Rig Seismic Survey 112, Modern Processes and Environmental Monitoring Strategies Offshore Sydney : A Joint Program between the Australian Geological Survey Organisation and the Water Board (Sydney)

Brief description

Increasing population densities in coastal areas, the diversity of human activities, and multiple sources of pollution all contribute to the potential for adverse environmentalimpacts on the marine environment in proximity to metropolitan areas. Fundamental to achieving an effective coastal zone strategy to manage the impacts of urban activities is an understanding of the effects of pollutants on marine organisms and processes. In the coastal waters near Sydney, pollutants derive from a number of sources such as sewage effluents, industrial input, agricultural runoff, stormwater discharges and non-point source urban runoff. Pollutants of concern include contaminants such aspesticides and trace metals, organic matter and nutrients, and pathogenic organisms.Many of these constituents can be introduced to the coastal zone from natural orhuman-derived sources. Determining the environmental impacts of urban pollution on the marine environment requires an understanding of baseline conditions with regard to naturally-occurringmarine processes in the coastal zone, particularly those that control the flow of energyand materials through the system and the recycling of many elements, such as oxygenand carbon and the essential nutrients (nitrogen and phosphorus) required to sustainthe activities of the various marine communities. It also requires identification of thesources and loads of the pollutants reaching the coastal zone. As a potentiallysignificant contributor of a number of pollutants to the coastal zone, the long termimpacts of discharge of Sydney's sewage effluent through three deep water oceanoutfalls are being assessed by the Water Board through ongoing monitoring andinvestigation. During 1991, the Australian Geological Survey Organisations (AGSO) and the WaterBoard (Sydney) conducted a pilot survey to test if light hydrocarbons in seawater maybe sensitive indicators of the plumes from the ocean outfalls, operated by the WaterBoard, which discharge into the sea offshore Sydney. The results of that survey arebriefly summarised and presented in Figure 1.1. The outcomes of that survey lead tothis Survey 112, and an Agreement between AGSO and the Water Board to conduct expanded scientific, baseline and process studies on the continental shelf offshore Sydney. The Environment Management Unit of the Water Board and the Marine Geoscience Program of AGSO combined facilities and skills to carry out a twelve day survey aboard the research vessel Rig Seismic. Three major issues were to beaddressed during the survey:- (i)Sedimentology of continental shelf sediments and the accumulation of contaminants (metals and organic toxicants) in the sediments; (ii)Geochemical characterisation of continental shelf sediments - with special reference to the microbiology, oxygen demand and the cycling of nutrients, nitrogenand phosphorus and, (iii) Continuous geochemical tracer studies of ocean outfalls and estuary/oceanexchanges with special reference to light hydrocarbons. This Record: (i) documents the samples collected, analysed and inventoried for later analyses, during the joint program and, (ii) presents a preliminary interpretation and abrief summary of the results of the analyses conducted in the shipboard laboratoriesduring the survey. The survey was focussed on the continental shelf offshore Sydney between Broken Bay and offshore Garie North Head, south of Port Hacking.

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