Reef Brief- All about Pica Pica - by Ann Hayden

The Island Newspaper, Ambergris Caye, Belize            Vol. 10, No. 17            April 27, 2000

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It's that time of year again. If you talk to most tour guides, they'll tell you that they've experienced it and have likely known quite a few people who have also. Every spring, cases of "Pica Pica" run rampant, and this season is no different. With a name meaning "itchy itchy" this annual phenomenon makes its presence known on the skin of divers and snorkelers with a rash similar to chicken pox. While the resulting rash is completely harmless, it is nonetheless uncomfortable and can last up to ten days. With the continued increase of Pica Pica outbreaks over the past few years, scientific research has helped identify the varying origins of this phenomenon and how it can best be recognized and avoided.

    The majority of Pica Pica cases were originally thought to be the result of spherical thimble jellyfish blooms that contain millions of unseen juvenile jellyfish. These creatures have a medusa, which bear nematocysts, poisonous microscopic structures that are activated by physical contact. While some cases of Pica Pica may result from these blooms, current research claims that there is an increase of cases resulting from cyanobacterial toxins in particular, Trichodesmium in the water.

    Dr. Gary Gaston, a Professor of Biology at the University of Mississippi has spent a significant amount of time in Belize, particularly around the South Water Caye area, and has witnessed an increase of Trichodesmium over the years. This type of blue-green algae blooms in a manner similar to that of jellyfish, resulting in a scattering of what is known as "sea sawdust" on the ocean surface. This algae has the ability to produce an array of potent toxins, all of which can have an adverse affect on humans who come into contact with it. Unlike the rash resulting from jellyfish blooms, this type of Pica Pica does not respond to topical home remedies of ammonia or vinegar; unfortunately, it responds to almost nothing at all for seven to ten days.

    Skin rashes are not the only problem that result from Trichodesmium. Around the world, these algae blooms have also been linked to liver and pulmonary damage, as well as gastrointestinal illnesses in humans. Furthermore, because these blooms can occur in both marine and freshwater environments, they can have a potentially adverse affect on drinking water supplies and freshwater fisheries. There have also been worldwide outbreaks that have poisoned farm animals, birds and fish.

    Interestingly, despite the negative effects of Trichodesmium blooms, they may play an important role in slowing down global warming. While it grows, Trichodesmium uses photosynthesis to remove carbon dioxide (a damaging greenhouse gas) from the atmosphere. Likewise, Trichodesmium has the ability to remove nitrogen from the atmosphere and use it for nourishment. Thus, Trichodesmium plays a critical role in keeping these gases in check and quite possibly delaying the progression of global warming.

    Clearly, further research about Trichodesmium algae blooms is needed to learn more about its potentially positive and negative effects. At the very least, we know enough now to possibly avoid contact with the blooms (patches of "sawdust") and prevent this type of Pica Pica from occurring.

    If you have a topic you would like featured in Reef Brief, you can write us at greenreef@btl.net or visit our web-site at www.ambergriscaye.com/greenreef.



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