Rising sea temperatures and increasing eutrophication alter the look and function of tropical reef ecosystems. Heat and high nutrient levels cause coral-dominated reefs to shift towards communities dominated by macroalgae, sponges, and benthic cyanobacterial mats (BCMs). These shifts have detrimental effects on ecosystem services, such as biodiversity, coastal protection, and fisheries. To predict the responses of coral reefs to environmental threats of high temperature and nutrient levels, the food web structure and species interactions of marginal reef communities in natural mesocosms are studied. Marine lakes found in Raja Ampat, Indonesia, are natural mesocosms suitable to study the effects of environmental change on reef communities. The major benthic groups (corals, algae, sponges, and BCMs) and their trophic and competitive interactions are assessed among gradients of temperature and nutrient levels consisting of marine lakes and open water reefs. First, trophic interactions between the benthic groups are quantified in aquarium incubations. Second, the metabolic fluxes of benthic communities are quantified with in situ incubations. Third, competitive interactions and growth rates of the benthic groups are recorded on 2D-photographed transects and 3D-modelled permanent quadrants. Last, food web structure and connectance are compared between communities by stable isotope analysis. These results will be incorporated into a model to predict the effects of environmental change at an ecosystem level and help identify strategies to mitigate anthropogenic stressors.
We provide a disciplinary and multidisciplinary research programme aimed at advanced understanding of environmental problems and advanced training of PhD candidates in this field.