Biological and chemical oceanographic processes in the waters surrounding the Harriet A production platform on the North West Shelf, Western Australia

In September 1994 and 1995, multi-disciplinary cruises were undertaken by the Australian Institute of Marine Science (AIMS) and the Australian Geological Survey Organization (AGSO) to the southern Northwest Shelf to examine physical, biological and geochemical processes affecting the fate of produced formation water (PFW) discharged into shallow Northwest Shelf waters. The 1994 cruise was used as a pilot study to define local biological and chemical conditions at the discharge site, while the 1995 cruise was designed to measure the dispersion of the discharged PFW and associated hydrocarbons and to measure water column processes likely to affect PFW constituents and their fate in the environment.

Vertical profiles of water temperature and salinity were measured at all stations with a Seabird SBE25 CTD. In 1995, the CTD was fitted with a Biospherical QSP-200 quantum sensor to measure subsurface irradiance. Discrete water samples were collected from three to seven depths through the water column with Niskin bottles. Subsamples taken from the Niskin bottles were analysed for dissolved inorganic nutrients (NH4+, NO2", NO3", PO42", Si), dissolved organic nutrients (DON, DOP, DOC), particulate matter (PN, PP, suspended solids) and plant pigments (chl a, phaeophytin).

On one occasion in 1994 and three times in 1995, samples of fresh PFW were obtained from the Harriet A production platform. A variety of nutrient and hydrocarbon analyses were made on the PFW. Primary production rates were determined by 14C incorporation into particulate organic matter.