Shifts in the metabolic potential of deep ocean prokaryotic communities across a productivity gradient

Abstract

The dark ocean contains the largest pool of microbes in aquatic systems and sustains half of the ocean's microbial activity. In contrast to the long-lasting paradigm of a homogenous and stable deep ocean, recent studies have unveiled that the deep realm displays great heterogeneity with an enormous and dynamic repository of microbial taxa, and that their physiological status is largely determined by the productivity of surface waters. Here we wanted to explore how the metabolic potential of deep ocean communities changes across a productivity gradient, likely as a consequence of the change in the intensity and frequency of surface-derived particles reaching the deep ocean. We used metagenomic data collected in a transect from the Eastern Mediterranean Sea to adjacent Atlantic waters and explored changes in gene content in the context of the environmental conditions and dissolved organic matter quality faced by the microbial assemblages. We unveiled that deep ocean communities from the phosphorus-limited Eastern Mediterranean Sea have less ability to colonize particles, less capacity to tune their metabolism in response to environmental changes, and more metabolic versatility than communities from the Atlantic ocean