Browsing by Author "Earth Sciences, School of Science"
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Item Acetoclastic Methanosaeta are dominant methanogens in organic-rich Antarctic marine sediments(Springer Nature, 2018-02) Carr, Stephanie A.; Schubotz, Florence; Dunbar, Robert B.; Mills, Christopher T.; Dias, Robert; Summons, Roger E.; Mandernack, Kevin W.; Earth Sciences, School of ScienceDespite accounting for the majority of sedimentary methane, the physiology and relative abundance of subsurface methanogens remain poorly understood. We combined intact polar lipid and metagenome techniques to better constrain the presence and functions of methanogens within the highly reducing, organic-rich sediments of Antarctica's Adélie Basin. The assembly of metagenomic sequence data identified phylogenic and functional marker genes of methanogens and generated the first Methanosaeta sp. genome from a deep subsurface sedimentary environment. Based on structural and isotopic measurements, glycerol dialkyl glycerol tetraethers with diglycosyl phosphatidylglycerol head groups were classified as biomarkers for active methanogens. The stable carbon isotope (δ13C) values of these biomarkers and the Methanosaeta partial genome suggest that these organisms are acetoclastic methanogens and represent a relatively small (0.2%) but active population. Metagenomic and lipid analyses suggest that Thaumarchaeota and heterotrophic bacteria co-exist with Methanosaeta and together contribute to increasing concentrations and δ13C values of dissolved inorganic carbon with depth. This study presents the first functional insights of deep subsurface Methanosaeta organisms and highlights their role in methane production and overall carbon cycling within sedimentary environments.Item Addressing Pollution-Related Global Environmental Health Burdens(AGU, 2018-02-19) Filippelli, Gabriel M.; Taylor, Mark P.; Earth Sciences, School of ScienceNew analyses are revealing the scale of pollution on global health, with a disproportionate share of the impact borne by lower‐income nations, minority and marginalized individuals. Common themes emerge on the drivers of this pollution impact, including a lack of regulation and its enforcement, research and expertise development, and innovative funding mechanisms for mitigation. Creative approaches need to be developed and applied to address and overcome these obstacles. The existing “business as usual” modus operandi continues to externalize human health costs related to pollution, which exerts a negative influence on global environmental health.Item Addressing the Need for Just GeoHealth Engagement: Evolving Models for Actionable Research That Transform Communities(AGU, 2021-12) Hayhow, Claire M.; Brabander, Dan J.; Jim, Rebecca; Lively, Martin; Filippelli, Gabriel M.; Earth Sciences, School of ScienceGeoHealth as a research paradigm offers the opportunity to re-evaluate common research engagement models and science training practices. GeoHealth challenges are often wicked problems that require both transdisciplinary approaches and the establishment of intimate and long-term partnerships with a range of community members. We examine four common modes of community engagement and explore how research projects are launched, who has the power in these relationships, and how projects evolve to become truly transformative for everyone involved.Item Advances and limitations of using satellites to monitor cyanobacterial harmful algal blooms(Associação Brasileira de Limnologia, 2019-06) Ogashawara, Igor; Earth Sciences, School of ScienceThe use of satellites for monitoring forests is common and well-known practice. However, the operational remote monitoring of water quality from space is still under development. In the United States of America (USA), the use of this type of data is just now being applied to operationally monitor cyanobacterial harmful algal blooms (CHABs). This powerful tool can be used to generate temporal and spatial assessments of CHABs, however the validation of the retrieved information is still a challenge - especially in tropical and equatorial countries. This commentary discusses the advantages and challenges of current initiatives that use Earth Observation data for managing CHABs such as “Lake Erie’s HAB Bulletin” and “Project CYAN” - both in the USA. Additionally, it was also discussed the application of remote sensing techniques to monitor CHABs in Brazilian inland waters.Item Advancing cyanobacteria biomass estimation from hyperspectral observations: Demonstrations with HICO and PRISMA imagery(Elsevier, 2021-12) O'Shea, Ryan E.; Pahlevan, Nima; Smith, Brandon; Bresciani, Mariano; Egerton, Todd; Giardino, Claudia; Li, Lin; Moore, Tim; Ruiz-Verdu, Antonio; Ruberg, Steve; Simis, Stefan G. H.; Stumpf, Richard; Vaičiūtė, Diana; Earth Sciences, School of ScienceRetrieval of the phycocyanin concentration (PC), a characteristic pigment of, and proxy for, cyanobacteria biomass, from hyperspectral satellite remote sensing measurements is challenging due to uncertainties in the remote sensing reflectance (∆Rrs) resulting from atmospheric correction and instrument radiometric noise. Although several individual algorithms have been proven to capture local variations in cyanobacteria biomass in specific regions, their performance has not been assessed on hyperspectral images from satellite sensors. Our work leverages a machine-learning model, Mixture Density Networks (MDNs), trained on a large (N = 939) dataset of collocated in situ chlorophyll-a concentrations (Chla), PCs, and remote sensing reflectance (Rrs) measurements to estimate PC from all relevant spectral bands. The performance of the developed model is demonstrated via PC maps produced from select images of the Hyperspectral Imager for the Coastal Ocean (HICO) and Italian Space Agency's PRecursore IperSpettrale della Missione Applicativa (PRISMA) using a matchup dataset. As input to the MDN, we incorporate a combination of widely used band ratios (BRs) and line heights (LHs) taken from existing multispectral algorithms, that have been proven for both Chla and PC estimation, as well as novel BRs and LHs to increase the overall cyanobacteria biomass estimation accuracy and reduce the sensitivity to ∆Rrs. When trained on a random half of the dataset, the MDN achieves uncertainties of 44.3%, which is less than half of the uncertainties of all viable optimized multispectral PC algorithms. The MDN is notably better than multispectral algorithms at preventing overestimation on low (<10 mg m−3) PC. Visibly, HICO and PRISMA PC maps show the wider dynamic range that can be represented by the MDN. The available in situ and satellite-derived Rrs matchups and measured in situ PC demonstrate the robustness of the MDN for estimating low (<10 mg m−3) PC and the reduced impact of ∆Rrs on medium-to-high in situ PC (>10 mg m−3). According to our extensive assessments, the developed model is anticipated to enable practical PC products from PRISMA and HICO, therefore the model is promising for planned hyperspectral missions, such as the Plankton Aerosol and Cloud Ecosystem (PACE). This advancement will enhance the complementary roles of hyperspectral radiometry from satellite and low-altitude platforms for quantifying and monitoring cyanobacteria harmful algal blooms at both large and local spatial scales.Item African dryland ecosystem changes controlled by soil water(Wiley, 2019-08) Wei, Fangli; Wang, Shuai; Fu, Bojie; Wang, Lixin; Liu, Yi Y.; Li, Yan; Earth Sciences, School of ScienceMonitoring long‐term vegetation dynamics in African drylands is of great importance for both ecosystem degradation studies and carbon‐cycle modelling. Here, we exploited the complementary use of optical and passive microwave satellite data— normalized difference vegetation index (NDVI) and vegetation optical depth (VOD)—to provide new insights of ecosystem changes in African drylands. During 1993–2012, 54% of African drylands experienced a significant increase of VOD, mainly located in southern Africa and west and central Africa, with an average rate of increase of (1.2 ± 2.7) × 10−3 yr−1. However, a significant decreasing NDVI was observed over 43% of the African drylands, in particular in western Niger and eastern Africa, with an average browning rate of (−0.13 ± 1.5) × 10−3 yr−1. The contrasting vegetation trends (increasing VOD and decreasing NDVI) were largely caused by an increase in the relative proportion of the woody component of the vegetation, as a result of the prevailing woody encroachment in African drylands during the study period. Soil water emerges as the dominant driver of ecosystem changes in African drylands, in particular in arid and semiarid areas. This is evidenced by a strong spatio‐temporal correlation between soil water and vegetation, where soil water changes explain about 48% of vegetation variations. This study emphasizes the potential of utilizing multiple satellite products with different strengths in monitoring different characteristics of ecosystems to evaluate ecosystem changes and reveal the underlying mechanisms of the observed changes.Item Age-related water use characteristics of Robinia pseudoacacia on the Loess Plateau(Elsevier, 2021-05) Wang, Jian; Fu, Bojie; Jiao, Lei; Lu, Nan; Li, Jianye; Chen, Weiliang; Wang, Lixin; Earth Sciences, School of ScienceUnderstanding water use characteristics of revegetation species is crucial for evaluating plant adaptability and guiding the sustainability of vegetation restoration in semiarid regions. Ecological restoration projects have been implemented for decades in degraded ecosystems, achieving significant changes in vegetation cover. However, water use characteristics of the main tree species at different ages remain poorly understood in such systems. We investigated water use characteristics of Robinia pseudoacacia in plantations of different stand-age (18 and 30 years). The species is the most widely planted tree in revegetation efforts on the Loess Plateau. The δ2H and δ18O of xylem and soil water within 500 cm of the soil surface and the δ13C values of plant leaves were measured during two consecutive hydrological years. The results showed that that water uptake proportions from across the soil columns changed in 18-yr R. pseudoacacia between a drier (2016) and wetter year (2017). In contrast, shallow soil water was largely comparable in a stand of 30-yr R. pseudoacacia in 2016 and 2017, and similarly the pattern of water uptake by roots from the middle and deep soil column was comparable. However, leaf-level water use efficiency (WUEi) of trees in the older plantation was higher during the wetter year, thereby partly alleviating a low infiltration to precipitation ratio. These findings suggest that different stand-age plantation trees have distinct water use characteristics and display different responses to variations in precipitation. Older plantation trees respond to increased water availability by increasing WUEi instead of switching water sources. This means that stand-age is an essential factor to be considered in ecological restoration management, which can enhance the effectiveness of vegetation restoration strategies. The study indicates useful input from research to management throughout the continuity of restoration effort.Item Are the shoreline and eutrophication of desert lakes related to desert development?(Springer, 2021-01) Luo, Lihui; Zhao, Wenzhi; Wang, Lixin; Ogashawara, Igor; Yang, Qiyue; Zhou, Hai; Yang, Rong; Duan, Quntao; Zhou, Chenglin; Zhuang, Yanli; Earth Sciences, School of ScienceDesert lakes are unique ecosystems found in oases within desert landscapes. Despite the numerous studies on oases, there are no reports regarding the spatiotemporal distribution and causes of eutrophication in the desert lakes that are located at the edge of the Linze Oasis in northwestern China. In this study, the seasonal shoreline and eutrophication of a desert lake were monitored using an unmanned aerial vehicle (UAV) and water sampling during three crop growth stages. The spatial extents of the shoreline and algal blooms and the chromophoric dissolved organic matter (CDOM) absorption coefficient were derived through UAV images. The desert lake shoreline declined during the crop growing stage, which exhibited the largest water demand and began to expand after this stage. The estimated CDOM absorption coefficient measurements and classified algal bloom area showed seasonal variations that increased from spring to late summer and then decreased in autumn. The first two crop growth stages accounted for most of the water and fertilizer requirements of the entire growth period, which may have contributed to large amounts of groundwater consumption and pollution and resulted in peak eutrophication of the lake in the second growth stage. However, the CDOM absorption coefficient of the third stage was not well correlated with that of the first two stages, suggesting that the lake may be affected by the dual effects of groundwater and precipitation recharge in the third stage. These results indicate that the water quality of desert lakes may be affected by agricultural cultivation. The agricultural demands for water and fertilizer may change the spatiotemporal changes in water quality in the lake, especially in the middle and early stages of crop growth.Item Assessing Temperate Forest Growth and Climate Sensitivity in Response to a Long-Term Whole-Watershed Acidification Experiment(Wiley, 2020-06) Malcomb, Jacob D.; Scanlon, Todd M.; Epstein, Howard E.; Druckenbrod, Daniel L.; Vadeboncoeur, Matthew A.; Lanning, Matthew; Adams, Mary Beth; Wang, Lixin; Earth Sciences, School of ScienceAcid deposition is a major biogeochemical driver in forest ecosystems, but the impacts of long-term changes in deposition on forest productivity remain unclear. Using a combination of tree ring and forest inventory data, we examined tree growth and climate sensitivity in response to 26 years of whole-watershed ammonium sulfate ((NH4)2SO4) additions at the Fernow Experimental Forest (West Virginia, USA). Linear mixed effects models revealed species-specific responses to both treatment and hydroclimate variables. When controlling for environmental covariates, growth of northern red oak (Quercus rubra), red maple (Acer rubrum), and tulip poplar (Liriodendron tulipifera) was greater (40%, 52%, and 42%, respectively) in the control watershed compared to the treated watershed, but there was no difference in black cherry (Prunus serotina). Stem growth was generally positively associated with growing season water availability and spring temperature and negatively associated with vapor pressure deficit. Sensitivity of northern red oak, red maple, and tulip poplar growth to water availability was greater in the control watershed, suggesting that acidification treatment has altered tree response to climate. Results indicate that chronic acid deposition may reduce both forest growth and climate sensitivity, with potentially significant implications for forest carbon and water cycling in deposition-affected regions.Item Balancing the Global Distribution of Phosphorus With a View Toward Sustainability and Equity(AGU, 2018) Filippelli, Gabriel M.; Earth Sciences, School of ScienceLimitations in the geological reserves of phosphate rock, the source of fertilizer phosphorus, are not currently considered in agricultural practices or global trade, a very short‐sighted approach considering that there is no “alternative fuel” for plant growth. Thus, it is important to understand the science of phosphorus‐crop growth dynamics as a function of grain type, plant uptake, climate, and past fertilizer phosphorus application history. Recent work on modeling these factors on the global scale (Kvakić et al., 2018) provides the first scientific backdrop for developing an understanding of fertilizer phosphorus balances, and for informing forward‐looking practices and policies that regulate toward long‐term sustainability rather than short‐term profit.