Water quality degradation at the Mai Po Marshes Nature Reserve (Hong Kong)with reference to nutrient enrichment

There are increasing threats from environmental degradation to wetland habi tats all over the world and the internationally important wetland ecosystem of the Mai Po Marshes Nature Reserve in the north-west quadrant of Hong Ko ng (P.R. China) is no exception. Polluted tidal water is channelled from th e Deep Bay to the traditional shallow shrimp ponds (gei wais), giving rise to growing concerns of potential pollution impacts on the biodiversity and productivity of the valuable wetlands. The present study assessed the pollu tion status by nutrient contents and faecal bacterial counts of the waterwa ys which drain the gei wais and evaluated the spatial and temporal variatio ns. Biochemical oxygen demand, total nitrogen, ammoniacal nitrogen, total p hosphorus, orthophosphate phosphorus and faecal bacteria counts were genera lly lower in the channel waters from the middle part of the Marshes than th ose of the southern and/or northern ends, indicating a distinctive spatial pollution pattern across the Marshes.