
%0 Journal Article
%A Heggie, David T. 
%A Skyring, Graham W. 
%A Orchardo, Joseph 
%A Longmore, Andrew R. 
%A Nicholson, Geoffrey J. 
%A Berelson, William M. 
%T Denitrification and denitrifying efficiencies in sediments of Port Phillip Bay: direct determinations of biogenic N<emph tye="8">2</emph> and N-metabolite fluxes with implications for water quality
%J Marine and Freshwater Research
%D 1999/07/21
%V 50
%N 6
%P 589-596
%K nitrogen, benthic flux, Australia.
%R https://doi.org/10.1071/MF98054
%U https://www.publish.csiro.au/paper/MF98054 
%X High-precision measurements of N2 in benthic chamber waters indicated that denitrification occurs within the major sedimentary facies in Port Phillip Bay. The integrated fluxes of biogenic N2 , ammonia, nitrate and nitrite showed that the stoichiometric relationship between organic C and N in the muddy sediments, occupying about 70% of the seafloor, was 5.7, this being similar to the Redfield ratio of 6.6. High denitrifying efficiencies (75&#8211;85%; denitrification rates ~1.3 mmol N2 m&#8211;2 day&#8211;1) at organic carbon loadings of ~15&#8211;25 mmol m&#8211;2 day&#8211;1 indicate that most N processed through the sediments was returned to the overlying waters as biologically (generally) unavailable N2. At sites of high organic carbon loadings to the sediments (&#62;100 mmol m&#8211;2 day&#8211;1) denitrification rates and denitrifying efficiencies were near zero and most N is returned to the Bay waters as biologically available ammonium. In chambers &#8216;spiked&#8217; with 15NO3 , denitrifyers used nitrate produced in the sediments in situ, rather than the exogenous nitrate in overlying waters. The sedimentary microbial processes of ammonification, nitrification and denitrification are therefore tightly coupled. 
