The culprit is microscopic in size, but its effects are monstrous. Deadly algal blooms- known as "red tide" for the reddish pigments contained in these single-celled organisms at the base of the ocean's food web-have caused the deaths of some 200 sea turtles.

The event occurred in November 2005 off the southern coast of El Salvador. Soon after the first appearance of the red-tinged water, some of the region's people fell ill. The government responded by closing shellfish beds in the area, warning against eating seafood from affected areas. The first reports of dead and dying sea turtles washing up on shore occurred in the second week of December. Most of the victims were olive ridley turtles, and a few green and hawksbill turtles were among those stranded.

Working quickly, the Salvadoran government and the US Agency for International Development (USAID) called for assistance. WCS veterinary pathologist Dr. Julie White traveled to the site of the crisis in January, where she performed post-mortem examinations on one of the turtles. While there, she also trained Salvadorian colleagues in tissue collection techniques. Samples were then sent to Florida's Fish and Wildlife Research Institute, operated by the National Marine Fisheries Service and the University of Florida. There, scientists diagnosed the problem: high densities of saxitoxin, which is produced by species of algae and sea plankton. The toxin affects the nervous systems of humans and animals alike.

"The rapid response and subsequent diagnosis in this outbreak demonstrates the power of collaboration among governments and non-governmental organizations," said White. "We are still testing samples from other turtles that died during this period, but we can say with some certainty that red tides first reported in November resulted in widespread sea turtle mortality."

Red tide events have become increasingly common around the world, degrading the marine ecosystem and causing massive economic losses. While algal blooms are natural occurrences, human wastes such as run-off containing fertilizers and sewage from urban areas may trigger the multiplying of these harmful plant cells.

No further sea turtle deaths have been reported from El Salvador since this red tide episode. A similar die-off was reported in Panama in early February. In El Salvador, the levels of toxins in shellfish have decreased but are still high enough to warrant a continued ban on harvesting shellfish.



Posted by: Kelly    Source