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A study of the eutrophication of North Lake, Western Australia

McDougall, Bryn (1988) A study of the eutrophication of North Lake, Western Australia. Honours thesis, Murdoch University.

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Abstract

The eutrophic state of North Lake is typical of other aquatic systems on the Swan Coastal plain. These bodies of water have long been regarded as convenient outlets for both urban and agricultural runoff. However, the runoff from such sources is high in phosphorus and nitrogen and as a consequence the ecosystem of the lake becomes dominated by free-floating single celled plant (algae). Their decay following peak growth periods leads to the production of noxious odours, and this in turn leads to complaints to the local council from nearby residents. This was the case at North Lake in December 1986.

This study was commenced in August 1987 to assess the problems of nuisance algal growth at North Lake and to review relevant management strategies.

The results of this study showed North Lake to be highly eutrophic throughout the year. Peak algal growth occurred during the winter months when the external loading of phosphorus and nitrogen to the lake was highest. Of the two external drains entering North Lake the south-east drain was the most significant contributor of nutrient to the lake. The catchment of this drain is the Murdoch University Veterinary Farm and contributes 73% of the total annual load of phosphorus and 56% of the total load nitrogen.

The most immediate courses for management of North Lake is the treatment of runoff from the Murdoch University Veterinary Farm. However, patterns in algal growth and results of sediment exchange experiments strongly indicate that the internal loading of phosphorus and nitrogen is sufficient to maintain the eutrophic state of North Lake. In the long term, if the lake fails to improve after treatment of drain water, dredging or chemical treatment to remove phosphorus may become necessary.

Publication Type: Thesis (Honours)
Murdoch Affiliation: School of Environmental and Life Sciences
Supervisor: Ho, Goen and Humphries, Bob
URI: http://researchrepository.murdoch.edu.au/id/eprint/38914
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