3. Harmful Algal Blooms (HABs)

Harmful algal blooms (HABs) are serious biological nuisances and become a global epidemic. This is primarily flagellate events, causing mass mortality, physiological impairment or other negative in situ effects. HABs are increasing their frequency, persistence, regional coverage/spatial extent and economic impact worldwide in recent decades as a result of changes in enhanced coastal eutrophication and climate change along with invasion of alien species through ballast water exchange. This also happens on account of the world’s increasing trend of unscientific and irrational exploitation on the coastal zone for shelter, food, construction, food, aquaculture, recreation and other commercial uses, which results in increasing eutrophication. Naturally occurring red tides and harmful algal blooms (HABs) are of increasing importance in the eutrophic coastal environment and can have remarkable adverse impacts on coastal benthic and epipelagic communities. Determining the key regulatory factors is somehow problematic since algal blooms are often unpredictable, irregular or of short duration. The chapter has addressed an illustrative account of all the six categories of HABs along with description of the causative agents and their associated clinical symptoms. The recent tools and techniques developed towards operational status for prediction or detection of HABs have described. Finally, climate change impact on the occurrence of algal blooms in a global scale has also been illustrated.