南海中北部海域秋季浮游细菌和病毒丰度及其影响因子

于南海中北部海域设置20个采样站位, 分别采集各站位5 m、25 m、75 m、150 m和200 m水层海水样品。应用流式细胞仪技术分析了浮游细菌和病毒的生态分布特征, 并对其与环境因子的相关性进行了分析。结果表明, 调查海区浮游细菌和病毒丰度分别为(1.19～151.65)104个mL-1和(1.37～326.70)105个mL-1。5 m和200 m层浮游细菌的平均丰度分别为(54.03 30.87)104个mL-1和( 4.94 4.15)104个mL-1, 浮游病毒丰度则分别为(121.9589.73)105个mL-1和(9.986.54)105个mL-1, 随水深的增加两者丰度基本呈现逐渐下降的趋势。5 m层和25 m层浮游细菌和病毒丰度均表现为北部区域大于南部区域的分布趋势。不同水层浮游细菌和病毒分布的影响因子存在一定差异。5 m层浮游细菌和病毒与磷酸盐显著正相关(P0.05), 说明南海中北部海域表层水存在磷限制。75 m层浮游细菌与硝酸盐、硅酸盐和总有机氮显著正相关, 而浮游病毒的分布则同时受到硝酸盐、硅酸盐、总有机氮和磷酸盐的影响, 说明该区域浮游细菌和病毒受到上行控制效应的影响。水深达到200 m时浮游细菌和病毒的主要限制因子是水温而不是营养盐。浮游细菌和病毒丰度之间在各个水层均极显著正相关(P0.01), 说明浮游细菌作为浮游病毒的寄主, 对浮游病毒的丰度产生较大的影响。

Abundance of bacterioplankton and virioplankton in the central and northern South China Sea in autumn

A cruise was conducted during November 2014, and water samples in 20 stations in the middle-north of the South China Sea were collected at 5 m, 25 m, 75 m, 150 mand 200 m layers, respectively. The distribution of virioplankton and bacterioplankton abundances in horizontal and vertical direction were studied by flow cytometry, and their relationships with environmental factors were also analyzed. The results show that the bacterioplankton and virioplankton densities in the water column were (1.19～151.65)104cellsmL-1 and (1.37～326.70)105 cellsmL-1, respectively. Bacterioplankton abundance at 5 m and 25 m layers were (54.03 30.87) 104 cellsmL-1 and (4.944.15)104 cellsmL-1; the number of virioplankton were (121.9589.73)105cellsmL-1 and (9.986.54)105 cellsmL-1 , respectively. According to the increase of water depth, the number of bacterioplankton and virioplankton both decreased gradually. Horizontal distribution of bacterioplankton and virioplankton show a similar variation tendency. Bacterial and viral abundances in most of the northern area stations were higher than those in the south at 5 mand 25 m layers. Impact factors of bacterioplankton and virioplankton varied at different water layers. Bacterioplankton and virioplankton distributions were positively correlated with phosphate (P0.05) , a limiting nutrient factor in the surface water of the South China Sea. Bacterial distribution was significantly correlated with nitrate, silicate and total organic nitrogen at 75 m, where positive correlations between virioplanktion abundance and nitrate, silicate, total organic nitrogen and silicate were also detected. Correlation between environmental factors and bacterial and viral distributions may demonstrate the existence of top-down control mechanism. Virioplankton was positively related to bacterioplankton, which reflects a closely coupling between viruses and host cell abundance (P0.01).