Denitrification measurements of sediments using cores and chambers: comparison of fluxes and denitrification efficiencies

Maintenance and Update Frequency: notPlanned | Statement: Benthic chambers were 0.4m lengths of clear polycarbonate pipe (~ 0.29m diameter) sealed at one end. The open end of the tube was pushed into the sediment to a depth of ~ 0.1m, enclosing ~ 20L of overlying water. Core cylinders (0.11 m diameter) were 0.5m in length and made from clear perspex. Core cylinders were pushed into the sediment to a depth of 0.4m and the top sealed with a removable cap, enclosing 1L of overlying water. The top sections of both the benthic chambers and core cylinders were equipped with: i) a sampling tube; ii) pressure/water compensating tube; iii) pulsed dissolved oxygen meter and iv) a mixing paddle. | Statement: 1.Source: a. Dataset: This dataset gives fluxes of i) dissolved oxygen (DO); ii) orthophosphate (PO4); ii) NO2-3, iv) nitrite (NO2-); v) ammonium (NH4+); vi) orthosilicate (SiO4); vii) nitrate (NO3-); viii) nitrogen gas (N2) and ix) dissolved inorganic nitrogen (DIN) between the sediment and water column. Fluxes were measured within cores cylinders incubated in the laboratory and in situ benthic chambers. Fluxes are expressed as µmol m-2 of seafloor surface day-1. Denitrification efficiency (DE), representing the percent DIN that was transformed to N2 is also given for cores and chambers at each study site. Studies were carried out in Port Phillip Bay at Clifton Springs and Williamstown, Victoria in March and May 2004, respectively. A full description of the core cylinders and benthic chambers are given in "collectionHardware". During each study, in situ chambers were embedded into the sediment to a depth of 0.1m at five random locations. Water samples were collected from benthic chambers ~ 0.5h after installation and a further sample collected ~ 20h later, additional water samples were also collected outside each chamber as a control. Core cylinders were embedded into the sediment next to chambers to a depth of 0.4m and subsequently transported to the laboratory for incubation. Dissolved oxygen levels were monitored at regular intervals within each chamber and core cylinder. Water samples were analysed for N2, DIN, NO3-, NO2- and NH4+ and fluxes calculated. Data files: MacreadieCliftonSpringsFluxCalculations and MacreadieWilliamstownFluxCalculations. Columns in each dataset are: Technique (Chambers, Cores); Sample source (Ambient, Chamber (1,3, 5, 6) or Core (1,3,5,6)); Incubation time (20hrs, 45hrs); The remaining data columns give the initial (C1) and final (C