Gregory K. Druschel

Permanent URI for this collection

https://hdl.handle.net/1805/43173

Browse

Now showing 1 - 10 of 30

Linking Dissolved Organic Matter Composition to Landscape Properties in Wetlands Across the United States of America
(Wiley, 2024-05-03) Kurek, Martin R.; Wickland, Kimberly P.; Nichols, Natalie A.; McKenna, Amy M.; Anderson, Steven M.; Dornblaser, Mark M.; Koupaei-Abyazani, Nikaan; Poulin, Brett A.; Bansal, Sheel; Fellman, Jason B.; Druschel, Gregory K.; Bernhardt, Emily S.; Spencer, Robert G.M.
Wetlands are integral to the global carbon cycle, serving as both a source and a sink for organic carbon. Their potential for carbon storage will likely change in the coming decades in response to higher temperatures and variable precipitation patterns. We characterized the dissolved organic carbon (DOC) and dissolved organic matter (DOM) composition from 12 different wetland sites across the USA spanning gradients in climate, landcover, sampling depth, and hydroperiod for comparison to DOM in other inland waters. Using absorption spectroscopy, parallel factor analysis modeling, and ultra-high resolution mass spectroscopy, we identified differences in DOM sourcing and processing by geographic site. Wetland DOM composition was driven primarily by differences in landcover where forested sites contained greater aromatic and oxygenated DOM content compared to grassland/herbaceous sites which were more aliphatic and enriched in N and S molecular formulae. Furthermore, surface and porewater DOM was also influenced by properties such as soil type, organic matter content, and precipitation. Surface water DOM was relatively enriched in oxygenated higher molecular weight formulae representing HUPHigh O/C compounds than porewaters, whose DOM composition suggests abiotic sulfurization from dissolved inorganic sulfide. Finally, we identified a group of persistent molecular formulae (3,489) present across all sites and sampling depths (i.e., the signature of wetland DOM) that are likely important for riverine-to-coastal DOM transport. As anthropogenic disturbances continue to impact temperate wetlands, this study highlights drivers of DOM composition fundamental for understanding how wetland organic carbon will change, and thus its role in biogeochemical cycling.
Sulfide Oxidation Products Support Microbial Metabolism at Interface Environments in a Marine‐Like Serpentinizing Spring in Northern California
(Wiley, 2025) Trutschel, Leah; Kruger, Brittany; Czaja, Andrew; Brueck, Megan; Sackett, Joshua; Druschel, Gregory; Rowe, Annette; Earth and Environmental Sciences, School of Science
Interface environments between extreme and neutrophilic conditions are often hotspots of metabolic activity and taxonomic diversity. In serpentinizing systems, the mixing of high pH fluids with meteoric water, and/or the exposure of these fluids to the atmosphere can create interface environments with distinct but related metabolic activities and species. Investigating these systems can provide insights into the factors that stimulate microbial growth, and/or what attributes may be limiting microbial physiologies in native serpentinized fluids. To this aim, changes in geochemistry and microbial communities were investigated for different interface environments at Ney Springs-a marine-like terrestrial serpentinization system where the main serpentinized fluids have been well characterized geochemically and microbially. We found that reduced sulfur species from Ney Springs had large impacts on the community changes observed at interface environments. Oxygen availability at outflow environments resulted in a relative increase in the taxa observed that were capable of sulfur oxidation, and in some cases light-driven sulfur oxidation. A combination of cultivation work and metagenomics suggests these groups seem to predominantly target sulfur intermediates like polysulfide, elemental sulfur, and thiosulfate as electron donors, which are present and abundant to various degrees throughout the Ney system. Fluid mixing with meteoric water results in more neutral pH systems which in turn select for different sulfur-oxidizing taxa. Specifically, we see blooms of taxa that are not typically observed in the primary Ney fluids, such as Halothiobacillus in zones where fluids mix underground with meteoric water (~pH 10) or the introduction of Thiothrix into the nearby creek as fluids enter at the surface (~pH 8). This work points to the potential importance of oxidants for stimulating microbial respiration at Ney Springs, and the observation that these serpentinized fluids act as an important source of reduced sulfur, supporting diverse taxa around the Ney Springs system.
Bioenergetic characterization of a shallow-sea hydrothermal vent system: Milos Island, Greece
(Public Library of Science, 2020-06-05) Lu, Guang-Sin; LaRowe, Douglas E.; Fike, David A.; Druschel, Gregory K.; Gilhooly, William P., III; Price, Roy E.; Amend, Jan P.; Earth and Environmental Sciences, School of Science
Shallow-sea hydrothermal systems, like their deep-sea and terrestrial counterparts, can serve as relatively accessible portals into the microbial ecology of subsurface environments. In this study, we determined the chemical composition of 47 sediment porewater samples along a transect from a diffuse shallow-sea hydrothermal vent to a non-thermal background area in Paleochori Bay, Milos Island, Greece. These geochemical data were combined with thermodynamic calculations to quantify potential sources of energy that may support in situ chemolithotrophy. The Gibbs energies (ΔGr) of 730 redox reactions involving 23 inorganic H-, O-, C-, N-, S-, Fe-, Mn-, and As-bearing compounds were calculated. Of these reactions, 379 were exergonic at one or more sampling locations. The greatest energy yields were from anaerobic CO oxidation with NO2- (-136 to -162 kJ/mol e-), followed by reactions in which the electron acceptor/donor pairs were O2/CO, NO3-/CO, and NO2-/H2S. When expressed as energy densities (where the concentration of the limiting reactant is taken into account), a different set of redox reactions are the most exergonic: in sediments affected by hydrothermal input, sulfide oxidation with a range of electron acceptors or nitrite reduction with different electron donors provide 85~245 J per kg of sediment, whereas in sediments less affected or unaffected by hydrothermal input, various S0 oxidation reactions and aerobic respiration reactions with several different electron donors are most energy-yielding (80~95 J per kg of sediment). A model that considers seawater mixing with hydrothermal fluids revealed that there is up to ~50 times more energy available for microorganisms that can use S0 or H2S as electron donors and NO2- or O2 as electron acceptors compared to other reactions. In addition to revealing likely metabolic pathways in the near-surface and subsurface mixing zones, thermodynamic calculations like these can help guide novel microbial cultivation efforts to isolate new species.
Involvement of Intermediate Sulfur Species in Biological Reduction of Elemental Sulfur under Acidic, Hydrothermal Conditions
(American Society for Microbiology, 2013) Boyd, Eric S.; Druschel, Gregory K.; Earth and Environmental Sciences, School of Science
The thermoacidophile and obligate elemental sulfur (S(8)(0))-reducing anaerobe Acidilobus sulfurireducens 18D70 does not associate with bulk solid-phase sulfur during S(8)(0)-dependent batch culture growth. Cyclic voltammetry indicated the production of hydrogen sulfide (H(2)S) as well as polysulfides after 1 day of batch growth of the organism at pH 3.0 and 81°C. The production of polysulfide is likely due to the abiotic reaction between S(8)(0) and the biologically produced H(2)S, as evinced by a rapid cessation of polysulfide formation when the growth temperature was decreased, inhibiting the biological production of sulfide. After an additional 5 days of growth, nanoparticulate S(8)(0) was detected in the cultivation medium, a result of the hydrolysis of polysulfides in acidic medium. To examine whether soluble polysulfides and/or nanoparticulate S(8)(0) can serve as terminal electron acceptors (TEA) supporting the growth of A. sulfurireducens, total sulfide concentration and cell density were monitored in batch cultures with S(8)(0) provided as a solid phase in the medium or with S(8)(0) sequestered in dialysis tubing. The rates of sulfide production in 7-day-old cultures with S(8)(0) sequestered in dialysis tubing with pore sizes of 12 to 14 kDa and 6 to 8 kDa were 55% and 22%, respectively, of that of cultures with S(8)(0) provided as a solid phase in the medium. These results indicate that the TEA existed in a range of particle sizes that affected its ability to diffuse through dialysis tubing of different pore sizes. Dynamic light scattering revealed that S(8)(0) particles generated through polysulfide rapidly grew in size, a rate which was influenced by the pH of the medium and the presence of organic carbon. Thus, S(8)(0) particles formed through abiological hydrolysis of polysulfide under acidic conditions appeared to serve as a growth-promoting TEA for A. sulfurireducens.
Unraveling iron oxides as abiotic catalysts of organic phosphorus recycling in soil and sediment matrices
(Springer Nature, 2024-07-18) Basinski, Jade J.; Bone, Sharon E.; Klein, Annaleise R.; Thongsomboon, Wiriya; Mitchell, Valerie; Shukle, John T.; Druschel, Gregory K.; Thompson, Aaron; Aristilde, Ludmilla; Earth and Environmental Sciences, School of Science
In biogeochemical phosphorus cycling, iron oxide minerals are acknowledged as strong adsorbents of inorganic and organic phosphorus. Dephosphorylation of organic phosphorus is attributed only to biological processes, but iron oxides could also catalyze this reaction. Evidence of this abiotic catalysis has relied on monitoring products in solution, thereby ignoring iron oxides as both catalysts and adsorbents. Here we apply high-resolution mass spectrometry and X-ray absorption spectroscopy to characterize dissolved and particulate phosphorus species, respectively. In soil and sediment samples reacted with ribonucleotides, we uncover the abiotic production of particulate inorganic phosphate associated specifically with iron oxides. Reactions of various organic phosphorus compounds with the different minerals identified in the environmental samples reveal up to ten-fold greater catalytic reactivities with iron oxides than with silicate and aluminosilicate minerals. Importantly, accounting for inorganic phosphate both in solution and mineral-bound, the dephosphorylarion rates of iron oxides were within reported enzymatic rates in soils. Our findings thus imply a missing abiotic axiom for organic phosphorus mineralization in phosphorus cycling.
Multiple sulfur isotopes fractionations associated with abiotic sulfur transformations in Yellowstone National Park geothermal springs
(Springer Nature, 2014-05-28) Kamyshny, Alexey, Jr.; Druschel, Gregory; Mansaray, Zahra F.; Farquhar, James; Earth and Environmental Sciences, School of Science
Background: The paper presents a quantification of main (hydrogen sulfide and sulfate), as well as of intermediate sulfur species (zero-valent sulfur (ZVS), thiosulfate, sulfite, thiocyanate) in the Yellowstone National Park (YNP) hydrothermal springs and pools. We combined these measurements with the measurements of quadruple sulfur isotope composition of sulfate, hydrogen sulfide and zero-valent sulfur. The main goal of this research is to understand multiple sulfur isotope fractionation in the system, which is dominated by complex, mostly abiotic, sulfur cycling. Results: Water samples from six springs and pools in the Yellowstone National Park were characterized by pH, chloride to sulfate ratios, sulfide and intermediate sulfur species concentrations. Concentrations of sulfate in pools indicate either oxidation of sulfide by mixing of deep parent water with shallow oxic water, or surface oxidation of sulfide with atmospheric oxygen. Thiosulfate concentrations are low (<6 μmol L(-1)) in the pools with low pH due to fast disproportionation of thiosulfate. In the pools with higher pH, the concentration of thiosulfate varies, depending on different geochemical pathways of thiosulfate formation. The δ(34)S values of sulfate in four systems were close to those calculated using a mixing line of the model based on dilution and boiling of a deep hot parent water body. In two pools δ(34)S values of sulfate varied significantly from the values calculated from this model. Sulfur isotope fractionation between ZVS and hydrogen sulfide was close to zero at pH < 4. At higher pH zero-valent sulfur is slightly heavier than hydrogen sulfide due to equilibration in the rhombic sulfur-polysulfide - hydrogen sulfide system. Triple sulfur isotope ((32)S, (33)S, (34)S) fractionation patterns in waters of hydrothermal pools are more consistent with redox processes involving intermediate sulfur species than with bacterial sulfate reduction. Small but resolved differences in ∆(33)S among species and between pools are observed. Conclusions: The variation of sulfate isotopic composition, the origin of differences in isotopic composition of sulfide and zero-valent sulfur, as well as differences in ∆(33)S of sulfide and sulfate are likely due to a complex network of abiotic redox reactions, including disproportionation pathways.
The mobility of phosphorus, iron, and manganese through the sediment–water continuum of a shallow eutrophic freshwater lake under stratified and mixed water-column conditions
(Springer, 2016) Giles, Courtney D.; Isles, Peter D. F.; Manley, Tom; Xu, Yaoyang; Druschel, Gregory K.; Schroth, Andrew W.; Earth and Environmental Sciences, School of Science
The management of external nutrient inputs to eutrophic systems can be confounded due to a persistent pool of phosphorus (P) in lake sediments. The behaviors of P and trace metals depend largely on the reductive dissolution of amorphous iron (Fe) and manganese (Mn) (oxy)hydroxides in sediments; however, a holistic understanding of these dynamics in relation to the broader ecological and hydrodynamic conditions of the system remains elusive. We used a high-frequency monitoring approach to develop a comprehensive conceptual model of P, Mn, and Fe dynamics across the sediment water continuum of a shallow bay in Lake Champlain (Missisquoi Bay, USA). The greatest release of sediment P, Mn, and Fe occurred under stable hydrodynamic conditions, particularly during the onset of the cyanobacterial bloom and was associated with low available P and the accumulation of soluble Mn and Fe above the sediment–water interface (SWI). During the warmest part of the season, bloom severity and sediment P release was partially regulated by hydrodynamic drivers, which changed on hourly time scales to affect redox conditions at the SWI and bottom water concentrations of soluble P, Mn, and Fe. A geochemically distinct increase in soluble P and Fe concentrations, but not Mn, marked the influence of riverine inputs during a late season storm disturbance. Despite continued depletion of the reactive sediment P and metals pool into the bloom period, declining temperatures and a well-mixed water column resulted in bloom senescence and the return of P, Mn, and Fe to surface sediments. The closed cycling of P and metals in Missisquoi Bay poses a significant challenge for the long-term removal of P from this system. Multiple time-scale measures of physical and biogeochemical changes provide a basis for understanding P and trace metals behavior across sediments and the water column, which shape seasonally variable cyanobacterial blooms in shallow eutrophic systems.
Author Correction: Unraveling iron oxides as abiotic catalysts of organic phosphorus recycling in soil and sediment matrices
(Springer Nature, 2024-08-30) Basinski, Jade J.; Bone, Sharon E.; Klein, Annaleise R.; Thongsomboon, Wiriya; Mitchell, Valerie; Shukle, John T.; Druschel, Gregory K.; Thompson, Aaron; Aristilde, Ludmilla; Earth and Environmental Sciences, School of Science
Correction to: Nature Communications 10.1038/s41467-024-47931-z, published online 18 July 2024 The original version of this Article contained an error in the Abstract, which was previously incorrectly given as ‘ten-fold’. The correct version states ‘twenty-fold’ in place of ‘ten-fold’. This has been corrected in both the PDF and HTML versions of the Article.
Influence of Choline Chloride/Urea and Glycerol Plasticizers on the Mechanical Properties of Thermoplastic Starch Plastics
(MDPI, 2024-03-09) Staker, Jacob; Schott, Sydney; Singh, Riya; Collier, Kourtney; Druschel, Gregory; Siegel, Amanda P.; Tovar, Andres; Chemistry and Chemical Biology, School of Science
Bio-based plastics made of food-safe compostable materials, such as thermoplastic starch (TPS), can be designed into films that have potential to replace many non-biodegradable single-use plastic (SUP) items. TPS film characteristics, such as elongation at break and tensile strength, are largely affected by the choice of the plasticizers used in formulation. Our work identifies the mechanical properties and the chemical structural differences between TPS films made with two different plasticizer mixtures that have not yet been compared alongside one another: deep eutectic solvent choline chloride/urea (1:2) (CC:U) and glycerol with an acetic acid catalyst (AA:G). Potato-based TPS samples were formed by mixing each plasticizer with a consistent amount of potato starch and distilled water with heat. After gelation formation, the viscous TPS mixture was centrifuged to degas and extruded. Films were dried at controlled room temperature. Characterization included the tensile testing of coupons according to ASTM (American Society of Testing and Materials) standard D638, attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), melting point (MP), and scanning electron microscopy (SEM). The AA:G films displayed significantly higher tensile strength (M = 2.04 ± 1.24 MPa) than the CC:U films (M = 0.18 ± 0.08 MPa); however, the CC:U films had higher elongation at break (M = 47.2 ± 3.6%) than the AA:G films (M = 31.1 ± 12.6%). This can be explained by the difference in functional groups, composition, and the degree of crystallinity evidenced by the FTIR, XRD, MP, and SEM results. Our findings suggest that potato-based TPS films with an AA:G plasticizer mixture hold promise for SUP applications that require more strength, while CC:U films may be more suited for wraps and bags that require flexibility. These innovations can aid to mitigate the environmental impact of harmful plastic waste.
Sediment Disturbance Negatively Impacts Methanogen Abundance but Has Variable Effects on Total Methane Emissions
(Frontiers Media, 2022-02-21) Rowe, Annette; Urbanic, Megan; Trutschel, Leah; Shukle, John; Druschel, Gregory; Booth, Michael; Earth and Environmental Sciences, School of Science
Methane emissions from aquatic ecosystems are increasingly recognized as substantial, yet variable, contributions to global greenhouse gas emissions. This is in part due to the challenge of modeling biologic parameters that affect methane emissions from a wide range of sediments. For example, the impacts of fish bioturbation on methane emissions in the literature have been shown to result in a gradient of reduced to enhanced emissions from sediments. However, it is likely that variation in experimental fish density, and consequently the frequency of bioturbation by fish, impacts this outcome. To explore how the frequency of disturbance impacts the levels of methane emissions in our previous work we quantified greenhouse gas emissions in sediment microcosms treated with various frequencies of mechanical disturbance, analogous to different levels of activity in benthic feeding fish. Greenhouse gas emissions were largely driven by methane ebullition and were highest for the intermediate disturbance frequency (disturbance every 7 days). The lowest emissions were for the highest frequency treatment (3 days). This work investigated the corresponding impacts of disturbance treatments on the microbial communities associated with producing methane. In terms of total microbial community structure, no statistical difference was observed in the total community structure of any disturbance treatment (0, 3, 7, and 14 days) or sediment depth (1 and 3 cm) measured. Looking specifically at methanogenic Archaea however, a shift toward greater relative abundance of a putatively oxygen-tolerant methanogenic phylotype (ca. Methanothrix paradoxum) was observed for the highest frequency treatments and at depths impacted by disturbance (1 cm). Notably, quantitative analysis of ca. Methanothrix paradoxum demonstrated no change in abundance, suggesting disturbance negatively and preferentially impacted other methanogen populations, likely through oxygen exposure. This was further supported by a linear decrease in quantitative abundance of methanogens (assessed by qPCR of the mcrA gene), with increased disturbance frequency in bioturbated sediments (1 cm) as opposed to those below the zone of bioturbation (3 cm). However, total methane emissions were not simply a function of methanogen populations and were likely impacted by the residence time of methane in the lower frequency disturbance treatments. Low frequency mechanical disruption results in lower methane ebullition compared to higher frequency treatments, which in turn resulted in reduced overall methane release, likely through enhanced methanotrophic activities, though this could not be identified in this work. Overall, this work contributes to understanding how animal behavior may impact variation in greenhouse gas emissions and provides insight into how frequency of disturbance may impact emissions.

Browse

Recent Submissions