CANCOR
Carbon And Nitrogen fixation of CORal reefs in response to environmental factors
Tropical coral reefs are surrounded by oligotrophic waters yet show high productivity. Several key reef primary producers (e.g. corals, macro and turf algae) and substrates (e.g. reef sands, dead coral and rocky surfaces) exhibit associations with N2-fixing microbes. To evaluate the functional significance of such associations for primary production and growth, this research project aimed at quantifying both C and N2 fixation of key reef primary producers, evaluating biogeochemical coupling between the C and N cycle and the influence of environmental factors on these processes.
Results
The project involved 5 PhD students and several master students and resulted in multiple peer-reviewed papers. Although the funding period is now finished, analyses and publication of the last datasets are still underway. Key findings of the project indicate that: (a) benthic community changes and/or structural habitat loss will result in changes of inputs of fixed nitrogen to the reef ecosystem, (b) global stressors such as ocean warming and acidification have a high potential to influence symbiotic N2 fixation in scleractinian corals, and (c) high coral-cover areas of the reef are not only important for their primary productivity but also for their associated N2 fixation, with areal rates competing with those of flat sandy areas. In the face of climate change, these results are important as they show that modifications in biogeochemical nitrogen cycling on reefs may derive both from direct changes in diazotrophic communities’ structure and function, and from altered availability of benthic substrates favorable to these microorganisms.
