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Harmful Algal Blooms threaten human and ecosystem health, and disrupt aquaculture and wild fisheries, tourism, and other resources in marine and freshwater systems.

What are Harmful Algal Blooms (HABs)?

Marine and fresh waters teem with life, much of it microscopic and most of it beneficial and harmless. There are, however, some species of algae and cyanobacteria that cause harm, either through the production of potent toxins or through the accumulated biomass during their “blooms”. Impacts include human and wildlife illness and mortality, ecosystem disruption, and economic losses to coastal communities.

HAB Species

Learn about different toxic or harmful algal species, and the poisoning syndromes they cause


See where harmful algae are distributed in the U.S. and around the world


Discover how harmful algal blooms impact human health and coastal economies, wildlife, ecosystems, and more


Learn about the national and international research programs focused on understanding, managing, and preventing harmful algal blooms


Major programmatic and informational resources regarding harmful algal blooms, as well as fact sheets and hotlines


Programs and activities focused on prediction, control, mitigation, and HAB event response

News and Announcements

Save the date! 11th U.S. Symposium on Harmful Algae

November 23, 2021

We are pleased to announce that the 11th U.S. Symposium on Harmful Algae will be held on October 23-28, 2022, in Albany, New York, at the Hilton Albany. Local coordination is being led by NEIWPCC, New York State Department of Environmental Conservation, and U.S. Geological Survey with support from the U.S. National Office for Harmful…

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19th International Conference on Harmful Algae (ICHA)

October 4, 2021

Thanks to the organizers of this virtual event! The conference proceedings will be posted when they become available.

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OHHABS Summary Report Published , United States, 2019

October 4, 2021

The CDC published the 2019 US summary on harmful algal bloom (HAB) events and associated human or animal illnesses through the One Health Harmful Algal Bloom System (OHHABS). One Health is a multi-sectoral approach that involves engagement across disciplines including public health, animal health, and environmental health. Using the One Health approach, CDC collects data…

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HABs and Ocean Acidification Report Published

August 12, 2021

Now available is the workshop report for NOAA and NCCOS’s August 2020 workshop on interactions between HABs and ocean acidification. To read the report, please click here.

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EPA new Cyanotoxins Preparedness and Response Toolkit

June 3, 2021

The EPA posted a Cyanotoxins Preparedness and Response Toolkit (CPRT) online. The CPRT will help EPA’s state and tribal partners prepare for potential harmful algal blooms in freshwater bodies and respond to protect public health. Cyanobacterial Harmful Algal Blooms (CyanoHABs) can cause fouling of beaches and shorelines, economic and aesthetic losses, taste and odor problems…

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12th International Conference on Toxic Cyanobacteria

May 24, 2021

The 12th International Conference on Toxic Cyanobacteria (ICTC 12) will be held in Toledo, OH from May 22-27, 2022!  This rendition of ICTC will be a joint effort with the Interdisciplinary Freshwater Harmful Algal Blooms Workshop. As has been done at past ICTCs, submitted papers will also be published in a peer-reviewed journal. We are currently exploring…

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Proceedings of the Workshop on the Socio-economic Effects of Marine and Fresh Water Harmful Algal Blooms in the U.S.

March 23, 2021

The NCCOS Competitive Research Program (CRP) and the U.S. National Office for Harmful Algal Blooms are pleased to release the proceedings of the “Workshop on the Socio-economic Effects of Marine and Fresh Water Harmful Algal Blooms in the United States“, convened in August, 2020. The report documents the workshop’s proceedings and presents recommendations to advance…

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US HAB Early Career Symposium

February 16, 2021

Thank you for attending the 10.5 US Symposium on Harmful Algae, with the conference theme Emerging Voices and Blooming Careers. This meeting was held virtually from May 25-27, 2021.  You can access the meeting website here  and the conference program here.

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“Framework for the National Harmful Algal Bloom Observing Network: A Workshop Report” Now Available

January 13, 2021

This framework is a production of a workshop hosted by the National Centers for Coastal Ocean Science (NCCOS) and U.S. Integrated Ocean Observing System (IOOS), with representatives from five Line Offices of the National Oceanic and Atmospheric Administration (NOAA). The report is now available here.

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66th Edition of Harmful Algae News Released

December 23, 2020

A collaboration between the IOC and UNESCO, Harmful Algae News is a free newsletter describing recent updates in the global study of HABs, as well as publicizing networking and training opportunities for professionals. The newsletter can be found here.

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