Human fatalities related to a Phaeocystis harmful algal bloom in the North Sea

On May 11, 2020, five surfers drowned after asphyxiation in a massive foam bank near the Dutch coast. We present a detailed account of the event and an examination of factors that govern local foam events, that are traditionally caused by Phaeocystis globosa (Prymnesiophyceae). The data support the hypothesis that the foam originated from a Phaeocystis bloom which if correct would make this accident the first report of human fatalities due to a harmful algal bloom in The Netherlands, and the first globally due to a Phaeocystis bloom. The rarity of massive foam banks and the absence of local real-time plankton monitoring makes it difficult to accurately predict dangerous situations as in 2020. As a prevention, surfers and other water sportsmen need to apply good seamanship during stormy and foamy conditions.