Sediment trap arrays were deployed in May and June 1997 at three sites (Fly Slope, Kerema Canyon and South East Fields) in the Gulf of Papua, Papua New Guinea. Sediment trap arrays, each consisting of six stainless steel cylinders fitted into a weighted aluminium frame, were attached to wire moorings just below the euphotic zone at 300m below the water surface, and at 100m above the sea bottom, in water depths ranging from 960 to 1460 m. Traps were deployed for 50 days at the Fly Slope site, 44 days at the Kerema Canyon site and 29 days at the South East Fields site. On retrieval, water in the collection bottles attached to each cylinder was filtered through GFA filters and the filters were rinsed, wrapped in solvent-cleaned aluminium foil, packed in labelled polyethylene bags and frozen until analysis.Water samples were collected from 0 ppt salinity stations in the Purari and Kikori Rivers and from the salinity gradient of the Fly River. Initially water was collected from a depth of 1-2 m, using a series of 4 L brown bottles mounted in a stainless steel framework. Between 24-36 L of water was then pumped through an Infiltrex II (TM) semi-high volume sampler on board the vessel. After sampling, the filters were removed, packed in glass jars with foil-lined lids and frozen and the XAD-2 columns were resealed and stored under refrigeration. Analyses of the material in the sediment traps and water samples were conducted to determine: C/N and stable isotope ratios (13C/12C and 15N/14N); Total extractable Organic Matter (EOM); and the presence of aromatic hydrocarbons using UV Fluorescence analysis. After fractionation of the extract into polar classes by column chromatography on silica gel, the fractions were analyzed for the following parameters by Gas Chromatography-Mass Spectroscopy (GC-MS): F1-2 hydrocarbon composition and PAHs; F3 fatty acid methyl esters, wax esters, phytanic acid methyl ester and alkenones; F4 Sterols and alcohols; and F5 fatty acids. Major hopane and sterane biomarkers in sediment trap material was detected by Selected Ion Monitoring Gas Chromatography-Mass Spectroscopy (SIM GC-MS) and Metastable Reaction Monitoring Gas Chromatography-Mass Spectroscopy (MRM GC-MS) at Geoscience Australia.
This study was carried out to determine the magnitude of fluxes of organic matter and inorganic elements from the photic zone to deeper waters at the base of the continental slope in the Gulf of Papua and into the northern Coral Sea. The sources contributing to organic carbon fluxes, and the important redistribution and degradation processes affecting the organic matter were also examined.
This work is part of Project TROPICS (Tropical River Ocean Processes in Coastal Settings), a joint coastal oceanographic study by Australia, Indonesia, Papua New Guinea, and the USA.
