石斑鱼循环水养殖系统微生物群落结构

通过16S rRNA基因片段高通量测序研究了褐点石斑鱼(Epinephelus fuscoguttatus)和东星斑(Plectropomus leopardus)循环水养殖系统水体细菌种群结构。结果显示石斑鱼循环水养殖系统中优势细菌类群为变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)、蓝藻门(Cyanobacteria)、梭杆菌门(Fusobacteria)、厚壁菌门(Firmicutes)和硝化螺旋菌门(Nitrospira)。其中养殖塘、固液分离池、沉淀池和蛋白分离池中主要优势细菌为γ-变形菌纲(Gammaproteobacteria),紫外消毒池和补氧池中则以a-变形菌纲(Alphaproteobacteria)为主,而生物滤池中两者比例接近,均为优势种群。从养殖塘到补氧池细菌多样性指数先降低后升高,生物滤池中达到最高值,之后再次下降至紫外消毒池中达到最低值,补氧池中有所回升。PCoA分析和聚类分析结果表明,养殖水在紫外消毒前后其细菌群落组成有着明显的差异。水质理化指标检测表明,经过净化处理后,循环系统的养殖水溶解氧含量上升,氨氮和亚硝酸盐含量下降并维持在较低的浓度。环境因子与细菌群落结构相关性分析结果表明,磷酸盐、pH、溶解氧和温度等指标可能对细菌群落结构影响相对较大,但未发现两者间有很显著的相关性,这可能与实验样本较少有关。

Analysis of microbial community structure in recirculating aquaculture system for groupers (Epinephelus)

Groupers (Epinephelus) are part of the large fish family Serranidae and are an important marine-cultured genus.In China,groupers have been farmed for over 30 years.Innovative technologies such as recirculating aquaculture systems (RAS) have been developed to improve the efficiency and sustainability of intensive aquaculture.In RAS,bacterial communities that are critical to ecological processes are also closely correlated with diseases in aquaculture.This study aimed to clarify bacterial community characteristics in marine RAS for groupers.Water samples were collected from the following pond types:fish-production,solid-liquid separation,sedimentation,biofilter,protein-separation,ultraviolet-sterilization,and oxygen-increasing.Samples were filtered through 0.22 μm mixed cellulose ester membranes to collect microbial biomass.Bacterial community DNA was isolated from the membrane filters.High-throughput sequencing (Illumina MiSeq) of the V3-V4 hypervariable region in the 16S rRNA gene was used to investigate microbiome structural characters.The results showed that Proteobacteria was the most abundant phylum in the water supply.Other important phyla included Bacteroidetes,Cyanobacteria,Fusobacteria,Firmicutes,and Nitrospira.Principal coordinate analysis and cluster analysis indicated that bacterial composition differed significantly before and after UV irradiation.The most dominant class in the rearing,solid-liquid separation,sedimentation,and protein-separation ponds was γ-Proteobacteria,whereas a-Proteobacteria was the most dominant in the ultraviolet-sterilization and oxygen-increasing ponds.Both classes were dominant in the biological-filter pond.The Shannon diversity index decreased first and then increased,peaking in the biological filter pond before decreasing again to the lowest value in the ultraviolet-sterilization pond,followed by a slight increase in the oxygen-increasing pond.In addition,our analysis of the water environmental parameters showed that dissolved oxygen concentrations increased,whereas NH3 and NO2-concentrations decreased,remaining low after the water was purified.This outcome suggested that the RAS system has an effective water purification process.The correlations between microbial communities and environmental parameters were also investigated with canonical correspondence analysis,which showed that phosphates,pH,dissolved oxygen,and temperature had relatively stronger effects on bacterial communities than did other measured environmental variables.Overall,however,no significant association existed between environmental factors and microbial community structure,possibly due to small sample sizes.