Red Tides Disease

Description of the disease, Red Tides, how and where they form and what their impact is on surrounding areas.

Sometimes in nature strange occurrences take place that can have devastating impacts, and Red Tides are no exception. Red Tides have taken place throughout history in various locations, and according to the Encyclopedia of Marine Resources "the oldest references to the red water or red tide go back to the time of Moses(about 1500 BC)". The term "Red" tides is not necessarily literal, as the water can take on hues of pink, blue, green and black as well as red.

Red Tides usually occur during or soon after periods of heavy rainfall, and appears as an area or "slick" of discolored water. This "slick" continues to increase in thickness until it is has a syrupy consistency. There are generally two types of Red Tides, namely major and minor. A minor incident may only involve a small area and last for a few days, while a major incident can last up to several weeks and involve areas up to hundreds of square miles. There are both toxic and non-toxic Red Tides. Toxic types can result in the extermination of large numbers of marine life, and may have secondary impacts on birds and even man himself. Non-toxic Red Tides are actually considered beneficial to the marine ecosystem. Marine life such as zooplankton and/or shellfish thrive on the nutrient rich waters during a non-toxic Red Tide.

During toxic or non-toxic outbreaks, loss of oxygen is a problem for entrapped fish. Bottom dwellers such as the catfish and porcupine fish usually expire from the indirect effects of these Red Tides. Barnacles and turtles have also been observed as victims of these outbreaks. Birds such as pelicans and gulls have perished as a result of eating toxin filled fish. Even humans have been known to acquire paralytic shellfish poisoning after eating affected shellfish.



Basically what happens is that organisms (dinoflagellates) grow rapidly and concentrated in one localized area, and achieves such a density that the water appears colored. These dinoflagellates are one-celled plants that can contain a neurotoxin which has the ability to kill marine life. This toxin is released from the "body cells" of the dinoflagellates during a toxic Red Tide, poisoning some marine inhabitants. These organisms build up and are called water blooms and depending on the development stage of the bloom, changes the color of the water and itself different shades.

The largest percentage of Red Tides occur in subtropical and tropical areas, but have been known to occur in Northern areas of Iceland and Norway. Florida can be heavily hit with Red Tides and unfortunately for their economy occurs during the tourism season. The dead, poisoned fish that are washed ashore can depict a very unattractive view for the tourist. As well, these contaminated fish can emit gases which irritate mucous membranes and cause sneezing and coughing. There is continuing research into these outbreaks, but for now mechanical removal and burial of these dead fish alleviates the beach issues.

The exact cause and/or conditions required to form a Red Tide is not known. There have been theories offered regarding "precipitation or river run off" as a contributing factor, but nothing conclusive. It has also been suggested that warm temperatures and low salinity may actually encourage the growth of the organisms responsible. According to McClane's New Standard Fishing Encyclopedia, "The mixing of cold currents containing nutrients with warm currents containing dinoflagellates may cause red water". If this proved true it would explain the occurrence of Red Tides in and around upwelling areas, where cold nutrient-rich water is brought to the surface of the ocean to combine with the warm existing surface water.

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