Establishment, Goals, and Legacy of the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB) Programme

23 pages, 4 figures, 1 tableSingle-celled organisms called phytoplankton and cyanobacteria (often called blue-green algae), together with macroalgae, support healthy aquatic ecosystems by forming the base of the food web. This broad group of organisms fix carbon and produce oxygen through photosynthesis, providing approximately 50% of the oxygen on the planet. A small subset of these organisms can cause harm to aquatic ecosystems and to humans by producing water-borne toxins that can accumulate in the food web to produce toxic seafood. Whether toxic or not, these same organisms can also form “blooms” (high biomass of cells) causing harm or disrupting aquatic ecosystems. Ecosystem damaged by high-biomass blooms may include, for instance, disruption of food webs, fish killing by gill damage, or the development of low-oxygen “dead-zones” after bloom degradation. When these events discolour the water, they are often referred to colloquially as red tides (regardless of colour), whether they produce toxins or not and often whether they are harmful or not. Regardless of whether these algae and cyanobacteria are toxic and whether they form low or high biomass, they are collectively referred to as “harmful algal blooms” (HABs) when they exhibit negative consequences for human, ecosystem, or wildlife health or socioeconomic status of the environment (Hallegraeff 1993; Glibert et al. 2005; Anderson et al. 2012; Kudela et al. 2015). The definition of a HAB is therefore a societal concept rather than a scientific definition. [...]Peer reviewe