Marine bacterial, archaeal and eukaryotic diversity and community structure on the continental shelf of the Western Antarctic Peninsula

The classic view of polar ocean foodwebs emphasizes large predators sustained by energy and materials flow through short, efficient diatom-krill-predator food chains. Bacterial activity is generally low in cold polar waters compared to lower latitudes. This view appears to be changing, with new studies of microbial foodwebs in Arctic and Antarctic oceans. We characterized bacterial, archaeal, and eukaryotic community diversity and composition from two depths (near surface and below the euphotic zone) at four sites, including the inshore and offshore, and north and south corners of a sampling grid along the western coast of the Antarctic Peninsula (WAP). We detected up to 2-fold higher richness in microbial eukaryotes at surface and deep inshore northern stations as compared to southern ones but offshore northern and southern stations revealed either no trend or higher richness at depth in the south. In contrast, bacterial and archaeal richness showed no significant differences either inshore or offshore at northern versus southern extents but did vary with depth. Archaea were virtually absent in summer surface waters but were present in summer deep and winter surface samples. Overall, winter bacterial and archaeal assemblages most closely resembled summer sub-euphotic zone assemblages, reflecting well-established seasonal patterns of water column turnover and stratification that result in an isolated layer of winter water below the euphotic zone. Inter-domain heterotroph-phototroph interactions were evident from network analysis. The WAP is among the most rapidly warming regions on earth. Our results provide a baseline against which future change in microbial communities may be assessed.

传统对极地海洋食物网的认知强调大型捕食者依赖于通过短暂而高效的硅藻-磷虾-捕食者食物链中的能量和物质流动而得以维持。相较于低纬度地区，冷极地水域中的细菌活动普遍较低。这一观点似乎正在发生改变，随着对北极和南极海洋微生物食物网的新的研究。我们对两个深度（近表层和水下真光层）以及四个地点（包括近岸和远岸、南极半岛西海岸采样网格的南北角）的细菌、古菌和真核生物群落多样性和组成进行了表征。与南部站点相比，表面和深层近岸北部站点的微生物真核生物丰富度高达两倍，但北部和南部远岸站点则显示无显著趋势或南部深层的丰富度更高。相反，细菌和古菌的丰富度在北部和南部的近岸或远岸之间均未显示显著差异，但随深度变化。在夏季表层水中，古菌几乎不存在，但在夏季深层和冬季表层样本中存在。总体而言，冬季细菌和古菌群落与夏季亚真光层群落最为相似，反映了水柱周转和层化已建立的季节性模式，导致真光层以下形成了一个隔离的冬季水层。网络分析显示，跨域异养生物-光能自养生物相互作用明显。南极半岛西海岸（WAP）是全球最迅速变暖的地区之一。我们的研究结果为评估未来微生物群落变化提供了一个基准。