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Keeping an eye on marine sediment in the Pilbara
How do you know whether the marine environment is healthy without a reference point or a baseline from which to compare and contrast?
This question was raised by the coastal towns of Western Australia's Pilbara region during a community consultation project to establish environmental values and environmental quality objectives. Community representatives stressed the need for baselines and a coordinated monitoring and reporting system to ensure human uses were managed and environmental values protected.
Funding
In response a Baseline Sediment Quality Survey on the North West Shelf was undertaken with the help of $75,000 from the Australian Government and support from the State Government, through the Rangelands NRM Co-ordinating Group.
Activities
Project Manager Kevin McAlpine said few sampling programs had ever attempted to characterise unimpacted background chemical concentrations for the marine waters and sediments of the North West Shelf.
"The time is right to establish baseline data because the Pilbara region is rapidly developing its mineral, oil and gas resources, processing industries, port facilities and tourism - but there are still large expanses that are effectively pristine," Kevin said.
"The survey, carried out by the Department of Environment and Conservation to characterise natural levels of contaminants, surveyed six sites throughout the Pilbara including Exmouth Gulf, Ashburton River Mouth, Onslow, Dampier Archipelago, Dampier Port and the coast at Port Hedland.
"Contaminants analysed included heavy metals, metalloids and organic chemicals considered to be key contaminants of interest. The cores have been analysed and the results reveal that the quality of marine sediments in the region is generally very good, including the sediments sampled in Dampier Port.
Achievements
"The finer, more muddy sediments near the Ashburton River Mouth were found to contain higher levels of some metals, but these appear to be natural and are unlikely to affect the plants and animals that live there."
Metals are generally held by the very fine clay and silt fractions of marine sediments and are therefore found at higher concentrations in fine sediments relative to coarse sediments.
The results also suggest levels of arsenic in marine sediments across the region may be slightly elevated compared to other parts of Western Australia, and this is natural and likely to be related to the nearby terrestrial geology.
"This data has been used to set specific criteria that will become the performance measures for assessing the impact of current and future human activities on the marine environment," Kevin said. "This information is what future management plans and research will be based on."
More information
- Kevin McAlpine, Project manager: (08) 9222 8324 or kevin.mcalpine@environment.wa.gov.au
- Download the Marine Technical Report from Department of Environment and Conservation: www.dec.wa.gov.au
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