In the summer of 1987, unprecedented numbers of dead and dying bottlenose dolphins were washed up along the coast of New Jersey, in the eastern United States. By early 1988, the total had reached 750, scattered along large stretches of the Atlantic coastline from New Jersey south to Florida. Including the many more that died unseen in the open ocean, it has been estimated that more than half the Atlantic coastal population of bottlenose dolphins died during this period.
Aside from the sheer number of dolphins involved, the condition of those washed ashore was astonishing. Many looked as though they had been dipped in acid.
'It was like nothing in recorded history,' said Brian Gorman, a government spokesman. 'The dolphins were coming in, their skin falling off, sores and lesions all over their bodies...'
At the same time as the dead dolphins first began to appear, millions of dead fish were also washed up, on the beaches of Long Island Sound in New York. Beaches along the US east coast were closed to the public as they were littered with raw sewage, tar balls and used syringes. Newspapers carried stories of bathers becoming sick after swimming in polluted waters. To many, the dying dolphins were a tragic symbol of a decaying coastal ecosystem.
Within two weeks of first being notified of the phenomenon, the US Government's National Oceanic and Atmospheric Administration (NOAA) began organization a major investigation, involving a wide variety of government agencies and scientists, into the cause of this massive and unprecedented die-off.
The team's initial findings suggested that the dolphins had succumbed to a wide variety of secondary infections and disorders. For reasons yet undetermined, the dolphins had been rendered unable to combat naturally occurring pathogens. So began the search for the factor, or factors, responsible for damaging the dolphins' immune system.
NOAA announced its findings 17 months later, on 1 February, 1989; the dolphins, they declared, had been poisoned by eating fish tainted with a naturally-occuring toxin produced by 'red tide' algae.
A 'red tide' is the result of an explosive growth of dinoflagellates (a class of one-celled,plant-like, organisms called phytoplankton) which occurs when certain environmental factors combine. High levels of organic or inorganic nutrients in the presence of adequate sunlight and the right water temperature and salinity levels provide the ideal conditions. Such blooms can cause a discoloration of the surface waters, thus justifying their name.
Among the plankton involved in 'red tides' is a species called Ptychodiscus brevis, which produces a poison known as 'brevetoxin', and it was this toxin, according to NOAA, that killed the dolphins.
The official theory was that part of a red tide bloom that occurred in 1987 in the Gulf of mexico was swept into the Atlantic where it was ingested by fish such as manhaden. These and other fish migrated up the coast where they, in turn, were eaten by the dolphins. Those dolphins that were not fatally poisoned by the brevetoxin were sufficiently weakened to succumb to other infections.
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