Microbial communities in marine sediments are highly diverse, yet the processes that give rise to this complexity are unclear. It has been proposed that benthic microbial communities must be continuously re-seeded from the water column because dispersal within the sediment is severely limited. Previous studies consistently report that the composition of the microbial community gradually changes with sediment depth. However, the relative contributions of the processes that underlie these compositional gradients have not been determined, and it is unknown whether microbial dispersal is indeed too slow to outpace burial. Here, we applied ecological statistical frameworks to 16S rRNA gene amplicon-based community composition data from Atacama Trench sediments to investigate the links between biogeochemistry, burial, and microbial community assembly processes. We confirm that dispersal limitation affects microbial communities and find that gradual changes in community composition are driven by selective pressures that change abruptly across the discrete boundaries between redox zones rather than along continuous biogeochemical gradients, while selective pressures are uniform within each zone. The gradual changes in community composition over centimetres of depth within a zone hence reflects a decades-long response to the abruptly changing selective pressures.
Bibliografisk noteFunding Information:
The authors thank Kasper Urup Kjeldsen, Mauricio Shimabukuro, John Paul Balmonte, David Berrry, Petra Pjevac, and Bela Hausmann for fruitful discussions and perspectives on biogeochemistry and microbial ecology, the eScience centre of SDU for computational resources as well as technical support. The authors would like to acknowledge the two anonymous reviewers of this study for providing very constructive feedback. Funding for the study was provided by ERC Advanced Grant HADES #669947 and DNRF145 awarded to Ronnie N. Glud and by ERC Advanced Grant NOVAMOX #695599 awarded to Bo Thamdrup.
© 2023 The Authors. Environmental Microbiology published by Applied Microbiology International and John Wiley & Sons Ltd.