Spatiotemporal variations of aquatic ecosystem health status in Tolo Harbor, Hong Kong from 1986 to 2014

摘要

Tolo Harbor is a nearly land-locked body of water located northeast of Hong Kong with only one narrow exit opening to the sea at Mirs Bay. Rapid urbanization accompanied by various anthropogenic stresses caused the frequent occurrences of red tides and associated fish kills, as well as coral deaths, in Tolo Harbor in the late 1980s. To stop "Hong Kong's First Marine Disaster", the Tolo Harbor Action Plan (THAP) has been employed by the Hong Kong Government since 1988. The present study evaluated the spatiotemporal variations of aquatic ecosystem health (AEH) in Tolo Harbor, using monthly monitoring data from 1986 to 2014. The Physical-Chemical-Biological index Triangle Area Method (PCBTAM) was developed to integrate physical, chemical and biological indicators and to identify the dominating factors. The results showed that the AEH of Tolo Harbor would be divided into six periods with two deteriorations and two convalescences. The first deterioration was caused by violent anthropogenic impacts, mainly from urban areas. With the implementation of THAP, the AEH was significantly improved. Later, the harbor underwent a physical index-dominated deterioration. With the rapid decrease of the physical index in 2009, Tolo Harbor came into a stable healthy stage. A spatial gradient of AEH in Tolo Harbor, from bad to good, was: Harbor Subzone Buffer Subzone Channel Subzone. In addition, seasonal component extraction illustrated that the AEH had a bad tendency in most months and the biological index dominated the AEH tendency pattern.