Seafood Poisoning Syndromes Caused by Toxic Algae in Florida

A synopsis of human seafood poisoning syndromes associated with toxic algae in Florida's coastal waters.

Most marine phytoplankton are beneficial – they make up the base of the marine food web and produce half of the world’s oxygen; however, some species produce toxins, which can cause human illnesses and, in extreme cases, fatalities. Fish and shellfish that feed on toxic phytoplankton during blooms can become contaminated with toxins, either directly by filter-feeding toxic phytoplankton, or indirectly by eating filter-feeding prey. In turn, humans are exposed to marine algal toxins by eating contaminated seafood. In partnership with the Florida Department of Agriculture and Consumer Services (FDACS), the Florida Fish and Wildlife Conservation Commission (FWC) monitors shellfish harvesting areas to detect toxic phytoplankton and prevent the occurrence of the following syndromes, including poisoning due to the Florida red tide organism Karenia brevis. Since this partnership between FWC and FDACS was initiated during the 1970s, state officials have prevented occurrences of poisoning due to K. brevis from lawfully harvested shellfish.



Associated Toxins

Toxin-Producing Species

Symptoms (list not comprehensive)

Shellfish Poisoning



 Karenia brevis

Karenia brevis


  • Numbness/tingling of mouth and extremities
  • Nausea, vomiting, diarrhea
  • Reversal of hot/cold sensations

Shellfish Poisoning (PSP) and Saxitoxin Pufferfish Poisoning (SPFP)



 Pyrodinium bahamense

Pyrodinium bahamense
(also Alexandrium species, Gymnodinium catenatum)


  • Numbness/tingling of face/arms/legs
  • Nausea, vomiting
  • Respiratory distress

Ciguatera Fish   Poisoning



Gambierdiscus species



  • Nausea, vomiting, diarrhea accompanied by numbness/tingling of the mouth and other extremities
  • Reversal of hot/cold sensations

Shellfish Poisoning


domoic acid

Pseudo-nitzschia species

Pseudo-nitzschia species


  • Short-term memory loss
  • Dizziness, disorientation
  • Respiratory distress

Shellfish Poisoning (DSP)


okadaic acid

Dinophysis species

Dinophysis species
(also Prorocentrum species)

  • Diarrhea, nausea, vomiting
  • Abdominal cramps
  • Chills


NSP and DSP are not known to be lethal to humans; however, PSP, CFP, and ASP can be deadly. Cooking or freezing  shellfish or fish does not remove toxins. These syndromes are associated with different types of seafood, as follows: clams, oysters, mussels, whelk (NSP, DSP), bivalve shellfish and puffer fish (PSP), clams, scallops, oysters, mussels (ASP), and large reef fish species such as barracuda, grouper, snapper, jack, mackerel, and triggerfish (CFP).

To protect public health, the Florida Department of Agriculture and Consumer Services closes oyster, clam and mussel harvesting areas during blooms of toxic phytoplankton. Before harvesting shellfish in Florida waters, check the status of shellfish harvesting areas by visiting the department’s Division of Aquaculture website. For more information or to report health issues related to exposure to marine algal toxins, please call the Florida Poison Information Center at (800) 222-1222. Additional information on the health effects of phytoplankton toxins can be found on the Florida Department of Health website.


FWC Facts:
Groupers are very slow-growing fish, taking anywhere from 4-8 years to reach sexual maturity.

Learn More at AskFWC