The project seeks to determine the potential impacts of ocean acidification on aquaculture practices of the Eastern oyster, Crassostrea virginica. Seawater has decreased by 0.1 pH units and may decrease by another 0.3 by 2100 threatening the health of shelled organisms. Extremely low aragonite saturation events have been found to have the most impact on the health and survival of oysters. Chen and colleagues will characterize the variability in pH and pCO2 continuously in Duxbury and Barnstable Harbor (hatchery) and its causes. Two ocean acidification monitoring systems will be constructed and deployed. The Endurance Ocean Acidification System (EOAS) will be deployed permanently at the Duxbury Harbor Town Pier. The Pioneer Ocean Acidification System (POAS) will be deployed at a variety of coastal sites for periods of 6-12 months, initially at Barnstable Harbor. pH of surface seawater will be measured continuously (every 15 min) using a spectrometric method and calibrated using discrete seawater measurements. pCO2 will be measured using an equilibrator and a LI-COR infrared CO2 detector and calibrated using reference gases. That data will then be used to predict future levels and durations of pH, pCO2 and aragonite saturation. Characterization of future ocean acidification variability over short and long terms can inform the oyster aquaculture industry to develop resilient and sustainable aquacultural practices. Researchers plan to work closely with stakeholders to determine potential impacts on the aquaculture industry. Data from this project will be used to inform the Massachusetts Shellfish Initiative.