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长荡湖流域地处太湖流域上游,是太湖重要水系。流域总面积2 161.46 km2,地势西高东低;流域内水系发达,流向复杂,主要流向为自西向东。由于大规模的农业耕作、淡水养殖以及快速城镇化,导致长荡湖流域氮、磷污染严重。据报道目前长荡湖流域水质恶化,水体受富营养化和蓝藻水华暴发的影响,进而威胁太湖流域生态安全[1-3]。而研究表明入湖河流是湖泊的主要污染来源[4-5]。如黄明雨[6]研究发现洱海入湖河流的氮磷输入是洱海氮磷的重要来源。谢培等[7]基于EFDC模型模拟不同调水方案下千岛湖上游入流和湖周入流CODMn变化对湖内CODMn的影响,发现上游入流是影响千岛湖湖内CODMn的主要因素。因此对长荡湖入湖河流的水生态环境现状进行全面调查研究是十分必要的。
微生物在维持水生态系统的功能和健康中起着至关重要的作用,它既是全球生物地球化学循环的主要驱动者,也是水生态系统中污染物的主要分解者[8]。由于微生物的存在,水中复杂且难降解的有机污染物才得以分解[9],水生态系统才能良性循环。早期微生物检测技术主要是分离培养法,但此种方法存在培养难度大、周期长等缺陷。为弥补传统培养方法的不足,现代分子生物学技术应运而生,常见的分子生物学方法有高通量测序技术、实时荧光定量PCR和宏基因组测序技术等[10-12]。相比第一代DNA测序技术,高通量测序技术在读取样本数量、测序范围和准确性等方面有绝对优势[13],因此被广泛应用于环境样品的16S rRNA、真菌的ITS区和功能基因的分析中[14]。作为水生态系统重要组成部分,微生物的群落结构与多样性受水体理化性质和外部环境因素的共同影响。张烨以南太湖流域长兴港和西苕溪为研究对象,发现季节变化是引起微生物群落多样性差异的主要因素,且微生物群落特征受水体理化因子影响,如入湖河流中水杆菌属(Aquabacterium)、不动杆菌属(Acinetobacter)、脱氯单胞菌属(Dechloromonas)、噬氢菌属(Hydrogenophaga)与NH4+-N呈正相关、DO呈负相关[15]。刘峰等[16]利用高通量测序技术和典范对应分析(CCA)发现汾河与黄河微生物群落组成具有一定的差异,不同环境因子对不同微生物的影响程度不同,pH和溶解氧是汾河入黄口微生物群落结构的主要影响因子。SHANG等[17]基于16S rRNA高通量测序技术发现温度、pH和DO的快速变化可能是影响呼伦湖季节性细菌多样性变化趋势的主要因素。因此研究水体中微生物群落与环境因子的响应关系,对保护水体、维护水生生态系统平衡具有重要意义。
目前长荡湖流域的研究主要聚焦于长荡湖湖体的水质变化、浮游动物和底栖动物的群落结构特征以及沉积物污染风险等[3,18-21]。如王礼权等[18]采用非度量多维尺度变换(NMDS)和冗余分析等方法探讨了长荡湖浮游植物群落结构组成特征及其与环境因子的关系。巫丹等[19]则利用正定矩阵因子(PMF)模型和主成分分析多元线性回归(PCA-MLR)模型对湖泊重金属污染来源进行解析,并评估了长荡湖沉积物重金属的风险等级。但鲜有研究关注长荡湖入湖河流的微生物群落结构特征及与环境因子的关系。鉴于丰水期水中微生物多样性较高且雨量充沛;同时渔业养殖、农业生产活动强,对入湖河流水质造成较大冲击,且较其他季节的污染更为严重[22-23]。因此本研究基于2021年6月长荡湖入湖河流的采样数据,分析入湖河流的微生物群落结构特征以及与环境因子的关系,以期为长荡湖及其入湖河流污染防治和生态修复提供参考。
丰水期长荡湖入湖河流微生物群落结构特征及影响因素
Characteristics of microbial community structure and influencing factors in rivers entering Changdang Lake during the wet season
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摘要: 为探究长荡湖入湖河流微生物群落结构特征及与环境因子的响应关系,在综合考虑主要入湖河流和污染源类型等因素的基础上进行分组,分析入湖河流中溶解氧(DO)、pH、氮磷比(TN/TP)、水温(WT)、总有机碳(TOC)、总氮(TN)和总磷(TP)共7个理化因子的分布特征。基于16S rRNA高通量测序技术并结合Circos、ANOSIM和冗余分析(RDA)等方法分析微生物群落结构特征的差异以及微生物群落与理化因子的关系。结果表明:不同污染类型的长荡湖入湖河流中优势菌门、菌属种类相似,但相对丰度却有所差别。优势菌门包括变形菌门(Proteobacteria)、放线菌门(Actinobacteria)和拟杆菌门(Bacteroidetes);优势菌属包含hgcI clade、CL500-29 marine group、Acinetobacter、Comamonadaceae-Unclassified和Hydrogenophaga。ANOSIM分析表明长荡湖入湖河流微生物群落结构特征与污染源类型相关。冗余分析(RDA)结果显示pH、TP与长荡湖入湖河流的优势菌门呈显著相关(P<0.05);DO、pH与长荡湖入湖河流的优势菌属呈显著相关(P<0.05)。入湖河流的微生物群落在门、属分类水平上具有较高多样性且与污染源类型和理化因子相关,这为长荡湖入湖河流污染防治和生态修复提供了数据支撑。Abstract: To understand the structural characteristics of microbial communities in rivers entering Changdang Lake and the response relationship with environmental factors, this study classified these communities based on the comprehensive assessment of the primary rivers flowing into Changdang Lake and the types of pollutant sources. The distribution characteristics of seven physicochemical indices were analyzed in rivers entering Changdang Lake, including dissolved oxygen (DO), pH, ratio of total nitrogen to total phosphorus (TN/TP), water temperature (WT), total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP). The differences in the structural characteristics of microbial communities and the relationship between microbial communities and physicochemical factors were analyzed based on 16S rRNA high-throughput sequencing technology with Circos, ANOSIM and redundancy analysis (RDA). The results showed that the dominant phyla and genera of microorganisms in rivers entering Changdang Lake with various pollution types were similar, though the relative abundance differed. The dominant phyla included Proteobacteria, Actinobacteria and Bacteroidetes; the dominant genera included hgcI clade, CL500-29 marine group, Acinetobacter, Comamonadaceae-Unclassified and Hydrogenophaga. ANOSIM analyses showed that the microbial community structure characteristics of rivers entering Changdang Lake were related to the type of pollution source. The results of redundancy analysis (RDA) showed that pH and TP were significantly associated with the dominant phylum of bacteria in rivers entering Changdang Lake (P<0.05); DO and pH were extremely associated with the dominant genus of bacteria in rivers entering Changdang Lake (P<0.05). The microbial communities in rivers entering the Changdang Lake were highly diverse at the phylum and genus levels and were correlated with type of pollution sources and physicochemical factors, which provided basis for the pollution prevention and ecological restoration of rivers entering the Changdang Lake.
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表 1 长荡湖入湖河流采样点位置信息
Table 1. Sampling locations in rivers entering Changdang Lake
污染类型 采样点编号 经度 纬度 农村生活污染 W152 119°29′28.67″E 31°37′13.51″N W153 119°29′25.54″E 31°35′1.75″N W154 119°29′9.86″E 31°34′32.47″N W155 119°29′36.09″E 31°32′45.49″N W162 119°35′39.21″E 31°40′28.72″N 农业面源污染 W150 119°31′15.62″E 31°39′31.88″N W151 119°30′30.00″E 31°38′18.13″N 渔业养殖污染 W157 119°33′27.30″E 31°34′43.09″N W159 119°36′34.12″E 31°36′52.48″N W161 119°36′30.18″E 31°39′23.19″N W164 119°32′57.24″E 31°40′17.43″N 表 2 长荡湖入湖河流水体理化指标
Table 2. Physical-chemical indicators of rivers entering Changdang Lake
污染类型 点位 TOC/(mg·L−1) TN/(mg·L−1) TP/(mg·L−1) WT/( ℃) pH DO/(mg·L−1) TN/TP 农村生活污染 W152 2.70 1.98 0.10 24.7 7.9 6.34 19.80 W153 5.90 1.94 0.10 26.9 8.02 6.77 19.40 W154 6.10 1.88 0.10 26.6 7.97 5.63 18.80 W155 6.30 1.83 0.11 27.4 8.02 6.56 16.64 W162 4.10 0.69 0.03 27.1 8.09 7.49 23.00 农业面源污染 W150 3.20 2.71 0.12 24.9 7.72 4.55 22.58 W151 3.00 2.83 0.10 24.5 7.83 5.71 28.30 渔业养殖污染 W157 4.20 0.70 0.04 27.2 8.14 7.28 17.50 W159 4.00 0.72 0.04 27.6 8.02 6.43 18.00 W161 4.00 0.64 0.04 28 8.01 7.89 16.00 W164 3.10 1.79 0.05 26.2 8.03 6.57 35.80 表 3 长荡湖入湖河流微生物Alpha多样性指数
Table 3. Alpha diversity index of microorganisms in rivers entering Changdang Lake
污染类型 点位名称 Ace Chao1 Shannon Simpson Coverage 农村生活污染 W152 5897 5619 8.5312 0.0114 0.974 W153 5733 5537 8.3473 0.0129 0.978 W154 6051 5856 8.6283 0.0101 0.977 W155 6738 6415 8.7358 0.0118 0.970 W162 4443 4243 8.0785 0.0166 0.973 农业面源污染 W150 4134 4125 6.5501 0.0572 0.977 W151 3805 3687 6.8585 0.0376 0.983 渔业养殖污染 W157 3698 3619 7.9462 0.0133 0.973 W159 3733 3606 7.4672 0.0249 0.975 W161 3763 3632 7.3288 0.0339 0.978 W164 4997 4849 8.2801 0.0135 0.973 -
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