Joint ICES/IOC Working Group on Harmful Algal Bloom Dynamics (WGHABD; outputs from 2020 meeting).

The ICES/ IOC Working Group on Harmful Algal Bloom Dynamics (WGHABD), co-sponsored by the International Oceanographic Commission (IOC) of UNESCO Intergovernmental Panel for Harmful Algal Blooms (IPHAB), looks at the dynamics of harmful algal blooms (HABs). HABs continue to impact the ICES area and delegates presented national reports of HABs and their impacts, including widespread closures of shellfish harvesting areas across the ICES area due to levels of shellfish toxins exceeding regulatory thresholds, marine mammal and fish mor-talities, brown tides, human illness due to ciguatera poisoning (CP) and beach closures due to cyanobacteria blooms. Closures of shellfish harvesting areas were also enforced due to levels of Tetrodotoxin exceeding regulatory thresholds in the Netherlands. A range of ‘new findings’ re-lating to HABs were presented including developments in satellite imagery of HABs, molecular methods, impacts of viruses on cyanobacteria, oomycete parasites of diatoms, records of Ostre-opsis cf. siamensis in the Bay of Biscay and interpretation of shellfish toxin monitoring data. The ecology of selected HAB groups were reviewed including CP producing species Gambierdis-cus and Fukuyoa, Arctic HAB species and fish killing algae. CP continues to present a health risk in the Canary Islands and annual updates of developments in investigating CP and its causative organisms were presented. The role of HABs in the assessment of ‘Good Environmental Status’ for the EU Marine Strategy Framework Directive were reviewed. New methodologies and their utilisation were also discussed and outcomes of a CoClime qPCR workshop, presented. WGHABD main focus was the updating of the IOC-ICES-PICES Harmful Algal Event Database, production of text for an ICES Harmful Algal Event Status Report and contributions towards the IOC Global HAB Status report (GHSR). HAEDAT data was updated and graphical products de-veloped. HAEDAT data from the ICES area has contributed to an additional seven presentations at conferences and one book chapter. Five manuscripts have been submitted to the scientific journal Harmful Algae analysing HAEDAT data from the ICES area and delegates from WGH-ABD are co-authors on a global synthesis paper for the GHSR. HAEDAT maps were provided as example outputs developed by ICES and IOC at the UN Decade of Ocean Science North At-lantic Workshop. These maps were highlighted during the Workshop general summary as a template for compiling and integrating various HAB and other data to deliver products to a broader user community such as hazard maps and potential risk for early warning systems (EWS). Throughout 2018–2020 WGHABD continued to report to the IOC Intergovernmental Panel for Harmful Algal Blooms and represent ICES on the IOC SCOR GlobalHAB Scientific Steering Committee.