PALM BEACH POST (Florida) 29 July 06 Loggerheads lagging - The shrinking number of turtle nests has scientists concerned. (Rachel Simmonsen)
Midway through sea turtle nesting season, several Florida scientists are wondering much the same thing: Where are all the loggerheads?
The number of loggerhead turtle nests on Treasure Coast beaches has dropped from the number reported this time last year, prompting some scientists to predict that 2006 will follow a statewide trend of decline that started about seven years ago.
"We believe it's a real decline that is statistically significant, not just a blip on the radar screen," said Blair Witherington, a research scientist with the Florida Fish and Wildlife Conservation Commission in Melbourne Beach.
In Palm Beach County, there has been a continued decline in loggerhead nests in Boca Raton, said the Gumbo Limbo Nature Center's marine conservationist, Kirt Rusenko. He also said he believes it's part of a larger trend.
But Palm Beach County's environmental program supervisor said county beaches, including those in Jupiter and Ocean Ridge, have shown a slight rise in nests so far this season. And even though the loggerhead season is winding down, there may be one more spike in nesting, based on past seasons, program supervisor Leanne Welch said.
Statewide loggerhead nesting numbers generally grew from 1979 until 1998, when a record 85,054 nests were reported. But loggerhead nesting numbers now appear to be on a downward slope, declining in four of the past seven years. Since 2001, the statewide tally hasn't climbed above 69,657.
Last year, scientists were pleasantly surprised by the number of loggerhead nests on the Treasure Coast, which jumped slightly from the year before despite dramatic changes in beaches caused by hurricanes and beach restoration projects. By early September 2005, scientists had found 292 loggerhead nests at the St. Lucie Inlet Preserve State Park in Martin County; the year before, they had found 244.
Scientists had hoped it meant that loggerhead nesting was on the rebound after a few years of sluggish numbers. But many now think last year was an anomaly in a longer period of declining numbers.
"When you look at the 10-year average for loggerheads, this is the lowest year for us by far," said Ed DeMaye, a biologist who monitors about 12 miles of beaches in St. Lucie County.
As of Thursday, DeMaye reported 1,532 loggerhead nests, a 38 percent drop from last year. Of the past 10 years, 2004 is the second-lowest year on record, but even then, there were 2,278 loggerhead nests, DeMaye said.
On the southern half of South Hutchinson Island, which includes parts of both St. Lucie and Martin counties, scientists had counted 1,909 loggerhead nests by July 20, about 500 fewer than at that time in July 2005, according to Erik Martin, a senior scientist with the environmental firm Ecological Associates. On Boca Raton beaches, only about 400 loggerheads have nested this year, compared with an average of about 1,000 in previous years, Rusenko said.
Treasure Coast counters say it's unlikely this year's loggerhead numbers will improve much. Though nesting for all Florida species of sea turtles continues through September, loggerhead nesting typically tapers off after July.
"I haven't got any idea what is going on," said Pete Quincy, who monitors sea turtle nesting on about 6.5 miles of Jupiter Island beaches. As of Monday, Quincy had reported 2,232 loggerhead nests. By that date last year, there were about 2,400.
"The first couple of years, I would have thought maybe Lake Okeechobee has altered the water," Quincy said of the declining number.
But during this year's nesting season, water managers haven't made discharges from Lake Okeechobee, which often send a polluted, chocolate-colored plume of freshwater into the ocean.
It could be that adult loggerhead turtles have been affected by illness or some other environmental factor that makes them unfit for nesting. In late 2000, for instance, dozens of loggerhead turtles turned up with pneumonia along the coastline stretching between Indian River and Charlotte counties. By the end of the year, scientists there reported 100 loggerhead deaths, about three times more than usual.
Weather also might have played a role. Several years ago, extremely cold water moved near shore, which could have affected loggerhead turtles' food supply. Without enough lobster, clams and crabs in their diets, female turtles might not fatten up enough to produce eggs, Martin said.
Another possibility is that the decline in loggerhead nesting numbers is simply part of a longer-term natural cycle that scientists don't yet understand. Statewide data has been compiled only for about 25 years, Quincy said.
Whatever the cause, scientists say there still are signs to suggest a rebound could be on the horizon.
Scientists at the St. Lucie Nuclear Power Plant have been capturing more juvenile loggerhead turtles in the past three years, which suggests they might see a spike in nesting numbers in five to 10 years, when those turtles come of nesting age, said Rick Herren, a biologist who monitors nesting in Indian River County.
Also, numbers for green and leatherback turtles remain fairly high.
Leatherback nesting numbers dropped slightly this year from where they were at this time last here. But "last year was the third highest year for them," Martin said. "Even though it's low this year, it's still in the realm of high nesting for leatherbacks."
Loggerheads lagging