Project 1: Drivers of interannual and intrabloom toxicity dynamics in Gulf of Maine HABs

Alexandrium catenella and Pseudo-nitzschia spp. threaten human health through their production of potent neurotoxins that respectively cause Paralytic Shellfish Poisoning and Amnesic Shellfish Poisoning. Both are widespread across coastal waters of the U.S. and globally. Environmental factors alter marine ecosystems in many unanticipated ways, and a major concern is that the occurrence of these harmful algal blooms (HABs) and their concomitant human health impacts will grow. This project addresses key uncertainties regarding the impact of environmental variability on the timing and severity of HABs through detailed biological and ecological study of Alexandrium and Pseudo-nitzschia blooms within the Gulf of Maine (GOM). The GOM is an ideal system because of the long history of regional HAB issues and associated groundbreaking research by WHCOHH. Comprehensive studies of bloom physiology, toxicity, and oceanographic drivers have led to construction of coupled physical-biological models that have improved our understanding of key HAB dynamics and set the stage for continued interdisciplinary investigation of mechanisms at the cellular-to-GOM scale that are relevant to human exposure and health. In particular, the physiological responses of these HABs — growth, toxicity, and life cycle transitions — to shifting environmental conditions remain uncertain. We hypothesize that long-term trends in HAB risks in the GOM are inherently linked to physiological processes and toxin dynamics that are driven by ecological stimuli. This project’s aims are designed to illuminate the role of life cycle dynamics and cellular physiology in determining the occurrence of Alexandrium and Pseudo-nitzschia blooms. We apply a wide variety of innovative approaches for study of natural populations in situ, leveraging a unique region-scale HAB observing system (HABON-NE). Aims 1 and 2 focus on A. catenella and seek to characterize cyst dormancy cycles, cyst formation, and subsequent bloom termination. These aims build upon prior successful approaches and models from study of inshore systems, asking the question if open water populations of the GOM are governed by similar dynamics. Aim 3 investigates the physiology underlying the emerging bloom dynamics of Pseudo-nitzschia in the GOM with in situ physiological observation coupled with targeted metatranscriptomics. Through the direct assessment of life cycle processes and physiology of HABs in the GOM, the results from this work will be directly applicable to the successful integration of physiology into models (Project 2) and inform estimates of potential risk for human exposure to HAB toxins (Project 3).