Sorbonne Université, UMR 7618 CNRS-INRA- RD-Paris Cité-UPEC, Institut d'Ecologie et des Sciences de l'Environnement de Paris (iEES-Paris), 4 place Jussieu, Paris cedex 05 75252, France.
Sorbonne Université, UMR 7618 CNRS-INRA- RD-Paris Cité-UPEC, Institut d'Ecologie et des Sciences de l'Environnement de Paris (iEES-Paris), 4 place Jussieu, Paris cedex 05 75252, France; Department of Soil and Environment, Swedish University of Agricultural Sciences, P.O. Box 7014, Uppsala 75007, Sweden.
Harmful Algae. 2023 Jul;126:102436. doi: 10.1016/j.hal.2023.102436. Epub 2023 Apr 27.
Bloom-forming phytoplankton dynamics are still unpredictable, even though it is known that several abiotic factors, such as nutrient availability and temperature, are key factors for bloom development. We investigated whether biotic factors, i.e. the bacterioplankton composition (via 16SrDNA metabarcoding), were correlated with phytoplankton dynamics, through a weekly monitoring of a shallow lake known to host recurrent cyanobacterial blooms. We detected concomitant changes in both bacterial and phytoplankton community biomass and diversity. During the bloom event, a significant decrease in phytoplankton diversity, was detected, with a first co-dominance of Ceratium, Microcystis and Aphanizomenon, followed by a co-dominance of the two cyanobacterial genera. In the same time, we observed a decrease of the particle-associated (PA) bacterial richness and the emergence of a specific bacterial consortium that was potentially better adapted to the new nutritional niche. Unexpectedly, changes in PA bacterial communities occurred just before the development the emergence of the phytoplanktonic bloom and the associated modification of the phytoplanktonic community composition, suggesting that changes in environmental conditions leading to the bloom, were first sensed by the bacterial PA community. This last was quite stable throughout the bloom event, even though there were changes in the blooming species, suggesting that the association between cyanobacterial species and bacterial communities may not be as tight as previously described for monospecific blooming communities. Finally, the dynamics of the free-living (FL) bacterial communities displayed a different trajectory from those of the PA and phytoplankton communities. This FL communities can be viewed as a reservoir for bacterial recruitment for the PA fraction. Altogether, these data also highlight s that the spatial organization within these different microenvironments in the water column is a relevant factor in the structuring of these communities.
尽管已经知道，营养物质的可利用性和温度等几种非生物因素是水华发展的关键因素，但形成水华的浮游植物动态仍然是不可预测的。我们通过每周监测一个已知存在周期性蓝藻水华的浅水湖，研究了生物因素（即通过 16SrDNA 宏条形码检测的细菌浮游微生物区系组成）是否与浮游植物动态有关。我们检测到细菌和浮游植物群落生物量和多样性同时发生变化。在水华事件期间，浮游植物多样性明显下降，首先是角毛藻、微囊藻和鱼腥藻共同占优势，然后是两种蓝藻属共同占优势。与此同时，我们观察到颗粒相关（PA）细菌丰富度降低，并且出现了一种可能更适应新营养生态位的特定细菌共生体。出乎意料的是，PA 细菌群落的变化发生在浮游植物水华出现之前，并且与浮游植物群落组成的相关变化同时发生，这表明导致水华的环境条件变化首先被 PA 细菌群落所感知。尽管浮游植物物种发生了变化，但 PA 细菌群落整个水华事件都相当稳定，这表明蓝藻物种与细菌群落之间的联系并不像以前描述的那样紧密用于单种水华群落。最后，自由生活（FL）细菌群落的动态与 PA 和浮游植物群落的动态不同。这种 FL 群落可以被视为 PA 部分细菌招募的储库。总的来说，这些数据还强调了水柱中这些不同微环境内的空间组织是这些群落结构的一个相关因素。
