Assessing environmental drivers of microbial communities in estuarine soils of the Aconcagua River in Central Chile.

Sebastián Fuentes,Kornelia Smalla,Guo-Chun Ding,Franco Cárdenas,Michael Seeger,Patricia Sobecky

doi:10.1093/femsec/fiv110

Abstract

Aconcagua River basin (Central Chile) harbors diverse economic activities such as agriculture, mining and a crude oil refinery. The aim of this study was to assess environmental drivers of microbial communities in Aconcagua River estuarine soils, which may be influenced by anthropogenic activities taking place upstream and by natural processes such as tides and flood runoffs. Physicochemical parameters were measured in floodplain soils along the estuary. Bacteria, Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Pseudomonas, Bacillus and Fungi were studied by DGGE fingerprinting of 16S rRNA gene and ribosomal ITS-1 amplified from community DNA. Correlations between environment and communities were assessed by distance-based redundancy analysis. Mainly hydrocarbons, pH and the composed variable copper/arsenic/calcium but in less extent nitrogen and organic matter/phosphorous/magnesium correlated with community structures at different taxonomic levels. Aromatic hydrocarbons degradation potential by bacterial community was studied. Polycyclic aromatic hydrocarbon ring-hydroxylating dioxygenases genes were detected only at upstream sites. Naphthalene dioxygenase ndo genes were heterogeneously distributed along estuary, and related to Pseudomonas, Delftia, Comamonas and Ralstonia. IncP-1 plasmids were mainly present at downstream sites, whereas IncP-7 and IncP-9 plasmids showed a heterogeneous distribution. This study strongly suggests that pH, copper, arsenic and hydrocarbons are main drivers of microbial communities in Aconcagua River estuarine soils.

Highlights

Coastal estuaries are changing ecosystems influenced by several dynamic processes
Actinobacteria, Alphaproteobacteria, Betaproteobacteria, Pseudomonas, Bacillus and Fungi were studied by Denaturant gradient gel electrophoresis (DGGE) fingerprinting of 16S rRNA gene and ribosomal internal transcribed spacer (ITS)-1 amplified from community DNA
Denaturant gradient gel electrophoresis (DGGE) fingerprinting of 16S rRNA gene fragments amplified from total community DNA was used to analyze the bacterial and fungal structure at five soils, from ∼10 m from seashore until ∼1500 m upstream

Summary

Introduction

Brackish water formed by the confluence of sea- and freshwater, and sediments carried by each fraction, provides a buffer zone with particular physicochemical and sedimentological properties Organisms developing in this environment are usually euryhaline. Estuarine soils at river shore ( called floodplain soils) are submerged or not depending on the tide level and flooding regime These soils are the result of interactions between the soil and its aquatic environment and are considered as semiterrestrial soils (Cordova-Kreylos et al 2006; Du Laing et al 2009). Most human activities develop close to rivers, and seaports are usually settled on estuaries. These environments are of economic, social and ecological relevance. Microbial communities are largely affected by environmental disturbances, such as agriculture (Suzuki et al 2012; Ding et al 2013; Vasileiadis et al 2013), pH changes (Gonzalez-Toril et al 2003; Lauber et al 2009; Rousk, Brookes and Baa ̊ th 2009; Baffico 2010; Rousk et al 2010), heavy metal pollution (Cordova-Kreylos et al 2006; Altimira et al 2012), pesticide application (Morgante et al 2010; Hernandez et al 2011) and hydrocarbon pollution (Gomes et al 2007; Ding et al 2010; Yergeau et al 2012)

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Results