Sediment microbial communities at CO2 seeps in Papua New Guinea

To understand how ocean acidification (OA) influences sediment microbial communities, naturally CO2-rich sites are increasingly being used as OA analogues. However, the characterization of these naturally CO2-rich sites is often limited to OA-related variables, neglecting additional environmental variables that may confound OA effects. Here, we used an extensive array of sediment and bottom water parameters to evaluate pH effects on sediment microbial communities at hydrothermal CO2 seeps in Papua New Guinea. The geochemical composition of the sediment pore water showed variations in the hydrothermal signature at seep sites with comparable pH, allowing the identification of sites that may better represent future OA scenarios. At these sites, we detected a 60% shift in the microbial community composition compared with reference sites, mostly related to increases in Chloroflexi sequences. pH was among the factors significantly, yet not mainly, explaining changes in microbial community composition. pH variation may therefore often not be the primary cause of microbial changes when sampling is done along complex environmental gradients. Thus, we recommend an ecosystem approach when assessing OA effects on sediment microbial communities under natural conditions. This will enable a more reliable quantification of OA effects via a reduction of potential confounding effects.

为阐明海洋酸化（Ocean Acidification, OA）对沉积物微生物群落的影响，富含二氧化碳的自然位点正日益被用作海洋酸化的模拟环境。然而，当前针对这类富二氧化碳自然位点的表征工作，往往仅局限于与酸化相关的环境变量，却忽略了可能干扰酸化效应解析的其他环境因子。本研究以巴布亚新几内亚的热液二氧化碳喷口为研究对象，通过系统性测定沉积物与底层水的多类参数，评估pH值对沉积物微生物群落的调控效应。沉积物孔隙水的地球化学组成显示，在pH值相近的喷口位点中，热液活动特征存在显著差异，这使得我们能够甄别出更能代表未来海洋酸化情景的理想研究位点。在这类位点中，我们观测到微生物群落组成相较于对照位点发生了60%的转变，其主要关联于绿弯菌门（Chloroflexi）序列丰度的提升。pH值虽是可显著解释微生物群落组成变化的影响因子之一，但并非主导因素。因此，当沿复杂环境梯度开展采样研究时，pH值变化往往并非驱动微生物群落改变的首要原因。据此，我们建议在自然环境下评估海洋酸化对沉积物微生物群落的影响时，应采用生态系统整体性研究范式。该范式可通过降低潜在的混淆效应，实现对海洋酸化效应更为可靠的定量评估。