Background Image

Guidelines for the study of climate change effects on harmful algal blooms now available

Date: 14 February 2022

Guidelines for the study of climate change effects on harmful algal blooms (HABs) are now available to all researchers who try to better understand if and how HAB events may evolve in the future due to climate change.

HABs are natural phenomena consisting of the proliferation of certain algae  in marine, estuarine and freshwater systems. The impacts of HABs are diverse, including massive fish kills, contamination of seafood and drinking water with phycotoxins affecting human health,  and alteration of ecosystems in ways that humans perceive as harmful. As noted by Elisa Berdalet, Chair of the international scientific programme on HABs, GlobalHAB Programme: “There is concern that climate-driven changes in aquatic systems will further increase the frequency, distribution, and intensity of these ecological events with additional impacts on human societies and ecosystems."


obis map

OBIS maps and time series of records of potentially toxic and non-toxic species of the genera Alexandrium and Pseudo-nitzschia between 1950 and 2019, obtained by merging the datasets specifically established within HABMAP-OBIS with all data from other sources that are present in OBIS. These data are consistent with, but do not demonstrate, climate-driven increases in blooms of these species in some areas.

HAB science today is founded on studies dealing with a great diversity of topics and harmful organisms, using a variety of continuously evolving experimental methods and approaches.

These newly published guidelines aim to provide the scientific community with standardized strategies, tools and protocols to assess how climate change drivers may increase or decrease future HAB prevalence in aquatic ecosystems.

“Developing the foundation for HAB prediction under accelerating shifts in environmental conditions will rely on a quantitative, mechanistic-based understanding of climate-HAB linkages. Addressing this challenge requires a common strategy based on the multidisciplinary knowledge gained in recent years and the new available methodologies.” -  explains Mark Wells, Editor in Chief of the publication.

These guidelines are expected to evolve with time, as HAB-climate change research advances. "The guidelines are designed and published as an on-line resource to the HAB-climate change research community, who is invited to contribute to future updates of the document" - adds Mark Wells.

The Guidelines for the study of climate change effects on HABs were published jointly by the IOC, SCOR, PICES and ICES.

More information on IOC’s work on HABs is available at