There And Back Again -- Unraveling Mechanisms Of Bacterial Biogeography In The North Pacific Subtropical Gyre To And From Station ALOHA

Lindh, M. V.

doi:10.1101/141085

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There And Back Again -- Unraveling Mechanisms Of Bacterial Biogeography In The North Pacific Subtropical Gyre To And From Station ALOHA

Lindh, M. V.

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Abstract

Bacterially-mediated fluxes of energy and matter are dynamic in time and space coupled with shifts in bacterial community structure. Yet, our understanding of mechanisms shaping bacterial biogeography remains limited. Near-surface seawater was collected during transits between Honolulu and Station ALOHA in the North Pacific Subtropical Gyre to examine the shape of occupancy-frequency distributions (the different number of populations occupying different number of sites) and determine bacterial metapopulation dynamics. Bacterial 16S rRNA gene amplicons were sequenced from whole seawater and filter-size fractionated plankton DNA samples while also separating the community into distinct taxonomic groups at phyla/class and analyzing these compartments separately. For the total seawater (i.e. the >0.2 m size fraction) and picoplankton communities (i.e. the size fraction >0.2 m and < 3.0 m), but not the large size fraction community (i.e. the >3.0 m size fraction), most individual operational taxonomic units (OTUs) occupied a single site and the number of OTUs occupying different number of sites followed a significant bimodal pattern with several core OTUs occupying all sites. Nevertheless, only Cyanobacteria (in particular Prochlorococcus sp.) and in a few instances also Alphaproteobacteria (in particular SAR11 clade and Aegan-169 marine group bacteria) exhibited bimodal occupancy-frequency patterns. As expected, Prochlorococcus sp. had an inversed bimodal occupancy-frequency distribution with most OTUs found at all sites. Yet, there were individual satellite OTUs affiliated with Prochlorococcus sp. that were phylogenetically distinct from the core OTUs and only found at a single site. Collectively, these findings indicate that different compartments (size fractions and taxa) have different metapopulation dynamics. Bimodal patterns among the low diversity total and picoplankton communities but not in the high diversity large size fraction suggest that positive feedbacks between local abundance and occupancy are important when environmental conditions are homogenous and diversity is low.

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Lindh, M. V.. 2017-05-23. There And Back Again -- Unraveling Mechanisms Of Bacterial Biogeography In The North Pacific Subtropical Gyre To And From Station ALOHA. https://doi.org/10.1101/141085

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