Blue Green Algae Bloom Effects

Blue-green algae (Cyanobacteria) blooms are simple, plant-like organisms found worldwide in the standing water of lakes, ponds, lagoons and ditches. Blue-green algae occurs naturally and can quickly multiply into a bloom when the temperature, nutrients, wind patterns and light conditions are favorable. While most blue-green algae species aren't harmful in any way, some species release toxins that can make people and animals very sick if they come into contact with the substance.


Some blue-green algae species, including Lyngbya and Oscillatoria, produce toxins called aplysiatoxins. Direct contact with these blue-green algae toxins, such as while swimming, bathing or wading, can cause individuals to suffer severe skin irritations, particularly hives, rashes and blisters. Inhaling these toxins can also cause extreme irritation of the nose, throat and eyes. Some patients suffer from acute inflammation of the respiratory tract after exposure to blue-green algae blooms.

Microcystin Toxiocis

A few blue-green algae species, including Oscillatoria and Planktothrix, produce the microcystin toxin, which is a hepatotoxin that targets the liver. Signs of microcystin toxiocis include the flu-like symptoms of nausea, vomiting, diarrhea and abdominal pain. This toxin can also cause the liver to bleed and frequently leads to acute liver failure. Initial symptoms begin 30 minutes to 24 hours after exposure, depending on the amount of blue green algae bloom consumed and the size of the person or animal. Other possible microcystin toxiocis symptoms include shock, jaundice, extreme thirst, weak heart rate, rapid pulse and death.

Anatoxin-a Toxicosis

Several species of blue-green algae, including Anabaena circinalis, produce the neurotoxin called anatoxin-a, which affects the nerve synapses and blocks neuron signals. This toxin works very rapidly, sometimes killing the victim just a few minutes following exposure. Animals suffering from anatoxin-a toxicosis frequently start gasping, staggering, twitching and convulsing. Many victims quickly become paralyzed. People often exhibit the same symptoms, plus experience slurred speech and a tingling sensation around the fingertips or mouth.


Some blue-green algae species, including Nodularia spumigena, produce the toxin called nodularin. Blue-green algae blooms producing the nodularin toxin are commonly associated with phosphorus enrichment. Even low-level exposure to this toxin is thought to promote liver cancer and chronic disorders of the gastrointestinal tract.

Environmental Effects

Both non-toxic and toxic blue green algae blooms can damage and disrupt sensitive ecosystems. The algae blooms usually keep sunlight from reaching submerged vegetation, which reduces the amount of oxygen available to other living organisms in the area. Blue green algae blooms can also introduce toxins that pass through entire food chains and accumulate in fish and seafood. Toxic blue green algae blooms often cause the death of large numbers of fish and waterfowl.

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About this Author

Cat Carson has been a writer, editor and researcher for more than 10 years. She has professional experience in a variety of media, including the Internet, newspapers, newsletters and magazines. Her work has appeared on various websites. Carson holds master’s degrees in both writing and cultural anthropology, and is currently working toward her doctorate degree.