Eutrophication coupled to climate change disturbs the balance between competition and coexistence in microbial communities including the partitioning of organic and inorganic nutrients between phytoplankton and bacteria. Competition for inorganic nutrients has been regarded as one of the drivers affecting the productivity of the eutrophied coastal Baltic Sea. Yet, it is unknown at the molecular expression level how resources are competed for, by phytoplankton and bacteria, and what impact this competition has on the community composition. Here we use metatranscriptomics and amplicon sequencing and compare known metabolic pathways of both phytoplankton and bacteria co-occurring during a summer bloom in the archipelago of Åland in the Baltic Sea to examine phytoplankton bacteria resource partitioning. The expression of selected pathways of carbon (C), nitrogen (N), and phosphorus (P) metabolism varied over time, independently, for both phytoplankton and bacteria, indicating partitioning of the available organic and inorganic resources. This occurs regardless of eukaryotic plankton growth phase (exponential or stationary), based on expression data, and microbial community composition. Further, the availability of different nutrient resources affected the functional response by the bacteria, observed as minor compositional changes, at class level, in an otherwise taxonomically stable bacterial community. Resource partitioning and functional flexibility seem necessary in order to maintain phytoplankton-bacteria interactions at stable environmental conditions. More detailed knowledge of which organisms utilize certain nutrient species are important for more accurate projections of the fate of coastal waters.

中文翻译：

---

波罗的海沿岸浮游植物与细菌的资源分配

富营养化与气候变化相结合，扰乱了微生物群落竞争与共存之间的平衡，包括浮游植物和细菌之间有机和无机营养物质的分配。对无机养分的竞争被认为是影响富营养化沿海波罗的海生产力的驱动因素之一。然而，在分子表达水平上尚不清楚浮游植物和细菌如何竞争资源，以及这种竞争对群落组成有何影响。在这里，我们使用宏转录组学和扩增子测序，并比较波罗的海奥兰群岛夏季开花期间共同发生的浮游植物和细菌的已知代谢途径，以检查浮游植物细菌资源分配。对于浮游植物和细菌，碳 (C)、氮 (N) 和磷 (P) 代谢的选定途径的表达随时间独立地变化，表明可用有机和无机资源的分配。根据表达数据和微生物群落组成，无论真核浮游生物的生长阶段（指数或静止）如何，都会发生这种情况。此外，不同营养资源的可用性影响细菌的功能反应，观察到在分类水平上，在分类学上稳定的细菌群落中，微小的组成变化。为了在稳定的环境条件下维持浮游植物-细菌的相互作用，资源分配和功能灵活性似乎是必要的。