Science Serving Maryland's Coasts

Zachary Nickerson, Indiana State University

Class Year: 

Project Title: 

Locating the Source of Denitrification in a Restored Oyster Reef


Reefs created by the eastern oyster (Crassostrea virginica) provide a number of ecosystem services, and their re-establishment is a priority in Chesapeake Bay restoration strategies. While nitrogen removal via denitrification has been shown to be a valuable ecosystem service of oyster reefs, mechanisms by which remineralized nitrogen is transformed have been incompletely identified. Oyster reef community components such as intact oysters, oyster shell and sediment were collected at restoration sites and denitrification was measured using the N2:Ar approach under ambient conditions and after experimental manipulations. Denitrification was observed in all reef segments, perhaps most consistently in oyster shells that supported a polychaete worm community that may create microenvironments conducive to coupled nitrification-denitrification. These results suggest oyster shell and associated microbial and metazoan communities may be important for oyster reef denitrification. Ambient sediment denitrification rates were low, but increased greatly with nitrate amendment, suggesting sediment nitrification rates were low. Understanding how the components of oyster reefs transform nitrogen is a first step in the development of models to predict denitrification rates in reefs with different community structure and physical-chemical conditions.