A first-ever UN report shows that nearly 10 000 ocean Harmful Algal Blooms were recorded worldwide over 33 years, and that impacts are increasing with rising seafood demand and coastal development.
109 scientists from 35 countries analysed over 9 500 HAB events including 7 million microalgae data points, of which nearly 290 000 toxic algae species occurrences, using the Harmful Algal Event Database (HAEDAT). The widely suggested idea that blooms are increasing with climate change is not confirmed, with blooms increasing in some areas of the world and decreasing or steady in others. Increases in reported HAB events are correlated to increased monitoring and increases in perception are probably related to increased aquacultural production and coastal development. Both Europe and the Mediterranean regions show an increase trend in reported HAB events over the study period (from 1985 to 2018), but possibly with an apparent peak around the year 2000 and after that a decrease in HAB events in the Mediterranean region and fluctuations without a clear increase in Europe (see Hallegraeff et al. Fig. 3 p. 5).
A large proportion of the societal impact of blooms was resulting closure of shellfish harvesting, with only rare cases of human poisoning. Economic losses caused by HABs to aquaculture are considerable, whereas in the open ocean wild fish can simply swim away from HABs. The number of recorded HABs over time was strongly correlated with intensification of aquaculture, but this is probably largely due to more intense monitoring. Data on nutrient pollution is considered inadequate to reach conclusions as what extent aquaculture contributes to causing HABs.
Report published by UNESCO (United Nations) and the Intergovernmental Panel on Harmful Algal Blooms (IOC-IPHAB, part of UNESCO’s Intergovernmental Oceanographic Commission), 8 June 2021 http://hab.ioc-unesco.org/index.php
Harmful Agal Bloom Information Portal: https://data.hais.ioc-unesco.org/
“Perceived global increase in algal blooms is attributable to intensified monitoring and emerging bloom impacts”, G. Hallegraeff et al., Nature Communications Earth & Environment (2021) 2:117 https://doi.org/10.1038/s43247-021-00178-8