FOR IMMEDIATE RELEASE: June 29, 1994 CONTACT: Wendell D. Calhoun 202-482-3048 Mary K. Skoruppa 512-985-6266
Freshwater wetlands are important for the survival of thousands of wildlife species, particularly redhead ducks wintering in coastal southern Texas. A recent study conducted by the National Biological Survey (NBS) illustrates that freshwater wetlands in southern Texas may be vulnerable to contamination caused by heavy redhead use during dry years.
Southern Texas is extremely valuable to redheads because of the abundant seagrasses in the Laguna Madre, a 110-mile long saltwater lagoon. These seagrasses are the main winter food source for the redheads.
The Laguna Madre provides saltwater wintering habitat to about 80 percent of the North American population of redheads. Freshwater wetlands also must be available to support the approximately 300,000-600,000 wintering redheads in southern Texas. Fresh water compensates for the salt redheads ingest while feeding on seagrasses in the Laguna Madre. Fresh water supply is especially important to redheads when rainfall is low and the Laguna Madre becomes extremely saline.
Scientists at the NBS Texas Gulf Coast Field Station, Corpus Christi, Tex., have recently completed a study suggesting that freshwater ponds in southern Texas, during periods of heavy redhead use, acquire high levels of chlorophyll-a, a plant pigment often used to estimate the density of algae in water.
NBS scientists have deduced that the increased chlorophyll levels may result from excessive amounts of redhead fecal material in the water, triggering the growth and rapid reproduction of algae, an important source of energy in a wetland ecosystem. A population explosion of algae (an "algal bloom"), however, can eventually cause oxygen depletion in the water, killing fish and other organisms in the wetlands.
NBS researchers used a Corpus Christi freshwater pond for a two- year water quality study. According to the scientists, the eight- acre pond has experienced overcrowding by more than 10,000 redhead ducks. Additionally, high levels of chlorophyll-a coincide with heavy redhead use.
"Redheads have been known to abandon wetlands when nutrient and algae concentrations reach very high levels," explained Research Biologist Mary Kay Skoruppa. "The possibility of the redheads being forced to abandon this freshwater site could pose a major problem for the ducks if there are no other suitable freshwater wetlands in the area."
NBS researchers are convinced that the scarcity of freshwater wetlands in the southern Texas area may force too many redheads to use the pond and thus lower its water quality.
"The results of this research are still preliminary, but may indicate that more sources of fresh water are needed," said Skoruppa.
The water quality work on freshwater wetlands is only one facet of redhead research at the NBS Texas Gulf Coast Field Station. redhead habitat use, feeding ecology, and nutrition are also elements of the redhead duck research in southern Texas.
Other major research in Corpus Christi includes investigating the ecology of seagrasses and the effects of a mysterious "brown tide" organism on the seagrasses in the Laguna Madre.
NBS scientists are also studying the effects of natural disasters such as hurricanes, and habitat loss from urban and pasture development on the breeding and stopover habitats used by neotropical migratory landbirds along the northern coast of the Gulf of Mexico.
The NBS Southern Science Center (SSC), Lafayette, La., serves as the headquarters for the Texas Gulf Coast Field Station, Coastal restoration Field Station, Baton Rouge, La., and the Mississippi valley Field Station, Vicksburg, Miss.