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Benthic diatom communities of coastal marine environments in the Windmill Islands, Antarctica

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Cunningham, LK (2003) Benthic diatom communities of coastal marine environments in the Windmill Islands, Antarctica. PhD thesis, University of Tasmania.

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Abstract

This project examined the effects of ecological factors and anthropogenic
contaminants on benthic diatom communities near Casey Station, in the Windmill
Islands, Antarctica. Preliminary sampling indicated significant compositional
differences occurred between diatom communities in bays immediately adjacent to
Casey Station and those more distant. Subsequently, a more detailed appraisal of
spatial variability in benthic diatom communities was undertaken. Significant
differences in community composition were demonstrated for all scales examined,
however, increased distances between samples typically corresponded to increased
dissimilarity.
The influence of environmental factors on spatial variability was assessed using
direct gradient ordination techniques. Grainsize, particularly the mud content,
accounted for the majority of variation in diatom abundances explained by the
measured environmental variables. Differences in light availability, water depth and
grain-size explained 60% of the variation in community composition observed
between locations. The remaining 40% of the variation in diatom community
composition remains unexplained; potential causes include freshwater input, and
chemical contamination.
A preliminary analysis of temporal variability in benthic diatom communities from
the Windmill Islands is presented. Seasonal, short-term (l00's of years) and long term
(1000's of years) changes in community composition were examined at several
locations. Temporal variability of the diatom communities within Brown Bay was
also assessed, in conjunction with metal and Pb210 data. Within one core, a shift in
community composition was detected subsequent to the onset of chemical
contamination. Some changes in species abundance exceeded the natural variability
observed in control cores, and thus were attributable to chemical contamination. Relationships between diatom abundances and concentrations of different metals
within Brown Bay were examined using direct gradient analyses. Approximately
50% of the variation in the diatom community composition was related to metal
concentrations. Further clarification of the interactions between metals, sediment
grain-size and diatom community composition would be required prior to the
development of predictive models. Direct gradient analyses also demonstrated a
weak correlation between diatom community composition and hydrocarbon
distribution.
Manipulative field experiments were used to demonstrate that the composition of
diatom communities can be influenc.ed by both metal and hydrocarbon contaminants
at concentrations comparable to levels produced by station activities. This supports
the conclusion that anthropogenic contaminants are responsible for some
compositional differences observed in diatom communities, both within Brown Bay
and between Brown Bay and reference locations.

Item Type: Thesis (PhD)
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Date Deposited: 19 Nov 2013 23:15
Last Modified: 15 Sep 2017 01:06
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