April 30, 2013
USGS Study Finds Green Sea Turtles Are Utilizing Protected Habitat
April Flowers for redOrbit.com - Your Universe Online
According to a new US Geological Survey (USGS) study, nesting green sea turtles are benefiting from marine protected areas by using habitats found within their boundaries. This study is the first to track the federally protected turtles in Dry Tortugas National Park.
In Florida, the green sea turtles are listed as an endangered species, while in the rest of their range they are considered threatened. The habits of these turtles after their forays to nest on beaches in the Southeast US have long remained a mystery. Scientists didn´t know if the turtles made use of existing protected areas until now, and few details were available as to whether these areas were suited to supporting the green sea turtle´s survival.
By tracking nesting turtles with satellite tags, USGS researchers confirmed the turtles´ use of the protected areas. The tags allowed the scientists to analyze the animals´ movement patterns after they left the beaches. The findings of this study were published in the journal Biological Conservation.
"Our goal was to better understand what types of habitats they used at sea and whether they were in fact putting these designated areas to use. This study not only shows managers that these designated protected areas are already being used by turtles, but provides insight into the types of habitats they use most," said Kristen Hart, who works as a research ecologist for the USGS.
Green sea turtle mothers were fitted with satellite tags after they came onto beaches within Dry Tortugas National Park to nest. The team tracked their movements and analyzed their time at sea to locate the areas turtles used between their nesting events. They then determined where turtles traveled after the nesting season was over, finding green sea turtles spend much of their time in protected sites within both Dry Tortugas National Park and the surrounding areas of the Florida Keys Marine National Sanctuary.
"We were thrilled to find that these turtles used some areas already under 'protected' status. The ultimate goal is to help managers understand where these endangered turtles are spending their time both during the breeding period and then when they are at feeding areas. Given that worldwide declines in seagrasses — one of the most important habitats they rely on for food — has already been documented, this type of data is critical for managers," said Hart.
Habitat needs of the turtles during nesting season were assessed using ATRIS, a geo-referenced, underwater camera system developed by the USGS to collect over 195,000 seafloor images. The team photographed the seafloor in a series of parallel lines over 43 miles to survey the areas the turtles frequented within the Dry Tortugas National Park. They developed a habitat map from those photographs, finding most turtles commonly use shallow seagrass beds and degraded coral reefs that are overgrown by a mixed assemblage of other organisms, such such as sea fans, sponges, and fire coral.
Nesting season is concentrated in June and July, although it lasts throughout the summer. Females nest at roughly two week intervals, producing an average of five nests, or “clutches,” with approximately 135 eggs each. The eggs hatch after two months of incubation.
"Our synergistic approach of combining satellite telemetry data with an extensive habitat map proved to be an effective way to find out exactly what habitats these nesting turtles were using in the Park," said Dave Zawada, a USGS research oceanographer.
The Dry Tortugas´ population´s migrations were shorter than those typically seen in other green sea turtle populations around the world, according to the study, which is only the second published study to show green sea turtles taking up residence at feeding grounds located quite near their breeding grounds.
"We hope to keep pushing the frontier of what is known about in-water sea turtle habitat use, as this type of scientific information is vital for understanding whether conservation measures are effective," said Hart.