US: Red tide kills turtles in record numbers

It's been a bad year for sea life, and particularly endangered species, along the Southwest Florida coast.

Red tide is killing sea turtles in record numbers. This month alone, 46 stranded sea turtles have been discovered in Sarasota waters. Six dead dolphins have also washed up in that time. Earlier this year nearly four dozen Manatees died.

Mote Marine Laboratory has already logged more sick or dead turtles than it did during all of last year, bringing in 113 so far, up from 83 in 2004.

Earlier this month, researchers found low oxygen levels, poor visibility and dead and dying sea creatures in the dead zone off the coast of Port Richey south to Sarasota.

Scientists can't pin down exactly where the turtles are dying and won't link them to the 2,200 square-mile dead zone in the Gulf of Mexico.

"Nothing definite, other than all of the turtle deaths are occurring in the same general area as the dead zone," said Mote's chief veterinarian Charles Manire.

A record number of dead turtles have been found in Pinellas, Hillsborough, Manatee and Sarasota counties. Manire said there has been an increase in dolphin deaths, too, but at less startling rates.

The Florida Fish and Wildlife Research Institute is reporting a dramatic increase in turtle deaths between June 26 and August 15. This year 106 turtle strandings have been reported. The 10-year average for that same period is 17.

Red tide poisoning affects turtles' brains. Symptoms include muscle twitching and an inability to control their neck functions, Manire said. It takes four to five days for them to recover from "rubber neck," he said. Scientists don't know how long it takes for red tide to make animals sick.

If an affected turtle is brought to Mote and survives red tide poisoning, Manire said, it takes between one and two weeks to get the toxin out of its system. Mote is currently treating two loggerhead and two Kemp's Ridley -- the most endangered turtle species -- at its hospital.

Even though scientists aren't sure how the turtles are poisoned, Manire believes they get sick from breathing the toxin and eating infected crabs, shrimp and small fish. When turtles surface they inhale the toxin that hovers just above the surface.

Red tide, a single cell organism in the algal bloom, Karenia brevis, has been present in waters off the coast of Southwest Florida from Pinellas County to Charlotte Harbor in varying strengths all year.

The organism exists in the Gulf in small quantities all the time. But, when the alga blooms, the neurotoxin it produces known as Brevetoxin increases. The toxin kills fish and other sea life, including manatees and stingrays.

Manatee deaths -- there were 47 here earlier this year -- usually occur with winter blooms, said Cindy Heil, senior research scientist and leader of the Red Tide group for the Fish and Wildlife Research Institute.

Researchers believe the deaths occur as manatees migrate from warm water habitats into colder waters and feed on sea grasses, which are coated with toxin residues. The manatees' immune systems are compromised from poor feeding and stress from the cold. The animals die after eating affected grasses and inhaling the toxin.

Scientists at Mote have begun a study on the effects of red tide on turtles. The Sea Turtle license plate provided $20,000 for the research.

This bloom is not the longest on record affecting Sarasota. There have been two larger, longer-lasting blooms, one in 1985 and another in 1995.

Source: www.heraldtribune.com