Plankton diversity and community characteristics in Danjiangkou Reservoir based on environmental DNA metabarcoding

Abstract

为了解丹江口库区浮游生物群落的多样性，本研究于2020年7月在丹江口库区丹库、汉库和入库支流等区域共计9个样点采集水体样品，抽滤并提取总DNA样本后，基于18S和16S分子标记进行单分子实时测序，分别探究真核和原核浮游生物群落的多样性及其群落特征.结果表明：（1）真核浮游生物群落的主要优势类群包括节肢动物、链型植物、绿藻门、硅藻门等；本研究在种水平上鉴定出库区分布广泛且相对丰度较大的物种，包括弯曲隐藻、对蛋白核隐藻和空球藻等，它们与库区化学需氧量密切相关；库区化学需氧量是影响真核浮游生物群落格局的重要环境因子.（2）原核浮游生物群落的主要优势类群为变形菌门；原核生物中相对丰度较大的不动杆菌Acinetobacter是污水污染的指示菌群；群落中起重要作用的Limnohabitans与水体的富营养化密切相关；尽管库区蓝藻相对丰度较低，但与蓝藻关系密切的CL500-29_marine_group和hgcI_clade两类细菌在浮游生物群落中也起着重要作用；原核生物群落中的各类物种均指示丹江口水库的水生态健康存在一定风险，需要加强监测以预防生态环境的恶化.（3）丹江口水库不同区域的浮游生物群落异质性较大，tb-RDA分析显示丹江口的浮游生物群落可以分为丹库型、汉库型和入库支流型，其组间差异要大于组内差异.综上所述，丹江口水库的浮游生物群落具有明显的空间异质性，整个库区的群落结构与水体富营养化、水体有机污染和污水污染等方面相关，需要加强对丹江口库区的水生态监测.;The diversity of plankton community in Danjiangkou Reservoir was investigated, water samples were collected from 9 locations in Danku, Hanku and tributary of Danjiangkou Reservoir in July 2020, based on single molecule real-time sequencing. The 18S and 16S gene were used to explore the diversity and community characteristics of eukaryotic and prokaryotic, respectively. Our study has found several aspects:(1) The dominant species of eukaryotic plankton community belong to Arthropoda, Streptophyta, Chlorophyta and Bacillariophyta. We identified the most widely distributed species with high relative abundance, include Cryptomonas curvata, Cryptomonas pyrenoidifera, Eudorina elegans etc., they all associated with the chemical oxygen demand. Thus, the chemical oxygen demand is the key environmental factor for the eukaryotic plankton community. (2) The dominant species of prokaryotic plankton community belong to Proteobacteria. Acinetobacter with high relative abundance is the indicator of sewage pollution, the important species Limnohabitans is associated with eutrophication. Cyanobacteria showed a low relative abundance, but bacteria associated with cyanobacteria like CL500-29_marine_group and hgcI_clade played a pivotal role in the prokaryotic community. Thus, the bioindicator showed the Danjiangkou Reservoir has risk in ecological health and needs further monitor. (3) The plankton community showed a high heterogeneity in different area, the tb-RDA analysis revealed the plankton community in Danjiangkou Reservoir can be divided into three different types, Danku type, Hanku type and tributary type, the difference was higher between different groups than within group, the roots of the difference between these groups lie in the different richness in the community. To sum up, the plankton community showed obvious spatial heterogeneity in Danjiangkou Reservoir, their community structure is associated with water eutrophication, organic pollution, sewage pollution etc., aquatic ecosystem monitoring should be strengthened urgently.