Harmful Algal Bloom and Hypoxia Research and Control Amendments Act of 2023

This bill amends the Harmful Algal Blooms and Hypoxia Research and Control Act of 1998 to improve federal coordination and research on harmful algal blooms and hypoxia. It requires the Interagency Working Group to develop a comprehensive Action Strategy every five years examining both marine and freshwater harmful algal blooms, their causes, ecological impacts, and potential solutions. The bill establishes a National Harmful Algal Bloom Observing Network to leverage existing systems and new technologies for better monitoring and forecasting, and creates a new "Event of Significance" fund to support assessments and mitigation for particularly severe events. These changes directly affect federal agencies like NOAA and EPA, state and local governments, Tribal communities, and industries like fisheries that rely on healthy water resources.