Sydney water authorities have tried out a new set of sensors to gauge the health of waterways, turning to a natural alarm to check for contamination.

Sydney rock oysters are particularly sensitive to metal contamination in suspended sediments, according to a new study.

Oysters may just find a job keeping an eye out (or valve) for harmful pollutants in our vital supplies, after recent findings of a strong association between cell damage in oysters’ digestive glands and the level of contamination in sedimentary water.

The UNSW-led team of researchers carried out their major study of this new approach to environmental monitoring, by assessing the health of oysters placed in ten estuaries along the NSW coast for a period of three months.

“Our results suggest that oysters could be a cost effective and sensitive way of monitoring injury to marine life from environmental contaminants,” says senior author, Professor Emma Johnston, of the UNSW School of Biological, Earth and Environmental Sciences.

Currently, scientists measure levels of contaminants in the air, sediments, water or biological tissues. While this can identify contamination hotspots, it only provides an estimate of the risk of harm to organisms rather than evidence of harmful effects on them.

“It is vital that the toxic effects of human activity be monitored so management of discharges can be assessed and remediation of sites considered,” Professor Johnston says.

The team placed cages containing 20 oysters at seven sites in each of 10 estuaries and left them for three months.

The ten estuaries were found to vary in their levels of contamination, with suspended sediments from Port Jackson, Port Kembla and Botany Bay containing the considerable levels of metals, including copper, lead and zinc.

The oysters in these estuaries were found to be significantly stressed, with cell damage rates to their digestive glands as high as 70 per cent.

By comparison, gland cell damage rates were as low as 25 per cent for oysters left in the least contaminated estuaries

The team included researchers from UNSW, CSIRO, the NSW Office of Environment and Heritage, and the Sydney Institute of Marine Science.

Their study is published in the journal Chemosphere.