Table_1_Effects of Ocean Acidification on Resident and Active Microbial Communities of Stylophora pistillata.DOCX

Ocean warming and ocean acidification (OA) are direct consequences of climate change and affect coral reefs worldwide. While the effect of ocean warming manifests itself in increased frequency and severity of coral bleaching, the effects of ocean acidification on corals are less clear. In particular, long-term effects of OA on the bacterial communities associated with corals are largely unknown. In this study, we investigated the effects of ocean acidification on the resident and active microbiome of long-term aquaria-maintained Stylophora pistillata colonies by assessing 16S rRNA gene diversity on the DNA (resident community) and RNA level (active community). Coral colony fragments of S. pistillata were kept in aquaria for 2 years at four different pCO2 levels ranging from current pH conditions to increased acidification scenarios (i.e., pH 7.2, 7.4, 7.8, and 8). We identified 154 bacterial families encompassing 2,047 taxa (OTUs) in the resident and 89 bacterial families including 1,659 OTUs in the active communities. Resident communities were dominated by members of Alteromonadaceae, Flavobacteriaceae, and Colwelliaceae, while active communities were dominated by families Cyclobacteriacea and Amoebophilaceae. Besides the overall differences between resident and active community composition, significant differences were seen between the control (pH 8) and the two lower pH treatments (7.2 and 7.4) in the active community, but only between pH 8 and 7.2 in the resident community. Our analyses revealed profound differences between the resident and active microbial communities, and we found that OA exerted stronger effects on the active community. Further, our results suggest that rDNA- and rRNA-based sequencing should be considered complementary tools to investigate the effects of environmental change on microbial assemblage structure and activity.

海洋变暖和海洋酸化（Ocean Acidification，OA）是气候变化的直接后果，对全球珊瑚礁均造成影响。海洋变暖的影响表现为珊瑚白化事件的发生频率与严重程度上升，但海洋酸化对珊瑚的作用机制尚未明确。具体而言，海洋酸化对珊瑚共生细菌群落的长期影响仍鲜为人知。本研究针对长期水族箱饲养的指状鹿角珊瑚（Stylophora pistillata）群落，通过分别检测DNA（对应驻留微生物群落）与RNA（对应活性微生物群落）水平下的16S rRNA基因多样性，探究了海洋酸化对其驻留与活性微生物组的影响。本实验将指状鹿角珊瑚的群落片段置于水族箱中培养2年，设置4组不同的pCO₂水平，覆盖当前海洋pH条件至酸化加剧场景（即pH值分别为7.2、7.4、7.8与8）。研究共在驻留微生物群落中鉴定出154个细菌科、总计2047个操作分类单元（Operational Taxonomic Unit，OTU），在活性微生物群落中则鉴定出89个细菌科、1659个OTU。驻留微生物群落以交替单胞菌科（Alteromonadaceae）、黄杆菌科（Flavobacteriaceae）与科尔韦尔氏菌科（Colwelliaceae）的类群为主，而活性微生物群落的优势类群则为循环杆菌科（Cyclobacteriaceae）与嗜阿米巴菌科（Amoebophilaceae）。除驻留与活性微生物群落组成间的整体差异外，活性群落中可见对照组（pH 8）与两个低pH处理组（pH 7.2、7.4）间存在显著差异，而驻留群落仅在pH 8与pH 7.2组间存在显著差异。本研究分析结果显示驻留与活性微生物群落间存在显著差异，且海洋酸化对活性微生物群落的影响更为显著。此外，本研究结果表明，基于rDNA与rRNA的测序技术可作为互补工具，用于探究环境变化对微生物群落结构与活性的影响。