OCEAN_HK (https://ocean.ust.hk/) is under the Theme-based Research Scheme (TRS) funded by Hong Kong Research Grants Council. The team of this interdisciplinary project consists of researchers from five local universities, two Mainland institutions and one Taiwanese university, as well as international collaborators from the USA.  The objective of OCEAN_HK is to conduct diagnosis and prognosis of intensifying eutrophication, hypoxia and the ecosystem consequences around Hong Kong waters by conducting coupled physical-biogeochemical-pollution studies. We investigate the status, causes, consequences and trends of eutrophication and hypoxia around Hong Kong (HK) in the vicinity of the Pearl River estuary (PRE), in order to derive a new scientifically based cost-effective water treatment/protection strategy and scheme. Derived from repeated field measurements, laboratory experiments and coupled physical-biogeochemistry-pollution modelling, this presentation highlights our recent achievements on pursuing scientific understanding of eutrophication, hypoxia and acidification in the Pearl River Estuary, Hong Kong waters and adjacent shelf. The new findings on the concerned issue are illustrated in four interlinked aspects of a) sources and sinks of nutrients and biogeochemical controls; (b) ecosystem dynamics and biological controls; (c) pollutant and ecosystem impacts; (d) physical controls, synthesis, and future trends.