Trace Metal Availability Affects Greenhouse Gas Emissions and Microbial Functional Group Abundance in Freshwater Wetland Sediments

Authors

George Giannopoulos
Katherine R. Hartop
Bonnie L. Brown
Bongkeun Song, Virginia Institute of Marine ScienceFollow
Lars Elsgaard
Rima B. Franklin

Document Type

Article

Department/Program

Virginia Institute of Marine Science

Publication Date

9-30-2020

Journal

Frontiers in Microbiology

Volume

11

First Page

560861

Abstract

We investigated the effects of trace metal additions on microbial nitrogen (N) and carbon (C) cycling using freshwater wetland sediment microcosms amended with micromolar concentrations of copper (Cu), molybdenum (Mo), iron (Fe), and all combinations thereof. In addition to monitoring inorganic N transformations (NO₃^–, NO₂^–, N₂O, NH₄⁺) and carbon mineralization (CO₂, CH₄), we tracked changes in functional gene abundance associated with denitrification (nirS, nirK, nosZ), dissimilatory nitrate reduction to ammonium (DNRA; nrfA), and methanogenesis (mcrA). With regards to N cycling, greater availability of Cu led to more complete denitrification (i.e., less N₂O accumulation) and a higher abundance of the nirK and nosZ genes, which encode for Cu-dependent reductases. In contrast, we found sparse biochemical evidence of DNRA activity and no consistent effect of the trace metal additions on nrfA gene abundance. With regards to C mineralization, CO₂ production was unaffected, but the amendments stimulated net CH₄ production and Mo additions led to increased mcrA gene abundance. These findings demonstrate that trace metal effects on sediment microbial physiology can impact community-level function. We observed direct and indirect effects on both N and C biogeochemistry that resulted in increased production of greenhouse gasses, which may have been mediated through the documented changes in microbial community composition and shifts in functional group abundance. Overall, this work supports a more nuanced consideration of metal effects on environmental microbial communities that recognizes the key role that metal limitation plays in microbial physiology.

DOI

10.3389/fmicb.2020.560861

Keywords

denitrification, DNRA, carbon mineralization, wetland microbes, trace metals

Recommended Citation

Giannopoulos, George; Hartop, Katherine R.; Brown, Bonnie L.; Song, Bongkeun; Elsgaard, Lars; and Franklin, Rima B., Trace Metal Availability Affects Greenhouse Gas Emissions and Microbial Functional Group Abundance in Freshwater Wetland Sediments (2020). Frontiers in Microbiology, 11, 560861.

10.3389/fmicb.2020.560861