Abstract: Based on integrative model and supported by Geographic Information System (GIS),the pollution level and potential ecological risk of heavy metals in surface water and surface sediment in Kaozhou Bay were assessed synthetically with chemical and ecological methods,and the results of different methods were compared.The pollution indexes of heavy metals in the water of the whole bay were lower than 0.5 in dry season and even lower than 0.2 in flooding season,which indicated that the contents of heavy metals were low and insufficient to affect the ecological system in the bay.In dry season,the potential ecological risk indexes of heavy metals in the surface sediment of most part of the bay varied from 20 to 70 with the dense area occurring in the west and northwestern part,with sediments slightly affected by heavy metals.While in flooding season,the risk indexes in the whole bay were lower than 20 and would not affect the ecological system.As for ecological assessment,food organism level in dry season in most part of the bay ranged from grade 2 to grade 3 with the dense area occurring in the northwestern part,the mouth of the bay and the estuary of Jilong River,whose levels reaching grade 4,indicating rich food organisms in these parts.In flooding season,the dense area was distributed in the middle part of the bay and the coastal area along Wangjingzhou with the level of grade 4～5,and followed by the mouth of the bay with the level of grade 4,while in the west and northwest of the bay the levels were the lowest with grade 1～2.Because of the low level of heavy metal pollution,the environmental factors,such as water temperature,salinity and nutrients,had turned into the major factors which affected the ecological system in the bay.Comparing for the various assessment methods,synthetic assessment was an effective approach to describe the pollution of heavy metals and forecast the impact on the ecological system.

Key words: Tree species diversity, Tropical montane rain forest, Xishuangbanna