| Summary: | Coral reefs are one of the most diverse and complex ecosystems on the planet and provide incomes, food, and important ecosystem services for hundreds of millions of people. However, reefs are in global decline and are changing from highly diverse and topographically complex ecosystems dominated by coral species to species-poor and structurally simple ecosystems dominated by macroalgae. The reason of this decline is complex but can be attributed to multiple local stressors such as overfishing, marine pollution and declining water quality, and global stressors such as global warming and ocean acidification product of anthropogenic activities. Corals and algae compete intensely for space, light and nutrients in coral reefs, and this competition is a structuring and shaping process which determines the abundance of both groups of species. Therefore, the general aim of this thesis is to explore experimentally and descriptively the dynamics between corals and macroalgae in coral reefs from three approaches. The first approach focuses on the temporal variability of coral-algal interaction and its implications for coral mortality in different reef habitats. The second study explores the spatial variability of coral-algal interactions and coral health at the local and regional scales within a terrestrial gradient of influence. The third study addresses the potential effects of ocean acidification on competitive mechanisms utilised by algae during coral-algal competition and explores coral-algal competitive outcomes under different levels of ocean acidification. This study was carried out in Heron Island and Keppel Islands, in the southern Great Barrier Reef, Australia. Thesis (PhD Doctorate) Doctor of Philosophy (PhD) Griffith School of Environment Science, Environment, Engineering and Technology Full Text
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