Data_Sheet_5_Impact of Ocean Acidification on the Intestinal Microbiota of the Marine Sea Bream (Sparus aurata L.).PDF

Within a scenario of increasing atmospheric CO2 and ocean acidification (OA), it is highly relevant to investigate its impacts not only on fish performance but also on fish intestinal microbiome and how that reflects on host performance and health. The main objective of this study was to establish if the intestinal microbiota of the sea bream (Sparus aurata) was affected by high level of CO2 in line with the predictions for this century. The bacterial communities of the intestinal fluid were characterized in animals kept at the present-day level of CO2 (400 μatm) and in animals switched to high CO2 (1200 μatm) for 1 month. Bacterial taxa identification was based on molecular methods, using the DNA coding for the 16S ribosomal RNA and primers targeting the regions V1–V3. Amplicons obtained from DNA samples of animals in the same tank were combined, cloned to obtain a bacterial DNA library, and the clones were sequenced. No significant differences were found between the two treatments for alpha diversity. However, beta diversity analysis revealed distinct dysbiosis in response to hypercapnia, with phylum Firmicutes absent from the bacterial communities of fish exposed to 1200 μatm CO2, whereas Proteobacteria relative abundance was increased at elevated CO2, due to the presence of Gammaproteobacteria (Vibrionaceae and Alteromonadaceae), a class not present in the control samples. This study provides a first glimpse at the impact of OA in fish intestinal microbiota and highlights potential downstream effects to the general condition of fishes under hypercapnia.

在大气二氧化碳浓度升高与海洋酸化（Ocean Acidification, OA）的背景下，探究其对鱼类生理机能以及鱼类肠道微生物组的影响，以及该影响如何反映宿主的生理状态与健康状况，均具有极高的研究价值。本研究的核心目标为验证金头鲷（Sparus aurata）的肠道微生物群是否会受到契合本世纪预测情景的高浓度二氧化碳的影响。本研究对两组实验鱼的肠道液细菌群落进行了表征：一组置于当前二氧化碳浓度（400 μatm）环境中饲养，另一组则切换至高浓度二氧化碳（1200 μatm）环境中饲养1个月。细菌类群的鉴定采用分子生物学手段，以编码16S核糖体RNA（16S ribosomal RNA）的DNA为扩增模板，使用靶向V1-V3区域的引物完成扩增。将同一养殖缸内实验鱼的DNA样本所获扩增子进行混合，通过克隆构建细菌DNA文库，随后对克隆菌株进行测序。两组处理的α多样性（alpha diversity）未出现显著差异。然而，β多样性（beta diversity）分析显示，高碳酸胁迫下鱼类肠道菌群出现显著的菌群失调：暴露于1200 μatm CO₂环境的实验鱼肠道菌群中完全缺失厚壁菌门（Firmicutes）；而变形菌门（Proteobacteria）的相对丰度显著升高，这源于γ-变形菌纲（Gammaproteobacteria）的出现——该纲包含弧菌科（Vibrionaceae）与交替单胞菌科（Alteromonadaceae），而对照组样本中未检测到此类类群。本研究首次揭示了海洋酸化对鱼类肠道微生物群的影响，并指出高碳酸胁迫下鱼类整体健康状况可能存在的下游连锁效应。