A modeling tool to evaluate regional coral reef responses to changes in climate and ocean chemistry

Abstract

We developed a spreadsheet-based model for the use of managers, conservationists, and biologists for projecting the effects of climate change on coral reefs at local-to-regional scales. The COMBO (Coral Mortality and Bleaching Output) model calculates the impacts to coral reefs from changes in average SST and CO 2 concentrations, and from high temperature mortality (bleaching) events. The model uses a probabilistic assessment of the frequency of high temperature events under a future climate to address scientific uncertainties about potential adverse effects. COMBO offers data libraries and default factors for three selected regions (Hawai'i, Great Barrier Reef, and Caribbean), but it is structured with user-selectable parameter values and data input options, making possible modifications to reflect local conditions or to incorporate local expertise. Preliminary results from sensitivity analyses and simulation examples for Hawai'i demonstrate the relative importance of high temperature events, increased average temperature, and increased CO 2 concentration on the future status of coral reefs; illustrate significant interactions among variables; and allow comparisons of past environmental history with future predictions.

Modelling coral calcification accounting for the impacts of coral bleaching and ocean acidification

“…Other researchers have modelled the temperature response of corals with cubic polynomials (e.g. Edmunds, 2005;Buddemeier et al, 2008). We found that the additional constraints imposed on the form of α aid in the interpretation and comparison of experimental results.…”

“…The new model presented here can be viewed as extending and bringing together existing models of coral growth that include responses to temperature and ocean acidification (Silverman et al, 2009;Buddemeier et al, 2008) that have different foci and limitations. The approach of Buddemeier et al (2008) consisted of a high-resolution model in time, focusing on specific locations and species, while that of Silverman et al (2009) considered large-scale trends and takes a global view.…”

“…The approach of Buddemeier et al (2008) consisted of a high-resolution model in time, focusing on specific locations and species, while that of Silverman et al (2009) considered large-scale trends and takes a global view. This new model brings together the low-level detail of species-level responses and adaption to local environments that underpins the COMBO model (Buddemeier et al, 2008), and by comparing across species and locations it distills the trends and patterns that emerge on a global scale (Silverman et al, 2009).…”

“…As a consequence, it is difficult to relate risk of bleaching given by the DHW metric to calcification rates (e.g. Buddemeier et al, 2008). Furthermore, there are a number of ways to estimate the thermal thresholds that underpin the DHW metric, and little consensus exists as to which approach is best suited to a given location.…”

“…Studies and models (e.g. Guinotte et al, 2003;Buddemeier et al, 2008;Silverman et al, 2009) that account for both the impact of ocean acidification and warming have not, as yet, mechanistically linked these two processes to calcification rates.…”