Pyrodinium bahamense: A Toxic Threat in Tampa Bay

FWRI researchers routinely monitor blooms of Pyrodinium bahamense in the Tampa Bay area.
  Pyrodinium bahamense
   Pyrodinium bahamense
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View an image of a bloom
of Pyrodinium bahamense
in Old Tampa Bay


Harmful algal blooms are a familiar occurrence to coastal dwellers, even if the tongue-twisting names of these microorganisms are hardly household words. Many Sunshine State residents know how Florida red tide affects their beach days and marine life, yet several are unaware of the other harmful algal blooms that occur regularly, especially during the summer months.

For a number of years, Pyrodinium bahamense has bloomed in Tampa Bay, noticeably discoloring the water. Florida strains of this organism were initially thought to be nontoxic, but in 2002, human illnesses associated with eating puffer fish were traced to toxins from a bloom in the Indian River Lagoon. After an extensive bloom in Old Tampa Bay during 2008, FWRI Ecosystem Assessment and Restoration biologists began routine monitoring of summer P. bahamense blooms in the Tampa Bay area.

Researchers with the Harmful Algal Blooms group—with help from Marine Fisheries Research biologists and other partners—sample bay waters from shore and by boat. Sampling is most frequent during the summer months, when annual blooms occur, as well as anytime a bloom takes place outside that period. Project scientists analyze the sampled water to count the microorganisms and measure toxins and dissolved nutrients. They also record environmental data such as salinity, water temperature, and dissolved oxygen. With these data and data collected during laboratory experiments, researchers can examine the relationship between water quality and bloom toxicity.  

Project scientists have confirmed that P. bahamense blooms in Tampa Bay produce toxins, though at lower levels than in the Indian River Lagoon. Experiments suggest that the amounts and types of nutrients in the water can affect toxicity. Understanding how will help researchers better predict when these blooms are most threatening.

Since water quality can vary greatly along Florida’s coastline, the relationship between water quality and bloom toxicity has important water management implications. Other regulatory agencies can use the results of this study when assessing health risks associated with algal blooms. Among those health risks is shellfish poisoning, as certain shellfish species can take up the toxins and cause Paralytic Shellfish Poisoning in those who eat them. As researchers continue to analyze samples and compare data from the Indian River Lagoon and Tampa Bay, they develop a greater understanding of these blooms and their potential to harm marine life and public health.



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