Seasonal and diel changes in salinity, temperature, dissolved oxygen and sulphide at a station in the upper Derwent estuary, southeastern Tasmania.

Temperature, salinity, oxygen saturation and sulphide levels fluctuated widely both seasonally and with depth at a station on the upper Derwent estuary just downstream from a pulp and paper mill. In summer (February) oxygen saturation at the bottom reached a minimum of about 20% and sulphide levels peaked at 11 mg L- Conditions at this time would be expected to be lethal to a wide variety of organisms. Some of the possible causes for these changes are discussed