Oyster Bay highly polluted with heavy metals, study finds

A University of Wollongong study of sediment collected from more than 50 sites in Oyster Bay over a year found the area to be "highly contaminated" with lead, zinc and copper, with "moderate" levels of arsenic.

"The level of toxicity in parts of Oyster Bay has meant it is virtually uninhabitable for some species of bottom-dwelling invertebrates and micro-organisms," Yasir Alyazichi, a PhD candidate at the university, and lead author of the study, published in the Bulletin of Environmental Contamination and Toxicology.

"These organisms form the start of the food chain and contaminant levels may build up higher in the food chain," Mr Alyazichi said.

Sandy areas were low in pollutants and the area's oyster beds were also safe compared with other seafood. "You would need to consume contaminated seafood regularly over a long period of time to fall ill," Mr Alyazichi said.

Although sources of the metals have largely been curbed, such as bans on the use of leaded petrol, levels of sediment pollution have increased slightly since a smaller study of the area was done in 1996, he said. Industrial works in the Georges River region ranged from metal working, such as chrome plating, and wool scouring.

Errol McLean, an honorary principal fellow at the University of Wollongong and co-author of the paper, said the use of chemicals to coat the undersides of boats to curb plant growth was another source of the pollutants.

"Things are getting better, but there is no reason to be complacent  because there're still residual pollutants in these bays, and there are pollutants associated with our current use," Mr McLean said.

Stan Konstantaras, president of the Recreational Fishing Alliance, said his group was concerned that another waterway has been identified to contain toxins.

"Any recreational angler who fishes in or around Oyster Bay would be concerned hearing the results of this report, particularly when targeting apex predators like the mulloway and flathead, staples of our estuaries," Mr Konstantaras said.

Superficial beauty

Other areas around Sydney had worse levels of contamination, such as Salt Pan Creek, also in the Georges River region, and the Homebush Bay and Parramatta River areas flowing into Sydney Harbour, Mr McLean said.

"The water in the water column may be beautiful, and fairly freely of pollutants," Mr McLean added, noting that more fish were entering the regions, giving a misleading indicator of the health risks.

"Because of the concentration of [human] population at the back of these bays, we still do have a considerable entry of pollutants in our urban estuaries," he said.

The Environment Protection Authority will consider the findings of the report and potential implications, a spokeswoman said. The agency has also sent it to Office of Environment and Heritage scientists.

"The EPA will provide its view on whether Oyster Bay specifically needs any different action to other Sydney estuaries, once it has advice on the report in question and, if necessary, consulted with other agencies," the spokeswoman said. She said "leaving contaminated sediments undisturbed is often the most effective mechanism" to preventing the contamination entering the food chain.

"Many estuaries in Sydney have elevated metal and other contaminant levels," she said.

Sharyn Cullis, secretary of the Georges River Environmental Alliance, said cuts to the EPA research funding had limited public knowledge about the risks in rivers and bays.

"It is indeed fortunate that academic researchers are working in the Georges River, and are on to the issue of toxic metal concentration in riverbed sediments," Ms Cullis said.

"Funding cuts to every responsible public agency in NSW (such as the EPA and Department of Primary Indusries) have crippled them," she said. "They can no longer either uncover these threats to the environment and public health, or act on them."

A spokeswoman for Sutherland Shire said its own studies of Oyster Creek, which flows into Oyster Bay, showed that suspended solids concentrations in the water were below average for other urban areas in the shire and even below those of control sites representing natural conditions.

Water sampling from Oyster Bay itself over the last 20 years also indicates that levels of metal pollution are below the Australian and New Zealand Environment Conservation Council (ANZECC) guidelines for the protection of marine ecosystems, the spokeswoman said, adding, "this shows that the metals detected in the sediments in Oyster Bay referred to in the report are most likely from historic sources."