Variability in Marginal Coral Reef Communities: Implications for Marine Protected Area Management

Abstract

Human impacts on ecosystem health and functioning are an important and increasing problem for marine ecosystems. In order to properly implement effective management techniques for the amelioration or reversal of these impacts, we require accurate information regarding the degree to which these systems vary naturally and what factors primarily drive this variability. Further, understanding where the influence of particular management interventions rank relative to other potential drivers of community structure is important in understanding potential and realised management success. In addition, it is likely that different factors, and therefore different disturbances and management interventions, will have different effects for different ecosystem components. On coral reefs, phase shifts to less desirable macroalgal dominated states are often an indicator of changes in ecosystem functioning driven by either overfishing or nutrient enrichment, or both. N a-take marine protected areas (MPAs) have been shown to reverse some of these effects, but cannot prevent the diffusion of nutrients or sediments across their boundaries. In this thesis, I assess the scale and drivers of variability within benthic communities and fish communities within and outside no-take MPAs in the marginal coral reef habitats of Moreton Bay in subtropical eastern Australia. I focus on the interaction between macroalgae and herbivorous fish and hypothesise that by determining the drivers operating on these components of the marginal reef habitat, I might be able to ascertain the potential for MPAs to elicit community-wide change.