Oysters are in peril. In recent decades, the edible ectotherms have suffered as rising ocean temperatures alter their environment and affect their physiology.
With a North Carolina Sea Grant and funding from sources including the National Science Foundation, UNC Charlotte Associate Professor of Biological Sciences Inna Sokolova studies these creatures that have managed for millennia to adapt and survive in extreme conditions.
Oysters have been a staple in North Carolina’s aquaculture economy and a lynchpin in the complex ecosystem of the state’s estuaries. In addition to their economic import, oysters provide an essential service by forming elaborate reefs that house sea life. The oysters settle on top of one another to create habitats for more than 300 species of plants and animals. With their built-in biofiltration systems, the oysters cleanse the water, removing excess algae and vegetation.
Man-made conditions have led to a 99 percent decline in North Carolina’s oyster reefs in the last century. As a result, oyster restoration and protection has become a priority of state policy makers and universities.
Fifteen-gallon salt water tanks containing hundreds of oysters pepper Sokolova’s laboratory. Sokolova and colleagues made headlines last year when they demonstrated that marine organisms become more sensitive to pollution as ocean temperatures rise.
The research team recently presented their findings on the affects of high carbon dioxide on oyster survival, growth and shell hardness at the Global Change and Global Science: Comparative Physiology in a Changing World conference in Westminster, Colo.
They found that oysters kept in high CO2 conditions suffered from stunted growth and softer shells. The effects of the high CO2 environment were most pronounced in juvenile oysters, which use more energy than adults.
According to Sokolova, as they struggle to defend themselves against the toxic onslaught, the oysters are left with an energy deficit. Thus, they lack the extra energy they need to invest in growth and protect themselves against threats such as parasitic diseases.
“On top of this, if the parasite can better and faster proliferate in the warmth, the balance can be tipped towards disease,” Sokolova said.
Currently, Sokolova and her team are investigating a method that would kick-start the oysters’ defense mechanisms. While she is hopeful her research will provide a viable solution for the aquaculture industry, she warns that the effects of rising temperatures and heavy metal contamination on metabolic chemistry will likely not be limited to oysters. She said further research into the interactive effects between pollutant toxicity and elevated temperatures is needed.