Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Global Distribution and Biogeochemical Significance of Magnetotactic Bacteria in Deep-Sea Cold Seep Ecosystems","authors":"Kelei Zhu,&nbsp;Peiyu Liu,&nbsp;Yan Liu,&nbsp;Lulu Fu,&nbsp;Zengfeng Du,&nbsp;Rongrong Zhang,&nbsp;Jiawei Liu,&nbsp;Xin Zhang,&nbsp;Jinhua Li","doi":"10.1029/2025JG008888","DOIUrl":"https://doi.org/10.1029/2025JG008888","url":null,"abstract":"<p>Magnetotactic bacteria (MTB) are distinguished by their ability to navigate along Earth's magnetic field and form diverse intracellular minerals, including nanocrystals of magnetite or greigite (i.e., magnetosomes). Although MTB are widespread in oxic-anoxic transition zones of aquatic systems worldwide, their presence in deep-sea environments has been less explored largely due to challenges in sampling and analytical methods. Here, we investigated deep-sea sediments from two active cold seeps in the South China Sea using metagenomic, magnetic, and microscopic techniques and extended our study to a global-scale metagenomic analysis of cold seep ecosystems. Our results reveal a wide distribution and high phylogenetic diversity of MTB in cold seeps worldwide with the phylum <i>Desulfobacterota</i> being particularly prevalent. Genome-scale metabolic reconstructions suggest that MTB contribute to iron and sulfur cycling potentially coupled with anaerobic methane oxidation in these deep-sea habitats. These findings not only broaden our understanding of MTB diversity and distribution in the deep sea but also underscore their important roles in biogeochemical processes within cold seep ecosystems.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144758661","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dust Aerosols Enhance China's Gross Primary Productivity by Increasing Diffuse Radiation","authors":"Minghui Qi,&nbsp;Hongquan Song","doi":"10.1029/2024JG008578","DOIUrl":"https://doi.org/10.1029/2024JG008578","url":null,"abstract":"<p>Dust aerosols play a crucial role in Earth's biogeochemical processes by modulating solar radiation and affecting terrestrial ecosystem productivity. In China, extensive arid and semi-arid regions contribute to high dust aerosol emissions, yet the long-term impact of dust aerosols on gross primary productivity (GPP) remains insufficiently quantified. This study coupled the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and the Joint UK Land Environment Simulator (JULES) to quantify the impact of dust aerosol radiative forcing on GPP in China's terrestrial ecosystems from 2000 to 2020. Results indicated that dust aerosols significantly alter surface solar radiation components by reducing direct radiation and enhancing diffuse radiation. The mean annual decrease in direct radiation due to dust aerosols was −8.2 ± 0.2 W m⁻², while the increase in diffuse radiation was 5.3 ± 0.1 W m⁻², leading to a net reduction in total surface solar radiation of around −2.9 W m⁻². These radiative changes resulted in an average annual increase in GPP of approximately 0.11 ± 0.024 Pg C yr⁻¹, accounting for around 2% of China's mean annual GPP of 6.44 ± 0.18 Pg C yr⁻¹ during the study period. The enhancement was particularly pronounced in regions with high dust aerosol loads, such as northwest China, and exhibited notable interannual variability. This study underscores the complex interactions between dust aerosols and terrestrial ecosystems, highlighting the importance of considering aerosol radiative effects in carbon cycle assessments and climate models.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144740532","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigating the Atmospheric Microbial Ecosystem Through Theory, Bioenergetics, and Numerical Modeling: A Breath of Fresh Air for Aeromicrobiology","authors":"Eloi Martinez-Rabert,&nbsp;Laura Molares Moncayo,&nbsp;Elizabeth Trembath-Reichert,&nbsp;Rachael Lappan,&nbsp;Chris Greening,&nbsp;Jacqueline Goordial,&nbsp;James A. Bradley","doi":"10.1029/2025JG009071","DOIUrl":"https://doi.org/10.1029/2025JG009071","url":null,"abstract":"<p>The atmosphere may constitute the Earth's largest microbial ecosystem, yet it remains the least understood. While microorganisms can persist and may even thrive in the polyextremes of the Earth's atmosphere, it is still unknown whether the atmosphere sustains an active microbial community. Despite growing awareness of the role of the aeromicrobiome in shaping global biogeography, epidemiology, and climate, fundamental questions about its metabolic activity and ecological significance remain unanswered. Here, we outline how theoretical approaches and numerical modeling tools provide powerful avenues to investigate the atmospheric microbial ecosystem, offering unique insights that complement experimental and observational-based studies and can overcome many of the challenges they face. We consider frameworks that integrate (a) theoretical considerations for microbial metabolism across a range of catabolic and anabolic processes, (b) microbial physiology and metabolic states, (c) thermodynamics and bioenergetics, (d) the chemical and physical conditions of the atmosphere and bioaerosols, (e) transport and residence time of microorganisms, and (f) bottom-up and top-down approaches. Theory and modeling-based investigations into the aeromicrobiome can generate and test theory and model-informed hypotheses, formulate mechanistic explanations of biological processes and observations, and inform targeted sampling strategies and experimentation. Together, these approaches bring us closer to determining whether the Earth's atmosphere is a <i>true</i> ecosystem—that is, a metabolically active community of organisms interacting with each other and with the environment. Advances in aeromicrobiology research brought about by theory and modeling can reveal significant insights into global biogeography, biogeochemical cycles, climate processes, and the limits for life.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009071","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725430","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamics of Dissolved Inorganic Carbon and CO2 Emission Controlled by Reservoir Regulation in the Yellow River","authors":"Jingbo Chen,&nbsp;Ming Liu,&nbsp;Xiaolin Ren,&nbsp;Xinying Che,&nbsp;Xueshi Sun,&nbsp;Dejiang Fan","doi":"10.1029/2025JG009021","DOIUrl":"https://doi.org/10.1029/2025JG009021","url":null,"abstract":"<p>Reservoir construction has significantly modified the export and residence of riverine carbon in global rivers; however, various strategies of reservoir operation also introduce great uncertainties into aquatic carbon transformation and associated ecological effects. The material transport in the Yellow River (YR) is currently manipulated by water-sediment regulation scheme (WSRS) of Xiaolangdi Reservoir (XLDR), an effective strategy for managing sediment-laden rivers worldwide. Here, we investigated the spatiotemporal variability of water chemistry and dissolved inorganic carbon (DIC), from within XLDR to downstream YR. The results revealed that during the water regulation of XLDR, downstream DIC export was controlled by carbonate weathering but influenced by enhanced oxidation of dissolved organic carbon and soil CO₂ flushing. In contrast, during the sediment regulation, XLDR-released particulate organic carbon (POC) underwent significant mineralization within ∼400 km transport range, resulting in water acidification, hypoxia and extremely high CO₂ partial pressure. Furthermore, the substantial CO₂ production markedly intensified the carbonate weathering of XLDR-released sediments. Major cation and isotopic analyses indicated that 81%–82% of the downstream DIC production originated from OC mineralization, while 18%–19% contributed by carbonate mineral dissolution. As a strong CO₂ source, the WSRS significantly accelerated the CO₂ evasion along the downstream YR, which was estimated at 0.27 ± 0.05 Tg C within a month, corresponding to a 27% increase in annual downstream CO₂ efflux. The CO₂ evasion was primarily driven by the reservoir sediment release and OC mineralization. These findings highlight the crucial role of reservoir regulation in modulating riverine carbon transformation and emissions.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144725431","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distinct Streamflow and Nutrient Export Dynamics in Wildfire-Impacted Nonperennial Streams in Central Coastal California","authors":"Lauren Giggy,&nbsp;Riley Barton,&nbsp;Sasha Wagner,&nbsp;Margaret Zimmer","doi":"10.1029/2024JG008553","DOIUrl":"https://doi.org/10.1029/2024JG008553","url":null,"abstract":"<p>Wildfires impact water quality by altering nutrient supply and hydrology with changes often perceptible during the first major storm events. However, many factors influence water quality, including wildfire characteristics, weather patterns, and watershed properties. Such factors create challenges for predicting and mitigating water quality, highlighting the ongoing need for work across diverse hydroclimatic settings. The Santa Clara Unit Lightning Complex (SCU) Fire impacted two adjacent headwater catchments in central coastal California. Previous work showed that despite similar biophysical characteristics, the two catchments are hydrologically distinct with one catchment displaying flashier streamflow and higher dissolved organic carbon (DOC) concentrations likely driven by distinct bedrock. Although prefire data are not available, here we expand on this work with detailed observations of total dissolved nitrogen, phosphate (PO₄³⁻), and DOC concentrations and loads, over the first two years following the wildfire. We observed 2–13 times higher annual solute export from the catchment with flashier streamflow behavior. We hypothesize that elevated solute export occurred due to shallow hydrologic flow paths dominating runoff generation regardless of surface-level alterations from the wildfire. Additionally, we did not observe the highest solute concentrations during the first major storms following the wildfire. Instead, solute concentrations peaked during high-intensity rainfall in year two. This work showcases the importance of the hydrogeologic setting and hydrologic routing on solute export. Additionally, these results highlight challenges in predicting water quality responses in disturbed catchments and teasing apart the role of wildfire, ongoing drought, and high-intensity precipitation in semiarid climates.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008553","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716821","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Linking Ecosystem CH4 Fluxes to Soil Profile CH4 Concentrations and Oxidation Rates: Year-Round Measurements and Drought Effects in a Danish Farmland","authors":"Peiyan Wang,&nbsp;Bingqian Zhao,&nbsp;Line Vinther Hansen,&nbsp;Wenxin Zhang,&nbsp;Louise H. Mortensen,&nbsp;Andreas Brændholt,&nbsp;Sander Bruun,&nbsp;Per Ambus,&nbsp;Bo Elberling","doi":"10.1029/2025JG008829","DOIUrl":"https://doi.org/10.1029/2025JG008829","url":null,"abstract":"<p>Methane (CH₄) oxidation in well-drained soils is a key process contributing to the global CH₄ sink. Yet, temporal and depth-specific CH₄ oxidation is rarely described despite being critical for the surface net CH₄ uptake. Here, we linked year-round field observations of CH₄ fluxes in well-drained cultivated soils with subsurface CH₄ concentrations, laboratory incubations, and process-based modeling to uncover these mechanisms. Field observed CH₄ fluxes ranged from −0.43 to 0.19 mg CH₄ m⁻² day⁻¹ with an average of −0.15 ± 0.01 mg CH₄ m⁻² day⁻¹ over the year-round study period. Much higher CH₄ uptakes were observed in summer than in winter, indicating marked seasonal variations. Modeling using the CoupModel to simulate soil temperatures and water content as drivers, along with an analytic reaction-based model to simulate CH₄ fluxes, shows that the depth infiltration of atmospheric CH₄ is a critical parameter for defining a CH₄ oxidation reaction zone below the surface. The thickness of the reaction zone varied seasonally. Sensitivity tests of CH₄ concentrations and oxidation profiles in response to contrasting precipitation scenarios reveal that CH₄ oxidation during drought scenarios is increased at deeper depths due to higher CH₄ availability. However, CH₄ oxidation in near-surface layers decreased due to low soil water content, resulting in a significantly lower net surface CH₄ uptake. Our findings suggest that both the depth-specific CH₄ oxidation profile and net surface CH₄ fluxes will likely change under future warmer and drier periods.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG008829","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Shrub Expansion Can Counteract Carbon Losses From Warming Tundra","authors":"Theresia Yazbeck,&nbsp;Gil Bohrer,&nbsp;Oliver Sonnentag,&nbsp;Bo Qu,&nbsp;Matteo Detto,&nbsp;Gabriel Hould-Gosselin,&nbsp;Vincent Graveline,&nbsp;Haley Alcock,&nbsp;Bruno Lecavalier,&nbsp;Philip Marsh,&nbsp;Alex Cannon,&nbsp;William J. Riley,&nbsp;Qing Zhu,&nbsp;Fengming Yuan,&nbsp;Benjamin Sulman","doi":"10.1029/2024JG008721","DOIUrl":"https://doi.org/10.1029/2024JG008721","url":null,"abstract":"<p>Arctic warming is causing substantial compositional, structural, and functional changes in tundra vegetation including shrub and tree-line expansion and densification. However, predicting the carbon trajectories of the changing Arctic is challenging due to interacting feedbacks between vegetation composition and structure, and surface characteristics. We conduct a sensitivity analysis of the current-date to 2100 projected surface energy fluxes, soil carbon pools, and CO₂ fluxes to different shrub expansion rates under future emission scenarios (intermediate—RCP4.5, and high—RCP8.5) using the Arctic-focused configuration of E3SM Land Model (ELM). We focus on Trail Valley Creek (TVC), an upland tundra site in the western Canadian Arctic, which is experiencing shrub densification and expansion. We find that shrub expansion did not significantly alter the modeled surface energy and water budgets. However, the carbon balance was sensitive to shrub expansion, which drove higher rates of carbon sequestration as a consequence of higher shrubification rates. Thus, at low shrub expansion rates, the site would become a carbon source, especially under RCP8.5, due to higher temperatures, which deepen the active layer and enhance soil respiration. At higher shrub expansion rates, TVC would become a net CO₂ sink under both Representative Concentration Pathway scenarios due to higher shrub productivity outweighing temperature-driven respiration increase. Our simulations highlight the effect of shrub expansion on Arctic ecosystem carbon fluxes and stocks. We predict that at TVC, shrubification rate would interact with climate change intensity to determine whether the site would become a carbon sink or source under projected future climate.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 8","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008721","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144716822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Microorganisms Contributing to the Biological Pump in the Western Arctic Ocean During Late Summer","authors":"Hongwei Qin,&nbsp;Hisashi Endo,&nbsp;Akiko Ebihara,&nbsp;Amane Fujiwara,&nbsp;Jonaotaro Onodera,&nbsp;Yosuke Yamada,&nbsp;Hideki Fukuda,&nbsp;Toshi Nagata,&nbsp;Takuhei Shiozaki","doi":"10.1029/2024JG008568","DOIUrl":"https://doi.org/10.1029/2024JG008568","url":null,"abstract":"<p>Marine particles can be classified into sinking and suspended particles, and recent studies have revealed that the microbial communities associated with each particle are distinct. The western Arctic Ocean has undergone significant environmental changes due to sea ice loss in recent years, which may impact the biological pump. While microbial communities on suspended particles in this region have been studied, those on sinking particles remain largely unexplored. We analyzed the eukaryotic and prokaryotic community structures of suspended and sinking particles collected from subsurface chlorophyll maximum layers in the western Arctic Ocean during late summer 2021 using a marine snow catcher. A significant difference between the two particle types in overall eukaryotic community structures was observed, while differences in prokaryotic communities were evident at more specific taxonomic levels. Carbon sinking flux ranged from 68.7 to 774 mg C m⁻² d⁻¹ and showed a significant positive correlation with chlorophyll <i>a</i> concentrations. Correlation network analysis identified microbial modules, including diatoms, parasites in Syndiniales and Peronosporomycetes as well as Desulfobacterota, which positively correlated with carbon sinking flux. Our findings highlight previously unrecognized microbial contributors to the biological pump in the western Arctic Ocean, and these organisms maybe key to elucidating biogeochemical cycles in the changing Arctic Ocean.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024JG008568","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705154","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduce Revenue Versus Increase Expenditure: Fires and Plant Invasion Drive Soil Carbon Loss With Different Mechanisms in a Mediterranean Shrubland","authors":"Liyuan He,&nbsp;David A. Lipson,&nbsp;Elsa E. Cleland,&nbsp;Xiaofeng Xu","doi":"10.1029/2025JG008964","DOIUrl":"https://doi.org/10.1029/2025JG008964","url":null,"abstract":"<p>Fires and plant invasions threaten Mediterranean ecosystems substantially, particularly in the context of changing climate. Our study utilized a data-model integration approach to assess the response of soil organic carbon (SOC) to fires and plant invasion under three Shared Socio-Economic Pathway (SSP) scenarios (SSP1-26, SSP2-45, and SSP5-85). We parameterized the CLM-Microbe model and then investigated the individual and interactive impacts of fires and plant invasion on soil C by comparing factorial simulations of initialization (fire/no wildfire in 2021), fire module on/off, and with and without plant invasion during 2023–2100 in a Mediterranean ecosystem. The simulations indicated a marked C loss due to the 2021 wildfire, projected fires, and plant invasion across all future climate scenarios. Specifically, the 2021 wildfire, projected fires, and plant invasion reduced the SOC (0–30 cm) by 0.12, 0.26, and 0.15 kg C m⁻² under SSP1-26, 0.12, 0.30, and 0.12 kg C m⁻² under SSP2-45, and 0.12, 0.24, and 0.13 kg C m⁻² under SSP5-85, respectively. However, fires and plant invasion decreased SOC through distinct mechanisms. The effects of the 2021 wildfire occurred due to its negative legacy on soil microbial community and, thus, litter accumulation, suppressing the formation of soil carbon via decomposition. Influences of projected fires happen via consuming fuel and suppressing carbon input to soils. In contrast, the impacts of plant invasions were due to enhanced microbial respiration, leading to C loss. These findings emphasize the need for tailored C sequestration strategies considering the disparate effects of fires and plant invasions in the Mediterranean climate.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144688146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Longitudinal Patterns in Nitrate Revealed Through Drone-Based Measurements in an Agriculturally Influenced Midwestern U.S. River","authors":"Alyssa Gerhardt,&nbsp;Peter S. Levi,&nbsp;Natalie A. Griffiths,&nbsp;Christopher R. DeRolph,&nbsp;Jeffery S. Riggs,&nbsp;Allison M. Fortner","doi":"10.1029/2024JG008342","DOIUrl":"https://doi.org/10.1029/2024JG008342","url":null,"abstract":"<p>Nitrate concentrations in streams and rivers in the Midwestern United States are often elevated, reflecting the predominance of agriculture in the surrounding landscape. Recent advances in technology, including surface water drones and more precise sensors, provide opportunities to investigate nitrate dynamics with high spatial and temporal resolution. We deployed an aquatic drone, the AquaBOT, in a sixth-order, agriculturally influenced river to examine longitudinal patterns in water quality. Our goal was to measure the spatial and temporal heterogeneity in nitrate and nitrate removal processes and determine the influence of tributary inputs on main stem chemistry. We navigated the drone along a 12-km reach of the Des Moines River (Iowa, USA) nine times between June 2021 and August 2022. Across the deployments, mean nitrate concentration was positively related to discharge and was nearly two orders of magnitude higher in spring than summer. We observed contrasting patterns in main stem nitrate, which decreased downstream during some runs (e.g., 3.1–2.7 mg N L⁻¹ in June 2021), demonstrating net nitrate uptake along the reach, and remained constant on other dates. Similarly, tributaries to the Des Moines had a varied influence on riverine nitrate. Tributaries either increased or decreased main stem nitrate concentrations depending on the tributary and the date. Nitrate removal rates were spatially and temporally variable but showed some consistency at the subreach (2 km) scale, with two subreaches often showing elevated rates of nitrate removal across dates. Our study reveals nuanced heterogeneity in nitrate dynamics of the Des Moines River despite the homogeneity of agricultural land cover in the watershed.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"130 7","pages":""},"PeriodicalIF":3.7,"publicationDate":"2025-07-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144681175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}