Scholarly Work - Land Resources & Environmental Sciences
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/8680
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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 Geomicrobiology of Blood Falls: An iron-rich saline discharge at terminus of the Taylor Glacier, Antarctica(2004-09) Mikucki, Jill A.; Foreman, Christine M.; Sattler, Birgit; Lyons, W. Berry; Priscu, John C.Blood Falls, a saline subglacial discharge from the Taylor Glacier, Antarctica provides an example of the diverse physical and chemical niches available for life in the polar desert of the McMurdo Dry Valleys. Geochemical analysis of Blood Falls outflow resembles concentrated seawater remnant from the Pliocene intrusion of marine waters combined with products of weathering. The result is an iron-rich, salty seep at the terminus of Taylor Glacier, which is subject to episodic releases into permanently ice-covered Lake Bonney. Blood Falls influences the geochemistry of Lake Bonney, and provides organic carbon and viable microbes to the lakesystem. Here we present the first data on the geobiology of Blood Falls and relate it to the evolutionary history of this unique environment. The novel geological evolution of this subglacial environment makes Blood Falls an important site for the study of metabolic strategies in subglacial environments and the impact of subglacial efflux on associated lake ecosystems.Item Impact of episodic warming events(2004-09) Foreman, Christine M.; Wolf, Craig F.; Priscu, John C.Lakes in the Taylor Valley, Antarctica, were investigated to determine the impact of a significant air temperature warming event that occurred during the austral summer of 2001–2002. The warming in the valleys caused an increase in glacial run-off, record stream discharge, an increase in lake levels, and thinning of the permanent ice covers. These changes in the physical environment drove subsequent changes in the biogeochemistry of the lakes. Primary production in West Lake Bonney during the flood was reduced 23% as a consequence of stream induced water column turbidity. Increased nutrient levels within the lakes occurred in the year following the temperature induced high flow year. For example, soluble reactive phosphorus loading to Lake Fryxell was four-fold greater than the long-term average loading rates. These high nutrient levels corresponded to an increase in primary production in the upper water columns of Lakes Bonney and Fryxell. Depth integrated chlorophyll-a values increased 149% in East Lake Bonney, 48% in West Lake Bonney, and showed little change in Lake Fryxell; chlorophyll-a in Lake Hoare decreased 18% compared to long-term averages recorded as part of our ten year monitoring program, presumably from a reduction in under-ice PAR caused by increased sediment loads on the ice cover. Overall the warming event served to recharge the ecosystem with liquid water and associated nutrients. Such floods may play an important role in the long-term maintenance of liquid water in these dry valley lakes.Item Glacial ice cores: A model system for developing extraterrestrial decontamination protocols(2005-04) Christner, Brent C.; Mikucki, Jill A.; Foreman, Christine M.; Denson, Jackie; Priscu, John C.Evidence gathered from spacecraft orbiting Mars has shown that water ice exists at both poles and may form a large subsurface reservoir at lower latitudes. The recent exploration of the martian surface by unmanned landers and surface rovers, and the planned missions to eventually return samples to Earth have raised concerns regarding both forward and back contamination. Methods to search for life in these icy environments and adequate protocols to prevent contamination can be tested with earthly analogues. Studies of ice cores on Earth have established past climate changes and geological events, both globally and regionally, but only recently have these results been correlated with the biological materials (i.e., plant fragments, seeds, pollen grains, fungal spores, and microorganisms) that are entrapped and preserved within the ice. The inclusion of biology into ice coring research brings with it a whole new approach towards decontamination. Our investigations on ice from the Vostok core (Antarctica) have shown that the outer portion of the cores have up to 3 and 2 orders of magnitude higher bacterial density and dissolved organic carbon (DOC) than the inner portion of the cores, respectively, as a result of drilling and handling. The extreme gradients that exist between the outer and inner portion of these samples make contamination a very relevant aspect of geomicrobiological investigations with ice cores, particularly when the actual numbers of ambient bacterial cells are low. To address this issue and the inherent concern it raises for the integrity of future investigations with ice core materials from terrestrial and extraterrestrial environments, we employed a procedure to monitor the decontamination process in which ice core surfaces are painted with a solution containing a tracer microorganism, plasmid DNA, and fluorescent dye before sampling. Using this approach, a simple and direct method is proposed to verify the authenticity of geomicrobiological results obtained from ice core materials. Our protocol has important implications for the design of life detection experiments on Mars and the decontamination of samples that will eventually be returned to Earth.Item Biological materials in ice cores(2006) Priscu, John C.; Christner, Brent C.; Foreman, Christine M.; Royston-Bishop, GeorgeItem Limnological conditions in subglacial Lake Vostok, Antarctica(2006-11) Christner, Brent C.; Royston-Bishop, George; Foreman, Christine M.; Arnold, Brianna R.; Tranter, Martyn; Welch, Kathleen A.; Lyons, W. Berry; Tsapin, Alexandre I.; Studinger, Michael; Priscu, John C.Subglacial Lake Vostok is located ~4 km beneath the surface of the East Antarctic Ice Sheet and has been isolated from the atmosphere for >15 million yr. Concerns for environmental protection have prevented direct sampling of the lake water thus far. However, an ice core has been retrieved from above the lake in which the bottom ~85 m represents lake water that has accreted (i.e., frozen) to the bottom of the ice sheet. We measured selected constituents within the accretion ice core to predict geomicrobiological conditions within the surface waters of the lake. Bacterial density is two- to sevenfold higher in accretion ice than the overlying glacial ice, implying that Lake Vostok is a source of bacterial carbon beneath the ice sheet. Phylogenetic analysis of amplified small subunit ribosomal ribonucleic acid (rRNA) gene sequences in accretion ice formed over a deep portion of the lake revealed phylotypes that classify within the β-, y-, and δ-Proteobacteria. Cellular, major ion, and dissolved organic carbon levels all decreased with depth in the accretion ice (depth is a proxy for increasing distance from the shoreline), implying a greater potential for biological activity in the shallow shoreline waters of the lake. Although the exact nature of the biology within Lake Vostok awaits direct sampling of the lake water, our data from the accretion ice support the working hypothesis that a sustained microbial ecosystem is present in this subglacial lake environment, despite high pressure, constant cold, low nutrient input, potentially high oxygen concentrations, and an absence of sunlight.Item Metabolic activity and diversity of cyoconites in the Taylor Valley, Antarctica(2007-12) Foreman, Christine M.; Sattler, Birgit; Mikucki, Jill A.; Porazinska, D. L.; Priscu, John C.Metabolic activity and biogeochemical diversity within cryoconites from the Canada,Commonwealth, Howard, and Hughes glaciers in the McMurdo Dry Valleys revealed the presence of a productive microbial refuge in this polar desert ecosystem. Fluorescent in situ hybridization showed a high percentage of Cytophaga-Flavobacteria cells in cryoconite sediments (87.2%), while β-Proteobacterial cells dominated the ice overlying the sediment layer (54.2%). The biomass of bacterial cells in the sediments was also greater (4.82 µgC ml-1) than that in the overlying ice (0.18 mgC ml-1) and was related to bacterial productivity (on the basis of thymidine incorporation), which ranged from 36 ng C l-1 d-1 in the overlying ice to 3329 ng C l-1 d -1 in the sediment-containing layers. Bacteria within both the sediments and overlying ice were able to actively incorporate and respire radio-labeled glucose, as well as 17 other dissolved organic carbon compounds. The cryoconites in the Taylor Valley support an active, diverse assemblage of organisms despite the fact that they may remain sealed from the atmosphere for decades. Given the density of the cryoconites in the dry valleys ( ~4–6% of ablation zone surfaces), flushing of the cryoconites during warm years could provide a vital nutrient and organic carbon source to the surrounding polar desert.