Concern for the habitat that supports about 80 percent of the world’s redhead ducks has led Ducks Unlimited de México (DUMAC) and the University of Tamaulipas’ (UT) Institute of Applied Ecology to launch a partnership to better understand the status of seagrasses in the Laguna Madre. This research will evaluate whether past declines in seagrass and changes in its species composition has continued. It will also examine the relationships between the seagrass and environmental factors, such as salinity.
The Laguna Madre is a hypersaline lagoon that stretches approximately 220 miles along the southern Texas coast and the state of Tamaulipas in northeast Mexico. Partially walled off from the waters of the Gulf of Mexico by extensive barrier islands, the waters inside the lagoon evaporate and can become much more saline than normal seawater. This creates a unique environment, and the Laguna Madre is one of only five such hypersaline coastal ecosystems in the world.
Past studies have documented troubling changes in the amount and nature of the seagrasses in the Laguna Madre. In 1994, research by DUMAC and UT documented a 63-percent decline in the vegetative biomass since 1975. Other studies on the U.S. side of the border have documented similar declines, as well as changes in species composition. The total area covered by seagrasses of all kinds has declined, with areas of bare bottom increasing. In addition, shoalgrass (Halodule wrightii) beds have significantly declined, and have been only partially replaced by turtle grass (Thalassia testudinum) and manatee grass (Syringodium filiforme), which are less desirable species.
These changes are important to waterfowl conservation and other marine and estuarine fish and wildlife because this relatively small area is the world’s most important wintering habitat for redhead ducks, which use shoalgrass rhizomes (parts of the roots) as their primary food source. Thirty-six percent of North America’ redheads winter in Mexico’s portion of Laguna Madre, as well as many northern pintails and American wigeon.
he new research project was launched in November, and is determining the current extent and species composition of the seagrass beds, shoalgrass biomass and salinity patterns in Tamaulipas’ Laguna Madre. While initial data indicate that shoalgrass has remained the dominant species, two species of seagrasses commonly found in less saline marine ecosystems were recorded for the first time. Researchers also documented lower salinity levels than had been observed in previous studies. Taken together, these preliminary results suggest that decreases in salinity and related declines in wildlife habitat could be associated with the creation of openings in the barrier island to facilitate boat traffic in and out of the Gulf.
“This project is important because it will allow us to better understand the current availability of foraging resources for waterfowl, especially redheads, in the Laguna,” said Eduardo Carrera, National Executive Director and CEO of DUMAC. “The research will also evaluate the spatial distribution of shoalgrass beds and their relationship to freshwater wetlands adjacent to the Laguna Madre. These wetlands are critical for helping the birds eliminate the high salt loads they ingest while feeding on shoalgrass. This information will help us better target our future conservation actions and inform the development of public policies related to the opening of coastal bars for boating access.”
Funding for this research is provided by Ed & Sally Futch Foundation, Universidad de Tamaulipas and DUMAC.
Overall, approximately 20 percent of the North America’s waterfowl winter in Mexico. This includes 85 percent of the continent’s Pacific brant, 36 percent of redheads, 20 percent of northern pintails, 15 percent of northern shovelers and 10 percent of green-winged teal. Eighty percent of blue-winged teal either winter in or pass through Mexico.
Source: Ducks Unlimited