Ocean Circulation, Ecosystem, HypoxiA and CoNsequences (OCEAN_HK) Seminar 2020
Organised by Ocean Circulation, Ecosystem, HypoxiA and CoNsequences (OCEAN_HK), the Zoom semiar 'Biogeochemical cycles and benthic-pelagic coupling' was successfully held on 5 August 2020.
In this talk, Prof. Jiying Li of Department of Ocean Science, HKUST, first introduced the dynamic benthic-pelagic biogeochemical couplings in various systems and present recent work that combines field and laboratory analyses with modeling to characterize the geochemistry of water column and sediments, quantify elemental fluxes, transformation pathways and rates, and unravel their fundamental controls. She then examined how dynamics of oxygen and sedimentation regulate sedimentary processes, and how sediments sequestrate carbon and remove nutrients (N and P) from the systems, control nutrient dynamics in the water column, and contribute to consumption of oxygen. Prof. Li also outlined future research avenues and prospects of multidisciplinary collaborations, such as studying the effects of physical processes on sediments transport, interplays of nutrient dynamics and plankton metabolisms, interactions between benthos and sediments, and element and energy flows on ecosystem scales.
Task 3: Marine Ecology
DO (dissolve oxygen) was the key variable shaping the microbiota communities in water and sediment. A hypoxic zone (DO level <2.8mg/L) was observed at the mouth of Pearl River Estuary (PRE), which is close to the coasts of Macau and Hong Kong. The sediment from close to the coastline of Lantau Island in Hong Kong had the least diversity and richness among the sampled Stations, including less DO (1.1 mg/L) and pH, but comparatively higher NH4+ (170.8 µg/kg) and organic content (7.8%) than the other most Stations of PRE. Organic matter in sediment is inversely associated with the bulk density in sediment and DO in seawater, due to the increased colonization of heterotrophic bacteria and oxygen consumption during remineralization of organic matter which further reduced the microbiota. Positive correlations were found between DO and sulfate-reducing bacteria in Desulfococcus and GOUTA19 genera in the sediment of the SCS. Nutrients, salinity and phytoplankton (Chl a) are significantly associated with the microbial community dynamics in seawater and sediment. Correlation analysis found that Fluviicola and Nitrosopumilus genera were significantly positively associated with the nutrients (NO2−, NO3− and SiO32−) in onshore of PRE, but negatively associated with salinity. Nitrosopumilus bacteria consume oxygen and helps to make more hypoxic condition (e.g. less DO) by oxidizing ammonia to nitrite. Low concentrations of perfluoroalkyl substances (PFASs) were not found to exert significant effects on the hypoxia, eutrophication, acidic conditions and microbial structure of PRE compared to other environmental factors. However, the levels of benzophenone-4 (BP-4) decreased with increasing water temperature and acidic conditions and ethylhexyl methoxycinnamate (EHMC) was degraded more easily from estuary waters to the open sea waters. Moreover, water temperature positively related to hypoxic conditions. The results concluded that the hypoxic and acidic conditions enhanced the degradation of contaminants such as BP-4. Offshore of the SCS had more oxygen-producing bacteria (Synechococcus, Prochlorococcus, and photosynthetic cyanobacteria) than the onshore sites. Positive correlations were observed among per- or polyfluoroalkyl acids (PFAAs), nutrients, and Chl a, suggesting that they share the same source, potentially being carried by Pearl River to the estuary and increased amounts of nutrients facilitated the eutrophication by reproduction of phytoplankton in PRE. This further supported by their inverse relationships with salinity because concentrations of PFAAs, EHMC, nutrients and Chl a will gradually decrease from onshore to offshore when salinity is increasing. Finally, the hypoxic condition, eutrophication, acidification and different contaminants including, organic UV-filters and PFASs concurrently decreased from estuary to open seawater of the SCS.
Ocean Circulation, Ecosystem, HypoxiA and CoNsequences (OCEAN_HK) Workshop 2020
OCEAN_HK members have gathered in Nansha on 8-9 Jan 2020 to have a 2-day workshop. All Co-Principal Investigators and Co-Investigators have presented their most updated research progress with other members. Some young scientists also shared their new scientific results with peers.
Invited guests from National Sun Yat-sen University, Sun Yat-sen University, Southern University of Science and Technology, etc. have also shared a lot of new ideas in the workshop. It was a scarce opportunity to have an interactive and in-depth scientific discussion with all brilliant scientists.
Symposium on OCEAN_HK 2019
“Symposium on Ocean Circulation, Ecosystem, HypoxiA and CoNsequences (OCEAN) 2019” was successfully held on 13 and 14 June at The Hong Kong University of Science and Technology.
This symposium is organized by the OCEAN-HK Theme-based Research Scheme project, and co-organized by HKUST School of Science, Department of Mathematics, Department of Ocean Science and Division of Environment and Sustainability.
The objective of this symposium is to have focused scientific presentation, discussion and synthesis about our theme “Ocean Circulation, Ecosystem, HypoxiA” in Hong Kong water. This symposium also is a scarce platform for high-level discussion and exchange in Ocean Science in Hong Kong.
This symposium was attended by more than 70 scientists, professionals, specialists from Hong Kong, Mainland China, United States, Norway, Sweden and other countries/ regions, in addition with representatives from government units.
OCEAN_HK Project Meeting
Project Coordinator, Co-Principal Investigator and Co-Investigator had a project meeting at HKUST IAS building on 2 May 2019. Each Co-PI/ Co-I reported their work progress and new result. This meeting provided a platform for portential collaboration between different groups. Project office also reported the progress on symposium preparation and some project administration to all Co-PIs/ Co-Is.
International Workshop on Ocean Sustainability in the Great Bay Area of the Pearl River Delta
International Workshop on Ocean Sustainability in the Great Bay Area of the Pearl River Delta has been held at HKUST on 28-28 Jan 2019, and was co-sponsored by the China Council for International Cooperation on Environment and Development (CCICED) Special Policy Study on Ocean Governance, TRS project OCEAN_HK, and State Key Laboratory of Marine Environmental Science (Xiamen University)
The workshop bought the CCICED experts, scientists from OCEAN_HK project and stakeholders from Hong Kong and Macau government together. It will serve to overview the ocean governance progress and practices in the Great Bay Area of the Pearl River Delta with special focus on the Hong Kong area. Participants was expected to assess the experiences and lessons learned from the regional practices of ocean governance and to identify challenges in the region. Along with other regional cases and the general practices in China at large, this workshop would attempt to generate important policy related recommendations to both the central government of China and regional governments such as the Hong Kong SAR.
The workshop has programmed participants to visit Siu Ho Wan Seawage Treatment Plant. Representatives from Environmental Protection Department, Agriculture and Fishery Conservation Department, Civil Engineering and Development Department, Drainage Services Department, and Hong Kong Observatory also reported their current status, challenges, and perspectives on sustainable development of Hong Kong related to ocean development, environment, ecosystem and climate changes. CCICED members also had an in-depth discussion on developing significant science-based ocean governance concept to the new initiative to be launched as a major development of high technologies in the Guangdong-Hong Kong-Macao Bay Area.
OCEAN_HK Poster Session in XMAS-IV
The Fourth Xiamen Symposium on Marine Environmental Sciences (XMAS-IV, http://mel.xmu.edu.cn/conference/4xmas) will be held in Xiamen from Jan 6th to 9th, 2019. OCEAN_HK Team displayed 13 posters during the symposium.
There are more than 800 participants from more than 50 countries attended XMAS-IV . It was a precious chance and effective platform for trained students to display their science work and for the achievements of the project OCEAN_HK to be communicated and shared amongst the research community.
Visit Research Vessel “Xiang Yang Hong 03”
Project Co-ordinator, Porf. Jianping Gan, led his team to visit Xiang Yang Hong 03 on 8 Jan 2019.
Xiang Yang Hong 03 is a research vessel with length 99.8m, 17.8m width, 5.6m draught and 15,000 nautical mile cruising endurability. It is a world class research vessel with integrated observation technique reaching world class level, and it is managed undre Third Instititute of Oceanography, Ministry of Natural Resources.
The scale of Xiang Yang Hong 03 is very impressive, and it is remarkable advancement of marine science expedition in China.
Task 4: Coupled Shelf-Bay Circulation Dynamics
We conducted observational and numerical modeling studies to investigate the coupled circulation between Mirs Bay to the east of Hong Kong and the adjacent shelf sea during an upwelling season. We synthesized long- and short-term observations to characterize the circulations in the bay-shelf region and identified their linkage. We utilized a three-dimensional circulation model with realistic topography and forced with time-dependent wind, tides and lateral fluxes from the nearby shelf and Pearl River to identify the processes and physics in the circulation of the coupled bay-shelf regime.
Based on the validated model, we found that a strong northeastward coastal upwelling jet persisted over the shelf with highly variable topography outside the bay, and a strong upslope current occurred where the topography was sharply convex. This upslope current intruded into the bay in the lower layer (>10 m) as a cold-water stream. An anti-cyclonic circulation formed inside the bay with a seaward outflow in the upper layer (<10 m). Our momentum and vorticity analyses showed that a southwestward along-isobath pressure gradient force over the convex isobaths off the bay intensified that bay-ward intrusion. Negative relative vorticity advection from the jet was responsible for this pressure gradient force. The anti-cyclonic circulation and elevation fluctuation inside the bay were determined by the interaction between the intruding shelf current and the trough inside the bay, and they were also baroclinically modulated by the intrusion of denser shelf waters. Wind over Mirs Bay intensified exchange flow across its entrance, but suppressed the inside anti-cyclonic circulation.
Figure1: (a-c) The simulated horizontal velocity (m s-1) vectors on the shelf neighboring Mirs Bay and averaged over the (a) upper (0-10 m), (b) intermediate (10-20 m), and (c) lower (20 m – bottom) layers. The velocity (m s-1) component in the cross-isobath direction is illustrated in (d-f). A positive value in (d-f) represents a shoreward velocity component crossing the isobath. The color scale in (a) is larger than that in (b) and (c). The contour lines are the 30 m, 25 m, 20 m, and 15 m isobaths from the shelf towards the bay. The cruise transects and time-series observations for Station MBT are illustrated in (a).
TRS On-site Review of Funded Project by RGC panel
An one-day on-site review visit conducted by the RGC Monitoring and Assessment (M&A) Panel Members has been held on 23 October 2018 in The Hong Kong University of Science and Technology.
Project team scheduled a series of presentations and discussion sessions to reported the most updated finding and achievement to the panel, the programme involved participants from senior researchers to junior research students who have take part in this project, so as to cover all voice from all levels.
The day started with presentations by Project Coordinator, Prof. Jianping Gan, and Co-Principal Investigators, Prof. Minhan Dai, Prof. Hongbin Liu) and Prof. Paul Lam. Then follow with prsentation by younger researchers, Dr. Naomi Geeraert and Dr. Zhongming Lu. The panel also had time to intereact with research staff and students during the poster session and discussion session. The day was end with a in depth disucssion session between Project Coordinator, Co-Principal Investigators and Co-Investigators.