Multiple anthropogenic stressors in Indonesia : Impacts on metabolism, spatial distribution and community composition of coral reef organisms

Abstract

Coral reefs in Jakarta Bay (JB) and along the outer Thousand Islands off Jakarta in Indonesia, one of the largest megacities worldwide, are facing extreme environmental pressure by multiple anthropogenic stressors. In this thesis, spatial impacts of stressors as well as physiological responses to pollutants and reduced water quality were determined on coral reef communities. A spatial patchwork of differentially degraded reefs was found along the islands as a result of localized anthropogenic effects rather than regional gradients. Surfactants and diesel-borne compounds are common local pollutants and caused metabolic stress in the fish Siganus guttatus and the scleractinian coral Pocillopora verrucosa. Additional elevated temperature increased stress responses and the complexity of stressors interactions. Furthermore, reduced water quality in JB may control abundance and metabolism of dominant soft corals. This thesis demonstrates that anthropogenic stressors in the JB/Thousand Islands reef complex interact closely. Considering the importance of coral reefs for local livelihoods, improved coral reef management is necessary.