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Ecological impacts of pollution on marine soft-sediment assemblages


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Banks, J (2006) Ecological impacts of pollution on marine soft-sediment assemblages. Honours thesis, University of Tasmania.

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In this study, manipulative laboratory experiments were used to define the mechanisms responsible for observed relationships between heavy metal pollution and soft-sediment assemblages evident from field surveys. Heavily polluted and lightly polluted sites were selected based on previous surveys. Assemblages from the polluted site were 60% less taxonomically rich and 38% less diverse, with a less consistent community composition dominated by a small number of non-indigenous or cryptogenic species. Polychaetes were more abundant; however, 96% of the individuals belonged to a single tolerant species, which consistently dominated samples throughout the survey period. Fluctuations in the abundance of two r-selected, opportunistic species were responsible for a comparatively higher degree of temporal variability in community composition. Manipulative experiments demonstrated the direct effects of pollution. Fauna from the reference site challenged with heavily polluted sediment became more like those normally found at the polluted site, supporting fewer families, derived from fewer taxa. Bivalves and polychaetes were reduced, while crustaceans generally did not survive within the experimental mesocosms irrespective of the extent of pollution they were subject to. Challenging faunal assemblages with sediments either containing the natural fauna or from which fauna were removed tested indirect effects of sediment contamination. Sediments with residents intact led to a greater decline in abundance of potentially establishing fauna, suggesting that some fauna may be excluded from the polluted site because of biotic interactions. This study provides additional evidence that contamination of sediments by anthropogenic pollutants can have serious consequences for the ecology of benthic environments. Importantly, it shows that impacts on fauna may occur by multiple mechanisms.

Item Type: Thesis (Honours)
Keywords: metal pollution, soft-sediment assemblages, direct effects, indirect effects, metal tolerance
Additional Information: Copyright the Author
Date Deposited: 16 May 2012 07:47
Last Modified: 11 Mar 2016 05:54
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