Response of planktonic bacterial abundance to eutrophication and salinization in Lake Bosten, Xinjiang

Abstract

本文以地处干旱地区我国最大的内陆淡水湖——博斯腾湖为研究对象, 于2010年6月, 在博斯腾湖大小湖区共选取23个采样点, 采用表面荧光显微镜直接计数法(FDC)研究了水体中浮游细菌丰度的空间分布规律及其与环境因子的关系.结果表明:博斯腾湖水体中总氮(TN)浓度在0.26-1.45mg/L之间变动(均值0.91mg/L), 已达到中营养和富营养水平.水体的矿化度(TDS)在219-1696mg/L之间变动(均值1125mg/L), 已达到微咸水湖的标准.水体中浮游细菌的丰度变动在1.41×10⁶-4.57×10⁶ cells/ml之间(均值2.89×10⁶ cells/ml), 其峰值出现在人为活动强烈的金沙滩(5^#点)与污染较重的西北部湖区, 最低值出现在盐度最低、污染最轻的河口区(14^#点).聚类分析结果显示, 博斯腾湖的23个采样点可以分为淡水区(FR)和微咸水区(BLR)两个类群.微咸水区的TDS、电导率、盐度、TN、高锰酸盐指数、氯化物、硫酸盐的含量及浮游细菌的丰度均显著高于淡水区, 浮游细菌的丰度与COD_Mn及Cl^-呈显著正相关.浮游细菌的空间分布差异是其作为一个敏感指标对水体富营养化及咸化加剧的响应。;To investigate the response of planktonic bacterial abundance to lake eutrophication and salinization in drought zones, water samples of 23 stations in Lake Bosten were collected in June, 2010.The DAPI-combined epifluorescence direct counting method (DAPI-FDC) was used to identify the spatial distribution pattern of planktonic bacterial abundance and the relationship with the environmental parameters.The results showed that the epilimnetic total nitrogen (TN) concentration in Lake Bosten was ranged 0.26-1.45 mg/L (mean=0.91 mg/L), indicating a mesotrophic and eutrophic level.The concentration of total dissolved solids (TDS) varied from 219 mg/L to 1696 mg/L (mean=1125 mg/L), which indicated that Lake Bosten is a brackish lake now.The abundance of planktonic bacteria was ranged (1.41-4.57)×10⁶ cells/ml (mean=2.89×10⁶ cells/ml), with the higher values appeared in station 5 and other heavily polluted northwest lake regions, and the lowest value appeared in the station 14 located in the estuary.Cluster analysis showed that the 23 sampling stations can be divided into two groups:freshwater region (FR) and brackish lake region (BLR).Compared with freshwater region, the concentrations of TDS, electrical conductivity, salinity, COD_Mn, chloride and sulfate in brackish lake region were significantly higher.The bacterial abundance was significantly positive correlated with COD_Mn and Cl^-.In summary, the spatial distribution pattern of bacterial abundance was a response to different levels of nutrients and salinity in Lake Bosten.Hence the abundance of bacteria was a sensitive indicator reflecting the eutrophication and salinization.