Denitrification pathways and rates in the sandy sediments of the Georgia continental shelf,USA |
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Authors: | Email author" target="_blank">Cynthia?Vance-HarrisEmail author Ellery?Ingall |
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Institution: | (1) School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, 30332 |
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Abstract: | Denitrification in continental shelf sediments has been estimated to be a significant sink of oceanic fixed nitrogen (N).
The significance and mechanisms of denitrification in organic-poor sands, which comprise 70% of continental shelf sediments,
are not well known. Core incubations and isotope tracer techniques were employed to determine processes and rates of denitrification
in the coarse-grained, sandy sediments of the Georgia continental shelf. In these sediments, heterotrophic denitrification
was the dominant process for fixed N removal. Processes such as coupled nitrification-denitrification, anammox (anaerobic
ammonium oxidation), and oxygen-limited autotrophic nitrification-denitrification were not evident over the 24 and 48 h time
scale of the incubation experiments. Heterotrophic denitrification processes produce 22.8–34.1 μmole N m-2 d-1 of N2 in these coarse-grained sediments. These denitrification rates are approximately two orders of magnitude lower than rates
determined in fine-grained shelf sediments. These lower rates may help reconcile unbalanced marine N budgets which calculate
global N losses exceeding N inputs. |
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