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The temporal and spatial distribution patterns of diatoms colonising artificial substrates were used to develop a model indicating different levels of degradation in urban streams of the Swan River, Perth, Western Australia. Diatom and algal based matrices were used to develop a multimetric index used to categorise the environmental condition of stream sites into four urban groups: (1) Streams in forested catchments with good to excellent ecological integrity and lOkm from the estuary (2) Streams receiving estuarine water with partial stream degradation (3) Streams in proximity to agricultural land with moderate to severe stream degradation and 5-1Okm from the estuary (4) Streams in proximity to industrial sites with moderate to severe stream degradation and

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Dr Chris Siva is a Research Co-ordinator in the Faculty of Law in Monash University Australia. His diverse research interests include environmental law and the application of bioindicators in urban pollution studies. Dr Siva has also published refereed articles on thermophilic and hypersaline microalgae.

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