高密度杂交鳢养殖围隔沉积物微生物群落结构垂直变化规律及其与理化因子的关系

为研究高密度养殖系统沉积物微生物群落结构垂直变化规律以及与其对应深度的环境因子的关系,实验选取了华南地区高密度养殖的典型模式——杂交鳢养殖模式,使用PCR-DGGE技术分析了养殖围隔不同深度(0~50 cm)沉积物中的微生物群落结构,同时使用透析装置采集对应沉积物的原位间隙水,并使用微量分光光度法测定间隙水中理化指标,从而探讨高密度养殖系统微生物群落结构垂直变化规律及其与沉积物间隙水理化因子的关系。结果显示,①不同深度的养殖围隔沉积物微生物群落结构通过聚类分析可分3个差异显著的类群:上层(0~6 cm)、中层(7~38 cm)和深层(39~50 cm),其中中层微生物多样性最为丰富。②DGGE电泳共获得46个条带,其中中层条带最多,深层沉积物条带最少。主要微生物类群归属于拟杆菌门、变形菌门、厚壁菌门、疣微菌门和浮霉菌门。③测定的沉积物间隙水中离子,NO_3~--N、SO_4~(2-)-S和Fe~(2+)在沉积物中垂直分布均匀,无明显梯度变化;而NH_4~+-N、NO_2~--N和PO_4~(3-)-P浓度变化较大。NH_4~+-N浓度随深度增加而逐渐增加,在15~18 cm后趋于稳定,为10.98~77.87 mg/L,PO_4~(3-)-P浓度随深度增加而减少,在9~10 cm后趋于稳定,为0.01~0.14 mg/L。④微生物群落结构与理化因子的相关性分析结果表明,NH_4~+-N和PO_4~(3-)-P为影响微生物群落结构垂直分布最大的理化因子组合,其中NH_4~+-N对微生物群落结构垂直分布的影响稍大于PO_4~(3-)-P。NH_4~+-N、PO_4~(3-)-P为影响微生物群落结构的主要理化因子,是杂交鳢养殖系统环境调控的主要控制指标。

Vertical characteristics of microbial community structures and the relationship with environmental factors in sediments of hybrid snakehead aquaculture enclosures

Substrates and electron acceptors essential for microorganisms in aquaculture systems were gradually scavenged in undisturbed sediments according to the efficiency of energy metabolisms along the depth, and the depth-related gradient of biogeochemical properties provided niches for metabolically diverse microorganisms. Vertical characteristic of microbial community structures may reflect the redox condition of the sediment which influences the quality of overlying water. In this study, the vertical microbial community composition of bacteria in high density culture of hybrid snakehead ponds sediment (0-50 cm) was investigated by PCR-DGGE, and the correlation between microbial communities with physicochemical characters of interstitial water were also discussed. Five phylum of bacteria including Bacteroidetes, Proteobacteria, Firmicutes, Verrucomicrobia, Planctomycetes were found. Hierarchial clustering (CLUSTER) and non-metic multidimensional scaling (MDS) analysis showed that microbial community of sediment core could be divided into three groups with significant differences, including the upper layer sediment (0-6 cm), middle layer sediment (7-38 cm) and the deep layer sediment (39-50 cm). Marglef's species richness index and Shannon-Wiener diversity index analysis of the vertical microbial communities indicated that middle layer of sediments had higher microbial diversities, which was similar with the studies of nature systems. The survey of vertical physicochemical characters of interstitial water revealed that NH4+-N concentrations ranged from 10.98 mg/L to 77.87 mg/L, increased with the sediment depth and stabilized after the depth of 15-18 cm, PO43--P concentrations ranged from 0.01 mg/L to 0.14 mg/L, declined with the sediment depth and stabilized after the depth of 9-10 cm, the concentrations of NO3-N, NO2-N, SO42-, Fe2 were relatively stable with little vertical variation. BIOENV/BEST analysis found that NH4 -N was the best environment factor had great impact on the microbial communities, then PO43--P. The two factors are the main environment parameters of quality control in aquaculture water.