Data_Sheet_9_Warming, but Not Acidification, Restructures Epibacterial Communities of the Baltic Macroalga Fucus vesiculosus With Seasonal Variability.PDF

Due to ocean acidification and global warming, surface seawater of the western Baltic Sea is expected to reach an average of ∼1100 μatm pCO2 and an increase of ∼5°C by the year 2100. In four consecutive experiments (spanning 10–11 weeks each) in all seasons within 1 year, the abiotic factors temperature (+5°C above in situ) and pCO2 (adjusted to ∼1100 μatm) were tested for their single and combined effects on epibacterial communities of the brown macroalga Fucus vesiculosus and on bacteria present in the surrounding seawater. The experiments were set up in three biological replicates using the Kiel Outdoor Benthocosm facility (Kiel, Germany). Phylogenetic analyses of the respective microbiota were performed by bacterial 16S (V1-V2) rDNA Illumina MiSeq amplicon sequencing after 0, 4, 8, and 10/11 weeks per season. The results demonstrate (I) that the bacterial community composition varied in time and (II) that relationships between operational taxonomic units (OTUs) within an OTU association network were mainly governed by the habitat. (III) Neither single pCO2 nor pCO2:Temperature interaction effects were statistically significant. However, significant impact of ocean warming was detected varying among seasons. (IV) An indicator OTU (iOTU) analysis identified several iOTUs that were strongly influenced by temperature in spring, summer, and winter. In the warming treatments of these three seasons, we observed decreasing numbers of bacteria that are commonly associated with a healthy marine microbial community and—particularly during spring and summer—an increase in potentially pathogenic and bacteria related to intensified microfouling. This might lead to severe consequences for the F. vesiculosus holobiont finally affecting the marine ecosystem.

受海洋酸化与全球变暖影响，预计到2100年，波罗的海西部表层海水的平均二氧化碳分压（pCO₂）将达到约1100 μatm，水温将升高约5℃。本研究在1年内的全季节开展了4项连续实验（每项实验持续10~11周），设置温度（较原位环境升高5℃）与pCO₂（调整至约1100 μatm）两个非生物因子，探究二者单独及联合作用对褐藻*Fucus vesiculosus*（墨角藻）附生细菌群落，以及周围海水中细菌群落的影响。实验采用德国基尔户外底栖微宇宙（Kiel Outdoor Benthocosm）装置，设置3次生物学重复。
在每个实验周期的第0、4、8、10/11周，分别对对应微生物群落开展细菌16S（V1-V2区）核糖体DNA（rDNA）的Illumina MiSeq扩增子测序，进行系统发育分析。
研究结果表明：（I）细菌群落组成随时间发生显著变化；（II）操作分类单元（operational taxonomic units, OTUs）关联网络内的OTU间关联关系主要受生境调控；（III）单独的pCO₂胁迫以及pCO₂与温度的交互作用均未表现出统计学显著性，但海洋变暖的显著影响存在季节差异；（IV）指示性操作分类单元（indicator OTU, iOTU）分析共鉴定出多个在春、夏、冬三季受温度显著影响的iOTUs。在这三个季节的升温处理组中，研究人员观察到通常与健康海洋微生物群落相关的细菌数量逐渐减少，且尤其在春夏季，潜在致病细菌以及与加剧微污损相关的细菌丰度出现上升。这一现象可能对*Fucus vesiculosus*共生体造成严重影响，最终波及海洋生态系统。