Re ECF Project: 2013-04

Project Title: Two centuries of nitrogen pollution in Hong Kong’s coastal waters reconstructed from hard-coral and octocoral δ15N records

Applicant: Dr. David Michael BAKER, School of Biological Sciences, The University of Hong Kong

Total Approved Grant: $498,425

Duration: 17/6/2014 to 16/12/2015

Project Status/Remarks: Completed

This project aims to reveal how Hong Kong’s anthropogenic nitrogen pollution in coastal marine habitats has varied over time using nitrogen stable isotope ratio (δ15N) records from hard coral and octocoral skeletons. δ15N records will be obtained for the last 200 years using a combination of cores extracted from century-old massive coral colonies as well as octocoral and hard coral specimens, from Hong Kong, held in global museum collections.

Summary of the Findings/Outcomes:
The southern part of Hong Kong was directly affected by the dissolved inorganic nitrogen (DIN) derived from the Pearl River although domestic sewage and/or manure DIN was also present, but in lesser proportions. The DIN in the eastern waters originated from domestic sewage and/or manure wastes from local and non-local sources. In 1850-1890 the coastal nitrogen pool was already dominated by domestic sewage and/or manure from the Pearl River Estuary (PRE) and other coastal cities, although it was unlikely that the Hong Kong population contributed significantly to this pollution at that time. Local sewage/manure emissions became significant in 1900-1950. In 1989-1994 the emissions of sewage and/or manure reached levels unseen in the last 160 years, most likely in link with the explosive land development that occurred around Tolo Harbour and in the PRE. These emissions were considerably reduced by the late 1990s early 2000s. Results were presented in public lecture and international conference.