Experimental sulfate amendment alters peatland bacterial community structure

Abstract

As part of a long-term, peatland-scale sulfate addition experiment, the impact of varying sulfate deposition on bacterial community responses was assessed using 16S tag encoded pyrosequencing. In three separate areas of the peatland, sulfate manipulations included an eight year quadrupling of atmospheric sulfate deposition (experimental), a 3-year recovery to background deposition following 5years of elevated deposition (recovery), and a control area. Peat concentrations of methylmercury (MeHg), a bioaccumulative neurotoxin, were measured, the production of which is attributable to a growing list of microorganisms, including many sulfate-reducing Deltaproteobacteria. The total bacterial and Deltaproteobacterial community structures in the experimental treatment differed significantly from those in the control and recovery treatments that were either indistinguishable or very similar to one another. Notably, the relatively rapid return (within three years) of bacterial community structure in the recovery treatment to a state similar to the control, demonstrates significant resilience of the peatland bacterial community to changes in atmospheric sulfate deposition. Changes in MeHg accumulation between sulfate treatments correlated with changes in the Deltaproteobacterial community, suggesting that sulfate may affect MeHg production through changes in the community structure of this group.

Molecular evidence for novel mercury methylating microorganisms in sulfate-impacted lakes

“…MeHg is produced from inorganic mercury by certain anaerobic microorganisms. Sulfate-reducing microorganisms are thought to be the primary mercury methylators in most environments [4,5], and sulfate introduction to otherwise low-sulfate ecosystems can stimulate MeHg production [6][7][8][9][10]. But more recently, MeHg production has also been associated with iron-reducing microorganisms [11][12][13], methanogens [14], and other anaerobes [15].…”

Mobility and transport of mercury and methylmercury in peat as a function of changes in water table regime and plant functional groups

“…Climate‐induced changes in the hydrological regimes of peatlands significantly influence microbial community structure, which may have profound effects on peat decomposition and carbon sequestration [ Nunes et al ., ; Peltoniemi et al ., ]. Changes in bacterial community structure also have important links to methylmercury production in peatlands [ Strickman et al ., ]. Alterations to the carbon storage abilities of peatlands due to climate‐induced changes in the hydrology and ecology of these systems may affect the biogeochemical cycling and mobility of Hg within, and export from, these wetland systems.…”

Microbial Communities in Boreal Peatlands: Responses to Climate Change and Atmospheric Nitrogen and Sulfur Depositions

“…The resistance and resilience of interactions between species (ecological networks), with regard to environmental perturbations, are essential for ecosystem stability and are dependent on the microbial community structure (reviewed in Griffiths and Philippot, 2013). For instance, the peat microbial community has been reported to be highly resilient after 8 years of increased sulfate deposition and resistant or resilient to 11 years of simulated warming (Strickman et al, 2016;Weedon et al, 2017). Microbial communities change their structures in response to climate change and environmental perturbations (e.g.…”

“…warming, altered precipitation, increased carbon dioxide (CO2), increased atmospheric nitrogen (N) and sulphur (S) depositions), and the extent to which this occurs is dependent on the ecosystem type (e.g. Castro et al, 2010;Fierer et al, 2012;Hu et al, 2013;Shen et al, 2014;Contosta et al, 2015;Strickman et al, 2016;Zeng et al, 2016). These changes in microbial community structure may affect ecosystem functioning and stability, which in turn may impact the climate system via changes in greenhouse gas (GHG) turnover and other ecosystem-scale processes.…”

“…The extent of shifts in microbial composition, biomass and diversity, and rates of decomposition are dependent on both ecosystem type and time-scale (e.g. Fierer et al, 2012;Hu et al, 2013;Contosta et al, 2015;Strickman et al, 2016;Zeng et al, 2016;Xu et al, 2017). In peatlands, for example, microbial decomposition rates have been found to increase with N loading, resulting in C loss (Bragazza et al, 2006;Currey et al, 2010).…”