Outer Darwin Harbour Shallow Water Sediment Survey 2016: Total oxygen uptake and total carbon dioxide fluxes of seabed sediments

Maintenance and Update Frequency: notPlanned | Statement: Bottom sediments were collected using a Shipek Grab or Box Core. One 5 cm diameter core of surface sediment was extracted from the grabs/boxcores by hand-pushing a 5 cm diameter core barrel into the sediments. The cores were overlain with 0.153 L of filtered (2 um) and uv-treated seawater, sealed and then were incubated in the dark for ~4-6 hours at ~25oC after a ~3 hour pre-incubation period (in which the cores remained open to exchange water with the incubator). Dissolved oxygen levels were measured at ~30 minute intervals using the Presens technology. Samples for dissolved inorganic carbon (DIC) analyses were taken at the start and finish of each incubation experiment. DIC concentrations were determined using a DIC analyser and infrared-based CO2 detector (at Geoscience Australia). CO2 production and O2 consumption rates were calculated by concentration differences (T=1 - T=0) over the course of the incubation. Accuracy of O2 measurements was ± 0.1 mg L-1. The O2 consumption and CO2 production rates of the 4 blank samples (filtered uv-treated seawater) run in intermittently and in duplicate (including the start and end of the field campaign), were -2.4 ± 2.7 and -0.2 ± 1.1 mmol m-2 d-1 respectively. | A benthic sediment sampling survey (GA0356) to the nearshore areas of outer Darwin Harbour was undertaken in the period from 03 July to 14 September 2016. Partners involved in the survey included Geoscience Australia (GA), the Australian Institute of Marine Science (AIMS) and the Department of Environment and Natural Resources within the Northern Territory Government (NT DENR) (formerly the Department of Land and Resource Management (DLRM)). This survey forms part of a four year (2014-2018) science program aimed at improving knowledge about the marine environments in the regions around Darwin and Bynoe Harbour’s through the collection and collation of baseline data that will enable the creation of thematic habitat maps to underpin marine resource management decisions. This project is being led by the Northern Territory Government and is supported by the INPEX-led Ichthys LNG Project, in collaboration with - and co-investment from GA and AIMS. The program builds upon an NT Government project (2011-2011) which saw the collection of baseline data (multibeam echosounder data, sediment samples and video transects) from inner Darwin Harbour. This dataset comprises total oxygen uptake and total carbon diox