Field Notes
U.S. Fish & Wildlife Service
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USFWS Helps Restore Seagrasses in Galveston Bay, Texas
Southwest Region, April 21, 2001
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Gliding through thick fog on an early morning in February, a small pontoon boat drifts over the shallow waters of the Galveston Island State Park, along the Texas Gulf Coast. Its passengers ? a handful of biologists representing various state and federal agencies ? are looking for signs of seagrass beneath the water's surface, in spite of the visual challenges posed by the dense fog. To illustrate how dramatically the island has been sinking over the last century, U.S. Fish and Wildlife Service Biologist John Huffman steers the craft alongside a wheel-shaped concrete structure, 16 feet in diameter, entirely submerged beneath the water, and explains: ?This was once a watering tank for cattle that used to graze here.?

Subsidence ? the sinking of land ? and erosion have been steadily eating away at Galveston Island for ages. In recent decades, accelerated erosion and subsidence have been causing significant habitat loss that threatens the entire bay ecosystem. Productive coastal wetlands and marshes continue to slip away to the detriment of fish and wildlife and the seafood-based local economy. Seagrass is one vital element of the ecosystem - a carpet that protects the bay bottom - that has disappeared while noone seemed to notice.

Without healthy seagrass beds, the odds are dangerously stacked in favor of the forces of erosion and subsidence. The fragile underwater vegetation is fundamental in holding the soil together with its root structure, and locking in nutrient-rich sediment with a canopy that inhibits the resuspension of fine particles. The seagrass beds also provide a nursery ground for commercial and recreational shrimp, fish, and crabs; as well as food for microscopic organisms at the base of a complex food web. Green turtles, manatees, and migratory waterfowl such as redhead ducks rely on seagrasses as regular components of their diet. And in affiliation with tidal marshes, seagrasses help remove pollutants and buffer nutrient levels in bay and coastal waters. That's why their restoration is of such concern to the motley crew of partner biologists. ?Submerged aquatic vegetation beds have all but vanished from the Galveston Bay ecosystem,? says Huffman. ?In the 1950s, estimates of their aerial coverage range from 2,500 to 5,000 acres. In contrast, 1993 studies reveal they were down to less than 700 acres.?

Biologists knew something had to be done before it was too late so they began to investigate the possibility of replanting seagrasses. Where to plant the grasses became a key issue facing the project biologists, who took their cue from the appearance of wigeongrass (Ruppia maritima).

?Selecting appropriate sites for replanting is critical for successful seagrass reestablishment,? said Bryan Pridgeon, a U.S. Fish and Wildlife Biologist who helped initiate reestablishment efforts in Galveston in 1995. ?Around 1994 and '95, wigeongrass began to show up in West Bay, a segment of Galveston Bay that historically supported seagrasses. Rather than studying numerous sites in the bay for suitable aquatic growing conditions, Service biologists decided to follow nature's course and plant perrenial seagrasses adjacent to the wigeongrass which is often ephemeral.?

?But we still needed a source of planting material, so I went to the Central Power and Light Plant in Corpus Christi to see if we could use the plants in their cooling pond to replant Galveston Bay,? Pridgeon explained. ?While I was looking at their pond, it dawned on me that the pond was created in an upland site, and all of the seagrass growing in it had been delivered through their cooling water canal. If that material could vegetate an upland site, why couldn't it vegetate a bay??

At the power plant, large amounts of different sea-grass species drift in the water column and constantly collect on screens that protect a massive water intake structure. Normally, the material collects on the screens, which are regularly cleaned by mechanical rakes. The rakes deposit the material, consisting mostly of dead leaf litter, onto a conveyor belt that dumps the stuff into trucks, and the trucks take it to the local landfill. In October 1996, though, the first truckload of material was brought to Galveston, instead of the landfill.

Biologists chose to collect the material in Fall because staff at the power plant indicated there was a higher percentage of rooted material collecting on the screens at that time. Early winter storms and a large population of feeding waterfowl, which often uproot live plants, are considered to be the cause for the fragmented sea-grasses.

To protect and monitor this initial stock of recycled grasses, two enclosures were constructed in the waters of the State Park, near an area where wigeongrass had previously flourished. Initial monitoring after placement of the material yielded minimal results. But monitoring teams discovered several small patches of star grass (Halophila engelmanni) in 1998. As of December 2000, over 40 acres of star grass and shoalgrass (Halodule wrightii) ? two of the species collected in the power plant racks ? were flourishing.

Today, through an agreement with Galveston Bay Foundation, the Service has plans for Summer 2001 to collect more seagrass material from the power plant; and this cooperative recycling routine may eventually prove to be the most inexpensive and simple method to restore Galveston Bay's seagrass beds.

The expansion of these initial seagrass beds has spawned increased efforts throughout West Galveston Bay. With support from the U.S. Fish and Wildlife Service's Texas Coastal Program, the National Marine Fisheries Service is testing several planting techniques including the use of sea-grass racks, peat pot plugs, and mechanical injection methods. Using this last method - in cooperation with the Texas Parks and Wildlife Department - the Coastal Program has planted an additional two acres of sea-grass. The Coastal Program is also evaluating proposals to expand a seagrass nursery which will provide new planting stock, as well as proposed genetic research projects.

Together, along with extensive marsh growth stimulation techniques and erosion prevention strategies, these experiments hold the promise of rebuilding some of the ecosystem's many broken fragments, including the goal of 1,500 acres as set by the Plan of the Galveston Bay National Estuary Program.

Floating from site to site, the biologists document increasing numbers of established seagrass beds as the morning drifts into afternoon. With a collection of aerial photos on hand depicting accelerating rates of recovery, it is obvious the grasses are taking root and spreading. As the fog begins to lift, shafts of sunlight fall upon dark patches of Halophila engelmanni undulating delicately beneath the current.

[Article by Ben Ikenson appeared in Environmental News Network (enn.com); Albuquerque's Weekly Alibi; and People, Land & Water]

Contact Info: Martin Valdez, 505-248-6599, martin_valdez@fws.gov
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