title: Bacterial diversity across a highly stratified ecosystem: A salt-wedge Mediterranean estuary.
abstract: Highly stratified Mediterranean estuaries are unique environments where the tidal range is low and the tidal currents are almost negligible. The main characteristics of these environments are strong salinity gradients and other environmental parameters. In this study, 454 pyrosequencing of the 16S rRNA gene in combination with catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) was used to estimate the bacterial diversity across the Krka estuary in February and July 2013. The comparison of the data derived from these two techniques resulted in a significant but weak positive correlation (R=0.28) indicating a substantial difference in the bacterial community structure, depending on the applied method. The phytoplankton bloom observed in February was identified as one of the main factors shaping the bacterial community structure between the two environmentally contrasting sampling months. Roseobacter, Bacteroidetes and Gammaproteobacteria differed substantially between February and July. Typical freshwater bacterial classes (Actinobacteria and Betaproteobacteria) showed strong vertical distribution patterns depending on the salinity gradient. Cyanobacteria decreased in abundance in February due to competition with phytoplankton, while the SAR11 clade increased its abundance in July as a result of a better adaptation toward more oligotrophic conditions. The results provided the first detailed insight into the bacterial diversity in a highly stratified Mediterranean karstic estuary.
authors.affiliation: Center for Marine Research, Ruđer Bošković Institute, Rovinj, Croatia.
authors.forename: M
authors.initials: M
authors.lastname: Korlević
authors.affiliation: Paleobiology, Department of Earth Sciences, Uppsala University, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Šupraha
authors.affiliation: Division of Biology, Faculty of Science, University of Zagreb, Croatia.
authors.forename: Z
authors.initials: Z
authors.lastname: Ljubešić
authors.affiliation: Paleobiology, Department of Earth Sciences, Uppsala University, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Henderiks
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia.
authors.forename: I
authors.initials: I
authors.lastname: Ciglenečki
authors.affiliation: Division for Marine and Environmental Research, Ruđer Bošković Institute, Zagreb, Croatia.
authors.forename: J
authors.initials: J
authors.lastname: Dautović
authors.affiliation: Division of Material Chemistry, Ruđer Bošković Institute, Zagreb, Croatia; Center of Excellence for Science and Technology Integrating Mediterranean Region, Microbial Ecology, Zagreb, Croatia. Electronic address: sandi.orlic@irb.hr.
authors.forename: S
authors.initials: S
authors.lastname: Orlić
mesh_terms: D039903:Actinobacteria / Q000145:classification / Q000235:genetics; D001419:Bacteria / Q000145:classification* / Q000235:genetics*; D041963:Bacteroidetes / Q000145:classification / Q000235:genetics; D001483:Base Sequence; D020562:Betaproteobacteria / Q000145:classification / Q000235:genetics; D017523:Croatia; D000458:Cyanobacteria / Q000145:classification / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D017753:Ecosystem; D063366:Estuaries; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics; D017404:In Situ Hybridization, Fluorescence; D019083:Mediterranean Region; D059013:Microbial Consortia / Q000235:genetics*; D010839:Phytoplankton; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D041904:Roseobacter / Q000145:classification / Q000235:genetics; D012623:Seawater / Q000382:microbiology*; D017422:Sequence Analysis, DNA
chemical_list: D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S
keywords: 16S amplicon; CARD FISH; Diversity; Estuaries; Gradient; Phytoplankton bloom