The reef’s physical structure is the result of a mutually beneficial relationship between the coral and a species of algae called Symbiodinium. The algae gain refuge among the calcium carbonate shells of the coral and in return provide large amounts of energy to their animal host. Environmental stress in the form of increased ocean temperatures, acidification or nitrogen levels can cause the coral to expel the algae, resulting in coral bleaching. The ‘Environmnental stresses in a scleractinian coral-dinoflagellate symbiosis: a genomics approach’ (ESCOR) project studied the effect of environmental stress on corals at both the molecular and functional levels. This was done using state-of-the-art techniques such as polymerase chain reaction (PCR) and secondary ion mass spectrometry (NanoSIMS). The aim was to determine the level of expression of a number of key genes involved in regulating the relationship between Symbiodinium and coral in response to different climate change scenarios. Researchers also measured the change in uptake and transport of materials in response to man-made impacts such as high levels of dissolved inorganic nitrogen. Sampling was conducted at the northwest and southeast ends of the Australian Great Barrier Reef. Initial findings suggested significant molecular regulations in both the algae and coral host in response to increased temperature with alteration to the expression of key genes. The coral’s response to increased nitrogen levels was examined using NanoSIMS analysis, which provided fresh insights into the role of ammonium in the symbiotic relationship. This also enabled researchers to quantify the ability of the algae to fix nitrogen compared to their coral host cells following exposure to ammonium-enriched seawater. New data was provided by the ESCOR project on the expression of key genes and the metabolic changes occurring in corals during stress conditions. This research provided new insight into the complex mechanisms behind coral sensitivity to environmental changes. Techniques developed by the consortium can help identify the effects of stressors at the sub-lethal level, the point at which mitigating a response would have the greatest potential for positive outcome. Furthermore, the results will enable scientists and decision makers to develop more effective conservation and management policies and programmes.
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9 August 2020