基于B-IBI指数的温榆河生态健康评价

The assessment of river health using Benthic-Index of biotic integrity for Wenyu River

基于温榆河底栖动物和水质采样数据,采用底栖动物完整性指数(B-IBI)方法,进行温榆河生态健康评价,并探求河流水质与B-IBI指数的相关性。通过分布范围、判别能力以及相关性分析等,确定研究区B-IBI指标体系,包括总分类单元数、总生物量、优势分类单元个体相对丰度、敏感类群分类单元数、生物指数和粘附者个体丰度6个指标。根据参照点25%分位数确定温榆河底栖动物完整性评价标准,即B-IBI>1.821为健康,1.366—1.821为亚健康,0.910—1.366为一般,0.455—0.910为较差,0—0.455为极差。结果表明,温榆河27.3%河段处于健康状态,9.1%河段处于亚健康状态,13.6%河段处于一般状态,50%河段处于较差和极差状态。河流水质与B-IBI指数的相关系数为-0.549,表明生物指标作为水体评价的补充指标十分必要。

By applying the Benthic-Index of Biotic Integrity （B-IBI） to benthic macro-invertebrate and water quality data, we evaluate the health of Wenyu River and explore the relationship between water quality and B-IBI. Macro-invertebrate and water samples are collected from 22 river sites, where 4 are unimpaired or minimally impaired sites and 18 are impaired sites. We mainly consider twenty candidate metrics of macro-invertebrate and twelve water quality indexes. These twenty candidate metrics are total number of taxa, EPT taxa, Crustacea and Mollusca taxa, hironomidae taxa, total biomass, dominant taxa individual relative abundance, the first three dominant taxa individual relative abundance, Trichoptera individual relative abundance, Ephemeroptera individual relative abundance, Tubificida individual relative abundance, Chironomidae individual relative abundance, Hirudinea individual relative abundance, Crustacea and Mollusca individual relative abundance, number of sensitive taxa, tolerant taxa individual relative abundance, sensitive taxa individual relative abundance, biomass percentage of tolerant taxa, biomass percentage of sensitive taxa, BI index and clinger individual relative abundance and twelve water quality indexes are dissolved oxygen （DO）, temperature, PH, total suspended solids （TSS）, conductance, CODmn, BOD5, total nitrogen （TN）, total phosphorus （TP）, ammonia nitrogen （NH3）, nitrate （NO2） and nitrite （NO2）. The main results are given as follows： 1 ） Among these 20 cross box-plots of candidate metrics between reference site （ unimpaired sites） and impaired sites,12 metrics have the higher IQ （interquartile ranges, IQ t〉 2）. They are total number of taxa, EPT taxa, Crustacea and Mollusca taxa, total biomass, dominant taxa individual relative abundance, the first three dominant taxa individual relative abundance, Ephemeroptera individual relative abundance, number of sensitive taxa, sensitive taxa individual relative abundance, biomass percentage of tolerant taxa, and clinger individual relative abundance. 2） Since BI index does not follow the normal distribution, we use Pearson＇s correlation coefficient to evaluate the relationship between the remained 11 metrics. Metrics that are strongly correlated （r 〉 O. 75 ） indicate the overlapped information, and we choose one of them as a surrogate.. Based on the above analysis, the B-IBI of Wenyu River including total number of taxa, total biomass, relative abundance of the first dominant taxa individuals, number of sensitive taxa and relative abundance of clinger individuals, are constructed. 3 ） We use 25% percentile of B-IBI value in reference sites to determine the criteria of health ranking and divide the distribution range below 25% percentile into 4 quarters. The criterion for the benthic macro-invertebrate in Wenyu river is B-IBI 〉 1. 821, 1. 366--1. 821, 0. 910--1. 366, 0. 455--0. 910 and 0--0. 455, which are corresponding to health, sub- health, fair condition, poor condition and very poor condition, respeetively. 4） We find that 27.3% of the river reaehes are in health condition, 9.1% are in sub-heahh condition, 13.6% are in general condition, and 50% are in poor and very poor conditions. 5 ） The correlation coeffieient between B-IBI value and water quality of Wenyu River is -0. 549, which indicates that the biological index, such as benthic macro-invertebrate, should be taken into account for water environmental assessment.