Description and validation of production processes in the coral reef ecosystem model CAFFEE (Coral–Algae–Fish-Fisheries Ecosystem Energetics) with a fisheries closure and climatic disturbance

Abstract

Ecosystem models are well-established tools to investigate the effects of human activities and natural events on marine ecosystems. Recent modeling approaches advocate the integration of physical and biological processes and the coupling of fully-represented ecosystems. Here, we describe a coral reef ecosystem simulation model (CAFFEE) linking reef cover dynamics, benthic and pelagic production and metabolism, detrital pathways and reef formation processes. The model integrates 27 functional groups with coupled two-way trophic and spatial interactions and includes dynamic adjustment of benthic production and consumption processes. The model is validated with a 40 year time series of coral reef field data from Kenyan reefs responding to two disturbances: fisheries closures and a strong thermal anomaly, the 1998 coral bleaching event. The model simulations successfully replicated a number of patterns observed in empirical data, in particular the progression of communities toward greater calcium carbonate deposition following fisheries closure, and the temporal shift to algal-domination after bleaching events. Further validation of the model was garnered from comparisons of emergent model outputs with ecological ratios commonly used to parameterize comparable systems. The model simulations indicate trade-offs among the organic and inorganic (calcium carbonate) processes in coral reefs whereby fisheries closures promote inorganic production and bleaching disturbances favor the organic production processes of the reef.