Marine Ecology Enhancement Fund (MEEF)

Assessing the ecological impacts of anthropogenic activities on the coastal wetlands in Hong Kong from the optical properties of sedimentary dissolved organic matter.
This project aims to assess the ecological impact of anthropogenic activities (e.g., sewage, fuel oil, and microplastic pollution) on the sediments of Hong Kong coastal wetlands (e.g., mangroves, seagrass meadows, and tidal flats), by monitoring the optical and biochemical properties of sedimentary dissolved organic matter (DOM) in the coastal wetlands. Using the most advanced and rapid fluorescence spectrometer, the study will trace the source of DOM—an indicator of ecosystem health—in the sediment. In addition, by combining the carbon and nitrogen stable isotopes, chemical and physical bulk properties of DOM and the socio-economic parameters, the ecological impact of anthropogenic activities (e.g., sewage, fuel oil and microplastic pollution) on the sediments in the coastal wetlands of Hong Kong will be also evaluated. The results will provide a theoretical basis for predicting and regulating the material cycle in the coastal wetlands, as well as formulating policy on the conservation and management of the Hong Kong coastal wetland ecosystem.

Objectives of the Project
Hong Kong has a long coastline supporting a variety of coastal wetlands (e.g., mangroves, seagrass meadows, and tidal flats). These coastal wetlands provide multiple functions, such as sustained biodiversity, fisheries nursing, shoreline protection, tourism and education. Under the background of global warming and national carbon peak and carbon neutral policies, coastal wetlands are also considered as a natural way to sequestrate carbon. Although they occupy only 0.5% of the global seafloor area, they fix ~50% of the global oceanic carbon. Therefore, the conservation of coastal wetlands is very important.
As an international metropolis, Hong Kong has frequent human activities and urban construction, which likely affect the environment of coastal wetlands significantly, especially the composition of organic matter in sediments. Sewage, microplastics, and even fuel oil pollution can all affect the health of coastal wetlands. However, it is challenging to assess how these anthropogenic activities affect the environment and nutrient cycle of coastal wetlands. This has hindered the efforts of government, academia, and industry in coastal wetland conservation. Therefore, scientific research is needed to develop a rapid and efficient diagnostic approach. This will not only provide insight into the differences in organic composition across coastal wetlands, but also offer an opportunity to trace the source of anthropogenic organic pollution.
Dissolved organic carbon (DOM) in coastal wetland sediments is an effective indicator of the composition of organic matter. Industrialization and urbanization have led to a large input of allochthonous DOM in the coastal environment, further complicating the composition and properties of DOM. This makes DOM an ideal indicator for assessing anthropogenic impacts on coastal wetlands. The development of three-dimensional excitation-emission matrix (3D-EEM) fluorescence spectroscopy has allowed us to measure the composition of sediment DOM in a few minutes without complex sample preparation.
Four important coastal wetland areas in Hong Kong (Deep Bay, North Lantau, South Lantau, and Tolo Harbour) will form our study area. The proposed project has the following objectives.
Objective 1: To monitor the physicochemical properties and DOM content of different coastal wetland sediments.
Objective 2: To monitor the optical properties of DOM in coastal wetland sediments and to develop a 3D-EEM method to trace anthropogenic inputs and calculate their concentrations semi-quantitatively.
Objective 3: To monitor the spatial and seasonal characteristics of DOM in different wetland sediments.
Objective 4: To assess the relationship between coastal wetland sediment DOM and socio-economic indicators such as surrounding population density and urban construction.
Objective 5: To assess the ecological value of coastal wetland sediments in the carbon and nutrient cycle of Hong Kong coastal areas, and to provide decision support and a baseline for the government and related stakeholders.

Sampling map for the MEEF project in Hong Kong. Study wetlands are represented by yellow dots. The red circle indicates that we collected sediment samples from only mangroves and tidal flats; the blue circle indicates that we collected sediment samples from mangroves, tidal flats and gei wai; and the green circle indicates that we collected sediment samples from mangroves, tidal flats, and seagrass meadows.

(a) Seagrass meadows in Tung Chung Bay; (b) Seagrass meadows, tidal flats and mangroves in Tung Chung Bay; (c) The airport construction project across from Tung Chung Bay; (d) Seagrass sediment cores from Tung Chung; (e) The airport construction project, seagrass meadows and mangroves in Tung Chung Bay.

(a) Mai Po Nature Reserves; (b) Tida flats in Mai Po Nature Reserves; (c) Sample collecting in Mai Po; (d) Field work in Mai Po.