DO SEAGRASS BEDS CREATE LESS STRESS ON RESTORATION OF THE HARD CLAM MERCENARIA CAMPECHEIENSIS?

Owen Silvera, United States and Emily R Hall, Mote Marine Laboratory, Sarasota, United States
Abstract:
Climate change is causing oceans to acidify leading to reduced growth rates and dissolution of calcareous organisms such as bivalves which are economically important for fisheries. As a result, legislature is being put in place to help regulate factors which contribute to CO2 output and overall ocean acidification. With increasing atmospheric and oceanic CO2 levels, it is imperative to explore the usefulness of the environment to create natural remedies to anthropogenic problems. Seagrass is a possible sink for carbon dioxide in the water column, though it is unknown if this reduction of CO2 is enough to help reduce the stress placed on organisms by ocean acidification. Carbonate chemistry differences between seagrass beds and sandy bottoms may provide evidence that seagrass beds could act as a natural refugia to ocean acidification. Clams are important to the economy of Florida, yet natural numbers of clams have dropped in many estuarine environments. Because of this, there are currently major clam restoration efforts. It is important to understand best methods for restoration efforts, especially in light of a changing climate. For this study, we used Florida clams (Mercenaria campiechensis) from the commercially important quahog clam family, to study the effects of the presence of seagrass on clam growth and physiology. Clams were collected from the nursery at Mote Marine Laboratory and placed at in situ seagrass or sandy bottom sites within Sarasota Bay. We hypothesized that M. campiechensis would grow faster in seagrass beds as opposed to sandy beds because of the importance of seagrass beds as a carbon sink. We also hypothesized that respiration rates (an indicator of clam stress) would decrease in seagrass beds. Surprisingly, after one month, we found that clams placed in seagrass beds grew slower than clams placed in sandy bottoms, and there were no significant differences in respiration rates with bottom type or site. This study is continuing for another 6 months to determine if there are long term effects of growth within seagrass beds and to determine if there is any benefit of focusing restoration sites for clam restoration efforts.