马里亚纳海沟浮游病毒垂直分布及动态变化

为探究马里亚纳海沟浮游病毒生态特征的垂直变化规律,本研究于2015年12月采集马里纳亚海沟表层到8727m共六层水样,对浮游病毒丰度,浮游细菌丰度,微微型浮游植物丰度以及裂解性浮游病毒生产力进行了分析。流式细胞技术分析结果表明,马里亚纳海沟各层浮游病毒丰度范围为1.27×105—1.93×106VLP/mL,其中表层丰度最高,随后逐渐降低,最低值出现在3699m处。而在深渊海沟区域内病毒丰度略有上升,最深处8727m病毒丰度为2.85×105VLP/mL。马里亚纳海沟裂解性浮游病毒生产力变化范围为2.86×104—4.21×105VLP/(mL·h),其垂直分布呈现出与浮游病毒丰度相似的趋势,生产力最高值出现在表层,随后在相对较低的水平变动,而在深渊海沟区域内随深度略微上升, 8727m处生产力为4.08×104VLP/(mL·h)。同时本文根据假定的研究区域浮游病毒平均裂解量及宿主平均有机物质含量计算出病毒导致的细菌死亡率(VMM)以及相应的有机碳和有机氮释放量,其中VMM变化范围为1.59×103—2.34×104cells/(mL·h),8727m处VMM为2.27×103cells/(mL·h)。而每小时病毒导致的细菌死亡数在总细菌数量中占比在8727m处最低,为4.6%,这表明浮游病毒在深海环境中的侵染活性相对较低,可能由于极端环境下浮游病毒多以溶源状态存在。在深渊海沟内部观察到相对较高的浮游病毒丰度以及相对较低的病毒生产力水平,表明该水域浮游病毒死亡率较低,这或许与海沟内温度极低且环境相对隔离有关。各层浮游病毒丰度及生产力与环境因子间相关性分析结果表明,浮游病毒丰度和生产力均与浮游细菌丰度表现出较高的正相关关系(P0.05),同时病毒生产力也表现出与温度的显著正相关性,表明浮游病毒的活跃程度主要依赖于宿主细胞的浓度以及海水温度。

VERTICAL DISTRIBUTION AND DYNAMIC VARIATION OF VIRIOPLANKTON IN THE MARIANA TRENCH

To investigate the vertical variation of virioplankton and viral production in the Mariana Trench, six water samples were collected in December 2015 at the Mariana Trench from 0 to 8727m. The abundances of virioplankton, bacterioplankton, picophytoplankton, and lytic viral production were analyzed. The results show that the virioplankton abundance in the Mariana Trench ranged 1.27×10⁵-1.93×10⁶VLP/mL. The abundance of the surface layer was the highest and then decreased gradually with depth and the lowest at 3699m. The abundance of virus in the hadal trench area increased slightly. The virus abundance in the deepest layer at 8727m was 2.85×10⁵VLP/mL. The lytic viral production in the Mariana Trench varied from 2.86×10⁴ to 4.21×10⁵VLP/(mL·h), and its vertical distribution showed a similar trend to virioplankton abundance:the highest production in the surface, followed by a relatively low level of variation, but a slight increase in the hadal trench area; the production at 8727m was 4.08×10⁴VLP/(mL·h). At the same time, the virus-mediated bacteria mortality (VMM), and the related organic carbon and organic nitrogen release were calculated based on the assumed burst size and mean organic matter content of host cells. The VMM variation range was 1.59×10³-2.34×10⁴cells/(mL·h), and the VMM at 8727m was 2.27×10³cells/(mL·h). The bacterial loss caused by virus per hour at 8727m was 4.6%, being the lowest. This indicates that the virioplankton has a relatively low infection activity in a deep-sea environment, which is probably due to the high rate of lysogenic infection of virioplankton in an extreme environment. The relatively high virus abundance and relatively low viral production rates observed in the hadal trench area indicated low viral decay rates, which might be correlated with the very low temperature and isolated environment. Correlation analysis between virus abundance-and-production and environmental factors in each layer showed that both virioplankton abundance and production were positively correlated with the bacterioplankton abundance (P<0.05), and so did the viral production with temperature, which indicates that the activity of virioplankton depends mainly on the host cell concentration and seawater temperature.