Coastal eutrophication is caused by excessive nutrient loading which stimulates phytoplankton blooms when physical, chemical, and biological conditions are favorable. It may lead to harmful algal blooms (HABs) and hypoxia (or “dead zones”, where dissolved oxygen is generally below 2 mg/L), both of which threaten the ecosystem. Coastal eutrophication has been a global environmental issue for decades, yet its persistence reflects the scientific and socio-economic complexities involved in alleviating the problem.

The coastal waters around Hong Kong are also affected by persistent and increasing eutrophication. This deteriorating situation may increase the frequency of HABs, expand the area of hypoxic zones and lead to other ecosystem disruptions and worse of all, offset the environmental improvements achieved through the costly Harbour Area Treatment Scheme over the last decade. Eutrophication/hypoxia in Hong Kong waters is primarily caused by the ecosystem’s responses to the increasing nutrient discharge from the Pearl River and local sewage effluent. Meanwhile, increasing discharge of organic pollutants also modulates the biogeochemical pathways and ecological consequences and it further increases the severity of eutrophication/hypoxia. Highly variable oceanic currents transport the nutrients in the interactive river-estuary-shelf (RES) waters around Hong Kong, which undergo complex coupled physical-biogeochemical processes and modulate eutrophication/hypoxia. To date, these key processes have not been investigated in a comprehensive manner in our RES waters, and they remain largely unresolved in similar ecosystems elsewhere in the world. Understanding the full spectrum of intrinsic coupled physical, biogeochemical, and pollution processes in eutrophication is crucial to predicting and mitigating the impacts of eutrophication, and it remains a huge scientific challenge regionally and globally.

The intellectual merit of the proposed project is that, by adopting a global and local perspective and by conducting an interdisciplinary study with world-class methodology, we will investigate holistically the coupled physical-biological-chemical processes in this interactive RES system, and thereby develop tools for diagnosing and forecasting eutrophication/hypoxia. We will develop a novel, state-of-the-art marine monitoring system by conducting interdisciplinary mapping and time-series measurements, from which we will further develop a novel coupled physical-biogeochemical-pollutant modelling system. Our ultimate goal is to identify the factors driving the increasing eutrophication and hypoxia, and to provide analytical tools and a scientifically-based strategy for stabilizing or even reversing eutrophication and hypoxia and for ensuring the overall sustainability of the marine environment in Hong Kong. The research topics are covered by four interlinked tasks to determine: (1) sources and sinks of nutrients and their biogeochemical controls, (2) ecosystem dynamics and biological controls, (3) pollutant and ecosystem impacts, and (4) physical controls, synthesis, and future trends in the RES waters.

Theme-based Research Scheme

The Theme-based Research Scheme (TRS), launched in 2010 by the Research Grants Council, aims to focus academic research efforts of the UGC-funded universities on themes of strategic importance to the long-term development of Hong Kong, namely Promoting Good Health, Developing a Sustainable Environment, Enhancing Hong Kong’s Strategic Position as a Regional and International Business Centre and Advancing Emerging Research and Innovations Important to Hong Kong.