长江口及其邻近海域富营养化状况评价

Assessment of Eutrophication Status in the Changjiang River Estuary and Adjacent Sea Areas

通过对长江口及其邻近海域生态环境参数的背景值(20世纪50-60年代)和现状值(1997-2003年)的比较,应用欧盟“综合评价法”对长江口及其邻近海域的富营养化状况进行了评价。结果表明,长江向长江口海域输送总氮和总磷通量持续增大,长江口及其邻近海域无机氮浓度持续增高而硅浓度持续下降,并由此导致N/P/Si比值的显著变化;该海域叶绿素a浓度持续增大,浮游植物群落结构也发生了显著变化;该海域底栖生物种类和生物量都大大减少,底层水低氧区面积也显著扩大;该海域赤潮事件无论是规模还是频率都大大增加,藻类毒素DSP/PSP贻贝传染事件也时有发生。综合以上4类评价因子的评价结果得出结论:长江口及其邻近海域属于富营养化“问题海域”,即有充分证据表明,人为的富营养化已经对长江口及其邻近海域的海洋生态系统造成不良干扰。

Based on the comparison between the background values and status quo values of ecological and environmental parameters in the Changjiang River estuary and adjacent sea areas, the eutrophication status in the sea area was assessed by using the OSPAR-Comprehensive Procedure. It is shown from the assessment results that （1） both the TN and TP fluxes discharged from the Changjiang River to the Changjiang River estuary sea area increased continuedly, the DIN concentration in the sea areas increased continuedly, and the Si concentration decreased continuedly, which resulted in the significant changes in N/P/Si ratios; （2） the chlorophyll a concentration in the sea areas increased continuedly, and the significant changes in community structure of phytoplankton occurred; （3） the species and biomass of benthos declined greatly, and the bottom oxygen-poor water area increased significantly; （4） the range and occurrence frequency of red tide events in the sea areas increased greatly, and the algal toxic infection events of mussel were frequently found in the sea areas. It is concluded from the assessment results of 4 kinds of assessment factors that the Changjiang River estuary and adjacent sea areas have been classified as problem area with regard to eutrophication, namely, the anthropogenic eutrophication has made an adverse disturbance to the marine ecosystem in the Changjiang River estuary and adjacent sea areas.