About

Brandy Toner is a Professor in the Department of Soil, Water, and Climate at the University of Minnesota Twin Cities. She holds a BS from Bemidji State University, an MS, and a PhD from the University of California, Berkeley. Her research focuses on chemical and biological processes that influence the cycling of metals in the environment, with particular attention to metal speciation, transport, fate, and bioavailability. Her favorite metals are iron (Fe) and manganese (Mn), which are prevalent in terrestrial and aquatic environments and form reactive minerals such as Fe oxyhydroxides and Mn oxides that affect the partitioning of other elements like arsenic. Her work also explores how microbial activity complicates the speciation of these metals. Brandy Toner teaches courses including Soil Chemistry and Mineralogy, Issues in the Environment, and Land and Atmospheric Science Seminar. She has been recognized for her teaching excellence with the 2014 Distinguished Faculty Teaching Award from the CFANS Collegiate Awards.

Research topics

• Biology
• Chemistry
• Environmental chemistry
• Engineering ethics
• Engineering
• Aerospace engineering
• Organic chemistry
• Physical chemistry
• Inorganic chemistry
• Ecology
• Biochemistry
• Aeronautics
• Astrobiology

Selected publications

• Iron speciation and partitioning of micronutrient transition metals in laboratory synthesized hydrothermal plume particles

  Geochimica et Cosmochimica Acta · 2026-02-11

  article
  PublisherDOI

• Sulfur Redox Status in Peatland Soil and Outflow Waters Diverge with Climate Warming

  2026-03-14

  articleOpen access1st authorCorresponding

  Boreal peatlands are important continental reservoirs of carbon and other elements. Changes in climate, especially increasing temperatures and more variable precipitation, alter oxidation-reduction (redox) conditions and fluxes of atmospheric and aquatic pollutants from peatlands. Here, we measure the effect of warming and elevated carbon dioxide on the speciation of sulfur in boreal peatland soil and outflow water over three years. In whole ecosystem warming experiments, with temperature levels of +0 °C (control), +2.25 °C, +4.5 °C, +6.75 °C, and +9 °C above ambient, water table height was negatively correlated with warming. Warming was correlated with changes in the size of sulfur pools, specifically, sulfur content (weight%) decreased in soils and sulfate (SO 4 2- aq) concentrations increased in outflow. Reflecting the warmer and drier conditions, the percentage of oxidized sulfur in soil, asmeasured by X-ray absorption near edge structure (XANES) spectroscopy, increased with warming. Sulfur speciation in soil showed increases in ester-sulfate (R-O-SO 3 - ) content at the expense of organic disulfide (R-S-S-R’) content. In contrast to the soil, the percentage of oxidized sulfur decreased in outflow with warming. The changes in sulfur speciation in outflow were characterized by increased organic monosulfide (R-S-R’, R-S-H) content at theexpense of ester-sulfate. Overall, the peatland sulfur pools are becoming more oxidized in the soil and more chemically reduced in the outflow water in response to soil and air warming. The connection between these opposite redox trends is likely due to enhanced microbial activity in porewaters and outflow with warming. Specifically, we observed that ester-sulfate partitions from soil to outflow waters during heavy rainfall periods (based on weeklyprecipitation). We surmise that increases in ester-sulfate in outflow make it available for microbial sulfur reduction processes that are also enhanced at warmer temperatures. Our study indicates that the peatland response to climate warming is complex: oxidation of sulfur in soil and the chemical reduction of sulfur in the outflow water are both correlated with warming. Notably, no significant effect of elevated carbon dioxide on sulfur pools was detected. Our findings are consistent with a net export of organic sulfur from the peatland to receiving surface waters. Furthermore, the overall loss of sulfur from this peatland is consistent with enhanced decomposition and increased plant available nutrients reported previously for this whole ecosystem warming experiment. Warming-induced changes to sulfur pools in peatlands affect the fluxes of other constituents, such as organic carbon and the pollutant methyl-mercury, that have downstream consequences for climate and water quality.

  PublisherDOI

• The potential for coupled organic and inorganic sulfur cycles across the terrestrial deep subsurface biosphere

  Nature Communications · 2025-04-23 · 6 citations

  articleOpen access

  Organosulfur compounds (OrgS) are fundamental components of life’s biomass, yet the cycling of these compounds in the terrestrial deep subsurface, one of Earth’s largest ecosystems, has gone relatively unexplored. Here, we show that all subsurface microbial genomes reconstructed from Soudan Underground Mine State Park have the capacity to cycle organic sulfur species. Our findings suggest that OrgS degradation may be an integral link between the organic and inorganic sulfur cycle via the production of sulfite and sulfide. Furthermore, despite isolation from surface ecosystems, most Soudan microorganisms retained genes for dimethylsulfoniopropionate and taurine biosynthesis. Metagenomic analyses of an additional 54 deep subsurface sites spanning diverse lithologies revealed the capacity for OrgS cycling to be widespread, occurring in 89% of assembled metagenomes. Our results indicate that consideration of OrgS cycling may be necessary to accurately constrain sulfur fluxes, discern the energetic limits of deep life, and determine the impact of deep subsurface biogeochemical sulfur cycling on greater Earth system processes. Organic sulfur compounds are vital to life but often overlooked in the sulfur cycle, especially in the subsurface. Subsurface microbes can metabolize diverse organosulfur compounds, hinting at a more complex sulfur cycle than previously thought.

  PublisherOA PDFDOI

• Diverse Cooccurring Metabolisms Support Sulfur and Methane Cycling in Wetland Surficial Sediments

  Journal of Geophysical Research Biogeosciences · 2025-09-01

  articleOpen access

  Abstract The Prairie Pothole Region (PPR) of North America contains millions of small depressional wetlands with some of the highest methane (CH 4 ) fluxes ever reported in terrestrial ecosystems. In saturated soils, two conventional paradigms are (a) methanogenesis is the final step in the redox ladder, occurring only after more thermodynamically favorable electron acceptors (e.g., sulfate) are reduced, and (b) CH 4 is primarily produced by acetoclastic and hydrogenotrophic pathways. However, previous work in PPR wetlands observed co‐occurrence of sulfate‐reduction and methanogenesis and the presence of diverse methanogenic substrates (i.e., methanol, DMS). This study investigated how methylotrophic methanogenesis—in addition to acetoclastic and hydrogenotrophic methanogenesis—significantly contributes to CH 4 flux in surface sediments and thus allows for the co‐occurrence of competing redox processes in PPR sediments. We addressed this aim through field studies in two distinct high CH 4 emitting wetlands in the PPR complex, which coupled microbial community compositional and functional inferences with depth‐resolved electrochemistry measurements in surficial wetland sediments. This study revealed methylotrophic methanogens as the dominant group of methanogens in the presence of abundant organic sulfate esters, which are likely used for sulfate reduction. Resulting high sulfide concentrations likely caused sulfide toxicity in hydrogenotrophic and acetoclastic methanogens. Additionally, the use of non‐competitive substrates by many methylotrophic methanogens allows these metabolisms to bypass thermodynamic constraints and can explain co‐existence patterns of sulfate‐reduction and methanogenesis. This study demonstrates that the current models of methanogenesis in wetland ecosystems insufficiently represent carbon cycling in some of the highest CH 4 emitting environments.

  PublisherOA PDFDOI

• Nano-scale Investigation of Carbon, Iron, and Sulfur Speciation at Sediment-Water Interfaces from Prairie Pothole Region Ponds with Synchrotron Spectromicroscopy

  2025-01-01

  article
  PublisherDOI

• Atmospheric Greenhouse Gas Emissions from Wetlands: Dark Fenton-Hydroxyl Radical Production in Prairie Pothole Wetlands

  2025-01-01

  articleSenior author
  PublisherDOI

• Silica at Enceladus is an ambiguous sign of seafloor hydrothermal activity

  Research Square · 2025-08-18

  preprintOpen access
  PublisherOA PDFDOI

• Sulfide stress tolerance as a controller of methane production in temperate wetlands

  The ISME Journal · 2025-01-01 · 1 citations

  articleOpen access

  Wetlands are a major source of methane emissions and contribute to the observed increase in atmospheric methane over the last 20 years. Methane production in wetlands is the final step of carbon decomposition performed by anaerobic archaea. Although hydrogen/carbon dioxide and acetate are the substrates most often attributed to methanogenesis, other substrates-such as methylated compounds-may additionally play important roles in driving methane production in wetland systems. Here we conducted mesocosm experiments combined with genome-resolved metatranscriptomics to investigate the impact of diverse methanogenic substrate amendment on methanogenesis in two high methane-emitting wetlands with distinct geochemistry, termed P7 and P8. Methanol amendment resulted in high methane production at both sites, whereas acetate and formate amendment only stimulated methanogenesis in P7 mesocosms, where aqueous sulfide concentrations were lower. In P7 sediments, formate amendment fueled acetogenic microbes that produced acetate, which was subsequently utilized by acetoclastic methanogens. In contrast to expression profiles in P7 mesocosms, active methylotrophic methanogen genomes from P8 showed increased expression of genes related to membrane remodeling and DNA damage repair, indicative of stress tolerance mechanisms to counter sulfide toxicity. Methylotrophic methanogenesis generates higher free energy yields than acetoclastic methanogenesis, which likely enables allocation of more energy toward stress responses. These findings contribute to the growing body of literature highlighting methylotrophic methanogenesis as an important methane production pathway in wetlands. By using less competitive substrates like methanol that provide greater energy yields, methylotrophic methanogens may invest in physiological strategies that provide competitive advantages across a range of environmental stresses.

  PublisherOA PDFDOI

• Effects of Pore‐Scale Three‐Dimensional Flow and Fluid Inertia on Mineral Dissolution

  Water Resources Research · 2025-04-01 · 3 citations

  articleOpen access

  Abstract Mineral dissolution releases ions into fluids and alters pore structures, affecting geochemistry and subsurface fluid flow. Thus, mineral dissolution plays a crucial role in many subsurface processes and applications. Pore‐scale fluid flow often controls mineral dissolution by controlling concentration gradients at fluid‐solid interfaces. In particular, recent studies have shown that fluid inertia can significantly affect reactive transport in porous and fractured media by inducing unique flow structures such as recirculating flows. However, the effects of pore‐scale flow and fluid inertia on mineral dissolution remain largely unknown. To address this knowledge gap, we combined visual laboratory experiments and micro‐continuum pore‐scale reactive transport modeling to investigate the effects of pore‐scale flow and fluid inertia on mineral dissolution dynamics. Through flow topology analysis, we identified unique patterns of 2D and 3D recirculating flows and their distinctive effects on dissolution. The simulation results revealed that 3D flow topology and fluid inertia dramatically alter the spatiotemporal dynamics of mineral dissolution. Furthermore, we found that the 3D flow topology fundamentally changes the upscaled relationship between porosity and reactive surface area compared to a conventional relationship, which is commonly used in continuum‐scale modeling. These findings highlight the critical role of 3D flow and fluid inertia in modeling mineral dissolution across scales, from the pore scale to the Darcy scale.

  PublisherOA PDFDOI

• Hydrothermally Induced Refractory DOC Sinks in the Deep Pacific Ocean

  Global Biogeochemical Cycles · 2025-09-01 · 1 citations

  articleOpen accessSenior author

  Abstract Dissolved organic carbon (DOC) constitutes the largest pool of reduced carbon in the global ocean, with important contributions from both recently formed and aged, biologically refractory DOC (RDOC). The mechanisms regulating RDOC transformation and removal remain uncertain though hydrothermal vents have been identified as sources and sinks. This study examines RDOC sinks in the deep Pacific Ocean, highlighting the role of submarine hydrothermal systems. Geochemical survey data from GO‐SHIP and GEOTRACES projects, alongside specific investigations of Pacific hydrothermal systems, suggest that particulate iron introduced by hydrothermal systems plays a key role in scavenging DOC and delivering it to the seafloor, leaving a deficit in the RDOC of the deep ocean. Dilution of the oceanic water column by hydrothermal fluids exhibiting low DOC concentrations likely plays a secondary role.

  PublisherOA PDFDOI

Recent grants

• Collaborative Research: Integrating geochemistry, microbiology, and hydrodynamics: A model for trace element transport and fate in hydrothermal plumes

  NSF · $198k · 2010–2014

• Collaborative Research: GEOTRACES Pacific Section: The Geochemistry of Size-fractionated Suspended Particles Collected by In-situ Filtration

  NSF · $199k · 2013–2016

• Collaborative research: Banded together: modern water-microbe-mineral feedbacks in the deep Archean lithosphere

  NSF · $2.0M · 2018–2025

• Collaborative Research: From hot to cold in the dark - shifts in seafloor massive sulfide microbial communities as physical and geochemical conditions change after venting ceases

  NSF · $304k · 2018–2023

Frequent coauthors

• Sarah Nicholas

  Lamont-Doherty Earth Observatory

  109 shared

• Colleen Hoffman

  National Energy Technology Laboratory

  98 shared

• Paul Northrup

  Stony Brook University

  84 shared

• Rose M. Jones

  University of Minnesota

  82 shared

• Wen Hu

  81 shared

• Benjamin S. Twining

  81 shared

• Benjamín C. Bostick

  81 shared

• Alessandra C. Leri

  Marymount Manhattan College

  81 shared

Labs

• Toner LabPI

  low-temperature geochemistry

Awards & honors

• 2014 Distinguished Faculty Teaching Awards: Graduate, CFANS