title: Seasonal Succession of Free-Living Bacterial Communities in Coastal Waters of the Western Antarctic Peninsula.
abstract: The marine ecosystem along the Western Antarctic Peninsula undergoes a dramatic seasonal transition every spring, from almost total darkness to almost continuous sunlight, resulting in a cascade of environmental changes, including phytoplankton blooms that support a highly productive food web. Despite having important implications for the movement of energy and materials through this ecosystem, little is known about how these changes impact bacterial succession in this region. Using 16S rRNA gene amplicon sequencing, we measured changes in free-living bacterial community composition and richness during a 9-month period that spanned winter to the end of summer. Chlorophyllaconcentrations were relatively low until summer when a major phytoplankton bloom occurred, followed 3 weeks later by a high peak in bacterial production. Richness in bacterial communities varied between ~1,200 and 1,800 observed operational taxonomic units (OTUs) before the major phytoplankton bloom (out of ~43,000 sequences per sample). During peak bacterial production, OTU richness decreased to ~700 OTUs. The significant decrease in OTU richness only lasted a few weeks, after which time OTU richness increased again as bacterial production declined toward pre-bloom levels. OTU richness was negatively correlated with bacterial production and chlorophyllaconcentrations. Unlike the temporal pattern in OTU richness, community composition changed from winter to spring, prior to onset of the summer phytoplankton bloom. Community composition continued to change during the phytoplankton bloom, with increased relative abundance of several taxa associated with phytoplankton blooms, particularlyPolaribacter. Bacterial community composition began to revert toward pre-bloom conditions as bacterial production declined. Overall, our findings clearly demonstrate the temporal relationship between phytoplankton blooms and seasonal succession in bacterial growth and community composition. Our study highlights the importance of high-resolution time series sampling, especially during the relatively under-sampled Antarctic winter and spring, which enabled us to discover seasonal changes in bacterial community composition that preceded the summertime phytoplankton bloom.
authors.affiliation: Department of Ecology and Evolutionary Biology, Brown University, Providence RI, USA.
authors.forename: Catherine M
authors.initials: CM
authors.lastname: Luria
authors.affiliation: The Josephine Bay Paul Center for Comparative Molecular Biology and Evolution, Marine Biological Laboratory, Woods HoleMA, USA; Department of Earth, Environmental and Planetary Sciences, Brown University, ProvidenceRI, USA.
authors.forename: Linda A
authors.initials: LA
authors.lastname: Amaral-Zettler
authors.affiliation: Department of Earth and Environmental Sciences, Lamont-Doherty Earth Observatory of Columbia University, Palisades NY, USA.
authors.forename: Hugh W
authors.initials: HW
authors.lastname: Ducklow
authors.affiliation: School of Marine Sciences and Darling Marine Center, University of Maine, Walpole ME, USA.
authors.forename: Jeremy J
authors.initials: JJ
authors.lastname: Rich
keywords: 16S rRNA gene; Antarctica; Polaribacter; Rhodobacteraceae; bacterial community composition; bacterial production; ecological succession; pelagibacter ubique (SAR11)