Ocean acidification has led to a decrease in seawater pH, which decreases aragonite saturation levels. Aragonite is the crystal form of calcium carbonate that shellfish use to build their shell especially within the larval stages. Seawater pH buffering using sodium carbonate or soda ash (Na2CO3) has commonly been used by shellfish hatcheries across the United States to increase aragonite saturation levels to improve larval growth and survival. This has been especially important for Pacific oysters (Crassostrea gigas), as they are more sensitive to aragonite levels, but is also used for Eastern Oysters (Crassostrea virginica). The effects of water pH buffering during the larval stages on long-term oyster health (e.g., oyster spat survival and growth) are understudied.
To investigate these impacts Crassostrea virginica larvae were raised to the
pediveliger stage with and without soda ash buffering where 0.031g/L of Na2CO3 was added. Once the larvae reach the pediveliger stage they were set onto oyster shell to mimic oyster restoration reefs. The shells were outplanted in the Choptank River off the pier at the University of Maryland Center for Environmental Science Horn Point Oyster Hatchery in cages. Spat was measured for survival and size every three weeks with a total of 5 counts completed so far. This experiment was conducted at the UMCES Horn Point Oyster Hatchery starting in July 2024 and is still ongoing.
Preliminary results suggest that larvae treated with soda ash have decreased growth and slightly lower survival rate compared with the larvae now treated with soda ash (Fig. 1). Results will inform aquaculture and shellfish restoration success as the impacts of ocean acidification increase with climate change