大亚湾生态系统对人类活动的响应及健康评价

Responses of the Daya Bay ecosystem to human activities and health assessment

根据1982—2007年共26年的海洋生态调查数据,研究了大亚湾海洋生态环境与生物资源的演变趋势,并利用基于GIS的海湾生态系统健康评价法,对大亚湾海洋生态系统健康状况进行了评价与诊断。结果表明,2007年海水总无机氮(TIN)比1985年增长了338.1%,而活性磷酸盐和硅酸盐分别比1985年降低了88.6%和71.2%,氮磷比则从1.38∶1升高至大于50∶1,营养盐限制因子已由氮限制转变为磷限制,处于中等营养水平。浮游植物在1982—1990年和1994—2007年2个时段之间,硅藻平均减少了10属47种,甲藻平均减少了2属14种,以翼根管藻(Rhizosolenia alata)等为代表的细胞个体较大的藻类,所占比重由1982年的91.0%下降到2007年的19.6%,群落组成趋向小型化。浮游动物生物量总体呈增长趋势,其中湿重生物量2007年比1982年增长87.3%,1998—2007年比1982—1994年常见种减少了15种,球型侧腕水母(Pleurobrachia globosa)、夜光虫(Noctiluca scientillans)等取代部分桡足类成为优势种。底栖动物生物量呈上升趋势,但群落组成变化明显,2000年后底栖甲壳类完全退出优势种的行列。大亚湾游泳生物的渔获率总体呈下降趋势,2007年大亚湾海域渔获率比1985年下降33.9%,鱼类小型化和低值化的趋势十分明显。2007年大亚湾生态系统健康评价所得的健康综合指数平均值为0.64,仍处于"较好"水平,但面临着向"临界"状态转化的危险。大亚湾生态系统正经历着快速的退化过程,本研究结果可为基于生态系统水平的大亚湾综合管理提供科学依据。

Based on the marine ecosystem survey data over 26 years（ from 1982 to 2007）,a study was conducted on the changing trends in the marine ecological environment and biological resources. The assessment and judgment were also conducted on the health status of the marine ecosystem in Daya Bay by applying the GIS- based Marine Ecosystem Health Assessment method. The results indicated that the content of total inorganic nitrogen（ TIN） in sea water in2007 increased by 338. 1% as compared to that in 1985,while the content of phosphate and silicate reduced by88. 6% and 71. 2%,respectively,as compared to that in 1985. The nitrogen to phosphate ratio was increased from1. 38∶ 1 in 1985 to higher than 50∶ 1 in 2007. The limiting nutrient has been changed from the nitrogen limitation to phosphate limitation and nutritional level was in the moderate level. During the two periods of 1982—1990 and1994—2007,among the phytoplankton compositions,an average of 10 genus and 47 species were reduced in Bacillariophyta and an average of 2 genus and 14 species were reduced in Pyrrophyta. Taking Rhizosolenia alata as the representative of the algae whose cells are relatively large,the proportion of these larger algae was reduced from 91. 0% in1982 to 19. 6% in 2007 and the population compositions tended towards miniaturization. The biomass of zooplankton displayed an upward trend. Among which,the wet biomass of zooplankton was increased by 87. 3% in 2007 as compared to that in 1982. It indicated that the ecosystem of the Daya Bay was undergoing a rapid deterioration. This paper also provided the basic data for the ecosystem- based integrative management of Daya Bay in the future.