Use this URL to cite or link to this record in EThOS:
Title: Modelling the dynamics of CaCO3 budgets in changing environments using a Bayesian Belief Network approach
Author: Franco, Chiara
ISNI:       0000 0004 5358 8901
Awarding Body: University of Essex
Current Institution: University of Essex
Date of Award: 2014
Availability of Full Text:
Access from EThOS:
Multiple stressors on reefs are increasing the need for remedial actions to buffer anthropogenic pressure and reduce coral reef deterioration. In order to promote reef framework endurance, it is critical to identify and track down multiple stressor sources. To date, spatial and temporal variations of reef framework carbonate production and erosion have been estimated using carbonate budget assessments; however, these are limited in determining the extent to which various stressors are responsible for altering the budgetary state. This study has developed a Bayesian Network model (CARBNET) to identify and evaluate the extent to which anthropogenic and climatic disturbances affect coral reef budgetary state. The main adavantage of using this type of model for management purposes are related to its ability to adapt to changes and to quantify and incorporate uncertainty. In addition, it provides the opportunity to identify key gaps in the knowledge to inform future research priorities. Multi-scale scenario-based analyses, conducted for the Wakatobi (South-east Sulawesi, Indonesia) and Grenada (Caribbean) reefs, quantified the effects of multiple stressors on the reefal components, providing information on the actual state and possible future state of the framework. Reefs with high branching coral cover were likely to be found in a positive budgetary state, whilst low coral cover and reduced topographic complexity were associated with low carbonate production or negative budgetary state. In clear water settings, degraded reefs, characterised by high turbidity, sedimentation and nutrient concentrations, were likely to be found in a low carbonate production or erosional state. Conversely, high carbonate production was characteristic of reef environments with low turbidity, sedimentation and nutrient concentrations. At regional level, CARBNET predicted that reefs will accrete at a different pace; in Grenada reduced gross production and sustained erosion maintained the budget close to the equilibrium, whilst Wakatobi reefs were defined by positive budgetary states. At local level, reefs at shallow depths were likely to be associated with erosion or low positive net production in both regions, although in Indonesia high carbonate production offsets erosion at all sites. Anthropogenic and climatic disturbances acted synergistically in decreasing carbonate production, and degraded reefs with < 10% hard coral were predicted to be in an erosional state. This result suggests that degraded systems have lowered their tipping point to a net erosion shift. The benthic community was affected by sedimentation and elevated nutrients and changes in the key drivers of carbonate production resulted in reduced net carbonate production. External bioeroder densities were restrained by degradation of the nursery ground, whilst internal bioerosion increased in nutrient enriched waters. Overall, CARBNET is reliable in groundtruthing empirical data and is therefore a valuable addition to the reef management toolbox.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available