Tracy Woody has been harvesting oysters since the 1980s for his family business, Jeri’s Seafood, one of the largest private purveyors of oysters in the region.
For years, he’s been hearing about the increasing acidity of the water in Galveston Bay, the Gulf of Mexico and oceans worldwide, but now he thinks there may be something to it.
“It’s been the worst year ever for the oyster harvest and that’s not just here in Texas, it’s everywhere along the Gulf Coast and in other parts of the country too,” he said.
Woody said it requires more work to harvest fewer sacks of oysters, and he’s noticed more predators and parasites drilling into the oyster shells.
The Texas oyster population is facing an army of troubles but whether this will be the Alamo or San Jacinto for the popular bivalve is not yet known.
Xinping Hu, an assistant professor of chemical oceanography at Texas A&M University Corpus Christi, said the changing chemical balance in Texas bays and estuaries is one formidable risk to the state’s oyster beds. However, the tipping point for the worst effects is difficult to predict.
“It could be decades away or it could be sooner,” Hu said.
His study, published this month in “Environmental Science and Technology,” shows a steady trend in acidification in 16 of the 27 coastal bays in Texas, including Galveston Bay. The data used in his study were collected and analyzed by Texas Commission on Environmental Quality over four decades.
“Here’s what happens,” Hu said. “We have increasing carbon dioxide in the atmosphere, which dissolves into water as a weak acid. Seawater is alkaline and is able to neutralize the acid. However, as the levels of CO2 increase, we see that buffering process weaken; and what follows is the gradual acidifying of the oceans and bays.”
Higher acidity is bad for oysters because they need an alkaline environment to make a hard, protective shell. The troublemaker, carbon dioxide, is a byproduct of burning fossil fuels.
Lance Robinson, deputy division director for Coastal Fisheries with Texas Parks and Wildlife, said acidification is not a new problem.
“It’s basically been going on since the industrial revolution,” he said.
Still, that does not lessen the potential severity of the problem.
“Oysters and other shellfish and corals utilize calcium carbonate in the water to form their shells or exoskeletons with corals,” he said. “When the water becomes more acidic, the concentration of carbonate ions is reduced, which makes it harder for shellfish to produce shells.”
Exacerbating the problem is the diminishing volume of river water from the Trinity and other fresh water sources that have traditionally flowed into the Gulf of Mexico.
Fresh water bolsters alkalinity and is an important factor in keeping a neutral alkalinity balance for the bays. In recent years, drought conditions and the increasing demand for water to serve an expanding urban population, industry and agriculture, has kept much of that fresh water from making its way into the bay.
“Diverting freshwater from the rivers may contribute to the overall problem as many Texas rivers carry moderate to high levels of alkalinity and deliver it to the coastal ecosystems,” Hu said.
Hu’s study is not the only recent scientific warning.
Last month, a research study published in “Nature Climate Change,” identified the Gulf of Mexico as one of the communities most vulnerable to ocean acidification.
Authored by scientists at the Natural Resources Defense Council, The University of California-Davis, Ocean Conservancy, and Duke University, with other collaborators, the study looked at physical, economic and social data to assess each region’s overall vulnerability.
“We don’t know how urgent the threat is — all we’re saying is that there are risk factors in the Gulf worth noting,” Lisa Suatoni, a senior scientist with the Natural Resources Defense Council, said. “We won’t know how urgent it is until scientists have a better handle on how sensitive Gulf oysters are to the chemical parameters,” she said.
Local conservation groups have been concerned about these issues for some years, said Bob Stokes, president of the Galveston Bay Foundation.
“Decisions are being made today for how we will use our water 20 years down the road, and there are powerful interests who aren’t making Galveston Bay a priority,” he said.
Because more than half of the population of Texas lives in the Galveston Bay watershed, there is intense pressure on natural resources, especially water.
“Our message is this: we need fresh water for people, for industry, but also we need water to maintain the complex ecosystem of Galveston Bay.”
Stokes said it is a global issue and there are already places in the world, particularly coral reefs, that are dying from the effects of acidification.
The loss of shellfish populations, especially oysters, would be an environmental calamity, and not only because they are a multimillion dollar coastal industry.
“The oysters’ real value are in the ecosystem services they provide,” Robinson said. “They’re filter feeders and improve water quality by filtering out particulate matter. A single oyster can filter up to 50 gallons of water per day.”
Using a density of 10 oysters per square meter, 140 acres of oyster reef will filter about 283 million gallons of water per day. This is more than the entire city of Houston’s 41 wastewater plants combined, Robinson said. Oysters also provide a foraging habitat for transient fish and a refuge habitat for small fish and a wide variety of crabs, shrimp, and worms. The beds offer some protection from coastal erosion and flooding caused by waves; and they remove nitrogen, which may cause algae blooms and dead zones.
Long-term chemical change, acidification, is are not the only or even the most immediate challenge facing the Texas oyster beds.
“Reduced production in other Gulf states and a high demand in the market has increased the commercial harvest pressure on Texas’ oyster resources,” Robinson said. “Also, reduced freshwater inflows and the recent drought has increased salinity in the bays. Though oysters can survive in higher salinity, they’re exposed to increased predation by predatory snails and ‘dermo’ disease, caused by a protozoan parasite.”
Oysters may not be the only species being placed at risk by acidification. This is a new area of scientific inquiry and there is still much to learn.
“The shrimp industry could also be at risk,” Suatoni said. “There is potential direct impact to larval fish and to the food chain if animals like plankton are affected.”
Her major take-home message is that there is much that can be done now to reduce the risk to ocean acidification.
“We don’t need to sit around and wait for global agreements on CO2 reductions,” Suatoni said. “We can address local risk factors like nutrient pollution from land runoff and the diversion of fresh water.”
How local groups are helping the situation
Regional conservation groups are taking a small step to increase the alkalinity of the water by returning oyster shells to the bay. Doing so increases the alkalinity and helps the oysters in other ways.
One program, “Sink Your Shucks,” is led by Jennifer Pollock, an assistant professor at Texas A&M University-Corpus Christi whose focus is on conservation and restoration of marine organisms and habitats. The program, administered by the university, helps to replenish coastal bays with oyster shells recycled from restaurants.
“The returned shells not only provide critical habitats for many marine species, including oysters, but they dissolve and that helps to replenish water alkalinity inventory,” said Bob Stokes, president of the Galveston Bay Foundation.
“Right now we are working with seven restaurants in the Clear Lake area,” he said. “We collect and recycle shells right back into the bay. To date we have recycled over 200 tons. We’d love to do 10,000 tons. If any restaurant is interested, we’d love to talk with them.”
For more information, visit www.galvbay.org