Land Resources & Environmental Sciences
Permanent URI for this communityhttps://scholarworks.montana.edu/handle/1/11
The Department of Land Resources and Environmental Sciences at Montana State Universityoffers integrative, multi-disciplinary, science-based degree programs at the B.S., M.S., and Ph.D. levels.
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Item Multiscale analysis of autotroph-heterotroph interactions in a high-temperature microbial community(2018-09) Hunt, Kristopher A.; Jennings, Ryan deM.; Inskeep, William P.; Carlson, Ross P.Interactions among microbial community members can lead to emergent properties, such as enhanced productivity, stability, and robustness. Iron-oxide mats in acidic (pH 2–4), high-temperature (> 65 °C) springs of Yellowstone National Park contain relatively simple microbial communities and are well-characterized geochemically. Consequently, these communities are excellent model systems for studying the metabolic activity of individual populations and key microbial interactions. The primary goals of the current study were to integrate data collected in situ with in silico calculations across process-scales encompassing enzymatic activity, cellular metabolism, community interactions, and ecosystem biogeochemistry, as well as to predict and quantify the functional limits of autotroph-heterotroph interactions. Metagenomic and transcriptomic data were used to reconstruct carbon and energy metabolisms of an important autotroph (Metallosphaera yellowstonensis) and heterotroph (Geoarchaeum sp. OSPB) from the studied Fe(III)-oxide mat communities. Standard and hybrid elementary flux mode and flux balance analyses of metabolic models predicted cellular- and community-level metabolic acclimations to simulated environmental stresses, respectively. In situ geochemical analyses, including oxygen depth-profiles, Fe(III)-oxide deposition rates, stable carbon isotopes and mat biomass concentrations, were combined with cellular models to explore autotroph-heterotroph interactions important to community structure-function. Integration of metabolic modeling with in situ measurements, including the relative population abundance of autotrophs to heterotrophs, demonstrated that Fe(III)-oxide mat communities operate at their maximum total community growth rate (i.e. sum of autotroph and heterotroph growth rates), as opposed to net community growth rate (i.e. total community growth rate subtracting autotroph consumed by heterotroph), as predicted from the maximum power principle. Integration of multiscale data with ecological theory provides a basis for predicting autotroph-heterotroph interactions and community-level cellular organization.Item DOM composition alters ecosystem function during microbial processing of isolated sources(2019-01) D'Andrilli, Juliana; Junker, James R.; Smith, Heidi J.; Scholl, Eric A.; Foreman, Christine M.Dynamics of dissolved organic matter (DOM) in ecosystems are controlled by a suite of interacting physical, chemical, and biological factors. Growing recognition of the associations between microbial communities and metabolism and intrinsic DOM characteristics, highlight the potential importance of microbe-DOM relationships to modulate the role and fate of DOM, yet these relationships are difficult to isolate because they often operate across confounding environmental gradients. In a controlled laboratory incubation (44 days), we integrated DOM bulk and molecular characterization, bacterial abundances, microbial assemblage composition, nutrient concentrations, and cellular respiration to discern the structural dynamics of biological processing among DOM sources from different allochthonous litters (grass, deciduous leaves, and evergreen needles). We identified two periods, consistent among DOM sources, where processing dynamics differed. Further, bulk fluorescent analyses showed shifts from low to high excitation and emission wavelengths, indicating the biological production of more complex/degraded materials over time. Molecular level analyses revealed similar temporal patterns among DOM sources in the production and consumption of individual chemical components varying in reactivity and heteroatomic content. Despite these similarities, total carbon (C) removed and carbon dioxide (CO2) accumulation differed by ~ 20% and 25% among DOM sources. This range in C processing was apparently tied to key chemical properties of the DOM (e.g., initial DOM composition, N content, and labile nature) as well as differential reorganization of the microbial populations that decomposed the DOM. We conclude that the production, transformation, and consumption of C in aquatic ecosystems is strongly dependent on the source and character of DOM as well as the structure of the microbial communities present, both of which change as DOM is processed over time. It is crucial that stream C processing models represent this complexity accurately.Item Opportunities and Trade-offs among BECCS and the Food, Water, Energy, Biodiversity, and Social Systems Nexus at Regional Scales(2018-01) Stoy, Paul C.; Ahmed, Selena; Jarchow, Meghann; Rashford, Benjamin; Swanson, David; Albeke, Shannon; Bromley, Gabriel T.; Brookshire, E. N. Jack; Dixon, Mark D.; Haggerty, Julia Hobson; Miller, Perry R.; Peyton, Brent M.; Royem, Alisa; Spangler, Lee H.; Straub, Crista; Poulter, BenjaminCarbon dioxide must be removed from the atmosphere to limit climate change to 2°C or less. The integrated assessment models used to develop climate policy acknowledge the need to implement net negative carbon emission strategies, including bioenergy with carbon capture and storage (BECCS), to meet global climate imperatives. The implications of BECCS for the food, water, energy, biodiversity, and social systems (FWEBS) nexus at regional scales, however, remain unclear. Here, we present an interdisciplinary research framework to examine the trade-offs as well as the opportunities among BECCS scenarios and FWEBS on regional scales using the Upper Missouri River Basin (UMRB) as a case study. We describe the physical, biological, and social attributes of the UMRB, and we use grassland bird populations as an example of how biodiversity is influenced by energy transitions, including BECCS. We then outline a "conservation" BECCS strategy that incorporates societal values and emphasizes biodiversity conservation.Item A 21 000-year record of fluorescent organic matter markers in the WAIS Divide ice core(2017-05) D'Andrilli, Juliana; Foreman, Christine M.; Sigl, Michael; Priscu, John C.; McConnell, Joseph R.Englacial ice contains a significant reservoir of organic material (OM), preserving a chronological record of materials from Earth's past. Here, we investigate if OM composition surveys in ice core research can provide paleoecological information on the dynamic nature of our Earth through time. Temporal trends in OM composition from the early Holocene extending back to the Last Glacial Maximum (LGM) of the West Antarctic Ice Sheet Divide (WD) ice core were measured by fluorescence spectroscopy. Multivariate parallel factor (PARAFAC) analysis is widely used to isolate the chemical components that best describe the observed variation across three-dimensional fluorescence spectroscopy (excitation–emission matrices; EEMs) assays. Fluorescent OM markers identified by PARAFAC modeling of the EEMs from the LGM (27.0–18.0 kyr BP; before present 1950) through the last deglaciation (LD; 18.0–11.5 kyr BP), to the mid-Holocene (11.5–6.0 kyr BP) provided evidence of different types of fluorescent OM composition and origin in the WD ice core over 21.0 kyr. Low excitation–emission wavelength fluorescent PARAFAC component one (C1), associated with chemical species similar to simple lignin phenols was the greatest contributor throughout the ice core, suggesting a strong signature of terrestrial OM in all climate periods. The component two (C2) OM marker, encompassed distinct variability in the ice core describing chemical species similar to tannin- and phenylalanine-like material. Component three (C3), associated with humic-like terrestrial material further resistant to biodegradation, was only characteristic of the Holocene, suggesting that more complex organic polymers such as lignins or tannins may be an ecological marker of warmer climates. We suggest that fluorescent OM markers observed during the LGM were the result of greater continental dust loading of lignin precursor (monolignol) material in a drier climate, with lower marine influences when sea ice extent was higher and continents had more expansive tundra cover. As the climate warmed, the record of OM markers in the WD ice core changed, reflecting shifts in carbon productivity as a result of global ecosystem response..Item Viable microbes in ice: Application of molecular assays to McMurdo Dry Valley lake ice communities(2010-06) Dieser, Markus; Nocker, Andreas; Priscu, John C.; Foreman, Christine M.The permanent ice covers of the McMurdo Dry Valley lakes, Antarctica, are colonized by a diverse microbial assemblage. We collected ice cores from Lakes Fryxell, Hoare and Bonney. Propidium monoazide (PMA) was used in combination with quantitative PCR (qPCR) and denaturing gradient gel electrophoresis (DGGE) to examine membrane integrity of prokaryotes in these extreme environments. PMA selectively penetrates cells with compromised membranes and modifies their DNA resulting in the suppression of PCR amplification. Our results based on analysis of 16S rRNA genes demonstrate that despite the hostile conditions of the Dry Valleys, the permanent ice covers of the lakes support a ‘potentially viable’ microbial community. The level of membrane integrity, as well as diversity, was higher in samples where sediment was entrapped in the ice cover. Pronounced differences in the fraction of cells with intact and compromised cell membranes were found for Lake Fryxell and east lobe of Lake Bonney, both expressed in differences in DGGE banding patterns and qPCR signal reductions. Limitations in the ability to distinguish between intact or compromised cells occurred in samples from Lake Hoare and west lobe of Lake Bonney due to low DNA template concentrations recovered from the samples.Item Microbial formation of labile organic carbon in Antarctic glacial environments(2017-04) Smith, Heidi J.; Foster, Rachel A.; McKnight, Diane M.; Lisle, John T.; Littmann, Sten; Kuypers, Marcel M. M.; Foreman, Christine M.Roughly six petagrams of organic carbon are stored within ice worldwide. This organic carbon is thought to be of old age and highly bioavailable. Along with storage of ancient and new atmospherically deposited organic carbon, microorganisms may contribute substantially to the glacial organic carbon pool. Models of glacial microbial carbon cycling vary from net respiration to net carbon fixation. Supraglacial streams have not been considered in models although they are amongst the largest ecosystems on most glaciers and are inhabited by diverse microbial communities. Here we investigate the biogeochemical sequence of organic carbon production and uptake in an Antarctic supraglacial stream in the McMurdo Dry Valleys using nanometre-scale secondary ion mass spectrometry, fluorescence spectroscopy, stable isotope analysis and incubation experiments. We find that heterotrophic production relies on highly labile organic carbon freshly derived from photosynthetic bacteria rather than legacy organic carbon. Exudates from primary production were utilized by heterotrophs within 24 h, and supported bacterial growth demands. The tight coupling of microbially released organic carbon and rapid uptake by heterotrophs suggests a dynamic local carbon cycle. Moreover, as temperatures increase there is the potential for positive feedback between glacial melt and microbial transformations of organic carbon.Item Biofilms on glacial surfaces: hotspots for biological activity(2016-06) Smith, Heidi J.; Schmit, Amber; Foster, Rachel A.; Littmann, Sten; Kuypers, Marcel M. M.; Foreman, Christine M.Glaciers are important constituents in the Earth’s hydrological and carbon cycles, with predicted warming leading to increases in glacial melt and the transport of nutrients to adjacent and downstream aquatic ecosystems. Microbial activity on glacial surfaces has been linked to the biological darkening of cryoconite particles, affecting albedo and increased melt. This phenomenon, however, has only been demonstrated for alpine glaciers and the Greenland Ice Sheet, excluding Antarctica. In this study, we show via confocal laser scanning microscopy that microbial communities on glacial surfaces in Antarctica persist in biofilms. Overall, ~35% of the cryoconite sediment surfaces were covered by biofilm. Nanoscale scale secondary ion mass spectrometry measured significant enrichment of 13C and 15N above background in both Bacteroidetes and filamentous cyanobacteria (i.e., Oscillatoria) when incubated in the presence of 13C–NaHCO3 and 15NH4. This transfer of newly synthesised organic compounds was dependent on the distance of heterotrophic Bacteroidetes from filamentous Oscillatoria. We conclude that the spatial organisation within these biofilms promotes efficient transfer and cycling of nutrients. Further, these results support the hypothesis that biofilm formation leads to the accumulation of organic matter on cryoconite minerals, which could influence the surface albedo of glaciers.Item When a habitat freezes solid: Microorganisms over-winter within the ice column of a coastal Antarctic lake(2011-03) Foreman, Christine M.; Dieser, Markus; Greenwood, Mark C.; Cory, R. M.; Laybourn-Parry, Johanna; Lisle, John T.; Jaros, C.; Miller, P. L.; Chin, Yu-Ping; McKnight, Diane M.A major impediment to understanding the biology of microorganisms inhabiting Antarctic environments is the logistical constraint of conducting field work primarily during the summer season. However, organisms that persist throughout the year encounter severe environmental changes between seasons. In an attempt to bridge this gap, we collected ice core samples from Pony Lake in early November 2004 when the lake was frozen solid to its base, providing an archive for the biological and chemical processes that occurred during winter freezeup. The ice contained bacteria and virus-like particles, while flagellated algae and ciliates over-wintered in the form of inactive cysts and spores. Both bacteria and algae were metabolically active in the ice core melt water. Bacterial production ranged from 1.8 to 37.9 μg C L−1 day−1. Upon encountering favorable growth conditions in the melt water, primary production ranged from 51 to 931 μg C L−1 day−1. Because of the strong H2S odor and the presence of closely related anaerobic organisms assigned to Pony Lake bacterial 16S rRNA gene clones, we hypothesize that the microbial assemblage was strongly affected by oxygen gradients, which ultimately restricted the majority of phylotypes to distinct strata within the ice column. This study provides evidence that the microbial community over-winters in the ice column of Pony Lake and returns to a highly active metabolic state when spring melt is initiated.Item Assembly and Succession of Iron Oxide Microbial Mat Communities in Acidic Geothermal Springs(2016-02) Beam, Jacob P.; Bernstein, Hans C.; Jay, Zackary J.; Kozubal, Mark A.; Jennings, Ryan deM.; Tringe, Susannah G.; Inskeep, William P.Biomineralized ferric oxide microbial mats are ubiquitous features on Earth, are common in hot springs of Yellowstone National Park (YNP, WY, USA), and form due to direct interaction between microbial and physicochemical processes. The overall goal of this study was to determine the contribution of different community members to the assembly and succession of acidic high-temperature Fe(III)-oxide mat ecosystems. Spatial and temporal changes in Fe(III)-oxide accretion and the abundance of relevant community members were monitored over 70 days using sterile glass microscope slides incubated in the outflow channels of two acidic geothermal springs (pH = 3-3.5; temperature = 68-75°C) in YNP. Hydrogenobaculum spp. were the most abundant taxon identified during early successional stages (4-40 days), and have been shown to oxidize arsenite, sulfide, and hydrogen coupled to oxygen reduction. Iron-oxidizing populations of Metallosphaera yellowstonensis were detected within 4 days, and reached steady-state levels within 14-30 days, corresponding to visible Fe(III)-oxide accretion. Heterotrophic archaea colonized near 30 days, and emerged as the dominant functional guild after 70 days and in mature Fe(III)-oxide mats (1-2 cm thick). First-order rate constants of Fe(III)-oxide accretion ranged from 0.046 to 0.05 day^-1, and in situ microelectrode measurements showed that the oxidation of Fe(II) is limited by the diffusion of O2 into the Fe(III)-oxide mat. The formation of microterracettes also implicated O2 as a major variable controlling microbial growth and subsequent mat morphology. The assembly and succession of Fe(III)-oxide mat communities follows a repeatable pattern of colonization by lithoautotrophic organisms, and the subsequent growth of diverse organoheterotrophs. The unique geochemical signatures and micromorphology of extant biomineralized Fe(III)-oxide mats are also useful for understanding other Fe(II)-oxidizing systems.