http://www.floridatoday.com/article/20100624/NEWS01/6240309/Gulf-oil-leak-threatens-baby-turtles-food
While researchers scoop up endangered sea turtles coated in oil in the Gulf, a scientist warns that this summer’s fragile turtle hatchings could choke on tiny tar balls as they feed off the Space Coast.
Blair Witherington of the Florida Fish and Wildlife Commission in Melbourne returned recently from working with a federal and multistate team to rescue turtles. They captured 64, mostly a species called Kemp’s Ridley, which is among the rarest in Florida.
Back on the Atlantic side, the worry is more about loggerheads that nest here in some of the highest numbers in the world.
As the eggs hatch in the coming weeks, the baby turtles must head immediately to sea, where they swim as many as 25 miles to feed on Sargassum seaweed along the Gulf Stream. If oil and tar foul that algae off Brevard’s coast, turtles could mistake the toxic bits for their favorite food.
Or petroleum could poison and kill that food before the hatchlings reach it.
“I don’t know what goes through their little heads, but they do eat tar,” said Witherington, whose ongoing research had identified tar as a threat to the turtle population before the spill. “They tend to eat anything that floats by that looks interesting to them.”
He said he has found plastic and tar in the guts of about 90 percent of the baby turtles he has captured during research trips in the Gulf Stream. Either their mouths were sealed shut with tar, or their guts are lined with plastic.
Prime time for sea-turtle nesting in Brevard began May 1 and continues until Oct. 31. Female turtles lay as many as 125 eggs per nest in four to seven nests per season.
But experts estimate only one in 1,000 hatchlings survives to adulthood, with their food sources expanding beyond the Sargassum. Fewer live the 30 years needed before they are ready for reproduction.
Sargassum seaweed floats in “convergence zones” in the Gulf of Mexico and the Gulf Stream.
Many of the animals that live among the weed have origins along the bottom, but have evolved into species specific to the Sargassum habitat.
“It’s the basis and structure of an entire community,” Witherington said.
Fish, crabs, sea slugs and shrimp-like creatures float with and live off it. Pools of fish gather beneath.
Like a similar large gyre in the Pacific Ocean, the Sargassum Sea in the Atlantic, near Bermuda, also accumulates plastics.
“Some of the tar that we find is actually coating plastics that the turtles are eating,” Witherington said.
Baby turtles accidentally swallow plastics from milk bottles, bleach bottles and clear plastic bags while seeking a meal among Gulf Stream Sargassum lines.
Those impacts are ongoing, but no one knows how the spill will affect sea turtle populations long-term.
“We’re seeing probably more oiled sea turtles than anyone’s ever seen,” Witherington said.
Oil Damage
On Witherington’s trip to the Gulf, researchers cleaned up most of the rescued turtles and took them to rehabilitation centers, although some were found dead.
Another rescue mission headed out Tuesday. They’re a joint effort between the National Oceanic and Atmospheric Administration and state wildlife agencies from Florida, Louisiana and Georgia.
According to statistics this week from NOAA, 504 sea turtles had been verified within the designated spill area since surveying began April 30. Of those, 387 turtles, or 77 percent, died.
A total of 90 stranded or captured turtles were found with visible oil on them.
Only four rescued turtles have been released so far and 106 are in rehabilitation centers, NOAA said, including 73 heavily-oiled sea turtles captured as part of the on-water survey and rescue operations.
Direct exposure studies are limited, but past research shows oil can be deadly to sea turtles. Breathing the fumes can lead to kidney and liver damage, brain dysfunction, immune suppression, anemia, reproductive failure or death. Swallowing it can be worse.
And only four days of oil exposure can cause their skin to fall off in sheets.
Aftermath
Other studies, however, have shown that oil spilled even a few weeks before nesting season has little effect on egg development and hatchling fitness.
“All of these effects are speculative,” Witherington said, adding that scientists haven’t had much experience studying turtle impacts from large-scale oil spills.
Little research was done on turtle impacts after the Mexican government’s oil rig, Ixtoc 1, blew out in 1979, spewing an estimated 140 million gallons into the Gulf.
In U.S. waters, the most prevalent spills historically have involved refined fuel oils from barges or freighters and usually were the result of ships grounding.
The most recent and closest oil spill here came in August 2000. Tar balls and oil mats washed up on beaches near Fort Lauderdale, fouling about 20 miles of shoreline.
Most of the 20,000 gallons of fuel oil was removed within a few days, but wildlife casualties included an estimated 7,800 sea turtle hatchlings and untold fish and birds.
The cleanup cost $2.2 million, tapped from a federal cleanup trust fund.
Contact Waymer at 242-3663 or jwaymer@floridatoday.com.
Special thanks to Richard Charter