Anaerobic Ammonium Oxidation (Anammox) in Chesapeake Bay Sediments |
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Authors: | Jeremy J Rich Olivia R Dale Bongkeun Song Bess B Ward |
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Institution: | (1) Department of Geosciences, Princeton University, Princeton, New Jersey, USA;(2) Department of Biology and Marine Biology, University of North Carolina at Wilmington, Wilmington, North Carolina, USA;(3) Present address: Center for Environmental Studies, Brown University, Providence, Rhode Island, USA |
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Abstract: | Anaerobic ammonium oxidation (anammox) has recently been recognized as a pathway for the removal of fixed N from aquatic ecosystems.
However, the quantitative significance of anammox in estuarine sediments is variable, and measurements have been limited to
a few estuaries. We measured anammox and conventional denitrification activities in sediments along salinity gradients in
the Chesapeake Bay and two of its sub-estuaries, the Choptank River and Patuxent River. Homogenized sediments were incubated
with 14/15N amendments of , , and to determine relative activities of anammox and denitrification. The percent of N2 production due to anammox (ra%) ranged from 0 to 22% in the Chesapeake system, with the highest ra% in the freshwater portion
of the main stem of upper Chesapeake Bay, where water column concentrations are consistently high. Intermediate levels of relative anammox (10%) were detected at locations corresponding
to tidal freshwater and mesohaline locations in the Choptank River, whereas anammox was not detected in the tidal freshwater
location in the Patuxent River. Anammox activity was also not detected in the seaward end of Chesapeake Bay, where water column
concentrations are consistently low. The ra% did not correlate with accumulation rate in anoxic sediment incubations, but ra% was related to water column concentrations and salinity. Anammox bacterial communities were also examined by amplifying DNA extracted from the upper
Chesapeake Bay sediment with polymerase chain reaction (PCR) primers that are specific for 16S rRNA genes of anammox organisms.
A total of 35 anammox-like sequences were detected, and phylogenetic analysis grouped the sequences in two distinct clusters
belonging to the Candidatus “Scalindua” genus. |
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