Life Sciences, Soka University of America, Aliso Viejo, California, United States of America.
PLoS One. 2020 Oct 28;15(10):e0241183. doi: 10.1371/journal.pone.0241183. eCollection 2020.
Most literature exploring the biological effects of ocean acidification (OA) has focused on macroscopic organisms and far less is known about how marine microbial communities will respond. Studies of OA and microbial community composition and diversity have examined communities from a limited number of ocean regions where the ambient pH is near or above the global average. At San Juan Island (Salish Sea), a region that experiences naturally low pH (average = 7.8), the picoplankton (cell diameter is 0.2-2μm) community was predicted to show no response to experimental acidification in a three-week mesocosm experiment. Filtered seawater mesocosms were maintained via semicontinuous culturing. Three control mesocosms were maintained at pH 8.05 and three acidified mesocosms were maintained at pH 7.60. Total bacteria was quantified daily with a flow cytometer. Microbial communities were sampled every two days via filtration followed by DNA extraction, 16S rRNA amplification, and MiSeq sequencing. There was no significant difference in total bacteria between pH treatments throughout the experiment. Acidification significantly reduced Shannon's diversity over time. During the final week of the experiment, acidification resulted in a significant decrease in Shannon's diversity, Faith's phylogenetic distance, and Pielous's Evenness. ANCOM results revealed four bacterial ASVs (amplicon sequence variants), in families Flavobaceriaceae and Hyphomonadaceae that significantly decreased in relative frequency under acidification and two bacterial ASVs, in families Flavobacteriaceae and Alteromonadaceae, that significantly increased under acidification. This is the first OA study on the microbial community of the Salish Sea, a nutrient rich, low pH region, and the first of its kind to report a decrease in both picoplankton richness and evenness with acidification. These findings demonstrate that marine microbial communities that naturally experience acidic conditions are still sensitive to acidification.
大多数探索海洋酸化（OA）生物学效应的文献都集中在宏观生物上，而对于海洋微生物群落将如何反应知之甚少。关于 OA 和微生物群落组成和多样性的研究，仅检查了少数海洋区域的群落，这些区域的环境 pH 值接近或高于全球平均值。在圣胡安岛（萨利什海），一个经历自然低 pH 值（平均值=7.8）的地区，预测在为期三周的中观实验中，浮游植物（细胞直径为 0.2-2μm）群落对实验酸化没有反应。通过半连续培养维持过滤海水中观实验。三个对照中观实验维持在 pH 8.05，三个酸化中观实验维持在 pH 7.60。每天用流式细胞仪定量总细菌。每隔两天通过过滤采集微生物群落，然后进行 DNA 提取、16S rRNA 扩增和 MiSeq 测序。整个实验过程中，pH 处理之间的总细菌没有显著差异。酸化随时间显著降低 Shannon 多样性。在实验的最后一周，酸化导致 Shannon 多样性、Faith 系统发育距离和 Pielous 均匀度显著降低。ANCOM 结果显示，在丰度下降的情况下，有 4 个细菌 ASV（扩增子序列变体），分别属于 Flavobaceriaceae 和 Hyphomonadaceae 科，在酸化条件下，有 2 个细菌 ASV，分别属于 Flavobacteriaceae 和 Alteromonadaceae 科，丰度显著增加。这是萨利什海海洋微生物群落的第一项 OA 研究，萨利什海是一个营养丰富、pH 值较低的地区，也是第一项报告酸化导致浮游植物丰富度和均匀度降低的研究。这些发现表明，自然经历酸性条件的海洋微生物群落仍然对酸化敏感。
