Modeling of degraded reefs in Leyte Gulf, Philippines in the face of climate change and human-induced disturbances

Abstract

Philippine reefs are mega-diverse but, to date, few ecosystem models have been developed to understand their dynamics and functioning. This study assessed the status of reefs in 12 municipalities of Leyte Gulf, Philippines. It is an important fishing ground experiencing degradation and impacts of super typhoons—the strongest one was Haiyan (local name: Yolanda). Empirical and literature data were used to develop Ecopath (trophic) models and Ecosim simulations to evaluate the impacts of reduction and increase in coral cover or productivity on the Leyte Gulf Reef (LGR) ecosystem. Results showed that the LGR’s ecosystem is in a degraded state—dominated by small-medium herbivores and carnivores, with most productivity immediately returned to detritus. In addition, a comparative study of two Ecopath models showed that reduction in the coral cover (e.g., by Super-Typhoon Haiyan) will result in a decline in biomass of many functional groups. Changes in LGR’s productivity (e.g., eutrophication) will also strongly impact most functional groups (e.g., shift to overdominance of herbivores that take advantage of algal growth and extirpation of coral reef-dependent species). Moreover, additional climate-related or human-induced disturbances on the degraded LGR will further decrease the reef’s productivity. Therefore, effective recovery and management of degraded reef ecosystems is needed to sustain the LGR’s productivity (e.g., reef fisheries production).