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Marine Ecology Progress Series

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MEPS 621:95-105 (2019)  -  DOI:

Nitrogen and phosphorus cycling in the digestive system and shell biofilm of the eastern oyster Crassostrea virginica

Nicholas E. Ray1,*, Maria C. Henning2, Robinson W. Fulweiler1,2

1Boston University, Department of Biology, Boston, MA 02215, USA
2Department of Earth and Environment, Boston University, Boston, MA 02215, USA
*Corresponding author:

ABSTRACT: The shell and digestive system of bivalves provide microhabitats for an array of microbes that can mediate biogeochemical cycles. Here, we investigated nitrogen (N) and phosphorus (P) fluxes in these microhabitats in the eastern oyster Crassostrea virginica. From the anoxic oyster digestive system, we measured significant production of dinitrogen gas (N2-N; mean ± SE: 0.59 ± 0.20 µmol ind.-1 h-1) and nitrous oxide (N2O; 0.001 ± 0.0004 µmol ind.-1 h-1), indicative of denitrification. The oxic shell biofilm released N2O (0.0003 ± 0.0001 µmol ind.-1 h-1), as well as ammonium (NH4+; 1.26 ± 0.20 µmol ind.-1 h-1) and nitrite (NO2-; 0.05 ± 0.01 µmol ind.-1 h-1), but not N2-N, suggesting a combination of nitrification and heterotrophic activity. The biofilm released more dissolved inorganic P than the digestive system, although the rate of release from whole oysters was closer to the rate from the digestive system alone. N remineralized by oysters is released almost exclusively as NH4+, at a ratio of 18.4:1 with P, i.e. relatively close to the Redfield ratio (16:1). In an ecological context, this study supports the growing literature on the ability of oysters themselves to engage in denitrification activity and at rates potentially exceeding rates of sediment denitrification. The denitrification in the digestive system appears to proceed to completion and has a very small N2O cost (<1%). Restoring oyster populations may therefore be an important method for N reduction in coastal systems.

KEY WORDS: Oyster · Nitrogen · Denitrification · Nitrous oxide · Nitrification · Shellfish

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Cite this article as: Ray NE, Henning MC, Fulweiler RW (2019) Nitrogen and phosphorus cycling in the digestive system and shell biofilm of the eastern oyster Crassostrea virginica. Mar Ecol Prog Ser 621:95-105.

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