Some algae in oceans, bays and other salt water produce toxins that can make people and animals sick. People are exposed by eating seafood, going in the water, or breathing sea spray. Symptoms range from mild to life-threatening, depending on the kind and amount of toxin — and the serious ones usually come from eating seafood; swimming or breathing spray tends to cause milder symptoms.
If you think an algal bloom has made you sick, contact a health care provider or Poison Control at 1-800-222-1222 (poisonhelp.org).
Gulf of Mexico red tide
Red tides in the Gulf of Mexico are among the best-known harmful algal blooms in the United States. The alga Karenia brevis makes a toxin called brevetoxin.
| Exposure | Symptoms |
|---|---|
| Breathing sea spray or getting the water on your skin | coughing or sneezing, shortness of breath, sore throat, eye irritation, rash, asthma attacks |
| Eating shellfish — mussels, oysters, scallops — with brevetoxin: neurotoxic shellfish poisoning | nausea, vomiting, diarrhea, stomach pain, numb lips, tongue and throat, dizziness |
Other seafood poisonings
| Illness | Toxin | Seafood | Symptoms |
|---|---|---|---|
| Azaspiracid shellfish poisoning | azaspiracid | shellfish such as scallops, mussels | nausea, vomiting, diarrhea, stomach pain |
| Ciguatera poisoning | ciguatoxin, maitotoxin, scaritoxin | reef fish — barracuda, grouper, red snapper, amberjack | short-term: nausea, vomiting, diarrhea, stomach pain. Long-term: abnormal hot and cold sensations, pain, weakness, low blood pressure |
| Diarrhetic shellfish poisoning | okadaic acid | scallops, mussels, clams, oysters | nausea, vomiting, diarrhea, stomach pain, chills, headache, fever |
| Domoic acid / amnesic shellfish poisoning | domoic acid | scallops, mussels, clams, oysters; some fish | short-term: vomiting or diarrhea, shortness of breath, irregular heartbeat, abnormal hot and cold sensations, memory loss, disorientation, seizures or possibly coma. Long-term: possibly lasting amnesia |
| Paralytic shellfish poisoning | saxitoxin | fish and shellfish — scallops, mussels, clams, oysters, cockles, crabs | nausea and vomiting, diarrhea, shortness of breath, irregular heartbeat, numb mouth and lips, weakness, muscle paralysis |
CDC's chart of diseases from seafood contaminated with algal toxins sets out each alga, toxin, likely foods and symptoms; the Yellow Book covers marine toxin food poisoning for travelers.
Seafood you catch yourself
Seafood sold in U.S. stores and restaurants must meet federal safety standards — but those standards do not cover fish and shellfish you collect yourself. Check and follow local shellfish and fishing advisories first. More: preventing illness from harmful algal blooms.
Animals
Animals are poisoned by swimming in or swallowing bloom water, or by eating algae, fish or shellfish carrying toxins — which build up as bigger fish eat smaller ones. They can become seriously ill or die within hours to days, and blooms can cause mass die-offs.
| Animal | What happens |
|---|---|
| Dolphins | poisoned by Gulf red tides; large numbers sometimes strand on beaches |
| Manatees | brevetoxin can damage their lungs, sometimes fatally |
| California sea lions | domoic acid damages the nervous system, causing seizures or strange behavior |
| Birds — pelicans, cormorants | sickened or killed by eating contaminated algae, fish or shellfish; sometimes thousands die |
| Fish, shellfish and other sea life | Karenia brevis red tides can kill them in large numbers |
Wildlife deaths can hurt communities, businesses and ecosystems.
Sources
Based on "Symptoms Caused by Saltwater Harmful Algal Blooms," Centers for Disease Control and Prevention; a work of the United States government in the public domain. The original page's photographs are left out.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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