Abstract
Current warming in the Western Antarctic Peninsula (WAP) has multiple effects on the marine ecosystem, modifying the trophic web and the nutrient regime. In this study, the effect of decreased surface salinity on the marine microbial community as a consequence of freshening from nearby glaciers was investigated in Chile Bay, Greenwich Island, WAP. In the summer of 2016, samples were collected from glacier ice and transects along the bay for 16S rRNA gene sequencing, while in situ dilution experiments were conducted and analyzed using 16S rRNA gene sequencing and metatranscriptomic analysis. The results reveal that certain common seawater genera, such as Polaribacter, Pseudoalteromonas and HTCC2207, responded positively to decreased salinity in both the bay transect and experiments. The relative abundance of these bacteria slightly decreased, but their functional activity was maintained and increased the over time in the dilution experiments. However, while ice bacteria, such as Flavobacterium and Polaromonas, tolerated the increased salinity after mixing with seawater, their gene expression decreased considerably. We suggest that these bacterial taxa could be defined as sentinels of freshening events in the Antarctic coastal system. Furthermore, these results suggest that a significant portion of the microbial community is resilient and can adapt to disturbances, such as freshening due to the warming effect of climate change in Antarctica.
Highlights
IntroductionAs a consequence of climate change, polar regions are the most radically changing places on the planet [1,2]
Potential bacterial sentinels from ice were revealed to represent freshening in the bay
In marine coastal areas surrounded by glaciers, Flavobacterium could serve as a warning for a high melting face and freshening input to the marine system, whose melted glacier ice intrusion seems to be highly tolerable by dominant marine bacteria that have metabolic resilience to these changes
Summary
As a consequence of climate change, polar regions are the most radically changing places on the planet [1,2]. Over the past 50 years, the Western Antarctic Peninsula (WAP). Has warmed four times faster than the average rate of overall warming on Earth [3,4]. This accelerates the collapse of ice shelves, the retreat of glaciers and the exposure of new terrestrial habitats [2,4]. Climate models suggest a substantial retreat of the West. Antarctic Ice Sheet [5]. A further increase of 0.5 ◦ C beyond the present-day average global surface seawater temperature will lead to multiple impacts on a variety of organisms, from
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