Nature strikes back

Human interference with the coastal environment has led to growth of poisonous microbes

Published: Friday 31 October 1997

from killer algae to mind-altering microbes, coastal areas worldwide are facing an assault of some of the strangest micro-organisms known to humankind. While scientists have yet to establish the cause of this phenomenon, it is highly likely that human-induced changes to the coastal environment and pollution have disturbed the natural balance. This has favoured growth of these microbes (International Herald Tribune , September 24, 1997)

The 'seaborne saboteurs' include algae, diatoms, dinoflagellates and other single-celled organisms that form the base of the food chain. Some of these were known, but were not known to produce toxins.

Fish and birds have been most frequently affected. A minute fraction of these microscopic killers were known to produce neurotoxins and other poisons that can harm higher animal forms. These have decimated wildlife populations. Two years ago, for example, over 300 manatees died in Florida after an enormous 'red tide' of toxic dinoflagellates washed the sea shore. Some cases of poisoning of humans have also been reported in the past decade in Canada and the us .

Some scientists are of the opinion that devotion of research in this area in the past two decades has led to the 'discovery' of these species. "Ten years ago, people started realising these things were out there, and so more grant money is being spent to find them," said Stuart Hurlbert, a biologist with San Diego State University, usa .

While this argument is strong -- as increased rates of positive finds in other areas of scientific research has shown -- others are quick to point out that the occurrence of these 'algal blooms' has rapidly increased over the years. Between 1972 and 1995, according to a study, the number of us beaches and estuaries with major recurring attacks by harmful microbes more than doubled, from 16 to 36. "Twenty years ago, these kinds of outbreaks were rare," says Nancy Foster of the us National Oceanic and Atmospheric Administration's national oceans service. Jo Ann Burkholder, an aquatic botanist who first linked the microbe Pfiesteria piscicida with the death of thousands of fish in Maryland and North Carolina in the us , says that the number of harmful species of dinoflagellates known to scientists has nearly trebled in the last 13 years, from 22 to 60.

In the past two decades, scientists say, the natural balance seems to have shifted to allow "hidden flora" to blossom in new and deadly ways. Most of the micro-organisms have cropped up in poorly flushed bays and lagoons with an ever-growing volume of nutrients -- waste from sewage plants and factories, as well as runoff from farms, lawns and cities, which end up polluting waterways.

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