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Karenia brevis: Ecological Effects of Red Tide

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Karenia brevis: Ecological Effects of Florida Red Tide Chelsea Morales BIO 109, Section 03 Instructor Elliot Parsons November 16, 2007 Karenia brevis: Ecological Effects of Florida Red Tide Anticipating the blue waters of the Gulf and hoping to enjoy a nice sunny day, but instead it has been ruined by the reddish-brown color that now appears on select areas close to the shore and there are dead fish floating on the surface. Soon after, the overwhelming feelings of a cough, watery eyes, and a runny nose have now taken the place of serenity. This phenomenon is known as "Florida Red Tide" and is the result of the "massive multiplication", or algal blooms of marine dinoflagellates, microscopic, single-celled protists. Dinoflagellates are usually freshwater and marine, photosynthetic "algae" and are important components of the phytoplankton. Their blooms appear reddish brown, or pinkish orange due to the high levels of carotenoids, the most common pigments of plastids in dinoflagellates (Reece, 555). One particular dinoflagellate, Karenia brevis, occurs almost annually along the coasts of the Gulf of Mexico and Florida waters. ...read more.


Marine life is mainly exposed to brevetoxin producing blooms by eating them, breathing them, or simply coming into contact with them. The blooms of Karenia brevis secretes nine potent polyether brevetoxins (PbTxs) that bind to voltage-gated sodium channels in the neurons that disrupt neurological processes causing the illness "neurotoxic shellfish poisoning" (Wikipedia). This leads to disruptions in muscle functions, respiratory and cardiac distress. These toxins affect the counter current exchange of fish by entering the bloodstream through their gills causing rapid death to fish in high concentrations. This rapid cause of death is thought to be due to the lack of muscle coordination, paralysis, convulsions, and respiratory failure. Fish in lower concentrations develop high toxin buildup in their tissues. Brevetoxins can accumulate in shellfish, especially clams, oysters, and coquinas, which filter feed on the algae, as well as fish and marine mammals, that also become poisoned through filter feeding. If toxin levels in shellfish become high enough they can become potent and lead to "neurotoxic shellfish poisoning" in humans who consume them. ...read more.


Many of the respiratory symptoms can be reduced by common medicines like antihistamines, inhaled steroids, or bronchodilators, but only before exposure. Bronchodilators have been known to help with the reversal of respiratory symptoms after exposure. Studies have shown that people with chronic respiratory problems or asthma have a greater proportion of symptoms than those without chronic respiratory ailments. All these symptoms usually occur after only one hour of exposure to the aerosolized brevetoxins.(JSTOR, 644-649). There is more to be learned about this natural phenomenon and the damaging ecological effects that come with it. Dinoflagellates play an important role in the conversion of solar energy to chemical energy (photosynthesis), a process significant to the production of oxygen and essential to the survival of most marine animals, yet they also have the unique ability to produce neurotoxins. This peculiar, but harmful mechanism is still being understood on how the toxins are produced by blooms and what purpose do they serve in ecology. Through understanding and research, red tide can be controlled to help prevent serious ecological effects that include the pollution of air, massive mortalities of fish, marine mammals, invertebrates, and respiratory health problems in humans. ...read more.

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