标准化方法筛选参照点构建大型底栖动物生物完整性指数

Discussion on the standardized method of reference sites selection for establishing the Benthic-Index of Biotic Integrity

依据浑太河流域340个样点的栖息地和水质评价结果,采用标准化方法筛选参照点与受损点,构建大型底栖动物生物完整性评估指数(Benthic Macroinvertebrate Index of Biological Integrity,B-IBI),开展河流健康生物评价研究。标准化方法共筛选出参照点和6个受损点构建B-IBI指数。B-IBI指数包括8个大型底栖动物核心生物指标,涵盖了分类单元、相对丰度、耐污特征、优势类群和功能摄食类群的生物指标。利用构建的完整性指数开展浑太河河流健康评价结果显示,所有样点中"极好"与"好"占24.8%,"一般"占27.8%,"差"与"极差"的占47.4%,表明浑太河健康状况整体上偏差。B-IBI指数分值在参照、测试和受损点间的箱线图分布表明验证结果较为可靠;同时与2009年5月太子河全流域70个样点采用专家经验法构建的大型底栖动物生物完整性指数进行了对比,结果表明两种方法的评价结果一致性较高,健康等级完全一致的占58%,健康等级只相差一个等级的占40.6%。B-IBI与环境要素的回归分析显示,B-IBI指数与栖息地具有较高的直线线性回归关系(R2=0.25,P<0.01),与电导、高锰酸盐指数和氨氮(R2=0.23—0.34,P<0.01)均具有极显著的曲线相关关系。3个水质指标与B-IBI指数的回归方程的拐点分别约为1000μs/cm,5ml/L和1.0mg/L,当3个水质指标低于拐点值时,B-IBI指数表现为显著的下降趋势,当高于拐点值时,B-IBI指数的下降趋势明显减弱。表明高锰酸盐指数和氨氮在从清洁水体下降为III类的过程中,对大型底栖动物生物完整性的影响最为强烈。利用标准化方法筛选参照点构建的大型底栖动物完整性指数及其核心参数具有较好的敏感性,能够指示随人为活动强度增加河流生态系统健康状况的下降,适用于浑太河流域开展河流健康评估研究。

Benthic macroinvertebrate Index of Biological Integrity （B-IBI） was developed of relationships among habitat variables, water quality variables and benthic macroinvertebrate data from 340 sampling sites in the Huntai River for assessment of stream health and standardized reference and impaired sites selection. In this study, 9 reference sites and 6 impaired sites were selected to construct the B-IBI index. Five major benthic maeroinvertebrate metric parameters （i. e. taxonomic composition, relative abundance, pollution tolerance characteristics, dominant groups, and functional feedinggroups） were assessed by applying the B-IBI. The results showed that the Huntai River is highly degraded and loss of biological integrity in which 24.8% of sampling sites were in ＂excellent＂ and ＂good＂ conditions, 27.8% of sampling sites were in ＂normal＂ conditions, and 47.4% of sampling sites were in ＂poor＂ or ＂very poor＂ conditions. The box-plot distributions of B-IBI were highly clustered within the references sites, impaired sites and test sites indicated that the assessment was reliable. Moreover, the resulting B-IBI was highly correlated with the data set of macroinverterbates across 70 sampling sites in the Taizi River in May 2009, with 58% of the total sampling sites graded in the same stream health categories and 40.6% of total sampling sites with one grade difference in stream health. This correlation was employed to check the accuracy of the assessment result between standardized sites selection and ＂ expert option＂ reference sites selection and showed strong consistency between two methods. The regression between the B-IBI and habitat assessment was significant in linear regression （R2 =0.25 ,P〈0.01 ）. And the regressions between the B-IBI and conductivity （Cond.）, permanganate index （CODMn） and ammonia （NH3-N） were also significant in curved regressions （Rz= O. 23-0. 34, P〈 0. 01 ）. According to the regressions, the inflexion values of three water quality variables were around 1,000 μs/cm （ Cond. ）, 5.0mg/L （ CODMn ） and 1.0mg/L （ NH3-N） , respectively. The B-IBI decrease sharply when these water quality variables are lower than the inflexion value and decrease minimally when the concentration is higher than the inflexion value. The CODMn and NH3-N would have significant effect on the stream health and macroinvertebrates communities when the concentration is higher than the III grade of Chinese surface water standards. The sensitivity of the B-IBI and its component metrics to environmental stressors supports the use of this index for monitoring ecological conditions in streams in the Huntai River.