Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to page options Skip directly to site content

Marine Environments

Marine or saltwater harmful algal bloom (HAB) toxins can cause a variety of illnesses in humans and animals. Exposure to marine HAB toxins can occur through direct contact by swimming, breathing in aerosolized toxins (toxins in water turned into tiny airborne droplets or mist), or eating toxin-contaminated shellfish or finfish 1. Human illnesses are commonly caused by eating toxin-contaminated seafood, including shellfish and finfish 2. In marine mammals, fish, and other aquatic marine life, exposure to HAB toxins can cause widespread illness or death. Birds can also get sick by eating algae, drinking contaminated water, or eating contaminated marine fish or shellfish 3. For example, pelicans and cormorants have been poisoned by these toxins, and, in some cases, thousands of birds have died 4.

Two major groups of marine phytoplankton, diatoms and dinoflagellates, produce HAB toxins. Marine HABs have occurred in the Gulf of Mexico, the Atlantic coast, and the Pacific coast in the United States. Two major groups of marine phytoplankton, diatoms and dinoflagellates, produce HAB toxins. Some common marine HAB toxins include brevetoxins, azaspiracid, ciguatoxins, domoic acid, okadic acid, and dinophysistoxins 5.

Humans and Marine Water-associated Illnesses

Skin Contact and Inhalation

Marine HABs can cause a variety of illnesses in people. Marine HABs produced by dinoflagellates that appear red in color are commonly referred to as red tides. Florida red tides, the most well-known marine HABs in the United States, occur every year in the Gulf of Mexico. Florida red tides are caused by the dinoflagellate Karenia brevis which can produce toxins called brevetoxins. People can be exposed to brevetoxins through skin contact or inhalation. Exposure to brevetoxins in humans can cause various symptoms, including the following 1-4:

  • Respiratory irritation (coughing, sneezing)
  • Shortness of breath
  • Throat irritation
  • Eye irritation
  • Skin irritation
References
  1. Kirkpatrick B, Fleming LE, Squicciarini D, Backer LC, Clark R, Abraham W, Benson J, Cheng YS, Johnson D, Pierce R. Literature review of Florida red tide: implications for human health effects. Harmful Algae. 2004;3(2):99-115.
  2. Backer LC, Kirkpatrick B, Fleming LE, Cheng YS, Pierce R, Bean JA, Clark R, Johnson D, Wanner A, Tamer R. Occupational exposure to aerosolized brevetoxins during Florida red tide events: effects on a healthy worker population. Environ Health Perspect. 2005;113(5):644-9.
  3. Fleming LE, Kirkpatrick B, Backer LC, Bean JA, Wanner A, Dalpra D, Tamer R, Zaias J, Cheng YS, Pierce R. Initial evaluation of the effects of aerosolized Florida red tide toxins (brevetoxins) in persons with asthma. Environ Health Perspect. 2005;113(5):650-7.
  4. Kirkpatrick B, Fleming LE, Backer LC, Bean JA, Tamer R, Kirkpatrick G, Kane T, Wanner A, Dalpra D, Reich A. Environmental exposures to Florida red tides: Effects on emergency room respiratory diagnoses admissions. Harmful algae. 2006;5(5):526-33.

 

Ingestion: Eating Contaminated Seafood and Marine Toxin Poisoning

Marine HAB toxins can build up in seafood when fish or shellfish eat toxin-producing algae. Humans and animals that eat these contaminated fish or shellfish can become poisoned from HAB toxins, making them sick. Most human illnesses from HABs occur when people eat contaminated seafood 2,6. Symptoms of HAB toxin poisoning can vary depending on the type of HAB toxin. Marine toxins and toxin poisoning information is listed below.

Note: For information regarding seafood advisories, please visit the Environmental Protection Agency's (EPA) Choose Fish and Shellfish Wisely web pages.

Ciguatera Fish Poisoning (CFP)

The most commonly reported illness caused by a HAB toxin in food is ciguatera fish poisoning (CFP) 1. CFP is caused by eating fish with ciguatera toxins or ciguatoxins produced by a dinoflagellate species, Gambierdiscus toxicus. The dinoflagellates are eaten by plant-eating fish that are then eaten by fish-eating fish. As the toxins move through the food chain, they change and become poisonous. The toxins can build up in in both fish- and plant-eating reef fish in tropical and subtropical waters, such as those found around Hawaii, Puerto Rico, South Florida, and the Gulf of Mexico 2,3. When these fish are eaten, the ciguatoxins can cause stomach and intestinal symptoms, including the following 2,4:

  • Diarrhea
  • Abdominal pain
  • Nausea
  • Vomiting

These symptoms often start within 12–24 hours of eating the contaminated fish and might last for up to 4 days 2. Stomach and intestinal symptoms might be followed by symptoms related to the heart, blood vessels, and nerves, including 5:

  • Numbness and tingling in the extremities
  • Dizziness
  • Muscle aches
  • Decreased heart rate
  • Low blood pressure
  • Weakness
  • Heightened response to hot or cold temperatures

Symptoms have been reported to last anywhere from a few weeks to years 2,6. However, newer information suggests that symptoms from CFP typically go away within months and may be confused with symptoms of other chronic conditions 1.

References
  1. Friedman MA, Fleming LE, Fernandez M, Bienfang P, Schrank K, Dickey R, Bottein M-Y, Backer L, Ayyar R, Weisman R, Watkins S, Granade R, Reich A. Ciguatera fish poisoning: Treatment, prevention and management. Mar Drugs. 2008;6(3):456-79.
  2. EPA. Health and ecological effects. 2014.
  3. Woods Hole Oceanographic Institute. Distribution of HABs in the U.S. 2012.
  4. Goodman DM, Rogers J, Livingston EH. Ciguatera fish poisoning. JAMA. 2013;309(24):2608-08.
  5. Stewart I, Seawright AA, Shaw GR. Cyanobacterial poisoning in livestock, wild mammals and birds–an overview. Adv Exp Med Biol. 2008;619:613-37.
  6. Cetinkaya F, Mus TE. Shellfish poisoning and toxins. [PDF - 5 pages] J Biol Environ Sci. 2012;6:115-19.

Neurotoxic Shellfish Poisoning (NSP)

Neurotoxic Shellfish Poisoning (NSP) is caused by eating shellfish contaminated with brevetoxins, a toxin produced by a dinoflagellate species Karenia brevis. These toxins can be spread throughout the marine food chain and have been found in shellfish, including oysters, clams, and mussels. This toxin is most commonly found in shellfish from the Gulf of Mexico but has also been found in shellfish from the in Mid-Atlantic waters 1,2.

Symptoms of NSP are often related to the stomach, intestines, and nervous system. Symptoms begin 1–3 hours after eating the contaminated shellfish and can include the following 3:

  • Numbness
  • Tingling in the mouth, arms and legs
  • Loss of coordination
  • Vomiting
  • Diarrhea
  • Heightened response to hot or cold temperatures

Symptoms usually resolve in 2–3 days 2. There have been no reports of long-term effects from NSP, but there have been no follow-up studies of patients to confirm this.

References
  1. Woods Hole Oceanographic Institute. Distribution of HABs in the U.S. 2012.
  2. Cetinkaya F, Mus TE. Shellfish poisoning and toxins.[PDF - 5 pages] J Biol Environ Sci. 2012;6:115-19.
  3. Watkins SM, Reich A, Fleming LE, Hammond R. Neurotoxic shellfish poisoning. Mar Drugs. 2008;6(3):431-55.

Paralytic Shellfish Poisoning (PSP)

Paralytic Shellfish Poisoning (PSP) is caused by eating shellfish contaminated with saxitoxins, a toxin produced by dinoflagellates of the genus Alexandrium 1. Saxitoxins, also known as PSP toxins, cause symptoms related to the nervous system. PSP toxins can be found in shellfish (such as mussels, cockles, clams, scallops, oysters, crabs, and lobsters) that usually live in the colder coastal waters near the Pacific states and New England 2. A species of puffer fish found off the east coast of Florida was recently discovered that also contained saxitoxins 3,4.

Symptoms usually begin within 2 hours of eating contaminated shellfish, but can start anywhere from 15 minutes–10 hours after the meal. Symptoms are generally mild and can include the following 1:

  • Numbness or tingling of the face, arms, and legs
  • Headache
  • Dizziness
  • Nausea
  • Loss of coordination
  • A floating sensation
  • Muscle paralysis and respiratory failure can occur in severe cases

In cases of severe poisoning, muscle paralysis and respiratory failure can lead to death in 2–25 hours 1. The risk of death from PSP is reduced if healthcare professionals are able to rapidly provide ventilation if the ill person becomes paralyzed.

There are no reports of long-term effects, but there have not been any long-term follow-up studies of those affected.

References
  1. Cetinkaya F, Mus TE. Shellfish poisoning and toxins. [PDF - 5 pages] J Biol Environ Sci. 2012;6:115-19.
  2. Woods Hole Oceanographic Institute. Distribution of HABs in the U.S. 2012.
  3. Woods Hole Oceanographic Institute. Presence of PSP toxins in seafood in the U.S. 2012.
  4. Van Dolah FM, Doucette GJ, Gulland FM, Rowles TL, Bossart GD. 10 Impacts of algal toxins on marine mammals. In eds. Toxicology of Marine Mammals. 2003:247.

Domoic Acid Poisoning and Amnesiac Shellfish Poisoning (ASP)

Domoic acid poisoning is caused by eating shellfish contaminated with domoic acid, a toxin produced by the diatoms Psuedo-nitzschia, Nitzschia, and Amphora 1,2. These diatoms have been found in the United States along the Pacific coast, northeast coast, and the western coast of Florida 3,4.
Domoic acid poisoning has caused a variety of symptoms ranging from memory loss to death. The first reported human domoic acid poisoning event occurred in Canada in 1987 when 143 people became ill and 3 died from eating domoic acid-contaminated mussels 2,5. Reported signs of the poisoning were stomach and intestinal symptoms, confusion, disorientation, memory loss, coma, and death 2,5. The illness was named Amnesic Shellfish Poisoning (ASP).

Most of what we know about domoic acid poisoning comes from studies of marine mammals, particularly sea lions. Animals, including marine mammals (seals, walruses, and sea lions), have been poisoned by domoic acid, which results in neurologic behaviors and can be fatal 4,6-8.

Shellfish, such as mussels, can accumulate these toxins, making people who eat them sick with various symptoms including the following 1,2,5:

  • Vomiting and diarrhea within 24 hours of eating
  • Dizziness
  • Headache
  • Disorientation
  • Short-term memory loss
  • Seizures, weakness, paralysis, and death can occur in severe cases
References
  1. Cetinkaya F, Mus TE. Shellfish poisoning and toxins. [PDF - 5 pages] J Biol Environ Sci. 2012;6:115-19
  2. Lefebvre KA, Robertson A. Domoic acid and human exposure risks: a review. Toxicon. 2010;56(2):218-30.
  3. Woods Hole Oceanographic Institute. Presence of PSP toxins in seafood in the U.S. 2012.
  4. Todd EC. Domoic acid and amnesic shellfish poisoning-a review. [PDF - 14 pages] J Food Protect. 1993;56(1):69-83.
  5. Perl TM, Bédard L, Kosatsky T, Hockin JC, Todd ECD, Remis RS. An Outbreak of toxic encephalopathy caused by eating mussels contaminated with domoic acid. New Engl J Med. 1990;322(25):1775-80.
  6. Scholin CA, Gulland F, Doucette GJ, Benson S, Busman M, Chavez FP, Cordaro J, DeLong R, De Vogelaere A, Harvey J. Mortality of sea lions along the central California coast linked to a toxic diatom bloom. Nature. 2000;403(6765):80-84.
  7. Work TM, Barr B, Allison MB, Fritz L, Quilliam MA, Wright JLC. Epidemiology of domoic acid poisoning in brown pelicans (Pelecanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus) in California. J Zoo Wildl Med. 1993;24(1):54-62.
  8. Kizer K. Domoic acid poisoning. West J Med. 1994;161(1):59.

Diarrhetic Shellfish Poisoning (DSP)

Diarrhetic Shellfish Poisoning (DSP) is caused by eating shellfish contaminated with okadic acid and dinophysistoxins, toxins produced by the dinoflagellates Dinophysis and Procentrum 1,2. In the United States, these dinoflagellates have recently been found along the Gulf Coast of Texas.

DSP produces stomach and intestinal symptoms that usually begin 30 minutes to a few hours after eating contaminated shellfish and include 1,2:

  • Vomiting
  • Severe diarrhea
  • Nausea
  • Abdominal cramps
  • Chills

Recovery occurs within about 3 days, with or without medical treatment. DSP is generally not life-threatening 1.

References
  1. Cetinkaya F, Mus TE. Shellfish poisoning and toxins. [PDF - 5 pages] J Biol Environ Sci. 2012;6:115-19.
  2. Reguera B, Riobó P, Rodríguez F, Díaz PA, Pizarro G, Paz B, Franco JM, Blanco J. Dinophysis toxins: Causative organisms, distribution and fate in shellfish. Mar Drugs. 2014;12(1):394-461.

Azaspiracid Shellfish Poisoning (AZP)

Azaspiracid Shellfish Poisoning (AZP) is the most recently discovered human illness related to shellfish contaminated with a HAB toxin 1. AZP is believed to be caused by a dinoflagellate that produces toxins that have been found in Ireland, the Netherlands, Belgium, Morocco, and eastern Canada 1-3.

Eating contaminated shellfish can result in symptoms including 1-3:

  • Nausea
  • Vomiting
  • Diarrhea
  • Stomach cramps
References
  1. Furey A, O'Doherty S, O'Callaghan K, Lehane M, James KJ. Azaspiracid poisoning (AZP) toxins in shellfish: Toxicological and health considerations. Toxicon. 2010;56(2):173-90.
  2. Twiner MJ, Rehmann N, Hess P, Doucette GJ. Azaspiracid shellfish poisoning: a review on the chemistry, ecology, and toxicology with an emphasis on human health impacts. Mar Drugs. 2008;6(2):39-72.
  3. James K, Lehane M, Moroney C, Fernandez-Puente P, Satake M, Yasumoto T, Furey A. Azaspiracid shellfish poisoning: unusual toxin dynamics in shellfish and the increased risk of acute human intoxications. Food Add Contam. 2002;19(6):555-61.

What can I do to prevent poisoning by marine HAB toxins?

General Guidelines to Avoid Marine Toxin Poisoning

  • Although any person eating fish or shellfish containing HAB toxins may become ill, persons with weakened immune systems or chronic liver disease could potentially have more severe illnesses.
  • HAB toxins are not destroyed by storage, such as freezing or salting, or by cooking, such as grilling or frying.
  • Check with local health officials before collecting shellfish, and look for advisories about harmful algal blooms or water conditions that may be posted at fishing supply stores, by beach managers, or local health authorities. HAB advisories are posted online by many coastal states.
  • Do not eat finfish or shellfish sold as bait. Bait products do not need to meet the same food safety regulations as seafood for human consumption.

Animals and Marine Water-associated Illnesses

Skin Contact and Ingestion

Contact with marine HABs have been fatal for aquatic animals. During November-December 2007, a widespread die-off of seabirds was caused by a massive red tide produced by the dinoflagellate Akashiwo sanguinea in Monterey Bay, California 1. Affected birds that came into direct contact with the red tide were covered in a slimy material produced by the HAB which coated their feathers, affecting their natural water repellency. The birds’ feathers became soaked with water, and their body temperatures dropped dangerously low 1. There were no confirmed reports of human illness related to this HAB.

Marine HABs have also caused neurologic effects in animals including aquatic animals and birds 1,2. Over 400 sea lions, seals, and birds died or were affected by a HAB produced by the diatom Psuedonitzschia austrailis near Monterey Bay, California. The HAB produced domoic acid, a neurotoxin, which was also detected in mussels, anchovies, and sardines that were likely eaten by the sea lions 3.

References
  1. Jessup DA, Miller MA, Ryan JP, Nevins HM, Kerkering HA, Mekebri A, Crane DB, Johnson TA, Kudela RM. Mass stranding of marine birds caused by a surfactant-producing red tide. PLoS One. 2009;4(2):e4550.
  2. Work TM, Barr B, Allison MB, Fritz L, Quilliam MA, Wright JLC. Epidemiology of domoic acid poisoning in brown pelicans (Pelecanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus) in California. J Zoo Wildl Med. 1993;24(1):54-62.
  3. Scholin CA, Gulland F, Doucette GJ, Benson S, Busman M, Chavez FP, Cordaro J, DeLong R, De Vogelaere A, Harvey J. Mortality of sea lions along the central California coast linked to a toxic diatom bloom. Nature. 2000;403(6765):80-84.

 

References
  1. Fleming L, Backer L, Rowan A. The epidemiology of human illnesses associated with harmful algal blooms. In: Massaro E, ed. Handbook of Neurotoxicology: Humana Press; 2002:363-81
  2. Lipp EK, Rose JB. The role of seafood in foodborne diseases in the United States of America. Rev Sci Tech. 1997;16(2):620-40.
  3. Stewart I, Seawright AA, Shaw GR. Cyanobacterial poisoning in livestock, wild mammals and birds–an overview. Adv Exp Med Biol. 2008;619:613-37.
  4. Work TM, Barr B, Allison MB, Fritz L, Quilliam MA, Wright JLC. Epidemiology of domoic acid poisoning in brown pelicans (Pelecanus occidentalis) and Brandt's cormorants (Phalacrocorax penicillatus) in California. J Zoo Wildl Med. 1993;24(1):54-62.
  5. Van Dolah FM, Doucette GJ, Gulland FM, Rowles TL, Bossart GD. 10 Impacts of algal toxins on marine mammals. In eds. Toxicology of Marine Mammals. 2003:247.
  6. Masó M, Garcés E. Harmful microalgae blooms (HAB); problematic and conditions that induce them. Mar Pollut Bull. 2006;53(10–12):620-30.

Healthy Water Sites

Get Email Updates

To receive email updates about this page, enter your email address:

What's this?Submit
Top