Experiment: Marine fungi may benefit from ocean acidification@en

Recent studies have discussed the consequences of ocean acidification for bacterial processes and diversity. However, the decomposition of complex substrates in marine environments, a key part of the flow of energy in ecosystems, is largely mediated by marine fungi. Although marine fungi have frequently been reported to prefer low pH levels, this group has been neglected in ocean acidification research. We present the first investigation of direct pH effects on marine fungal abundance and community structure. In microcosm experiments repeated in 2 consecutive years, we incubated natural North Sea water for 4 wk at in situ seawater pH (8.10 and 8.26), pH 7.82 and pH 7.67. Fungal abundance was determined by colony forming unit (cfu) counts, and fungal community structure was investigated by the culture-independent fingerprint method Fungal Automated Ribosomal Intergenic Spacer Analysis (F-ARISA). Furthermore, pH at the study site was determined over a yearly cycle. Fungal cfu were on average 9 times higher at pH 7.82 and 34 times higher at pH 7.67 compared to in situ seawater pH, and we observed fungal community shifts predominantly at pH 7.67. Currently, surface seawater pH at Helgoland Roads remains >8.0 throughout the year; thus we cannot exclude that fungal responses may differ in regions regularly experiencing lower pH values. However, our results suggest that under realistic levels of ocean acidification, marine fungi will reach greater importance in marine biogeochemical cycles. The rise of this group of organisms will affect a variety of biotic interactions in the sea.已有研究探讨了海洋酸化对细菌过程及群落多样性的影响。然而，海洋环境中复杂底物的分解作用是生态系统能量流动的关键环节，其过程主要由海洋真菌介导。尽管已有研究表明海洋真菌偏好低pH环境，但该类群在海洋酸化研究中长期被忽视。本研究首次探究了pH值对海洋真菌丰度及群落结构的直接影响。在连续两年重复开展的微宇宙实验中，我们将天然北海海水分别置于原位海水pH（8.10与8.26）、pH 7.82及pH 7.67的条件下培养4周。真菌丰度通过菌落形成单位（colony forming unit, CFU）计数法测定，真菌群落结构则通过非培养依赖型指纹图谱技术——真菌自动化核糖体基因间区间隔分析（Fungal Automated Ribosomal Intergenic Spacer Analysis, F-ARISA）进行解析。此外，本研究还对实验站点的海水pH值开展了年度周期监测。与原位海水pH对照组相比，pH 7.82组的真菌CFU计数平均高出9倍，pH 7.67组则平均高出34倍；且仅在pH 7.67组中观测到真菌群落结构发生显著偏移。目前，黑尔戈兰湾海域（Helgoland Roads）的表层海水pH全年均维持在8.0以上，因此我们无法排除在长期处于低pH环境的海域中，海洋真菌的响应模式可能存在差异。但本研究结果表明，在海洋酸化的现实情境下，海洋真菌在海洋生物地球化学循环中的重要性将进一步提升，该类群的扩张将对海洋中多种生物互作关系产生影响。