Sandy surface sediments of tidal flats exhibit high microbial activity due to the fast and deep-reaching transport of oxygen and nutrients by porewater advection. On the other hand during low tide, limited transport results in nutrient and oxygen depletion concomitant to the accumulation of microbial metabolites. This study represents the first attempt to use flow-through reactors to investigate virus production, virus transport and the impact of tides and season in permeable sediments. The reactors were filled with intertidal sands of two sites (North beach site and backbarrier sand flat of Spiekeroog island in the German Wadden Sea) to best simulate advective porewater transport through the sediments. Virus and cell release along with oxygen consumption were measured in the effluents of reactors during continuous flow of water through the sediments as well as in tidal simulation experiments where alternating cycles with and without water flow (each for 6 h) were operated. The results showed net rates of virus production (0.3–13.2 × 106 viruses cm−3 h−1) and prokaryotic cell production (0.3–10.0 × 105 cells cm−3 h−1) as well as oxygen consumption rates (56–737 μmol l−1 h−1) to be linearly correlated reflecting differences in activity, season and location of the sediments. Calculations show that total virus turnover was fast with 2 to 4 days, whereas virus-mediated cell turnover was calculated to range between 5–13 or 33–91 days depending on the assumed burst sizes (number of viruses released upon cell lysis) of 14 or 100 viruses, respectively. During the experiments, the homogenized sediments in the reactors became vertically structured with decreasing microbial activities and increasing impact of viruses on prokaryotic mortality with depth. Tidal simulation clearly showed a strong accumulation of viruses and cells in the top sections of the reactors when the flow was halted indicating a consistently high virus production during low tide. In conclusion, cell lysis products due to virus production may fuel microbial communities in the absence of advection-driven nutrient input, but are eventually washed off the surface sediment during high tide and being transported into deeper sediment layers or into the water column together with the produced viruses.
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机译：由于通过孔隙水平流快速而深入地输送氧气和养分，潮滩的沙质表面沉积物显示出高的微生物活性。另一方面，在退潮期间，有限的运输会导致营养物质和氧气的消耗，从而导致微生物代谢产物的积累。这项研究是首次尝试使用流通式反应器来调查病毒的产生，病毒的运输以及潮汐和季节对可渗透沉积物中的影响。反应堆中充满了两个地点（德国瓦登海的斯皮科罗格岛的北海滩地点和施皮克罗格岛的后屏障砂滩）的潮间带沙子，以最好地模拟平流孔隙水在沉积物中的传输。在连续流过沉积物的过程中，以及在潮汐模拟实验中测量了病毒和细胞的释放以及耗氧量，潮汐模拟实验中进行了有水流和无水流的交替循环（每次持续6小时）。结果显示病毒产生的净速率（0.3–13.2×10 6 病毒cm -3 h -1 ）和原核细胞产生速率（0.3 –10.0×10 5 细胞cm −3 h −1 ）以及耗氧率（56–737μmoll - 1 h −1 ）线性相关，以反映沉积物的活动，季节和位置的差异。计算表明，总的病毒更新速度为2至4天，而病毒介导的细胞更新计算范围为5-13天或33-91天，具体取决于假定的爆发大小（细胞裂解后释放的病毒数量）14或100种病毒。在实验过程中，反应器中的均质沉积物呈垂直结构，微生物活性降低，病毒对深度的原核生物死亡率影响增加。潮汐模拟清楚地表明，在水流停止流动时，病毒和细胞在反应器顶部会大量积聚，这表明在退潮期间持续产生大量病毒。总之，在没有对流驱动的养分输入的情况下，由于病毒产生的细胞裂解产物可能会为微生物群落提供燃料，但最终在涨潮时会从表层沉积物中冲走，并与深层沉积物一起运输到更深的沉积物层或进入水柱中。产生的病毒。
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