| Summary: | Coral reefs are the oceans' most diverse and productive ecosystems. However, reef ecosystems are also one of the most endangered habitats on Earth, due to their fragility and exposure to both abiotic and biotic stressors. Understanding the impacts that environmental stressors have on the coral cellular mechanisms is integral for determining the coral health status. It also has important implications for persistence of coral reefs under rapidly changing climatic conditions. In this PhD study, I implemented a transcriptomic approach to investigate the response of the coral A. millepora to biotic and abiotic challenges in an attempt to better understand the molecular mechanisms underlying specific and general coral stress responses. In Chapter 2, I focus on the coral response to lipopolysaccharidae (LPS) challenge in order to better understand innate immunity in corals. By using differential gene expression analysis and comparative genomics, I provide evidence that the coral response to LPS challenge resembles that of vertebrates. In addition, the effect of pre-exposure to high pCO2 conditions on the response to LPS challenge was investigated where, as in vertebrates and Drosophila, hypercapnia impaired the innate immune response. The results obtained support the hypothesis that coral immunity is likely to be compromised by near-future ocean acidification conditions and that cumulative stressors may predispose corals to increased disease. In Chapter 3, I investigate the molecular mechanisms underlying the coral response to hypo-osmotic stress, again through application of transcriptomic approaches. Previous studies on corals and other marine invertebrates have enabled identification of a group of genes that respond to a wide range of stressors, whereas distinct sets of genes respond to specific stressors. Results described in this chapter illustrate that common responses to environmental stressors in Acropora sp. include up-regulation of genes involved in macromolecular and oxidative damage, while up-regulation of ...
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