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U.S. Department of the Interior
U.S. Geological Survey
National Wetlands Research Center
700 Cajundome Blvd.
Lafayette, LA 70506

Contact: Gabrielle Boudreaux Bodin
Phone: 337-266-8655
Fax: 337-266-8541
For Release: August 27, 1999



USGS Assesses Hurricane Bret's Effects on Wildlife and Ecosystems

The animals, plants and ecosystems of South Texas seem to have been as lucky as the human population in weathering the effects of Hurricane Bret, said several USGS biologists after conducting preliminary assessments of the biological impacts of the hurricane.

Kemp's Ridley Sea Turtles

A relieved Donna Shaver, turtle ecologist and station leader for the USGS Padre Island Field Station, said that two tagged adult female Kemp's ridley sea turtles rode out the stormy seas not far from the Padre Island National Seashore and made it through "just fine."

The timing of the hurricane worked in favor of Padre Island's nesting sea turtle population, said Shaver, but just barely for some hatchlings -- the last loggerhead hatchlings were released one week before the hurricane hit and the last Kemp's one month ago.

"Since we released the little turtles at the northern end of the park, where the hurricane had the least amount of impact, the hatchlings should have had enough time to drift far enough northward on the ocean currents before the hurricane hit to avoid much, if any, harm. We were extremely fortunate," Shaver said. "If there had been any nests left on the beach, they would not have survived the storm surge at the southern end of the beach."

The two satellite-tagged turtles that rode out the hurricane in the waters offshore of Padre Island have even provided valuable data for Shaver. "Scientists still don't know for sure how turtles 'handle' hurricanes, although we do know that they have survived them for millions of years." Both turtles, said Shaver, headed into deeper water farther offshore.

Kemp's ridleys are the world's most endangered sea turtles -- with the total adult population numbering about 5,000. The number of Kemp's ridleys nests found on Padre Islands has been increasing over the last few years, an encouraging sign to Shaver, who hopes to build the island into a second, secure nesting beach for this sea turtle. At present, the primary nesting beach for the species is Rancho Nuevo, off the Gulf Coast of Mexico. This year, said Shaver, 16 Kemp's ridley nests and two loggerhead nests were found on the Texas coast, most at Padre Island National Seashore.

Shaver said that although two turtle camps were blown away in the hurricane, the primary USGS station facilities -- the turtle incubation facility and the offices -- were fine. "Overall, we were very lucky. Even though Bret removed significant amounts of sand from the nesting beaches at the southern end of the island, the dunes will have several months to recover and rebuild before the turtles come ashore again to nest beginning in March."

Seagrasses and Laguna Madre

After aerial surveys of the southern Texas and northeastern Mexico coasts Tuesday and Wednesday, USGS biologists Dr. Chris Onuf and Dr. Tommy Michot, as well as U.S. Fish and Wildlife Service biologist Fred Roetker, reported that the storm apparently inflicted little long-term damage to the Laguna Madre of Texas or the Laguna Madre de Tamaulipas in Mexico. The Texas Laguna Madre is a bay extending 100 miles from Corpus Christi Bay to the Mexican border; it separates Padre Island from the mainland. A similar bay exists in Mexico south of the Rio Grande delta.

The biologists had been concerned about possible damage or burial of already-declining seagrass beds in the Laguna Madre, particularly of shoalgrass, the most common seagrass, which is the food that more than 75 percent of the world's population of redhead ducks exclusively depend upon when they migrate to the area each winter.

Salinity changes due to the Gulf Intracoastal Waterway, agricultural drainage and reduced water clarity due to dredging had already caused a 30 percent decline in Laguna Madre seagrass beds between the mid-1960s and 1988, said Onuf, a USGS biologist stationed in Corpus Christi whose research focuses on the ecology of the Laguna Madre ecosystem. In addition, said Onuf, since 1990 the Laguna has experienced algal blooms that shade seagrasses and reduce their numbers further.

"Historically," said Onuf, "seagrasses were so prevalent in the Laguna that they defined the physical environment, as well as providing a critical nursery function for the region's rich fisheries."

Although the hurricane created numerous washovers from the Gulf into the Laguna Madre, with water still flowing in some washovers, it does not appear that sand or sediment from Padre Island has entered into the permanently flooded part of the lagoon, Onuf said.

Michot, a USGS biologist and pilot stationed at the USGS National Wetlands Research Center in Lafayette, La., has studied redheads and seagrasses along the Gulf Coast for the last 15 years. He said that the impacts of Bret on those resources in Texas and Mexico are minimal compared with the severe and long-term effects of last year's Hurricane Georges on the same resources in the Chandeleur Islands off the Louisiana coast. This is primarily because Hurricane Bret made landfall in an area of higher elevation that does not support seagrasses, Michot said.

In Mexico, noted Michot, a significant amount of sediment was pushed from the beach into the vegetated land behind the beach, but little to no sediment was carried into the seagrass beds. "Apparently," said Onuf, "seagrasses were lucky for the same reason as the human inhabitants: the storm hit the coast not only where the human population was sparsest but also where there is the least seagrass cover in all of Laguna Madre."

In general, said Michot, species and ecosystems of the Gulf Coast are adapted to hurricanes and have taken advantage of the changing quilt of landscapes left behind by them for millennia. "However," he added, "the combination of increasing human pressures and the natural cycle of hurricane disturbance can magnify negative effects on biological resources."

USGS researchers will continue to assess the effects of Hurricane Bret on the region's plants, animals and ecosystems, as well as on the physical environment.

As the nation's largest water, earth and biological science and civilian mapping agency, the USGS works in cooperation with more than 2000 organizations across the country to provide reliable, impartial, scientific information to resource managers, planners, and other customers. This information is gathered in every state by USGS scientists to minimize the loss of life and property from natural disasters, contribute to the sound conservation, economic and physical development of the nation's natural resources, and enhance the quality of life by monitoring water, biological, energy and mineral resources.

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