News Release

UN to issue first-ever global report on harmful algal blooms

After 7 years' work, 100+ experts in 112 countries deliver 1st global assessment of HABs, synthesizing three decades of data

Peer-Reviewed Publication

Terry Collins Assoc

Harmful Algae Bloom, Japan

image: More than 100 scientists in 112 countries contributed to a synthesis and analysis of Harmful Algal Bloom data gathered from 1985 to 2018 -- a first-ever big data approach to detecting changes in the costly phenomenon's global distribution, frequency, and intensity. view more 

Credit: Melvil Japan

A seven-year analysis of almost 10,000 Harmful Algal Blooms (HAB) events worldwide over three decades will be published by the HAB Programme of UNESCO's Intergovernmental Oceanographic Commission.

More than 100 scientists in 112 countries contributed to the synthesis and analysis of HAB data gathered from 1985 to 2018 -- a first-ever big data approach to detecting changes in the costly phenomenon's global distribution, frequency, and intensity.

The authors detail the health and economic damages caused by harmful microalgae, including:

  • Bioaccumulation of toxins in seafood (the most dominant HAB problem, broken down by both region and by algae species)

  • Toxic or non-toxic microalgae blooms causing discoloured water, scum, mucilage or foam, harming tourism and/or fisheries

  • Mass fish kills, including in aquaculture operations

  • High biomass, causing closures of e.g. beaches or desalination plants

The researchers also examine whether and how rising marine resource exploitation and other factors affect HAB events.

The work assesses the occurrence of toxin-producing and other harmful microalgae, and the status and probability of change in HAB frequencies, intensities, and range resulting from environmental change at the local and global scale.

Publication of the key findings in a prominent journal will be followed by a complete set of 13 papers to be published in a special edition of Harmful Algae.

Databases mined

Thousands of microalgae species form the foundation of aquatic food chains, help control atmospheric CO2 levels, and produce roughly half of the world's oxygen.

The troublemakers are approximately 200 species that can produce potent toxins or cause harm through their sheer biomass, plus a similar number of non-toxic species that can harm fish gills, impair the beauty of the sea with strange colours, scums and foams, or deplete oxygen.

The study involved mining the global Harmful Algae Event Database (HAEDAT), consisting of 9,503 events with one or more impacts on human society, together with the Ocean Biodiversity Information System (OBIS), which contains 7 million microalgal records including 289,668 toxic algal species occurrences.

Due to differences in the levels of monitoring worldwide, trends within the HAEDAT database were examined regionally and corrected for sampling effort using OBIS phytoplankton species records as a proxy.

The work creates the first-ever baseline to facilitate future tracking and detection of changes in the world's HAB problems, and to help manage the problems in future.

Three key public databases

The Harmful Algal Event Database (HAEDAT,

The only existing database of information about harmful algal events from around the world, summarized into 'events' associated with a management action or negative economic / ecological impact. Includes cases of non-toxic water discolorations, mucilage, anoxia or other damage to fish.


A database on the geographic range of harmful algal species

HAEDAT and OBIS are both components of the IOC International Oceanographic Data and Information Exchange Programme (IODE).

The IOC-UNESCO Taxonomic Reference List of Harmful Microalgae

Includes formally accepted names of 150+ planktonic or benthic microalgae that have been proven to produce toxins. The number of species in the list has doubled over the years.

The work will help future researchers determine:

    1. The distribution of HAB species, HAB events, and toxins globally

    2. How the geographic distribution, characteristic, frequency and intensity of HABs are changing and if these changes are attributable to global change

    3. How climate change and other factors alter the impacts of HABs -- on human health, ecosystems, economics, food and water security

With more than 100 expert contributors from 112 countries, the work is piloted by 18 principal authors from 14 countries (including two from Australia, two from France, three from the USA):

    · Gustaaf M. Hallegraeff, University of Tasmania, Australia

    · Donald M. Anderson, Woods Hole Oceanographic Institution, USA

    · Catherine Belin, IFREMER, France

    · Marie-Yasmine Bottein, Ecotoxicologie et Développement Durable expertise, France

    · Eileen Bresnan, Marine Scotland, UK

    · Mireille Chinain, Institut Louis Malardé-UMR241, Tahiti

    · Henrik Enevoldsen, Intergovernmental Oceanographic Commission of UNESCO, University of Copenhagen, Denmark

    · Mitsunori Iwataki, University of Tokyo, Japan

    · Cynthia H. McKenzie, Fisheries and Oceans Canada, Canada

    · Inés Sunesen, CONICET - UNLP, Argentina

    · Grant C. Pitcher, University of Cape Town, South Africa

    · Pieter Provoost, Intergovernmental Oceanographic Commission of UNESCO, Oostende, Belgium

    · Anthony Richardson, CSIRO Oceans and Atmosphere, and University of Queensland, Australia

    · Laura Schweibold, Institut Universitaire Européen de la Mer, France

    · Patricia A. Tester, Ocean Tester, USA

    · Vera L. Trainer, National Oceanic and Atmospheric Administration, USA

    · Aletta T. Yñiguez, University of the Philippines, Philippines

    · Adriana Zingone, Stazione Zoologica Anton Dohrn, Italy

"The most frequently asked questions about Harmful Algal Blooms (HABs) are if they are increasing and expanding, and what are the mechanisms behind observed trends," the authors say.

"Indeed a global expansion of HABs and its causes have long been debated. Eutrophication, human-mediated introduction of alien harmful species, climatic variability, and aquaculture have all been mentioned as possible causes of an expansion and intensification of HABs. Our research sheds an authoritative light on the problem and will help guide responses to it for decades to come."

The IOC Intergovernmental Panel on HABs began the Global HAB Status Report in 2013.

The work is linked with the International Panel on Climate Change (IPCC) reporting mechanism, which increasingly is focusing on the biological impacts of climate change.

IOC UNESCO project partners include the International Atomic Energy Agency (IAEA), the International Council for Exploration of the Sea (ICES), the North Pacific Marine Science Organization (PICES) and the International Society for the Study of Harmful Algae (ISSHA). The initiative receives financial support from the Government of Flanders/FUST-DIPS.

Interested media and other parties may apply for advance, embargoed access to the papers, approximately one week prior to publication. Please email with the subject line: Advance access, UN HAB report


About the HAB Programme:

The Intergovernmental Panel on Harmful Algal Blooms (IOC-IPHAB), part of the Intergovernmental Oceanographic Commission of UNESCO, initiated the development of the Global HAB Status Report in Paris in April 2013, developed with the support of the Government of Flanders within the IOC International Oceanographic Data and Information Exchange (IODE) Programme, which manages both the Harmful Algae Event Data Base (HAEDAT) and the Ocean Biodiversity Information System (OBIS). Partners include ICES, PICES and IAEA.

OBIS focuses on the global distribution of all marine species including those HAB species that are toxic to humans and fish as covered by the IOC-UNESCO Taxonomic Reference list of Harmful MicroAlgae (a subset of the World Register of Marine Species), while HAEDAT holds information specifically on the HAB events that have adversely impact on human society, whether by high biomass (clogging of fishing nets, beach closures), aquaculture fish kills, or seafood toxin events leading to shellfish farm closures, human poisonings or even death.

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