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Title: Understanding human impacts on aquatic ecosystems : quantitative approaches to size-based community indicators
Author: Adams, Georgina
ISNI:       0000 0004 7232 5779
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2015
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Body size is a fundamental property of organisms that underpins the structure and function of aquatic communities. Human impacts such as climate or fishing can significantly alter the size structure of ecological communities. This thesis aimed to understand further the effect of those impacts on properties of size-based indicators in real communities, by examining trends at levels of organisation or scales that have not been studied in detail before. To do this, various quantitative approaches were developed that allowed 1) trends in size-based indicators to be decomposed into contributions of constituent parts, and 2) significance of indicators and trends in indicators to be appropriately assessed. Results revealed important features of community size structure that should be considered when assessing trends in indicators. A study of the response of body size to warming in a diatom community did not support the commonly held idea that reduced body size is a universal response to warming at either the species or community levels. Results further demonstrated that overall community trends in body size are not wholly representative of the responses of the components that made up the community. This was further supported by results from decomposing a size-based fisheries indicator, where the overall trend in the indicator was an average of wildly diverging contributions of both species and geographic locations. The methods developed also allowed finer structure of the size spectrum in the North Sea fish community to be examined, and found empirical evidence of biologically meaningful deviations in the overall size structure over time. Finally, the methods developed for assessing significance provided a useful tool for analysing the components of size-based indicators and their response to human pressures, and offer a solution for detecting significant trends in indicators calculated from trawl survey sampling data that has applications for management of marine systems.
Supervisor: Reuman, Daniel ; Pawar, Samraat Sponsor: Natural Environment Research Council ; Centre for Environment ; Fisheries and Aquaculture Science
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral