Cyanobacteria can be found in almost every terrestrial and aquatic habitat—oceans, fresh water, damp soil, temporarily moistened rocks in deserts, bare rock and soil, and even Antarctic rocks. They can occur as planktonic cells or form phototrophic biofilms.
Aquatic cyanobacteria are known for their extensive and highly visible blooms that can form in both freshwater and marine environments. The blooms can have the appearance of blue-green paint or scum. They grow rapidly in favorable conditions, such as calm nutrient-rich fresh or marine waters in warm climates or during the late summer months in cooler parts of the world. Blooms of cyanobacteria tend to occur repeatedly in the same water, posing a risk of repeated exposure to some human populations.
Cyanobacterial toxins in lakes, ponds and dugouts in various parts of the world have long been known to cause poisoning in animals and humans. They may cause massive fish kills, contaminate seafood, and alter ecosystems. Although HABs occurred long before human activities began to transform coastal ecosystems, the impact of HABs has increased dramatically over the last few decades affecting water bodies all over the world . The harmful effects of HABs extend well beyond direct economic losses and impacts on human health. When HABs contaminate or destroy coastal resources, the livelihoods of local residents are threatened and the sustenance of human populations is compromised.