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HABS & human health

Human Health Effects of HABs:

Algae are at the base of the food chain for both marine and freshwater life. Many types of alga are beneficial in a variety of ways, such as food for human consumption, animal feed and fertilizer, and pharmaceuticals. Sunlight, water temperature changes, and nutrient levels are contributing factors for the formation of algal blooms, some of which have adverse effects on fish, animals, and humans.

There are strict standards regulating seafood safety and water quality, and the list below is not intended to alarm, but rather to educate people about the negative human health effects of some toxin-producing HABs.

Amnesic Shellfish Poisoning (ASP):
A type of poisoning caused by domoic acid, which is produced by certain diatoms such as
Pseudo-nitzschia spp. Organisms affected include cormorants, sea lions, mussels, and scallops. If contaminated organisms are consumed, people may experience gastrointestinal and neurological symptoms. Found in North America, specifically the Pacific Northwest and Atlantic Northeast.

Ciguatera Fish Poisoning (CFP):
A type of poisoning caused by eating fish that have fed on certain dinoflagellates which produce ciguatoxin. CFP human health effects include gastrointestinal disturbance in 2-6 hours and neurological symptoms within 18 hours. Usually found in reef fish inhabiting tropical waters of the Pacific and Caribbean, but becoming more problematic as tropical fish are transported to U.S. markets.

Diarrhetic Shellfish Poisoning (DSP):
A type of poisoning caused by eating shellfish contaminated with okadaic acid, which is produced by dinoflagellates such as Dinophysis spp. Affected organisms are mussels, oysters, and scallops. People who eat contaminated shellfish may experience sever gastrointestinal disorders including nausea and abdominal pain. DSP is found worldwide, including provinces of Canada on the eastern seaboard.

Neurotoxic Shellfish Poisoning (NSP):
A type of poisoning caused by eating shellfish that contain brevetoxins derived from the dinoflagellate Karenia brevis. Bottlenose dolphins, oysters, clams, and fish are some of the organisms affected by NSP. Human health symptoms include tingling and numbness, throat irritation, and muscle aches. Typically found in the Gulf of Mexico, but can be carried around the base of Florida and northward by the Gulf Stream.

Paralytic Shellfish Poisoning (PSP):
A type of poisoning caused by eating shellfish that contain saxitoxin, a toxic chemical produced by dinoflagellates Alexandrium spp. Affected organisms include oysters, mussels, marine mammals, birds, and herring. Human consumption of contaminated shellfish results in a rapid onset of symptoms, including tingling and numbness, drowsiness, and, in the case of high doses, respiratory paralysis. The most widespread of all the algal-derived shellfish poisoning, PSP is found worldwide; in North America, PSP cases are in the Pacific Northwest and Atlantic Northeast.

Possible Estuary-Associated Syndrome (PEAS):
A condition associated with exposure to toxins produced by the dinoflagellate Pfiesteria piscicida. Pfiesteria is implicated in some fish kills: fish come into contact with the toxin, become sluggish, develop open sores or lesions, and die. Pfiesteria may also affect shellfish in the same way, however, there have been no reported human illness cases attributed to Pfiesteria from eating shellfish. Research continues on the effects of this dinoflagellate on fish and shellfish. Pfiesteria may affect humans through direct water-to-skin contact or by breathing air above the water in which the toxin is present. Found along the Atlantic Coast from Delaware to the Gulf of Mexico.


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