Date of Award
Master of Science (MS)
Oysters (Crassostrea virginica) are functionally extinct in the urbanized Hudson-Raritan estuary (HRE) in New York City, however, oyster restoration is promoted to mitigate nitrogen (N) pollution via oysters' filtration and excretion. Seasonally, I took 12 sediment cores (45 cm2) adjacent to and 10 m away from a recently constructed reef in the HRE. Cores were incubated in flow-through chambers with site water containing (1) no amendments, (2) 15N-ammonium, or (3) 15N-nitrate, from which I calculated coupled nitrification-denitrification and direct denitrification as isotope-enriched N2. Coupled denitrification was minimal at all sites while direct denitrification was elevated near the reef, suggesting organic matter in oyster waste stimulated direct denitrification of water column nitrate, however, high variability in field samples precluded statistical significance. To further investigate these effects, I designed a laboratory study to test how oysters influence direct and coupled denitrification in oligotrophic and eutrophic sediments, creating a 2x2 aquaria testing matrix with oyster presence and trophic state as factors while repeating the isotope treatments and sediment cores methods used in the field study. Overall, oyster presence increased direct denitrification, but caused only small changes in coupled denitrification, suggesting that oyster reef restoration may be useful for removing nitrate from coastal ecosystems.
Hassett, Michael, "The Influence of Eastern Oyster (Crassostrea virginica) Reef Restoration on Nitrogen Cycling in a Eutrophic Estuary." (2015). Master's Theses. 2785.
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Copyright © 2015 Michael Hassett