Hobbies And Interests
The Cause of Red Tides
Red tides occur in waters around the world, including the areas off both the Atlantic and Pacific coasts of the United States as well as around the Gulf of Mexico. The causes of a red tide are not clearly understood, but the net result is that for a period of time, conditions in the water favor the growth of large quantities of red algae. More than 60 different algae are known to cause red tides, of which only a handful generate dangerous toxins. Marine biologists use the phrase "harmful algal bloom," or "HAB," to differentiate the potentially lethal outbreaks from normal growths.
Detecting Red Tides
Some red tides are obvious to any onlooker, with large areas of ocean suddenly changing color. However, it isn't safe for laypersons to assume that a bloom is over just because the sea lacks a red tinge. Some dangerous algae lack the signature red coloration, so you must check with local authorities to ensure that shellfish are safe to eat. Making this determination is imperative if dead fish and seabirds are present on the beach or floating in the water.
Effect on Shellfish
Consumers can usually still eat finned fish in areas affected by a red tide if the fish are caught before the algae bloom kills them; the toxin kills the fish before they can absorb it into their tissues. Note that consumption is recommended for the fish fillets only and not for the liver or any other organs. Shellfish, however, are filter feeders, which means that they siphon their foods directly from the water; therefore, the algae that cause red tides are their natural prey. The filtration process causes the toxins to accumulate in shellfish tissues to a highly dangerous level.
Paralytic Shellfish Poisoning
Diners who eat shellfish affected by a red tide will find themselves very ill indeed, as soon as 30 minutes after consumption. The algae secrete a substance called "saxitoxin" that attacks the central nervous system. Victims will lose sensation in their lips and extremities, and they may appear drunk to the casual observer. This assumption is not unreasonable, since the person is, in fact, intoxicated under the influence of a toxin. No known antidote exists to saxitoxin, so palliative care is the only treatment possible until the toxin has passed through the victim's body.