Distribution of iron- and sulfate-reducing bacteria across a coastal acid sulfate soil (CASS) environment: implications for passive bioremediation by tidal inundation.

Yu-Chen Ling,John W Moreau,Richard Bush,Kliti Grice,Lyndon Berwick,Svenja Tulipani

doi:10.3389/fmicb.2015.00624

Yu-Chen Ling, John W Moreau + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2015.00624

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Abstract

Coastal acid sulfate soils (CASS) constitute a serious and global environmental problem. Oxidation of iron sulfide minerals exposed to air generates sulfuric acid with consequently negative impacts on coastal and estuarine ecosystems. Tidal inundation represents one current treatment strategy for CASS, with the aim of neutralizing acidity by triggering microbial iron- and sulfate-reduction and inducing the precipitation of iron-sulfides. Although well-known functional guilds of bacteria drive these processes, their distributions within CASS environments, as well as their relationships to tidal cycling and the availability of nutrients and electron acceptors, are poorly understood. These factors will determine the long-term efficacy of “passive” CASS remediation strategies. Here we studied microbial community structure and functional guild distribution in sediment cores obtained from 10 depths ranging from 0 to 20 cm in three sites located in the supra-, inter- and sub-tidal segments, respectively, of a CASS-affected salt marsh (East Trinity, Cairns, Australia). Whole community 16S rRNA gene diversity within each site was assessed by 454 pyrotag sequencing and bioinformatic analyses in the context of local hydrological, geochemical, and lithological factors. The results illustrate spatial overlap, or close association, of iron-, and sulfate-reducing bacteria (SRB) in an environment rich in organic matter and controlled by parameters such as acidity, redox potential, degree of water saturation, and mineralization. The observed spatial distribution implies the need for empirical understanding of the timing, relative to tidal cycling, of various terminal electron-accepting processes that control acid generation and biogeochemical iron and sulfur cycling.

Highlights

Coastal acid sulfate soils (CASS) constitute a major global environmental problem (Dent and Pons, 1995; White et al, 2007; Ljung et al, 2009)
We present results and analyses from an investigation of whole community 16S rRNA genes amplified from CASS-impacted sediments from the East Trinity wetlands (Cairns, Australia), a tidally influenced wetland located on the northeast coast of Australia
Organic Geochemistry Analyses The polar fractions from surface sediments of each transect site, as well as from the acidic control site, were dominated by a Shannon and Simpson diversity indices showed a significant difference among the three sites (P < 0.01, ANOVA), which is shown on the pH and Eh diagram with the inverse Simpson index (Figure 3)

Summary

Introduction

Coastal acid sulfate soils (CASS) constitute a major global environmental problem (Dent and Pons, 1995; White et al, 2007; Ljung et al, 2009). The resulting problems include fish kills (Powell and Martens, 2005; Stephens and Ingram, 2006), decreased rice yields (Bronswijk et al, 1995), release of greenhouse gases such as methane and dinitrogen oxide (Denmead et al, 2007), sulfur dioxide emissions (Macdonald et al, 2004), construction damage (Crammond, 2002), and changed mobility of toxic metals (Burton et al, 2008). Drainage allows oxygen to penetrate further into the subsurface, resulting in oxidation of iron sulfides and release of protons and sulfuric acid. The oxidation of pyrite by molecular oxygen (Hicks et al, 1999): FeS2 + 3.75O2 + 3.5H2O → Fe(OH)3 + 4H+ + 2SO24− (1)

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