By Julia Robins, Staff Writer
Before an oyster ends up on your dinner plate, it starts out as a tiny seed at a hatchery. Virginia’s hatcheries use Chesapeake Bay water to grow and supply seed for the state’s $55.9 million shellfish industry. Occasionally, water quality suddenly changes, and the tiny oysters don’t survive.
“There’s still a big question mark as to what’s causing the problems,” says David Kuhn, Virginia Tech researcher. With support from Virginia Sea Grant, Kuhn is documenting water chemistry and quality at six Virginia oyster hatcheries to see how it relates to larvae production.
One suspected culprit is ocean acidification. Ocean acidification is caused by increases in carbon dioxide in water. Where that carbon dioxide comes from can vary from place to place. Shellfish industry in the Pacific Northwest found their ocean acidification problems were caused by an upwelling of deep acidic waters. In the Chesapeake Bay, ocean acidification seems to be triggered when algae blooms begin.
“The causes are all different,” says Kuhn, “but the chemistry is the same.”
All water naturally has some dissolved carbon dioxide in it, and this carbon reacts in water to produce an acid that lowers the pH of the water. If more carbon dioxide gets into the water, it increases the amount of this acid. Acids react with and neutralize bases. One biologically important base is calcium carbonate. Oysters and clams rely on calcium to keep their shells strong, and because their shells are primarily made out of calcium, too much ocean acidification could weaken the shell.
“I think understanding all the carbonate chemistry parameters is very important so that we can figure out how they’re affecting the oyster negatively, and what we can implement for a solution when they do,” says Kuhn.
By monitoring water quality, Kuhn’s work could help determine what time of year or day is most problematic for larvae survival. The next step will be to try to relate water chemistry to larvae survival. He hopes to develop a tool to that will take all of these factors into account and generate a simple measurement to let hatcheries know when water quality is getting problematic for their shellfish.
Kuhn and his collaborators at Virginia Institute of Marine Science and at Virginia Tech will also develop a website to host the datasets that he’s been collecting.
Based on preliminary data from the VASG-funded work, Kuhn and his team received the National Marine Fisheries Service’s Saltonstall-Kennedy Grant to continue researching how carbonate chemistry impacts Virginia shellfish production through May 2017.
