米埔標誌：斑點魚郎

米埔 - 最新資訊

米埔保護區資料更新

Special Thanks to SGS Hong Kong Laboratory.

Introduction

Mai Po Nature Reserve forms part of the largest wetlands in Hong Kong, occupying an area of 381 ha. The diversity of wetland habitats at Mai Po and around inner Deep Bay are internationally important because they serve both as a wintering and a stopping-over site for some 100,000 migrating migratory waterbirds every year.

The traditionally operated shrimp ponds (gei wai) at Mai Po are managed by WWF Hong Kong to maintain the cultural value of the site, provide habitat for wildlife, particularly roosting and feeding ground for waterbirds. For example each winter, the gei wai are completely drained in turn to harvest the fish stock inside the ponds. At this time, up to 1,600 wintering waterbirds, such as herons, egrets and the endangered Black-faced Spoonbill Platalea minor, may be attracted into a single gei wai to feed on small non-commercial fish and shrimp in the shallow water at the bottom of the pond.

The traditional management of the Mai Po gei wai requires that water inside the pond be exchanged with that in Deep Bay during the spring and neap tides each month. This practice would allow juvenile shrimp and fish larvae from the Bay to be stocked into the pond as well as allow clean water from Deep Bay to enter the pond. However, the declining water quality in Deep Bay due to increasing pollution loads from the Shenzhen River and the Yuen Long / Kam Tin catchments are now exerting a serious threat to the aquatic environment at Mai Po and Inner Deep Bay, especially to the Mai Po gei wai.

As a result, WWF Hong Kong has a routine water quality monitoring in Mai Po Nature Reserve, to provide early indication of any adverse changes to the water quality in the gei wai within the Reserve. If such changes were found, then the Reserve would quickly implement any necessary actions to protect the Reserve and its wildlife.

Areas of particular concern include the problem of organic pollution affecting the survival of shrimps and fish in the gei wai and that of trace metal in the water and soil accumulating in animals, such as fish, oysters and shrimps. In addition, WWF Hong Kong has been creating rain-fed ponds in Mai Po to provide a freshwater habitat for wildlife. Over the past few years, these ponds have become a popular roosting place for many waterfowl especially during winter. However, the droppings from many waterfowl using these ponds causes a deterioration of the water quality of the ponds and this may eventually affect the health of the waterfowl.

We have compared the water and sediment quality of the gei wai and rain-fed ponds with the existing guidelines stated in Water Quality Objectives (WQO). For the analysis work, WWF Hong Kong would like to acknowledge SGS Hong Kong Laboratory for their kind technical support in conducting a half-year intensive water quality monitoring programme for the Reserve from June to December 2003.