The silver content of the ascidian Pyura stolonifera as an indicator of sewage pollution of the metropolitan beaches of Sydney, Australia
1997
Florence, T.M. | Stauber, J.L. | Dale, L.S. | Jones, L.
Pyura stolonifera is an ascidian which is common on the sandstone headlands of Sydney's metropolitan beaches. It strongly concentrates heavy metals from seawater, with an enrichment factor of 2 X 10(5) for silver. The concentration of silver is low (< 1 ng/L) in coastal seawater but is much higher in Sydney's sewage outfall water (0.5-5 micrograms/L), which makes the concentration of silver in Pyura a useful indicator of the extent of sewage pollution of the beaches. Silver in Pyura was measured before and after the extension of Sydney's major sewage outfall pipes into deep offshore water. Samples of Pyura collected from pristine areas contained 0.05 micrograms/g silver wet weight, whereas samples of the ascidian taken near Sydney's beaches had 0.15-0.75 micrograms/g silver wet weight (contents of sack). Extension of the sewage outfalls did not significantly decrease the silver concentrations in Pyura, and it is suggested that this is because the ascidian is concentrating silver from suspended particles from contaminated nearshore sediments.
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