There has been much interest in the last decade concerning the factors that influence diversity, especially how diversity and ecosystem processes may be linked. This study was based in small, cobble streams in South East Queensland. Its aim was to determine how the diversity and composition of consumers (the grazer guild) is influenced by both the production and composition of benthic algae, at different spatial scales. It also aimed to ascertain whether this response differs among grazer sub guilds with different dispersal capabilities. Ten sites in the Upper Brisbane and Mary catchments were sampled. The sites were selected to provide a range of productivity and composition. Grazers from these sites included snails and elmids, and larval mayflies, moths, and caddisflies. Grazer diversity and composition appeared to be structured by catchment scale influences, but environmental variables also affected which animals colonised patches and microhabitats (cobbles) within catchments. Primary productivity and algal composition could not be separated, with highly productive reaches also having a high cover of filamentous algal taxa. Grazer diversity displayed strongly positive, linear relationships with algal variables at the reach scale. It had a negative relationship with filamentous algae at the cobble scale, and a non-significant hump-shaped relationship with primary productivity. Survey data alone could not separate whether grazers were responding to habitat or food-related drivers, or to variations in productivity. Experimental manipulation of algal variables at the patch scale, using light and nutrients, also could not clearly uncouple the relationship between primary productivity and filamentous algal cover. Once reach scale variation was removed, grazer diversity displayed hump-shaped relationships with algal variables, including algal diversity. Much of this variation was due to patterns in mobile grazers, as sedentary grazers did not respond to algal variation at this scale. The density of the more mobile taxa showed similar patterns to those at the cobble scale (hump-shaped). A second field experiment was carried out in order to further investigate the responses of invertebrates to algal community composition at the cobble scale. Data from all three chapters suggested that as sites shifted to a dominance of filamentous algae, often with an associated increase in GPP, there was also a shift in the grazer community towards more sedentary grazers and away from the more mobile taxa. This also occurred at the cobble scale in the second experiment. The gut analysis and diet studies in the third chapter indicated that while many grazers consumed filamentous algae, it was not assimilated. This suggests that the preferences for sedentary taxa for cobbles and reaches dominated by filamentous algae are likely to be due to some other, possibly habitat-related, factor such as flow or predation refuge. The study provides a rare examination of relationships between primary productivity and consumer diversity in freshwater streams, and finds support for the pattern found in other systems of monotonic relationships of these two variables at large scales and hump-shaped relationships at smaller scales. It emphasises the importance of understanding other, potentially confounding, aspects of communities of producers, and investigates the possible roles of the most important of these (community composition) in structuring consumer communities in the small cobble streams of South-East Queensland.

Environmental sociology and the sociology of scientific knowledge provide a strong theoretical foundation for investigating the role of science in environmental disputes. The field of environmental dispute resolution has built a body of literature, outlining the techniques and practices that underpin the successful resolution of disputes, over controversial environmental issues. However, the literature on dispute resolution has generally neglected the role of science in environmental disputes. This thesis develops a theoretical framework based on concepts from environmental sociology and the sociology of scientific knowledge in order to critically examine the role of science in environmental disputes. In particular, this thesis combines the theory on claims-making from environmental sociology with actor-network theory and the theory on boundary-work from the sociology of scientific knowledge, to analyse the way in which science was involved in the dispute over phasing out extractive dredging from the Brisbane River. Data were collected from qualitative in-depth interviews with key players in the Brisbane River dredging dispute and combined with analysis of relevant documents and newspaper articles. Each of the components of the theoretical framework developed in this thesis contributes to an in-depth analysis of the way in which science was involved in the dredging dispute. The environmental claims-making analysis examines the way in which the claim that extractive dredging was an environmental problem for the Brisbane River was constructed and contested. The actor-network analysis compares the two competing actor-networks that were developed by one of the major concrete companies and by the anti-dredging campaigners. The boundary-work analysis examines the social construction of the science / politics border as an important site of boundary-work, before exploring other related forms of boundary-work within the case study. When combined, these theories highlight the social and political processes that underpin the inherent difficulties associated with applying science to effective environmental dispute resolution. The theoretical framework developed in this thesis highlights the way in which an analysis of environmental claims-making, actor-networks and boundary-work, extends the literature on environmental dispute resolution. This thesis therefore makes a significant contribution to the field of environmental dispute resolution, by illustrating the advantages of drawing on theoretical perspectives from environmental sociology and the sociology of scientific knowledge.