Chemistry of trace elements, humic substances and sedimentary organic matter in Macquarie Harbour, Tasmania

Abstract

A broad range of physical and chemical parameters was measured in waters of the Gordon and King Rivers and Macquarie Harbour, Tasmania, along with sedimentary organics at three sites. Most concentrations of dissolved heavy metals in the Gordon and upper King Rivers were similar to those found in normal coastal sea waters, but such concentrations were up to 100 times higher in the harbour waters and were higher still in the lower King River. Much of the large particulate load in the lower King was removed during estuarine mixing. In the harbour, low dissolved oxygen (< 175µM) was found in intermediate waters at two sites, accompanied by higher heavy-metal and lower iodate concentrations. Strong copper-complexing capacities were proportional to humic concentrations but were always exceeded by concentrations of dissolved copper. Total dissolved iodine was conservative, whereas dissolved iodate was reduced to iodide or organo-iodine in waters with salinities of less than 15. Humic substances were conservative and originated almost entirely from the Gordon River. The sedimentary lipid profiles were dominated by higher-plant-derived compounds, whereas microbial communities were largely prokaryotic, with biomarkers indicative of anaerobic microorganisms. Sediment near the mouth of the King River contained substantial amounts of anthropogenic petroleum-derived hydrocarbons.