Seasonal Variation of Bacterial Diversity Along the Marine Particulate Matter Continuum

14 pages, 6 figures, 1 table, supplementary material https://www.frontiersin.org/articles/10.3389/fmicb.2020.01590/full#supplementary-material.-- Data Availability Statement. The raw sequence data have been deposited at the National Center for Biotechnology Information (NCBI). The data can be accessed online (https://www.ncbi.nlm) with the code PRJNA345534Seasonal dynamics of ocean prokaryotic communities in the free-living fraction have been widely described, but less is known about the seasonality of prokaryotes inhabiting marine particles. We describe the seasonality of bacterial communities in the particulate matter continuum by sampling monthly over two years in a temperate oligotrophic coastal ecosystem and using a serial filtration (including six size-fractions spanning from 0.2 to 200 μm). We observed that bacterial communities in the particulate matter continuum had annual changes following harmonic seasonal oscillations, where alpha, beta, and gamma diversity increased during the warm period and decreased during the cold period. Communities in each size-fraction changed gradually over time, being the communities in larger size-fractions the ones with stronger annual changes. Annual community changes were driven mainly by day length and sea surface temperature, and each size-fraction was additionally affected by other variables (e.g., smaller size-fractions by dissolved PO4 and larger size-fractions by turbidity). While some taxonomic groups mantained their preference for a given size fraction during most of the year, others varied their distribution into different size fractions over time, as e.g., SAR11, which increased its presence in particles during the cold period. Our results indicate that the size-fractionation scheme provides novel seasonal patterns that are not possible to unveil by analyzing only free-living bacteria, and that help to better understand the temporal dynamics of prokaryotesThis research was funded by projects STORM (CTM2009-09352), ADEPT (CTM2011-23458), REMEI (CTM2015-70340-R), ANIMA (CTM2015-65720-R), and MIAU (RTI2018-101025-B-I00) funded by the former Spanish Ministries of Science and Innovation, Ministry of Economy and Competitiveness, and now Science, Innovation and Universities. JH was partially supported by the Chilean National Agency for Research and Development (ANID) (FONDECYT-POSTDOCTORADO 3180152). MM was supported by a CSIC JAEPredoc Grant, by the Ministry of Labor, Employment and Social Security of Spain and by the Chilean National Agency for Research and Development (ANID) (FONDAP-IDEAL 15150003 and FONDECYT-POSTDOCTORADO 3190369). The publication fee was supported by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI), SpainWith the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI)Peer reviewe