PROTECTING THE AQUACUTLURE INDUSTRY IN THE CHESAPEAKE BAY FROM A DYNAMIC CARBONATE CHEMISTRY ENVIRONMENT  

Oysters and clams are an essential part of Virginia's near-shore ecosystems and a vital part of life in our coastal communities. A healthy shellfish industry means a strong economy in Eastern Virginia and a healthier environment in the Chesapeake Bay. The high-value shellfish aquaculture industry is dependent on oyster and clam hatcheries. Over the last ten years, Virginia's shellfish aquaculture industry has developed rapidly, with the number of hatcheries increasing from one in 2005 to eight in 2010. For oysters alone, this resulted in a total number of oysters planted from approximately 6 million in 2005 to nearly 106 million in 2013. There is a consensus in the scientific and industry community that coastal water quality will continue to worsen as climate change and anthropogenic activities are accelerated. Over the last few years Virginia hatcheries have experienced suppressed larval production for intermittent times during a production season.

A water quality monitoring program was implemented between academic and State agency partners in Virginia and New Hampshire along with six shellfish hatcheries. This extension and outreach effort provided the training and resources for each hatchery to discretely monitor numerous water quality parameters such as alkalinity, ammonia-N, calcium, dissolved oxygen, nitrate-N, nitrite-N, pH, phosphate, and silica. Synchronizing data amongst the various hatcheries has provided a unique spatial and temporal data set that has yielded positive results by identifying issues and developing solutions to those issues. In 2014 the program was expanded to include the monitoring of carbonate chemistry. More specifically, a parameter that is particularly useful for the shellfish industry is the carbonate mineral saturation state for aragonite (Ω). Low Ω values can suppress larvae production success at our hatcheries. A pilot project was implemented with a robust state-of-the art system that continuously monitors the partial pressure of carbon dioxide (pCO₂). This system was developed by personnel at the University of New Hampshire Coastal Carbon Lab and implemented at one of our hatcheries. We use pCO2 data in conjunction with salinity, temperature to model Ω at the hatcheries. Over the last two years we collected a time series of Ω. From our data it is apparent that factors other than ocean acidification are very important for understanding carbonate chemistry in dynamic estuarine environments. Ω values fluctuate diurnally and seasonally and are influenced by factors such as algae activity, weather events, and likely sediment interactions. The outcomes of this project will directly benefit shellfish hatcheries, the industry, and ultimately the Chesapeake Bay, by increasing the ecological filtration services shellfish provide. In the early part of 2016 we will be deploying two more pCO₂ systems along with five less expensive, alternative CO₂ systems to establish a more robust carbonate chemistry data set and to assess whether or not the alternative sensors are adequate for assisting the industry.