Harmful Algal Blooms (HABs) are the excessive outgrows of several species of microalgae from dozens of genera, in costal and marine waters but also in freshwater environments. These blooms are known to affect aquatic ecosystems and food webs, aquaculture, fisheries, as well as tourism and public health.
There has been an increase in the occurrence, frequency, and duration of HABs on a global scale linked to anthropogenic activities and in several instances to climate change. However, an apparent increase in the occurrence and severity of these blooms in both marine and freshwater environments has been occurring over the past years. For instance, a large-scale bloom of Karenia brevis has recently been estimated to have caused a loss of as much as 2.7 billion USD. A more recent instance of large-scale bloom of another species of HAB, Karenia mikimotoi, in South Australia, has caused a loss in fisheries and aquaculture preliminarily estimated to one third or even half of the total production with devastating impacts on marine ecosystems, ranging from mass mortalities in benthic ecosystems to mortalities in marine mammals. This event has prompted a call to consider the long-lasting bloom linked to climate-change induced Marine Heat Waves (MHV) as a National Disaster.
In the present talk, a historical overview of HAB occurrence in marine and freshwater ecosystems (e.g. CyanoHAB, Alexandrium spp., Dinophysis spp. Karenias pp., Pseudo-nitzschia spp., Gambierdiscus spp., Ostreopsis spp.) with a special emphasis on the recent trends linked to climate change and pollution will be given. Data on our ongoing research on the impacts of HABs on aquaculture and fisheries will also be presented. The link between the global expansion and geographic shifts of HAB, food security, and the triple planetary crisis (Climate Change, Pollution, Biodiversity) – coined in 2020 by the UN Environment Programme and being addressed within the UN frameworks (e.g. UNFCCC, UN Global Biodiversity Framework) – will be discussed.