长江流域浮游植物群落的环境驱动及生态评价

Environmental Driving Factors and Assessment on the Aquatic Ecosystem of Periphytic Algae of Six Inflow Rivers in Yangtze River Basin

浮游植物常用于水生态健康评价,国内已有大量相关的研究开展,但多数研究涉及范围较为局限.从流域尺度开展浮游植物调查,在长江源区至入海口的干流重点区域、八大一级支流和三峡支流共布设了139个样点进行样品采集.在长江流域一共鉴定出浮游植物7门82属,其中隐藻门、蓝藻门和硅藻门为优势类群.首先对长江流域各区域的浮游植物群落组成进行分析,使用LEfSe分析各区域显著富集的物种,然后基于CCA探究了长江流域各区域浮游植物群落和环境因子之间的关系.在流域尺度上,广义线性模型显示TN和TP与浮游植物密度显著正相关,TITAN分析则揭示了环境指示种和它们对应的最适生长阈值范围.最后,分别从水生生物和水质两个方面对长江流域各区域进行评价,尽管两个方面的评价结果不一致,但基于随机森林算法综合所有指标进行评价,能够得到长江流域全面且客观的生态评价结果.

Phytoplankton is frequently utilized in the assessment of water ecological health,and a great number of related studies have been conducted in China;however,most of them are limited in scope.A phytoplankton survey was carried out at the basin scale in this study.A total of 139 sampling sites were set up in crucial locations of the main stream,from the Yangtze River's source region to the estuary,as well as the eight primary tributaries and the Three Gorges'tributaries.In the Yangtze River Basin,phytoplankton was found in seven phyla and 82 taxa,with Cryptophyta,Cyanophyta,and Bacillariophyta being the dominant species.To begin,the composition of phytoplankton communities in various sections of the Yangtze River Basin was studied,and LEfSe was utilized to identify highly enriched species in different regions.The association between phytoplankton communities and environmental factors in different sections of the Yangtze River Basin was then investigated using CCA.The generalized linear model demonstrated that TN and TP were strongly positively linked with phytoplankton density at the basin scale,whereas TITAN analysis identified the environmental indicator species and their corresponding optimal growth threshold range.Finally,the study assessed each Yangtze River Basin Region in terms of biotic and abiotic factors.Although the results of the two aspects were incongruent,the analysis of all indicators using the random forest method can yield comprehensive and objective ecological evaluation results for each section of the Yangtze River Basin.