Salt marsh on Texas coast gets an AgriLife Research helping hand

Writer: Kay Ledbetter, 806-677-5608, skledbetter@ag.tamu.edu
Dr. Rusty Feagin, 979-862-2612, feaginr@tamu.edu
Thomas Huff, thomas2013@tamu.edu

COLLEGE STATION – Troubled salt marshes, a crucial component of the Texas coast, recently got a helping hand from Texas A&M AgriLife Research and Texas A&M University.

The work was coordinated by Dr. Rusty Feagin, an AgriLife Research coastal scientist in the Coastal Ecology and Management Lab, part of the department of ecosystem science and management on the Texas A&M campus, and his doctoral student, Thomas Huff.

They have been able to restore tidal flow and fish access to several hundred acres of salt marsh that stretches between Magnolia Beach and Indianola after joining forces with Calhoun County, the Texas General Land Office, the National Oceanic and Atmospheric Administration Restoration Center, Mississippi-Alabama Sea Grant and Rexco Inc.

A large area of the wetlands had been dying and eroding, Feagin explained. Since the earliest images of this region taken in 1958, he estimated more than 500 acres of marsh had been lost in this system.

This is due in part to two different blockages, said Huff, who coordinated much of the on-ground action for the past two and half years. Combined, these two barriers completely blocked flow along several miles of marshes.

“We started by sampling the salinity, tides in the marsh and in the bay, and sampled the biology – the fish, birds, shrimp, etc.,” he said. “We also took an extensive look at the land cover of the marsh to quantify the loss in marsh area.”

This data along with some hydrologic models showed that the blockage at the north end of Magnolia inlet was the primary cause for the loss of marsh area, Huff said.

“The water could go over the top of the blockage at high tides, but then it was trapped by the debris dam. That water would then evaporate, leaving a hypersaline environment that killed fish and marsh vegetation,” he explained.

Huff said the marsh would be stuck in this state until another high tide was able to top the debris dam, which could be weeks, or in some cases a month or more, before significant quantities of water made it into the marsh.

The daily tidal range was less than an inch, he said. Their research also showed portions of the marsh were at least five times more salty than the ocean and were low in dissolved oxygen.

“This had been lethal for plants and fish,” Huff said. “The landowners had lost several hundred acres of land as the marshlands were slowly eroding. Fish and shrimp had been trapped or unable to access the habitat at times. Birds also suffered with fewer fish to eat in the eroding marsh.”

The major blockage was a debris and oyster shell plug at the north end of Magnolia Inlet. The plug blocked off all water flow from the bay into Old Town Lake, Zimmerman Marsh and further down to Fish Pass.

The research showed the only solution was removal of the debris plug, he said. This was accomplished with the help of specialized equipment to reach out over the marsh so as not to disturb the vegetation.

With the removal completed in July, Huff said the water is now able to flow into the marsh unimpeded.

“The prognosis for the marsh is a good one,” he said. “Within 10 days of the debris removal, we began seeing a change in water salinity throughout the marsh. The day after the debris dam was removed, we saw water levels in the marsh beginning to fluctuate with the tide.”

This tidal action exposed unvegetated mudflats, which are covered at high tides and exposed at low tide.

“It is our hope that these areas begin to revegetate with visible results in the next year or so,” Huff said.

But for residents and visitors of Magnolia Beach, the changes they see should be more immediate, he said. Large fish are now able to get through the channel into the marsh. Tidal action opens new locations for vegetation to spread and new habitat for wildlife.

With the work complete, the fisheries in West Matagorda Bay and Lavaca Bay should benefit, according to Feagin. Recreational fishermen, kayakers, bird-watchers and hunters could see greater opportunities in the area.

The marsh will continue to recover and there will likely still be small changes for up to 15 years, he said. Salt marsh systems are delicate but resilient, and after over a half century of decline the marsh now has the chance to start recovering.

“The shoreline in now protected,” Huff said. “Water can get in the marsh and that will help the fish, shrimp and crabs reproduce and help further the economic strength for communities across the central Texas coast.