Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
Center for Ecology and Evolution in Microbial Model Systems, Linnaeus University, Kalmar, Sweden.
Mol Ecol. 2021 Jul;30(14):3515-3529. doi: 10.1111/mec.15984. Epub 2021 Jun 11.
Phytoplankton comprises a large fraction of the vertical carbon flux to deep water via the sinking of particulate organic matter (POM). However, despite the importance of phytoplankton in the coupling of benthic-pelagic productivity, the extent to which its deposition in the sediment affects bacterial dynamics at the water-sediment interface is poorly understood. Here, we conducted a microcosm experiment in which varying mixtures of diatom and cyanobacteria, representing phytoplankton-derived POM of differing quality, served as inputs to sediment cores. Characterization of 16S rRNA gene of the bacterial communities at the water-sediment interface showed that bacterial α-diversity was not affected by POM addition, while bacterial β-diversity changed significantly along the POM quality gradient, with the variation driven by changes in relative abundance rather than in taxon replacement. Analysing individual taxa abundances across the POM gradient revealed two distinct bacterial responses, in which taxa within either diatom- or cyanobacteria-favoured groups were more phylogenetically closely related to one another than other taxa found in the water. Moreover, there was little overlap in taxon identity between sediment and water communities, suggesting the minor role played by sediment bacteria in influencing the observed changes in bacterial communities in the overlying water. Together, these results showed that variability in phytoplankton-originated POM can impact bacterial dynamics at the water-sediment interface. Our findings highlight the importance of considering the potential interactions between phytoplankton and bacteria in benthic-pelagic coupling in efforts to understand the structure and function of bacterial communities under a changing climate.
浮游植物通过颗粒有机物（POM）的下沉构成了很大一部分垂直碳通量向深海的输送。然而，尽管浮游植物在底栖-浮游生物生产力的耦合中具有重要意义，但它在沉积物中的沉积对水-沉积物界面细菌动态的影响程度仍知之甚少。在这里，我们进行了一项微宇宙实验，其中不同比例的硅藻和蓝藻，代表不同质量的浮游植物来源的 POM，作为输入物被添加到沉积物芯中。对水-沉积物界面细菌群落 16S rRNA 基因的特征分析表明，细菌 α-多样性不受 POM 添加的影响，而细菌 β-多样性沿着 POM 质量梯度显著变化，这种变化是由相对丰度的变化而不是分类群的替代驱动的。分析 POM 梯度上的单个分类群丰度揭示了两种不同的细菌响应，其中硅藻或蓝藻优势类群内的分类群彼此之间的亲缘关系比在水中发现的其他分类群更为密切。此外，沉积物和水群落之间的分类群身份几乎没有重叠，这表明沉积物细菌在影响上覆水中观察到的细菌群落变化方面作用较小。总之，这些结果表明，浮游植物来源的 POM 的可变性可以影响水-沉积物界面的细菌动态。我们的研究结果强调了在努力理解气候变化下细菌群落的结构和功能时，考虑浮游植物和细菌之间潜在相互作用的重要性，以了解底栖-浮游生物耦合。
