Matching Items (6)
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- All Subjects: Biogeochemistry
- Creators: Cadillo-Quiroz, Hinsby
Description
Despite the breadth of studies investigating ecosystem development, an underlying theory guiding this process remains elusive. Several principles have been proposed to explain ecosystem development, though few have garnered broad support in the literature. I used boreal wetland soils as a study system to test a notable goal oriented principle: The Maximum Power Principle (MPP). The MPP posits that ecosystems, and in fact all energy systems, develop to maximize power production or the rate of energy production. I conducted theoretical and empirical investigations to test the MPP in northern wetlands.
Permafrost degradation is leading to rapid wetland formation in northern peatland ecosystems, altering the role of these ecosystems in the global carbon cycle. I reviewed the literature on the history of the MPP theory, including tracing its origins to The Second Law of Thermodynamics. To empirically test the MPP, I collected soils along a gradient of ecosystem development and: 1) quantified the rate of adenosine triphosphate (ATP) production--literally cellular energy--to test the MPP; 2) quantified greenhouse gas production (CO2, CH4, and N2O) and microbial genes that produce enzymes catalyzing greenhouse gas production, and; 3) sequenced the 16s rRNA gene from soil microbes to investigate microbial community composition across the chronosequence of wetland development. My results suggested that the MPP and other related theoretical constructs have strong potential to further inform our understanding of ecosystem development. Soil system power (ATP) decreased temporarily as the ecosystem reorganized after disturbance to rates of power production that approached pre-disturbance levels. Rates of CH4 and N2O production were higher at the newly formed bog and microbial genes involved with greenhouse gas production were strongly related to the amount of greenhouse gas produced. DNA sequencing results showed that across the chronosequence of development, the two relatively mature ecosystems--the peatland forest ecosystem prior to permafrost degradation and the oldest bog--were more similar to one another than to the intermediate, less mature bog. Collectively, my results suggest that ecosystem age, rather than ecosystem state, was a more important driver for ecosystem structure and function.
Permafrost degradation is leading to rapid wetland formation in northern peatland ecosystems, altering the role of these ecosystems in the global carbon cycle. I reviewed the literature on the history of the MPP theory, including tracing its origins to The Second Law of Thermodynamics. To empirically test the MPP, I collected soils along a gradient of ecosystem development and: 1) quantified the rate of adenosine triphosphate (ATP) production--literally cellular energy--to test the MPP; 2) quantified greenhouse gas production (CO2, CH4, and N2O) and microbial genes that produce enzymes catalyzing greenhouse gas production, and; 3) sequenced the 16s rRNA gene from soil microbes to investigate microbial community composition across the chronosequence of wetland development. My results suggested that the MPP and other related theoretical constructs have strong potential to further inform our understanding of ecosystem development. Soil system power (ATP) decreased temporarily as the ecosystem reorganized after disturbance to rates of power production that approached pre-disturbance levels. Rates of CH4 and N2O production were higher at the newly formed bog and microbial genes involved with greenhouse gas production were strongly related to the amount of greenhouse gas produced. DNA sequencing results showed that across the chronosequence of development, the two relatively mature ecosystems--the peatland forest ecosystem prior to permafrost degradation and the oldest bog--were more similar to one another than to the intermediate, less mature bog. Collectively, my results suggest that ecosystem age, rather than ecosystem state, was a more important driver for ecosystem structure and function.
ContributorsChapman, Eric (Author) / Childers, Daniel L. (Thesis advisor) / Cadillo-Quiroz, Hinsby (Committee member) / Hall, Sharon J (Committee member) / Turetsky, Merritt (Committee member) / Arizona State University (Publisher)
Created2015
Description
Utilizing both 16S and 18S rRNA sequencing alongside energetic calculations from geochemical measurements offers a bridged perspective of prokaryotic and eukaryotic community diversities and their relationships to geochemical diversity. Yellowstone National Park hot spring outflows from varied geochemical compositions, ranging in pH from < 2 to > 9 and in temperature from < 30°C to > 90°C, were sampled across the photosynthetic fringe, a transition in these outflows from exclusively chemosynthetic microbial communities to those that include photosynthesis. Illumina sequencing was performed to document the diversity of both prokaryotes and eukaryotes above, at, and below the photosynthetic fringe of twelve hot spring systems. Additionally, field measurements of dissolved oxygen, ferrous iron, and total sulfide were combined with laboratory analyses of sulfate, nitrate, total ammonium, dissolved inorganic carbon, dissolved methane, dissolved hydrogen, and dissolved carbon monoxide were used to calculate the available energy from 58 potential metabolisms. Results were ranked to identify those that yield the most energy according to the geochemical conditions of each system. Of the 46 samples taken across twelve systems, all showed the greatest energy yields using oxygen as the main electron acceptor, followed by nitrate. On the other hand, ammonium or ammonia, depending on pH, showed the greatest energy yields as an electron donor, followed by H2S or HS-. While some sequenced taxa reflect potential biotic participants in the sulfur cycle of these hot spring systems, many sample locations that yield the most energy from ammonium/ammonia oxidation have low relative abundances of known ammonium/ammonia oxidizers, indicating potentially untapped sources of chemotrophic energy or perhaps poorly understood metabolic capabilities of cultured chemotrophs.
ContributorsRomero, Joseph Thomas (Author) / Shock, Everett L (Thesis advisor) / Cadillo-Quiroz, Hinsby (Committee member) / Till, Christy B. (Committee member) / Arizona State University (Publisher)
Created2018
Description
Nitrous oxide (N2O) is a major contributor to the greenhouse effect and to stratospheric ozone depletion. In soils, nitrogen reduction is performed by biotic and abiotic processes, including microbial denitrification and chemical denitrification. Chemical denitrification, or chemodenitrification, is the abiotic step-wise reduction of nitrate (NO3-), nitrite (NO2-), or nitric oxide (NO) to N2O in anoxic environments, with high turnover rates particularly in acidic soils. Chemodenitrification was identified in various environments, but the mechanism is still not understood. In this study, the factors influencing abiotic reduction of NO2- to N2O in acidic tropical peat soil are examined. These factors include pH, organic matter content, and dissolved ferrous iron. Anoxic peat soil from sites located in the Peruvian Amazon was used for incubations. The results show that peat soil (pH ~4.5) appears to reduce NO2- more quickly in the presence of lower pH and higher Fe(II) concentrations. NO2- is completely reduced in excess Fe(II), and Fe(II) is completely oxidized in excess NO2-, providing evidence for the proposed mechanism of chemodenitrification. In addition, first order reaction rate constants kFe(II) and kNO2- were calculated using concentration measurements over 4 hours, to test for the hypothesized reaction rate relationships kFe(II): kFe(II) kFe(II)~NO2- > kFe(II)>NO2- and kNO2-: kFe(II)NO2-. The NO2- k values followed the anticipated pattern, although the Fe(II) k value data was inconclusive. Organic material may also play a role in NO2- reduction through chemodenitrification, and future experimentation will test this possibility. How and to what extent the pH and the concentrations of organic matter and Fe(II) affect the kinetic rate of chemodenitrification will lend insight into the N2O production potential of natural tropical peatlands.
ContributorsTylor, Kaitlyn Marie (Author) / Cadillo-Quiroz, Hinsby (Thesis director) / Day, Thomas (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
Under current climate conditions northern peatlands mostly act as C sinks; however, changes in climate and environmental conditions, can change the soil carbon decomposition cascade, thus altering the sink status. Here I studied one of the most abundant northern peatland types, poor fen, situated along a climate gradient from tundra (Daring Lake, Canada) to boreal forest (Lutose, Canada) to temperate broadleaf and mixed forest (Bog Lake, MN and Chicago Bog, NY) biomes to assess patterns of microbial abundance across the climate gradient. Principal component regression analysis of the microbial community and environmental variables determined that mean annual temperature (MAT) (r2=0.85), mean annual precipitation (MAP) (r2=0.88), and soil temperature (r2=0.77), were the top significant drivers of microbial community composition (p < 0.001). Niche breadth analysis revealed the relative abundance of Intrasporangiaceae, Methanobacteriaceae and Candidatus Methanoflorentaceae fam. nov. to increase when MAT and MAP decrease. The same analysis showed Spirochaetaceae, Methanosaetaceae and Methanoregulaceae to increase in relative abundance when MAP, soil temperature and MAT increased, respectively. These findings indicated that climate variables were the strongest predictors of microbial community composition and that certain taxa, especially methanogenic families demonstrate distinct patterns across the climate gradient. To evaluate microbial production of methanogenic substrates, I carried out High Resolution-DNA-Stable Isotope Probing (HR-DNA-SIP) to evaluate the active portion of the community’s intermediary ecosystem metabolic processes. HR-DNA-SIP revealed several challenges in efficiency of labelling and statistical identification of responders, however families like Veillonellaceae, Magnetospirillaceae, Acidobacteriaceae 1, were found ubiquitously active in glucose amended incubations. Differences in metabolic byproducts from glucose amendments show distinct patterns in acetate and propionate accumulation across sites. Families like Spirochaetaceae and Sphingomonadaceae were only found to be active in select sites of propionate amended incubations. By-product analysis from propionate incubations indicate that the northernmost sites were acetate-accumulating communities.
These results indicate that microbial communities found in poor fen northern peatlands are strongly influenced by climate variables predicted to change under current climate scenarios. I have identified patterns of relative abundance and activity of select microbial taxa, indicating the potential for climate variables to influence the metabolic pathway in which carbon moves through peatland systems.
ContributorsSarno, Analissa Flores (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Garcia-Pichel, Ferran (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Childers, Daniel (Committee member) / Arizona State University (Publisher)
Created2022
Description
Nitrous oxide (N2O) is an important greenhouse gas and an oxidant respired by a
diverse range of anaerobic microbes, but its sources and sinks are poorly understood. The overarching goal of my dissertation is to explore abiotic N2O formation and microbial N2O consumption across reducing environments of the early and modern Earth. By combining experiments as well as diffusion and atmospheric modeling, I present evidence that N2O production can be catalyzed on iron mineral surfaces that may have been present in shallow waters of the Archean ocean. Using photochemical models, I showed that tropospheric N2O concentrations close to modern ones (ppb range) were possible before O2 accumulated. In peatlands of the Amazon basin (modern Earth), unexpected abiotic activity became apparent under anoxic conditions. However, care has to be taken to adequately disentangle abiotic from biotic reactions. I identified significant sterilant-induced changes in Fe2+ and dissolved organic matter pools (determined by fluorescence spectroscopy). Among all chemical and physical sterilants tested, γ - irradiation showed the least effect on reactant pools. Targeting geochemically diverse peatlands across Central and South America, I present evidence that coupled abiotic and biotic cycling of N2O could be a widespread phenomenon. Using isotopic tracers in the field, I showed that abiotic N2O fluxes rival biotic ones under in-situ conditions. Moreover, once N2O is produced, it is rapidly consumed by N2O-reducing microbes. Using amplicon sequencing and metagenomics, I demonstrated that this surprising N2O sink potential is associated with diverse bacteria, including the recently discovered clade II that is present in high proportions at Amazonian sites based on nosZ quantities. Finally, to evaluate the impact of nitrogen oxides on methane production in peatlands, I characterized soil nitrite (NO2–) and N2O abundances along soil profiles. I complemented field analyses with molecular work by deploying amplicon-based 16S rRNA and mcrA sequencing. The diversity and activity of soil methanogens was affected by the presence of NO2– and N2O, suggesting that methane emissions could be influenced by N2O cycling dynamics. Overall, my work proposes a key role for N2O in Earth systems across time and a central position in tropical microbial ecosystems.
diverse range of anaerobic microbes, but its sources and sinks are poorly understood. The overarching goal of my dissertation is to explore abiotic N2O formation and microbial N2O consumption across reducing environments of the early and modern Earth. By combining experiments as well as diffusion and atmospheric modeling, I present evidence that N2O production can be catalyzed on iron mineral surfaces that may have been present in shallow waters of the Archean ocean. Using photochemical models, I showed that tropospheric N2O concentrations close to modern ones (ppb range) were possible before O2 accumulated. In peatlands of the Amazon basin (modern Earth), unexpected abiotic activity became apparent under anoxic conditions. However, care has to be taken to adequately disentangle abiotic from biotic reactions. I identified significant sterilant-induced changes in Fe2+ and dissolved organic matter pools (determined by fluorescence spectroscopy). Among all chemical and physical sterilants tested, γ - irradiation showed the least effect on reactant pools. Targeting geochemically diverse peatlands across Central and South America, I present evidence that coupled abiotic and biotic cycling of N2O could be a widespread phenomenon. Using isotopic tracers in the field, I showed that abiotic N2O fluxes rival biotic ones under in-situ conditions. Moreover, once N2O is produced, it is rapidly consumed by N2O-reducing microbes. Using amplicon sequencing and metagenomics, I demonstrated that this surprising N2O sink potential is associated with diverse bacteria, including the recently discovered clade II that is present in high proportions at Amazonian sites based on nosZ quantities. Finally, to evaluate the impact of nitrogen oxides on methane production in peatlands, I characterized soil nitrite (NO2–) and N2O abundances along soil profiles. I complemented field analyses with molecular work by deploying amplicon-based 16S rRNA and mcrA sequencing. The diversity and activity of soil methanogens was affected by the presence of NO2– and N2O, suggesting that methane emissions could be influenced by N2O cycling dynamics. Overall, my work proposes a key role for N2O in Earth systems across time and a central position in tropical microbial ecosystems.
ContributorsBuessecker, Steffen (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Hartnett, Hilairy E (Committee member) / Glass, Jennifer B (Committee member) / Hall, Sharon J (Committee member) / Arizona State University (Publisher)
Created2020
Description
Cyanobacteria and algae living inside carbonate rocks (endoliths) have long been considered major contributors to bioerosion. Some bore into carbonates actively (euendoliths); others simply inhabit pre-existing pore spaces (cryptoendoliths). While naturalistic descriptions based on morphological identification have traditionally driven the field, modern microbial ecology has shown that this approach is insufficient to assess microbial diversity or make functional inferences. I examined endolithic microbiomes using 16S rRNA genes and lipid-soluble photosynthetic pigments as biomarkers, with the goal of reassessing endolith diversity by contrasting traditional and molecular approaches. This led to the unexpected finding that in all 41 littoral carbonate microbiomes investigated around Isla de Mona (Puerto Rico) and Menorca (Spain) populations of anoxygenic phototrophic bacteria (APBs) in the phyla Chloroflexi and Proteobacteria, were abundant, even sometimes dominant over cyanobacteria. This was not only novel, but it suggested that APBs may have been previously misidentified as morphologically similar cyanobacteria, and opened questions about their potential role as euendoliths. To test the euendolithic role of photosynthetic microbes, I set a time-course experiment exposing virgin non-porous carbonate substrate in situ, under the hypothesis that only euendoliths would be able to initially colonize it. This revealed that endolithic microbiomes, similar in biomass to those of mature natural communities, developed within nine months of exposure. And yet, APB populations were still marginal after this period, suggesting that they are secondary colonizers and not euendolithic. However, elucidating colonization dynamics to a sufficiently accurate level of molecular identification among cyanobacteria required the development of a curated cyanobacterial 16S rRNA gene reference database and web tool, Cydrasil. I could then detect that the pioneer euendoliths were in a novel cyanobacterial clade (named UBC), immediately followed by cyanobacteria assignable to known euendoliths. However, as bioerosion proceeded, a diverse set of likely cryptoendolithic cyanobacteria colonized the resulting pore spaces, displacing euendoliths. Endolithic colonization dynamics are thus swift but complex, and involve functionally diverse agents, only some of which are euendoliths. My work contributes a phylogenetically sound, functionally more defined understanding of the carbonate endolithic microbiome, and more specifically, Cydrasil provides a user-friendly framework to routinely move beyond morphology-based cyanobacterial systematics.
ContributorsRoush, Daniel (Author) / Garcia-Pichel, Ferran (Thesis advisor) / Anbar, Ariel (Committee member) / Cadillo-Quiroz, Hinsby (Committee member) / Cao, Huansheng (Committee member) / Arizona State University (Publisher)
Created2020