Abstract：
Bacterioplankton underpin biogeochemical cycles and an improved understanding of the patterns and drivers of variability in their distribution is needed to determine their wider functioning and importance. Sharp environmental gradients and dispersal barriers associated with ocean fronts are emerging as key determinants of bacterioplankton biodiversity patterns. We examined how the development of the Celtic Sea Front (CF), a tidal mixing front on the Northwest European Shelf affects bacterioplankton communities. We performed 16S-rRNA metabarcoding on 60 seawater samples collected from three depths (surface, 20 m and seafloor), across two research cruises (May and September 2018), encompassing the intra-annual range of the CF intensity. Communities above the thermocline of stratified frontal waters were clearly differentiated and less diverse than those below the thermocline and communities in the well-mixed waters of the Irish Sea. This effect was much more pronounced in September, when the CF was at its peak intensity. The stratified zone likely represents a stressful environment for bacterioplankton due to a combination of high temperatures and low nutrients, which fewer taxa can tolerate. Much of the observed variation was driven by Synechococcus spp. (cyanobacteria), which were more abundant within the stratified zone and are known to thrive in warm oligotrophic waters. Synechococcus spp. are key contributors to global primary productivity and carbon cycling and, as such, variability driven by the CF is likely to influence regional biogeochemical processes. However, further studies are required to explicitly link shifts in community structure to function and quantify their wider importance to pelagic ecosystems.
摘要：
浮游细菌是生物地球化学循环的基础，需要对其分布变化的模式和驱动因素有更深入的了解，以确定其更广泛的功能和重要性。与海洋前沿相关的尖锐环境梯度和扩散障碍正在成为浮游细菌生物多样性模式的关键决定因素。我们研究了凯尔特海锋(CF)的发展，西北欧大陆架上的潮汐混合前沿会影响浮游细菌群落。我们对从三个深度（表面，20米和海底)，在两次研究航行中（2018年5月和9月），涵盖CF强度的年内范围。分层额叶水域温跃层上方的社区明显分化，并且与爱尔兰海混合水域中温跃层下方的社区和社区相比，多样性较少。这种影响在9月份更加明显，当CF处于峰值强度时。由于高温和低养分的结合，分层区域可能代表浮游细菌的压力环境，更少的类群可以容忍。观察到的大部分变异是由Synechococcusspp驱动的。（蓝细菌），在分层区域内更丰富，并且已知在温暖的贫营养水域中茁壮成长。Synechococcusspp.是全球初级生产力和碳循环的关键贡献者，因此，CF驱动的变异性可能会影响区域生物地球化学过程。然而,需要进行进一步的研究，以明确地将群落结构的变化与功能联系起来，并量化它们对中上层生态系统的更广泛重要性。
