The Arctic Ocean subseabed holds vast reservoirs of the potent greenhouse gas methane (CH 4 ), often seeping into the ocean water column. In a continuously warming ocean as a result of climate change an increase of CH 4 seepage from the seabed is hypothesized. Today, CH 4 is largely retained in the water column due to the activity of methane‐oxidizing bacteria (MOB) that thrive there. Predicted future oceanographic changes, bo...

Summary Using the 16S rRNA and mcrA genes, we investigated the composition, abundance and activity of sediment archaeal communities within 18 high‐mountain lakes under contrasted metal levels from different origins (bedrock erosion, past‐mining activities and atmospheric depositions). Bathyarchaeota, Euryarchaeota and Woesearchaeota were the major phyla found at the meta‐community scale, representing 48%, 18.3% and 15.2% of th...

The description of a rare biosphere within microbial communities has created great interest because microbes play a fundamental role in the functioning of all ecosystems on earth. Despite recent progress in understanding the ecology of the rare biosphere, the concept itself is still discussed, and fundamental questions remain. Here, we target the seed bank compartment of the rare biosphere, assess the level of rarity at which...

Summary Growing evidence indicates that dense water formation and flow over the continental shelf is a globally relevant oceanographic process, potentially affecting microbial assemblages down to the deep ocean. However, the extent and consequences of this influence have yet to be investigated. Here it is shown that dense water propagation to the deep ocean increases the abundance of prokaryotic plankton, and stimulates carbon...

Understanding the link between community diversity and ecosystem function is a fundamental aspect of ecology. Systematic losses in biodiversity are widely acknowledged but the impact this may exert on ecosystem functioning remains ambiguous. There is growing evidence of a positive relationship between species richness and ecosystem productivity for terrestrial macro‐organisms, but similar links for marine micro‐organisms, whic...