Nov 1, 2013 12:48 PM
MATAGORDA BAY- A deep sea oyster reef restoration being touted as the largest ever in the Gulf of Mexico began in an unlikely place: a quarry in landlocked Missouri.
That is where years of research, planning and precise engineering led Mark Dumesnil, an associate director of restoration for the Nature Conservancy in Texas, as he sought to restore what was once a nearly 500-acre oyster reef and is now no more than hard sand and shell remains, with not one oyster in sight.
And so, about seven years after Dumesnil was first tipped off by wildlife ecosystem experts that restoration of Half Moon Reef might be possible, 36 barges carrying 93,000 tons of Missouri limestone traveled for 12 days down the Mississippi River, arriving in the Gulf in late October. Scientists, engineers, researchers and laborers will spend some eight weeks dropping the boulders onto a 54-acre plot 8 feet underwater as part of a $5.4 million, two-phase project designed to revitalize a damaged ecosystem.
The project also will provide a robust natural barrier from hurricanes and teach scientists whether reefs can rebuild in drought conditions, becoming another mechanism for marine habitats to withstand devastating dry spells.
"This project is designed to be innovative and different," said Dumesnil, who has financial backing from a variety of agencies, including the U.S. Army Corps of Engineers and the Texas General Land Office.
Oysters filter 50 gallons of water daily. Each acre of reef the oysters cling to filters another 24 million gallons of water daily. Together, they are vital to a healthy marine ecosystem and to commercial fisheries because they are home, feeding and breeding grounds for hundreds and even thousands of other fish, shrimp, clams, crabs and other life. In Texas alone, the oyster industry is a nearly $30 million a year industry, according to state statistics.
Oyster reefs, however, have been severely damaged by overfishing and other causes during the last century. Nearly 50 percent of the reefs in the Gulf, and 85 percent of those globally, have disappeared, according to The Nature Conservancy.
In 1907, a survey of Matagorda Bay done by the U.S. Bureau of Fisheries indicated Half Moon Reef covered 494 acres of seabed. Since then, however, a variety of factors led to a slow death, including the release in the 1920s of a major logjam in the Colorado River that allowed large amounts of freshwater to flow into the estuary about 10 years later, upsetting the delicate salinity levels that oysters need to thrive; rerouting in the 1940s of the intracoastal waterway, which released tons of sediments, and may have helped bury and kill oysters; commercial dredging of live and dead oyster shells between 1922 and 1983, often to build roads; and the damage from Hurricane Carla in 1961.
Oyster reef restoration has long been done along shorelines, successfully helping decrease erosion and protect sensitive coastal communities from tropical storms. Similar projects in deeper waters, including off the Virginia coast, have also been done, but generally on smaller scales and with flatter, less contoured materials and not typically limestone.
The idea behind this project, Dumesnil explained, and the reason boulders of varying sizes are being used, is to try to replicate as closely as possible a real reef, and to get the eventual growth of it to be vertical - as it would be if it were naturally occurring.
"If we were here 100 years ago ... we would see reef, oysters breaking the surface of the water. So you would see waves breaking on the oyster reef, it was that high, 6 to 7 feet high," said David Buzan, project manager for Atkins North America, a global engineering, design and project management consultancy firm. "Now, we're building a reef that's 3 feet high with the hopes that oysters will grow on it, colonize it and eventually return that oyster reef back to the height that it originally was 100 years ago."
The limestone from Missouri was specifically chosen because it was the precise material, Dumesnil said, needed to guarantee it wouldn't sink into the seabed allowing the oysters to build vertically. Project designers also decided to build 32 rows of 650-foot reefs, deliberately leaving space between them. The hope is that as the spat - or oyster babies - stick to the boulders they will eventually fill in the gaps while growing the reef vertically.
"What we were wanting to do is build in as much diversity in the design of the project," Dumesnil said. "The more diverse a habitat is the more diverse and types and kinds and numbers of species will use that."
Coincidentally, the project is being launched as Texas struggles through years of drought, which has increased the salinity of Matagorda Bay and other estuaries as less freshwater from rivers flows into the Gulf. This is allowing scientists to study the effects this has on oyster reefs and learn whether they can grow in drought conditions, an issue of increasing concern for scientists who expect more frequent dry spells due to global warming, said Laura Huffman, the director of the Nature Conservancy in Texas.
"We want to test the conditions at their more extreme," Huffman said.
2 hours ago
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