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Video Clip
Toxic Sediments [2:45]
Network
ABC Catalyst
Broadcast
3rd June 2010
Summary
Sydney Harbour's toxic legacy, 2010
Download Clip [11.02 MB]
Learning Area
Geography, Science
Strand/s
Science as a human endeavour, Science understanding
Year/s
6-12

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Description

This clip from the ABC's science program 'Catalyst' (2010) looks at the high level of toxins found in Sydney Harbour. Eco-toxicologist Dr Emma Johnston highlights the severity of the problem by reporting that the harbour has lost as much as 40 per cent of its invertebrates to toxic sediments. Associate–Professor Gavin Birch of the University of Sydney speaks about his findings that confirm world record levels of metallic contamination in Sydney Harbour. Serena Lee, also of the University of Sydney, discusses the role of currents in re-distributing toxins across the harbour.

Educational Value

This clip is a valuable resource for an exploration of the flow of matter in ecosystems and of how human activity can affect food chains. It explains the process of biological magnification, in which contaminants absorbed by marine algae are concentrated as they pass along the food chain. This can result in high-order consumers such as humans receiving dangerous doses in their food.

The clip illustrates how biodiversity can be used as an indicator of ecosystem health. If the number of species in a particular environment declines, the ecosystem is probably unstable and under stress. In parts of Sydney Harbour, 40 per cent of invertebrate species have disappeared, possibly as a result of contamination by metals and other toxic substances.

The clip makes the point that environmental problems often have causes that are closer to home than we realise. Some of the contamination in Sydney Harbour remains from the past dumping of industrial wastes. However the main source at present is stormwater run-off, which contains toxins from roads, farms and households. These toxins become trapped in particles suspended in the water and sink to the harbour floor as sediment.

Toxic substances do not remain in the area where they entered the harbour. The clip shows how currents can re-suspend the sediments and transport them so that they are distributed across the harbour floor.

More videos like this in:

Natural and man-made impacts on ecosystems

Related information:

› Catalyst story archive with story transcript and links

Metadata © Australian Broadcasting Corporation and Education Services Australia Ltd 2010 (except where otherwise indicated). Digital content © Australian Broadcasting Corporation 2010 (except where otherwise indicated). You may view, display, print out, copy and modify this material for non-commercial educational purposes provided you retain all acknowledgements associated with the material.