Microbial response to temperature and organic matter shifts in deep Antarctic sediments

The identification of the factors driving the biodiversity and metabolism of microbial components in deep-sea Antarctic ecosystems is crucial in light of their rapid transformations. Here, through a replicated and hierarchical sampling strategy, we investigated two deep-sea benthic areas in the Ross Sea (Antarctica) characterized by different bottom temperatures (ΔT ca. 1.3°C) and trophic conditions. The warmer and more oligotrophic deep seafloor showed higher bacterial and archaeal diversity and faster organic matter cycling, whilst the colder mesotrophic system displayed a higher organic matter content and microbial biomass. Proteobacterial assemblages dominated both areas, yet only 9.2% of the taxa were shared between the two sampling areas, indicating a major turnover in microbial biodiversity. Multiple linear regression models identified temperatures and organic matter as key drivers of prokaryotic assemblages and ecosystem functioning, with viral infections playing a potential role in organic matter cycling. These findings allow understanding how environmental changes in Antarctic benthic ecosystems, such as those potentially induced by climate change, could alter the biodiversity and metabolism of the microbial components and the organic matter cycling.