亚热带城市河流底栖动物完整性评价——以流溪河为例

根据2016年前、后汛期及枯水期流溪河14个断面底栖动物群落组成数据(4门8纲22目52科94属103种),采用底栖动物完整性指数(B-IBI),首次对亚热带地区河流进行健康评价。经筛选(32个候选指标),流溪河B-IBI体系由5个核心指标(总生物量,敏感类群个体%,EPT、摇蚊和耐污类群单元数)组成,评价标准为:健康3.24,亚健康3.24—2.43,一般2.43—1.62,差1.62—0.81,极差0.81,评价结果为:健康位点数占14.3%、亚健康50.0%、一般21.4%、差14.3%、无极差。总体上,B-IBI值反映流溪河上游健康状况较好,以EPT分类单元数和敏感类群个体%贡献最高,下游健康状况恶化,以耐污类群单元数贡献最高。此外,上游支流健康状况要优于上游干流,而下游则情况相反。相关性分析显示,B-IBI值与溶解氧呈极显著正相关(P0.01),与电导率、氨氮、总氮和总磷呈显著负相关(P0.05),反映流溪河当前健康水平受水体污染影响严重。核心指标与环境因子间CCA分析显示,前2主轴对环境因子解释度达68.1%,且对上、下游及干、支流有明显的梯度划分,说明所建B-IBI在流溪河有较高适用性。对比不同温度带研究结果发现,B-IBI体系受人为干扰和水体污染影响更加明显,体现其评价功能不受地理区域影响。

Ecological assessment of a subtropical urban river based on the Benthic-Index of Biotic Integrity-Liuxi River

Based on the community structure of macrozoobenthos in the Liuxi River, which was surveyed during the pre-flood, latter flood, and dry seasons in 2016, the Benthic-Index of Biotic Integrity (B-IBI) was first used to evaluate the ecological health of this subtropical river in China. Overall, 103 species of zoobenthos were identified, belonging to four phyla, eight classes, 22 orders, 52 families, and 94 genera. Selected from 32 candidate metrics, the B-IBI system of the Liuxi River was constructed using five key indicators, including total biomass, individual percentage of sensitive groups, and taxa number for EPT, Chironomidae, and tolerant groups. The health criteria were > 3.24, healthy; 3.24-2.43, sub-healthy; 2.43-1.62, fair; 1.62-0.81, fair-poor; < 0.81, poor. The proportion of healthy sites was 14.29%, sub-healthy sites 50.0%, good-fair sites 21.42%, fair sites 14.29%, and there were no poor sites. In general, the assessment of the B-IBI for the Liuxi River suggested that 1) the environments in the headwaters and upper stream had healthy conditions, with EPT taxa and sensitive groups contributing the most to B-IBI scores, and 2) the environments in the lower reaches deteriorated seriously, with the taxa number of tolerance groups contributing most to the B-IBI scores. The correlation analysis showed that the B-IBI values were positively correlated with dissolved oxygen (P < 0.01), but negatively correlated with electric conductivity, ammonia, total nitrogen, and phosphorous (P < 0.05). Canonical correspondence analysis showed that the first two axes of the B-IBI indicators explained 68.1% of environmental variables, which clearly distinguished the upstream from downstream, as well as main stems and tributaries in terms of health. Our results suggested that the B-IBI system constructed in this paper could objectively and precisely reflect the ecological health and water quality of the Liuxi River. In addition, compared with the subtropical climate zones where the Liuxi River is located, the influences of urban development and human disturbances on the B-IBI were much more serious, indicating the applicability of the B-IBI in different geographical regions.