Terrestrial nitrogen flows and their impacts on the nearshore coral reefs of Hainan Island, China

Coral reefs have been seriously degraded in recent years due to climate change and environmental pollution. The discharge of wastewater, as well as the excessive input of fertilizer for agricultural production, resulted in coastal water eutrophication, which drives the degradation of coral reef ecosystems. In the future, these problems may become more urgent because of increasing human activities and climate change, but currently, eutrophication remains underappreciated in coral conservation. The objectives of this thesis are to improve our understanding of (1) the contribution of terrestrial nitrogen to the coastal seawater pollution of Hainan Island, and (2) reducing terrestrial nitrogen pollution to protect the nearshore coral reefs of Hainan Island. To meet these objectives, firstly, I will analyze the impacts of nitrogen pollution on corals, and propose potential strategies to reduce the impact of nitrogen pollution through literature review. Secondly, I will make a connection between the stable isotope analysis of coral skeleton samples and terrestrial nitrogen emission, to reveal how the corals around Hainan have been affected by aquaculture and agriculture development. Third, I will develop a model on aquaculture nitrogen flow including freshwater and marine aquaculture, and a NUFER model with local parameters for nitrogen flow analysis in the past 30 years, which can then be aligned with the detected effects of nitrogen on the corals. Finally, a scenario analysis for optimal management of land-sourced nitrogen will be developed based on the nearshore coral reefs protection goals. The results will be transferred to administrative scales for policy-making.