Harmful algal blooms: a scientific summary for policy makers

• Harmful Algal Blooms (HABs) result from noxious and/or toxic algae that cause direct and indirect negative impacts to aquatic ecosystems, coastal resources, and human health.

• HABs are present in nearly all aquatic environments (freshwater, brackish and marine), as naturally occurring phenomena.

• Many HABs are increasing in severity and frequency, and biogeographical range. Causes are complex, but in some cases can be attributed to climate change and human impacts, including eutrophication, habitat modification, and human-mediated introduction of exogenous species.

• There is no plan, and nor realistic possibility, to eliminate HABs and/or their dependent consequences. Decades of research and monitoring have, however, improved our understanding of HAB events, leading to better monitoring and prediction strategies.

• HABs are a worldwide phenomenon requiring an international understanding leading ultimately to local and regional solutions. Continued progress in research, management, mitigation, and prediction of HABs benefits from international coordination. In this spirit, the international community has developed programmes sponsored by the Intergovernmental Oceanographic Commission (IOC) and Scientific Committee on Oceanic Research (SCOR) to coordinate international HAB research, framework activities, and capacity building.

• HABs are recognized as one facet of complex ecosystem interactions with human society. HAB research, monitoring, and management must be closely integrated with policy decisions that affect our global oceans.

• New initiatives, such as GlobalHAB sponsored by IOC and SCOR, will continue to provide the mechanisms to further understand, predict, and mitigate HABs. Research, management, and mitigation efforts directed towards HABs must be coordinated with other local, national, and international efforts focused on food and water security, human and ecosystem health, ocean observing, and climate change.