by Cosette Larash
The eastern oyster (Crassostrea virginica) is one of the most important species in Chesapeake Bay. These shellfish filter the water, their reefs provide shelter for other marine species, and they’re an important seafood resource. But their numbers have hit a historical low due to overfishing, diseases like Dermo, and stressors such as hypoxia (low dissolved oxygen) and acidification (low pH).
Biologists with the Smithsonian Environmental Research Center (SERC) want to find out whether the double stresses of low oxygen and acidification can stunt oyster growth. Studies have shown that juvenile oysters grown under low oxygen are generally smaller than oysters grown under normal oxygen conditions. However, scientists still don’t know how these oysters fare over the long term. The answers could help aquaculture and oyster restoration projects all over the Chesapeake adapt to the often extreme conditions beneath the surface.
“We are especially interested in looking at how exposure to both of those stresses early in life can lead to effects later in life,” said Matt Ogburn,a SERC marine ecologist.
SERC’s Marine & Estuarine Ecology Lab is running the experiment, with an assist from the Fish & Invertebrate Ecology Lab. The experiment has two main components: lab work and planting oysters in Chesapeake Bay.
Starting in May 2017, the biologists raised oysters in SERC’s laboratory and exposed them to various dissolved oxygen and pH concentrations. The treatments ran for five days a week, over an eight-week period. For the biologists, it’s critical to study low oxygen and acidity individually as well as together, to understand how each type of stress affects the oysters. Before deploying the oysters in the field, the scientists glued the oysters to tiles and snapped a picture of them, so they could track individual oyster growth rates throughout the experiment.
Once the oysters were glued and photographed, they were ready to be planted. The team deployed the oysters at four different stations in the Chesapeake Bay in July, and left them there for about three months. In October, they collected the oysters and began checking their growth in the lab. For each oyster, they’re measuring both shell length and shell area, weighing the shell and tissue separately, and snapping another photo.
With over 1500 oysters sent out into the field, SERC’s team is still analyzing data, but they expect to have results during 2018. “We’ll share those results with the both the aquaculture community and restoration community,” said Ogburn. “We think the results of this project will help inform how oysters are raised early in life history, to better condition them to survive when they are planted out into the Bay.”
