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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
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

Item Type: Thesis - Honours
Authors/Creators:Banks, J
Keywords: metal pollution, soft-sediment assemblages, direct effects, indirect effects, metal tolerance
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