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Denitrification and Denitrifying Efficiencies in Sediments of Port Phillip Bay: Direct Determinations of Biogenic N2 and N-metabolite Fluxes with Implications for Water Quality

Created 17/10/2025

Updated 17/10/2025

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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 (75-85%; denitrification rates ~1.3 mmol N2 m-2 day-1) at organic carbon loadings of ~15-25 mmol m-2 day-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 (>100 mmol m-2 day-1) denitrification rates and denitrifying efficiencies were near zero and most N is returned to the Bay waters as biologically available ammonium. In chambers 'spiked' 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.

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Title Denitrification and Denitrifying Efficiencies in Sediments of Port Phillip Bay: Direct Determinations of Biogenic N2 and N-metabolite Fluxes with Implications for Water Quality
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/135af634-c622-4d19-ad65-a37badf9d699
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period 22/04/2018
Geospatial Coverage
Map data © OpenStreetMap contributors
{
  "coordinates": [
    [
      [
        144.3,
        -38.4
      ],
      [
        145.1,
        -38.4
      ],
      [
        145.1,
        -37.8
      ],
      [
        144.3,
        -37.8
      ],
      [
        144.3,
        -38.4
      ]
    ]
  ],
  "type": "Polygon"
}
Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "Denitrification and Denitrifying Efficiencies in Sediments of Port Phillip Bay: Direct Determinations of Biogenic N2 and N-metabolite Fluxes with Implications for Water Quality". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/denitrification-and-denitrifying-efficiencies-in-sediments-of-port-phillip-bay-direct-determina