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Front. Microbiol. | doi: 10.3389/fmicb.2018.02836

Environmental drivers of free-living vs. particle-attached bacterial community composition in the Mauritania upwelling system

  • 1Leibniz Centre for Tropical Marine Research (LG), Germany
  • 2University of Bremen, Germany
  • 3Max Planck Institute for Marine Microbiology (MPG), Germany
  • 4Alfred Wegener Institut Helmholtz Zentrum für Polar und Meeresforschung, Helmholtz-Gemeinschaft Deutscher Forschungszentren (HZ), Germany
  • 5Center for Marine Environmental Sciences, University of Bremen, Germany
  • 6Leibniz-Institut für Gewässerökologie und Binnenfischerei, Germany
  • 7Universität Potsdam, Germany

Saharan dust input and seasonal upwelling along North-West Africa provide a model system for studying microbial processes related to the export and recycling of nutrients. This study offers the first molecular characterization of prokaryotic particle-attached (PA; >3.0µm) and free-living (FL; 0.2-3.0µm) players in this important ecosystem during August 2016. Environmental drivers for alpha-diversity, bacterial community composition and differences between FL and PA fractions were identified. The ultra-oligotrophic waters off Senegal were dominated by Cyanobacteria while higher relative abundances of Alphaproteobacteria, Bacteroidetes, Verrucomicrobia and Planctomycetes (known particle-degraders) occurred in the upwelling area. Temperature, proxy for different water masses, was the best predictor for changes in FL communities. PA community variation was best explained by temperature and ammonium. Bray Curtis dissimilarities between FL and PA were generally very high and correlated with temperature and salinity in surface waters. Greatest similarities between FL and PA occurred at the deep chlorophyll maximum, where bacterial substrate availability was likely highest. This indicates that environmental drivers do not only influence changes among FL and PA communities but also the differences between them. This could provide an explanation for contradicting results obtained by different studies regarding the dissimilarity/ similarity between FL and PA communities and their biogeochemical functions.

Keywords: Prokaryotes*, Biodiversity, microbial ecology, Alpha diversity and beta diversity, Bray Curtis dissimilarity, temperature, Salinity, 16S rRNA illumina sequencing

Received: 01 Aug 2018; Accepted: 05 Nov 2018.

Edited by:

Chuanlun Zhang, Southern University of Science and Technology, China

Reviewed by:

Stefan M. Sievert, Woods Hole Oceanographic Institution, United States
Eyal Rahav, Israel Oceanographic and Limnological Research, Israel  

Copyright: © 2018 Bachmann, Heimbach, Hassenrück, Kopprio, Iversen, Grossart and Gärdes. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Mrs. Jennifer Bachmann, Leibniz Centre for Tropical Marine Research (LG), Bremen, Germany, bynnej@gmail.com