Microcystins: A brief overview of their toxicity and effects, with special reference to fish, wildlife, and livestock

Cyanobacteria, also known as blue-green algae, are a family of single-celled algae that proliferate in water bodies such as ponds, lakes, reservoirs, and slow-moving streams when the water is warm and nutrients are available. Many cyanobacteria species produce a group of toxins known as microcystins, some of which are toxic. The species most commonly associated with microcystin production is Microcystis aeruginosa. Upon ingestion, toxic microcystins are actively absorbed by fish, birds and mammals. Microcystin primarily affects the liver, causing minor to widespread damage, depending on t

The blue-green algae Microcystis aeruginosa can produce a family of toxins known as microcystins. They can cause liver damage that can lead to death in dogs and livestock. No known deaths have been reported in humans from the ingestion of microcystins. Fish and birds are also at risk for microcystin toxicity. Regardless of species, the mechanism of action is the same – the inhibition of protein phosphatase which causes primarily liver damage, but also affects other organs. Microcystins also act as a tumor promoter.

While microcystins are not as toxic as many natural toxins, they are becoming more and more ubiquitous in California, leading to greater opportunities for exposures. Microcystis blooms occur in quiet, warm waters that are nutrient-rich; the type of conditions that are found in lakes, reservoirs, dammed rivers, and even agricultural drainage ditches throughout the state.

Microcystins have also been detected in the Delta. Steps are being taken to begin to address this problem. In 2008, the Klamath River was added to the Clean Water Act’s 303d list as an impaired waterbody as a result of microcystis blooms. It appears that some dams on this river will be removed along the Klamath, which should reduce the frequency or possibly eliminate toxic blooms. Affirmative steps such as these will help reduce the risk of exposure and adverse effects associated with microcystins.