An unprecedented analysis of almost 10,000 Harmful Algal Bloom (HAB) events worldwide over the past 33 years was launched today by UNESCO’s Intergovernmental Oceanographic Commission.
The first-ever global statistical analysis examined ~9,500 HABs events over 33 years and found that the harm caused by HABs rises in step with growth of the aquaculture industry and marine exploitation and calls for more research on linkages.
Conducted over seven years by 109 scientists in 35 countries, the study found that reported HAB events have increased in some regions and decreased or held steady in others. A widely-stated view that HABs are on the rise throughout the world, perhaps due to climate change, isn’t confirmed.
However, the study, “Perceived global increase in algal blooms is attributable to intensified monitoring and emerging bloom impacts,” published in the Nature journal Communications Earth & Environment, creates the world’s first baseline against which to track future shifts in the location, frequency and impacts of HABs, which differ depending on which of the 250 harmful marine algae species is involved and where, requiring assessment on a species-by-species and site-by-site basis.
A public webinar on Global HAB Status Report will take place Tuesday Jun 15, 2021 at 1 PM, Paris time. To register: https://bit.ly/3z3kjCB
Eight of nine regions used in the study showed increases in reports logged via HAEDAT of harmful events per year, of which six were statistically significant.
The OBIS dataset, meanwhile, generally showed an increase in sampling effort in five of the nine regions.
When all the information was combined, the researchers could find no statistically significant global trend overall.
They also found, however, that aquaculture production increased 16-fold from a global total 11.35 million tonnes of seafood in 1985 to 178.5 million tonnes in 2018, with the largest increases occurring in Southeast Asia and South America/Caribbean and Central America, with North America and Europe stabilising.
The number of recorded harmful algal bloom events over time was strongly correlated with intensified aquaculture production in all regions with data suitable for the study.
However, says lead author Gustaaf M. Hallegraeff of the University of Tasmania: Intensified aquaculture clearly drives an increase in HAB monitoring efforts essential to sustaining the industry and protecting human health.
“And, just as clearly, a secondary effect of aquaculture is nutrient pollution. But a major data gap exists here. Conducting a meta-analysis of HABs vs aquaculture we had data on HAB monitoring efforts using OBIS records as a proxy but data on nutrient pollution is inadequate. The relationship between aquaculture-related nutrients and HABs therefore represents an important direction for further research.”
2021 by the American Association for the Advancement of Science (AAAS)