Multilevel analysis of the bacterial diversity along the environmental gradient Río de la Plata–South Atlantic Ocean

Abstract

The Río de la Plata is the world's largest estuary, draining the second largest basin of South America. In spite of its key significance at the local and global scale, this is the first attempt made so far to characterize the bacterial diversity of this system. We employed a suite of molecular methods to analyze the bacterial diversity at different phylogenetic levels, both in terms of richness and evenness, and we related these findings to physicochemical parameters. A clear environmental gradient was observed with 3 distinctive zones (riverine, frontal, and marine). In turn, the bacterial communities appeared highly diverse and strongly structured by the environment. A high number (324) of different operational taxonomic units (OTUs) were identified by automated ribosomal intergenic spacer analysis (ARISA). The ARISA results suggested that the composition of bacterioplankton communities was strongly related to physicochemical water characteristics, and that the bacterioplankton had little overlap with the bacterial assemblage of the sediments. Catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) indicated that Betaproteobacteria and Actinobacteria were more abundant in the riverine zone, whereas Gammaproteobacteria and Planctomycetes preferred the marine waters. The relative abundance of Bacteroidetes peaked in the frontal zone, and Alphaproteobacteria were numerically dominant throughout the estuary. The analysis of about 300 almost full-length 16S rRNA gene sequences pointed to the existence of ubiquitous phylotypes, but also suggested habitat preferences among certain groups. This first look into the bacterial community of the Río de la Plata demonstrated marked diversity patterns, providing further insights into the ecology of globally distributed groups of aquatic bacteria.

Abundance and diversity of Planctomycetes in a Tyrrhenian coastal system of central Italy

“…at SAB1 at the beginning of July 2003 is, to our knowledge, the highest value reported for a coastal system, exceeding previous reports by one order of magnitude (Morris et al 2006, Alonso et al 2010, Simonato et al 2010. The values found by these authors are very similar to the maximum of 5 × 10 4 ml −1 that we counted at the adjacent nearshore marine sampling site, SAB4.…”

“…Furthermore, genomic and metagenomic evidence indicates the specialization of marine Planctomycetes for algal polymer degradation (Glöckner et al 2003, Woebken et al 2007b. Recent studies have shown the presence of Planctomycetes in the Venice Lagoon (Simonato et al 2010) and the Río de la Plata estuary (Alonso et al 2010). An in-depth assessment of the diversity, abundance and distribution of coastal Planctomycetes has only recently been initiated for the North Sea (Pizzetti et al 2011).…”

Bacterial diversity patterns of the intertidal biofilm in urban beaches of Río de la Plata

“…Gómez et al (2009) found that microbenthic communities of Río de la Plata were governed by two gradients, the first one determined by anthropic factors and the second one to conductivity and turbidity. In the case of bacterioplankton communities, Alonso et al (2010) showed that bacterial abundance and diversity patterns based on ARISA data were highest at the frontal zone, where turbid waters from Paraná and Uruguay rivers mix with the Atlantic Ocean (Nagy et al, 2008). In that work the authors also found a relatively high number of unique OTUs in the frontal zone, suggesting the existence of a bacterial assemblage specific of this zone of the estuary.…”

“…In that work the authors also found a relatively high number of unique OTUs in the frontal zone, suggesting the existence of a bacterial assemblage specific of this zone of the estuary. Moreover, among the most abundant bacterial phyla they found that Bacteroidetes accounted for about one third of all bacteria at the frontal zone (Alonso et al, 2010). Thus, there are some clues about the existence of bacterial assemblages that are specific of the transitional, dynamic and changing environmental conditions found at estuaries, as well as the relevance of anthropogenic influence over the microbenthos species distribution.…”

Seasonal variation in marine-snow-associated and ambient-water prokaryotic communities in the northern Adriatic Sea

“…4), most likely derived from the diatom bloom that typically occurs in late autumn (Mozeti et al 2012) and which was also observed in December 2009 (Tinta et al 2014). However, the presence or high abundance of bacterial groups characteristic of low salinity estuarine or fresh waters, like Betaproteobacteria, Verucomicrobia and Actinobacteria (Kirch man et al 2005, Alonso et al 2010) might indicate a freshwater origin for a part of the bacterial community detected in marine snow in December. In addition, some bacterial groups, such as Gemmatimonadetes (Polymenakou et al 2005), Acidobacteria and soil-or sediment-associated Thaumarchaeota might originate from the sediment in this shallow coastal sea.…”