Abstract
Seafloor sediments cover the majority of planet Earth and microorganisms inhabiting these environments play a central role in marine biogeochemical cycles. Yet, description of the biogeography and distribution of sedimentary microbial life is still too sparse to evaluate the relative contribution of processes driving this distribution, such as the levels of drift, connectivity, and specialization. To address this question, we analyzed 210 archaeal and bacterial metabarcoding libraries from a standardized and horizon-resolved collection of sediment samples from 18 stations along a longitudinal gradient from the eastern Mediterranean to the western Atlantic. Overall, we found that biogeographic patterns depended on the scale considered: while at local scale the selective influence of contemporary environmental conditions appeared strongest, the heritage of historic processes through dispersal limitation and drift became more apparent at regional scale, and ended up superseding contemporary influences at inter-regional scale. When looking at environmental factors, the structure of microbial communities was correlated primarily with water depth, with a clear transition between 800 and 1,200 meters below sea level. Oceanic basin, water temperature, and sediment depth were other important explanatory parameters of community structure. Finally, we propose increasing dispersal limitation and ecological drift with sediment depth as a probable factor for the enhanced divergence of deeper horizons communities.
Highlights
Marine sediments cover around 65% of the Earth’s surface and accumulate particulate organic matter settling from the water column, thereby representing the largest sink of oceanic organic matter (Seiter et al, 2005; Jørgensen and Boetius, 2007)
Building on previous work suggesting that assembly of subseafloor microbial communities initiates in the very first layers of sediment, we examined the evolution of microbial community structure with increasing depth in the surface sediments of the seafloor
Most of the contamination was dominated by a specific Amplicon Sequence Variants (ASVs) that accounted for 99% of reads in negative control libraries
Summary
Marine sediments cover around 65% of the Earth’s surface and accumulate particulate organic matter settling from the water column, thereby representing the largest sink of oceanic organic matter (Seiter et al, 2005; Jørgensen and Boetius, 2007). Thanks to recent technological advances, in sequencing techniques (e.g., Huber et al, 2006, reviewed in Salazar and Sunagawa, 2017), it is possible to perform nearexhaustive inventories of benthic microbial community diversity across large spatial scales, and to investigate patterns of microbial distribution Despite their essential role in the marine ecosystem (Nealson, 1997; del Giorgio and Duarte, 2002; Jørgensen and Boetius, 2007; Arístegui et al, 2009; Molari et al, 2013), processes shaping benthic prokaryotic community structure are still poorly understood, and the existence of biogeographic patterns has been questioned owing to their possible unlimited dispersal ability (Green and Bohannan, 2006; Astorga et al, 2012). Recent studies focusing on deep sea benthic microorganisms at local and regional scale (Jacob et al, 2013; Buttigieg and Ramette, 2015; Liu et al, 2020; Li et al, 2021) and meta-analyses (Bienhold et al, 2016; Petro et al, 2017; Hoshino et al, 2020) have clearly shown geographic structuration in these communities, even at reduced spatial scales
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
