Discover Your Island

Island University Study Uncovers Potential Threat to Gulf Shellfish

March 17, 2015

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CORPUS CHRISTI, Texas – A new study from Texas A&M University-Corpus Christi has uncovered a problem in the estuarine waters along the Gulf coast of Texas that could potentially threaten local economies and even lead right back to your dinner plate.

Dr. Xinping Hu, Assistant Professor of Chemical Oceanography in the Department of Physical and Environmental Sciences at A&M-Corpus Christi, together with colleagues Drs. Jennifer Pollack, Paul Montagna, of the Department of Life Sciences, and the Harte Research Institute for Gulf of Mexico Studies, respectively, and graduate student Melissa McCutcheon, and former visiting student, Zhangxian Ouyang, examined four decades of alkalinity and pH data, which were collected and maintained by Texas Commission on Environmental Quality, from 27 Texas coastal bays, and discovered a steady acidification trend in the water.

If you have ever owned a saltwater aquarium with corals and clams in, you know what a problem this can be. The aquarium needs steady supply of an alkaline material - literally baking soda, dissolved in water - to maintain healthy water chemistry for the corals to grow their skeletons and clams to grow their shells. Now, imagine it on the scale of hundreds of miles of coastline. The further south you go, the worse it gets. The alkalinity level decreases more, and shellfish could be the ultimate victims.

“Because a lot estuarine calcifying organisms such as oysters rely on the water alkalinity to make their shells, the reduced available alkalinity level could pose a potential threat to these organisms,” Hu said. “And the alkalinity level is positively correlated with water carbonate saturation state based on our ongoing study. Carbonate saturation state was recently verified to be the ultimate controlling factor on shellfish calcification, according to a recent report published in Nature Climate Change.”

Waters off the Gulf coast of Texas are home to countless oysters, clams, scallops, and other shellfish that the seafood industry catch for your favorite meals. As acidification harms these organisms and decreases their populations, it could become harder for growers and shellfish farmers to stay in business.  But perhaps more importantly, oysters, clams, scallops, and other shellfish provide benefits such as water filtration and coastal protection against storm surge. 

The study by Hu, which was recently published in Environmental Science and Technology, shows drought and the diverting of freshwater flowing down rivers and into bays could be the culprit, because many Texas rivers carry moderate to high levels of alkalinity and deliver it to the coastal ecosystems.  ­­

“This study is rather a broader scale data synthesis and we can only identify most likely causes to this problem,” he said. “Ongoing research is being conducted with more detailed studies that examine individual estuarine systems and what is needed to fully address this problem.”

The Texas Fresh Water Institute recognized the problem of fresh water diversion as far back as the late ‘70s.  As cities and towns grew, more and more water was taken off of rivers, streams, and lakes for residential and industrial use, along with increases in the use of ground water sources. As less fresh water made its way to the Gulf, it helped to create an imbalance.  The problem has been exacerbated by drought conditions in the past few years.

The information gathered from this new study will help researchers provide useful information to resource managers and policy makers to tackle the problem.

“There are still so many unknowns. For example, we do not know how much of a role groundwater plays in maintaining estuarine freshwater balance. But we do know we need to maintain sufficient environmental inflow from rivers, and this could be a challenge given current precipitation projections,” Hu said. 

As research continues, Hu advocates for programs like Sink Your Shucks, administered by Texas A&M University-Corpus Christi and led by Pollack, that replenish coastal bays with oyster shells recycled from restaurants. Other programs that restore estuarine reef using minerals such as limestone may be equally effective.

“The returned shells (carbonate) not only provide critical habitats for many marine species, including oysters, but they dissolve and that replenishes water alkalinity inventory,” he said.