rates of natural populations. In the coming years, we will explore inter-population differences among A. catenella occurring in New England and the Arctic through deployment of a network of observing platforms and new field efforts. We will also apply methods developed through studies of A. catenellato a number of emergent HAB taxa in our region including Dinophysis spp. , Karenia mikimotoi, Margalefidinium polykrikoides, and Pseudo-nitzschia spp.