Monitoring the 2023 Highly Unusual Algal Bloom in the Gulf of Maine: a Community-Led Rapid Response

A bloom of the dinoflagellate Tripos muelleri, dominated the western Gulf of Maine from April to August of 2023. In response to this highly unusual event a network of collaborators throughout the region shared observations in an effort to track the bloom's extent, progression, and impacts on fisheries and the ecosystem. Recognizing the need for a rapid response, the Northeastern Regional Association of Coastal Ocean Observing Systems (NERACOOS) in conjunction with the University of New Hampshire (UNH) worked towards organizing and expanding the monitoring effort. Of greatest concern was the possible development of a large hypoxic zone resulting from the sinking and decomposition of the bloom. Although low dissolved oxygen levels were detected the bloom ended without a major event. Ultimately, limited opportunities were available to expand sampling but the strong network of coastal ocean observers in the community enabled coordinated monitoring of the bloom. Following the bloom, NERACOOS and UNH hosted a seminar and workshop to advance an understanding of the bloom, to evaluate the monitoring response, and recommend improvements for the coastal ocean observing system. The workshop highlighted the need for enhanced monitoring to better understand and anticipate events like algal blooms, and communication infrastructure to facilitate coordination. Under future climate change scenarios extreme events are expected to become more common and necessitate rapid responses. Greater monitoring and communication infrastructure together with strong networks will aid in responding to such events and increasing climate resilience.