The central theme of this thesis was the search for ecologically meaningful ways to
quantify the relationships between the biota and ecosystem processes. This thesis
investigated whether a "functional group" approach, that characterised the fauna
according to similarities in their activities, could be successfully employed to
quantifiably link species' performance to important ecosystem processes.
Initially the abilities of traditional "trophic" and "bioturbatory" categories to
characterise the estuarine macrobenthic fauna and discriminate between estuarine
sites were examined. This thesis determined that the perceived inter-site similarity
within an estuary varied according to the function being investigated and that the
apparent associations between abiotic factors and biotic assemblages were also
heavily influenced by the choice of functional classification.
This study provided strong evidence that links between the macrobenthos and
abiotic factors were most easily detected if the species were grouped according to
their bioturbatory abilities. Thus, attempts to model the contribution of the estuarine
macrofauna to sediment mixing throughout an estuary were pursued in preference
to modelling trophic group distribution.
This thesis identified limitations of existing "bioturbation" categories and hence,
developed a novel classification system that incorporated species' activity rates,
magnitude and location within the sediment.
Strong evidence was found that estuarine macrobenthic communities should be
treated as two separate assemblages: one shallow assemblage occupying surface
and near surface layers, and one deep assemblage with the ability to exploit the
sediment at greater depths. The two separate assemblages displayed different
associations with the environmental factors examined in this study.
By developing new functional groupings of species' behaviour, and treating shallow
and deep assemblages as separate entities, this thesis was able to estimate the
contribution of the biota to sediment mixing and successfully develop and validate
generic predictive models of functional group distribution within the Tamar/Plym
estuarine system. Since the functional groups themselves convey information about
the magnitude of their effect and the sediment horizons impacted, this thesis
represents an important advance in our ability to predict biological contribution to
sediment mixing processes in estuarine ecosystems.
Date of Award | 2008 |
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Original language | English |
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Awarding Institution | |
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Sponsors | Plymouth Marine Laboratory |
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Linking biotic activity to ecosystem functioning
Sanders, J. (Author). 2008
Student thesis: PhD