Global Biogeochemical Cycles最新文献

{"title":"Machine Learning Methods Suggest That Large Regional Changes in Phytoplankton Biomass Produced by Earth System Models Do Not Reflect Realistic Responses to Changing Climate","authors":"Anand Gnanadesikan,&nbsp;Jingwen Liu,&nbsp;Sandupal Dutta,&nbsp;Brandon Feole,&nbsp;Faith McCarthy,&nbsp;John Qian","doi":"10.1029/2025GB008761","DOIUrl":"https://doi.org/10.1029/2025GB008761","url":null,"abstract":"<p>Surface phytoplankton biomass (measured in mol C m⁻³) represents a critical parameter within the Earth System that is measured from space and simulated in Earth System Models. Under climate change, the current generation of Earth System Models agrees that low-latitude biomass will decline and high-latitude biomass will increase. However, on a regional scale, the magnitude, phenology and spatial pattern of these changes are highly inconsistent across models. We use machine learning to investigate the sources of the divergence and evaluate the realism of the simulations. We train Random Forests driven by environmental drivers to simulate surface phytoplankton biomass under both pre-industrial control and SSP5-8.5 scenarios. Outside the Arctic, the bulk of the changes in biomass are driven by rearrangements in the spatiotemporal distribution of environmental predictors. Large regional changes in models, however, are associated either with unrealistically low pre-industrial levels of macronutrients or unrealistically strong responses to those macronutrients. Within the Arctic, relationships between environmental predictors and biomass change under global warming. While increased light drives increased biomass, the effect is largest in models with a high nutrient bias. Feeding inputs from an ensemble of models to an emulator trained on observations predicts observed biomass better than the ensemble of the models does, highlighting the fact that models do not produce the correct relationships between environmental predictors and biomass. However, this technique does not yield mechanistically consistent predictions of biomass under climate change. Skepticism of large regional changes in surface phytoplankton biomass produced by individual models is warranted.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 10","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Greenhouse Gas Budget of Southeast Asia for 2000–2019 and Pathways Toward Climate Neutrality","authors":"Masayuki Kondo,&nbsp;Prabir K. Patra,&nbsp;Josep G. Canadell,&nbsp;Philippe Ciais,&nbsp;Richard A. Houghton,&nbsp;Akihiko Ito,&nbsp;Chandra S. Deshmukh,&nbsp;Tomo'omi Kumagai,&nbsp;Xiangzhong Luo,&nbsp;Umakant Mishra,&nbsp;Atul K. Jain,&nbsp;Wei Li,&nbsp;Gerbrand Koren,&nbsp;Stephen Sitch,&nbsp;Ben Poulter,&nbsp;Hanqin Tian,&nbsp;Ana Bastos,&nbsp;Ronny Lauerwald,&nbsp;Judith A. Rosentreter,&nbsp;Naveen Chandra,&nbsp;Tazu Saeki,&nbsp;Marielle Saunois,&nbsp;Ingrid T. Luijkx,&nbsp;Takashi Maki,&nbsp;Takashi Nakamura,&nbsp;Kirari Hirabayashi,&nbsp;Takeshi Hirano,&nbsp;Nobuko Saigusa","doi":"10.1029/2024GB008256","DOIUrl":"https://doi.org/10.1029/2024GB008256","url":null,"abstract":"<p>Member countries of the Association of Southeast Asian Nations ratified the Paris Agreement and have initiated their own efforts to reduce greenhouse gas (GHG) emissions. However, the progress of these countries toward climate neutrality remains uncertain. Here, we estimated the combined budget for carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) in Southeast Asia for 2000–2019 using bottom-up and top-down approaches. The CO₂ emissions from deforestation were the largest source, followed by anthropogenic fire emissions, which together exceeded the CO₂ uptake by natural vegetation and land-use change legacy (e.g., regrowth), yielding a net source of CO₂ in the biosphere. The region's biosphere was also a net source of CH₄ and N₂O, which, combined with the CO₂ budget, makes the Southeast Asian biosphere a net source of GHGs to the atmosphere, ranging from 2,003.2 ± 406.1 Tg CO₂eq yr⁻¹ (bottom-up) to 2,227.5 ± 572.8 Tg CO₂eq yr⁻¹ (top-down) for 2000–2019. Among non-biospheric GHG emissions (e.g., fossil fuels and waste-related emissions), coal usage has resulted in an unprecedented increase in CO₂ emissions. The total GHG budget (the biospheric GHG budget plus the non-biospheric GHG fluxes) was calculated as a net source of 3,226.3 ± 406.2 Tg CO₂eq yr⁻¹ (bottom-up) and 3,406.4 ± 572.9 Tg CO₂eq yr⁻¹ (top-down) for 2000–2019. Our study revealed that Southeast Asia is experiencing the dual challenge of large emissions from deforestation and coal usage, necessitating the implementation of urgent mitigation strategies to ensure climate neutrality.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145146387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Distribution, Storage, and Factors Influencing Particulate and Mineral-Associated Organic Matter in Paddy Soils","authors":"Xia Wang,&nbsp;Zhaoliang Song,&nbsp;Xiaomin Yang,&nbsp;Yakov Kuzyakov,&nbsp;Yunying Fang,&nbsp;Laodong Guo,&nbsp;Iain P. Hartley,&nbsp;Qiang Li,&nbsp;Lele Wu,&nbsp;Zhenqing Zhang,&nbsp;Xiangbin Ran,&nbsp;Weiqi Wang,&nbsp;Yidong Wang,&nbsp;Yongchun Li,&nbsp;Yu Luo,&nbsp;Shaopan Xia,&nbsp;Zhengang Wang,&nbsp;Zhongkui Luo,&nbsp;Ji Chen,&nbsp;Cong-Qiang Liu,&nbsp;Hailong Wang","doi":"10.1029/2025GB008577","DOIUrl":"10.1029/2025GB008577","url":null,"abstract":"<p>Soil organic matter (SOM) reserves in paddies are approximately two times larger than those in upland soils, and therefore, rice paddies have a strong impact on terrestrial carbon (C) sequestration. Functional partitioning of SOM into particulate organic matter (POM) and mineral-associated organic matter (MAOM) facilitates our understanding of C sequestration capacity in paddy soils. We analyzed POM and MAOM contents in 104 samples of topsoil and 81 samples of subsoil collected from paddies, and investigated how climate, nitrogen (N) fertilization, and soil depth regulate POM and MAOM storage. MAOM was the predominant fraction (45.3%–63.7%) of SOM in all paddy soils. As the SOC content increased, POM increased linearly, while the increase rate of MAOM slowed down, indicating a tendency for MAOM to reach saturation. The influence of mineral types on POM and MAOM protection exhibited depth-dependent patterns: clay minerals showed stronger associations in topsoil, whereas amorphous iron oxides displayed increasing importance in subsoil. Climatic factors, particularly mean annual temperature (MAT), had contrasting effects on POM and MAOM storage: increasing MAT reduced MAOM content and stability while having a minor impact on POM. Increasing the N application rate had minimal impact on POM and MAOM storage due to crop harvest and the balance between microbial activity and mineral protection mediated by soil acidification. These findings are valuable for facilitating the sequestration and increasing the stability of SOM in paddies, providing information for global soil carbon storage strategies.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145101864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Tides Boost Primary Production in the Indian Ocean","authors":"S. J. Ditkovsky,&nbsp;L. Resplandy","doi":"10.1029/2025GB008596","DOIUrl":"10.1029/2025GB008596","url":null,"abstract":"<p>Tides are a critical source of energy and influence transport in the ocean, with potential implications for biogeochemical cycling and biological production. Here, we quantify the influence of tides on nutrient transport and primary production in the northern Indian Ocean, where topographic features generate hotspots of tidal processes and primary production supports important regional food supply via aquaculture and fisheries. Using a high-resolution regional ocean model, we investigate the effects of diabatic tidal mixing (i.e., irreversible mixing that stirs nutrients) and adiabatic motions associated with internal tides (i.e., reversible motions that shift water masses without mixing) on primary production. We find that tides increase regional primary production by 5% on average, with seasonal increases reaching up to 10%–15% in open ocean regions and 30% in coastal regions. Tidal mixing sets the magnitude of tide-driven production by supplying nutrients to the euphotic zone, and controls the contrast between the stronger coastal response and milder open ocean response. Background stratification and nutricline depth control the seasonality in tide-driven production at a given location: tides accelerate the onset and delay termination of blooms in productive regions (e.g., Arabian Sea) and reinforce bloom peak in less productive regions (e.g., Bay of Bengal). Adiabatic motions have only a small effect, indicating that tidal influences can be effectively parameterized in global models without costly high spatio-temporal resolution and explicit tidal forcing. We discuss the influence of tidal mixing on biogeochemistry beyond primary production and how it may change in a warmer and more stratified ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008596","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021983","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Wind-Driven Control of Shelf-Sea CO2 Sinks","authors":"Jamie D. Shutler,&nbsp;Daniel J. Ford,&nbsp;Thomas Holding,&nbsp;Clement Ubelmann,&nbsp;Lucile Gaultier,&nbsp;Fabrice Collard,&nbsp;Bertrand Chapron,&nbsp;Marie-Helene Rio,&nbsp;Callum Roberts,&nbsp;Craig Donlon","doi":"10.1029/2024GB008461","DOIUrl":"10.1029/2024GB008461","url":null,"abstract":"<p>Continental shelf surface waters are considered a variable but increasing sink of atmospheric carbon dioxide (CO₂), but the mechanisms controlling these increasing sinks are unclear. We identify that the winter wind-driven surface atmosphere-ocean CO₂ gas exchange and wind-driven movement of water onto (or off of) shelf seas are consistent with the atmospheric CO₂ uptake tendency of many shelf seas. A 20-year observational-based analysis shows that geostrophic, wind and wave driven currents all contribute to the surface shelf break water velocities, but the dominance of each is location and season dependent. Analyzing these flows for fourteen shelf-seas based on their 20-year long-term gradient in air-sea partial pressure of carbon dioxide (their atmospheric CO₂ uptake tendency) identifies significant relationships between uptake tendency and winter (<i>r</i>² = 0.72 ± 0.03, <i>p</i> &lt; 0.01, <i>n</i> = 14) and autumn (<i>r</i>² = 0.57 ± 0.05, <i>p</i> &lt; 0.01, <i>n</i> = 14) wind-driven surface flows. These signals are most strong in winter, but the results are consistent at annual scales. Including the wintertime wind-driven air-sea CO₂ gas exchange further enhances this result, and collectively they describe 82% of the variance in the atmospheric CO₂ uptake tendency data (<i>r</i>² = 0.82 ± 0.06, <i>p</i> &lt; 0.01, <i>n</i> = 14). These findings identify that long-term wind-driven water flow and surface gas exchange are key mechanisms for controlling their chemical evolution and their status as CO₂ sinks. This observational-based evidence highlights the need for these wind-driven processes to be resolved within methods used to predict or understand continental shelf-sea carbonate system state and ocean health.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008461","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145021982","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Role of Mesoscale Eddy Stirring and Microscale Turbulence in Sustaining Biological Production in the Subtropical Gyres","authors":"K. Oglethorpe,&nbsp;B. Fernández Castro,&nbsp;C. P. Spingys,&nbsp;A. C. Naveira Garabato,&nbsp;R. G. Williams","doi":"10.1029/2024GB008180","DOIUrl":"10.1029/2024GB008180","url":null,"abstract":"<p>Sustaining phytoplankton primary production and organic carbon export requires the physical supply of nutrients to the sunlit ocean. In the extensive downwelling regions of the subtropical gyres, the pathways of this nutrient supply remain unclear. Vertical sinking of organic matter from the sunlit layer and its remineralization below cause net downward nutrient transfer in the upper subtropical ocean. Microscale mixing of nutrients across density surfaces and upwelling by mesoscale eddies and submesoscale fronts have been invoked to re-supply nutrients from the thermocline to the sunlit layer. However, a physical mechanism is required to replenish nutrients exported across the thermocline base and sustain a quasi-steady state upper-ocean nutrient budget on inter-annual timescales. Stirring along density surfaces by mesoscale eddies has emerged as a possible supply mechanism to close this nutrient budget. Here, we quantify the relative importance of mesoscale stirring and microscale mixing in supplying nutrients to the oligotrophic regions of the upper subtropical oceans, using global observationally based data sets for nutrients and diapycnal and isopycnal diffusivities. Mesoscale stirring dominates nutrient replenishment in the thermocline of subtropical gyres over microscale turbulence, contributing to 70%–90% of combined supply by the two processes. The stirring supply is most important along gyre flanks, where boundary currents and upwelling zones promote sharp nutrient gradients and vigorous mesoscale activity. Mesoscale fluxes provide sufficient nutrients to offset depletion in the thermocline due to upward microscale mixing into the sunlit layer. This analysis suggests that eddy stirring is significant in maintaining organic carbon export within subtropical gyres.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008180","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144935183","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrothermally Induced Refractory DOC Sinks in the Deep Pacific Ocean","authors":"D. A. Hansell,&nbsp;C. R. German,&nbsp;C. A. Carlson,&nbsp;E. R. M. Druffel,&nbsp;W. J. Jenkins,&nbsp;S. Q. Lang,&nbsp;B. M. Toner","doi":"10.1029/2025GB008659","DOIUrl":"10.1029/2025GB008659","url":null,"abstract":"<p>Dissolved organic carbon (DOC) constitutes the largest pool of reduced carbon in the global ocean, with important contributions from both recently formed and aged, biologically refractory DOC (RDOC). The mechanisms regulating RDOC transformation and removal remain uncertain though hydrothermal vents have been identified as sources and sinks. This study examines RDOC sinks in the deep Pacific Ocean, highlighting the role of submarine hydrothermal systems. Geochemical survey data from GO-SHIP and GEOTRACES projects, alongside specific investigations of Pacific hydrothermal systems, suggest that particulate iron introduced by hydrothermal systems plays a key role in scavenging DOC and delivering it to the seafloor, leaving a deficit in the RDOC of the deep ocean. Dilution of the oceanic water column by hydrothermal fluids exhibiting low DOC concentrations likely plays a secondary role.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008659","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144929513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Variability and Export Timescales of Upper Ocean Particulate Trace Metals in the North Pacific Subtropical Gyre","authors":"Eleanor S. Bates,&nbsp;Angelicque E. White,&nbsp;Nicholas J. Hawco","doi":"10.1029/2025GB008657","DOIUrl":"10.1029/2025GB008657","url":null,"abstract":"<p>The transport of trace metals (TMs) in and out of the upper ocean is largely controlled by particulate phases, but the seasonal variability and residence time of these particles are not well known. Over three years and 21 cruises, we measured upper ocean particulate trace metal concentrations and export fluxes at 150 m at Station ALOHA in the North Pacific Subtropical Gyre. Vertical profiles for most metals were highest near the surface, but Al, Fe, Ni, and Cu also showed evidence of scavenging below the mixed layer. In contrast, labile particulate Mn and Cd had unique subsurface maxima driven by the photoinhibition of Mn-oxides in the euphotic zone and uptake of Cd near the base of the euphotic zone. Our sampling period captured pulses of lithogenic dust input, evident in high export fluxes of particulate Al, Ti, and Fe, which were exported on a timescale of ∼10 days. The mean export-based residence time for labile particulate Fe was 36 days, three times longer than that for recalcitrant Fe, indicating that labile particulate Fe is recycled several times before export. Particulate Cu and Co had mean residence times of 6 months, similar to particulate C, N, and P, suggesting that their export is controlled by the export of biomass. Labile particulate Mn, Ni, and Cd appear to be exported more efficiently with mean residence times of 1.8–3 months. The range of TM residence times underlines the differences in the recycling, biotic utilization, and scavenging of these metals in the upper ocean.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008657","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144927645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate Warming and Soil Drying Lead to a Reduction of Riverine Dissolved Organic Carbon in China","authors":"Lingli Yu,&nbsp;Mingxu Li,&nbsp;Xiaoyan Kang,&nbsp;Li Xu,&nbsp;Boming Liang,&nbsp;Jiankun Chen,&nbsp;Youbin Deng,&nbsp;Huai Chen,&nbsp;Nianpeng He","doi":"10.1029/2025GB008665","DOIUrl":"10.1029/2025GB008665","url":null,"abstract":"<p>Dissolved organic carbon (DOC) is a dynamic component of riverine carbon pools that plays a vital role in determining regional carbon balance. However, owing to limitations in observational data and methodologies, the spatiotemporal dynamics of riverine DOC at a regional scale and their underlying driving factors remain poorly understood. In this study, we compiled riverine DOC concentration measurements for China, using which we analyzed the spatial and temporal patterns of DOC concentrations from 1982 to 2020, and examined the potential driving factors, including climate, vegetation, soil, and hydrology. The results revealed that the average annual DOC concentration in Chinese rivers for the assessed period was 4.06 mg L⁻¹, with the highest concentrations found in Northeast China (i.e., the Songliao River). We also found that there had been a significant reduction in annual DOC concentrations in Chinese rivers from 1982 to 2020, associated with significant declines in DOC in spring and summer. Further analyses revealed that these reductions in DOC concentrations could mainly be attributed to the synergistic effect of climate warming and soil drying. In addition, the total flux of DOC from major rivers in China and the average DOC yield were estimated at 8.15 Tg yr⁻¹ and 1.16 g m² yr⁻¹, respectively. Our findings in this study provide foundational data support for the accurate assessment of regional carbon budgets and offer theoretical insights for developing a regional land-ocean-aquatic continuum (LOAC) carbon cycling model for China.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 9","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144910242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Climate Change and Urbanization Decouple Dissolved Organic Carbon Quantity and Composition in Streams","authors":"James D. Kelley,&nbsp;Sandra Klemet-N'Guessan,&nbsp;Nolan J. T. Pearce,&nbsp;Claire M. Stevens,&nbsp;Anthony J. Arsenault,&nbsp;Miracle Denga,&nbsp;P. V. Sasindu L. Gunawardana,&nbsp;Sarah S. E. King,&nbsp;Carolina N. Koebel,&nbsp;Sherryann A. Prowell,&nbsp;Most Shirina Begum,&nbsp;Marguerite A. Xenopoulos","doi":"10.1029/2025GB008534","DOIUrl":"10.1029/2025GB008534","url":null,"abstract":"<p>Dissolved organic carbon (DOC) is a ubiquitous component of freshwater ecosystems that is sensitive to global change. In turn, DOC controls fundamental biogeochemical processes and functions. These controls depend on both the amount and composition of organic molecules comprising the dissolved organic matter (DOM) pool, which reflects the relative contributions of catchment-derived terrestrial inputs and in situ production. Stream DOM fluctuates with land use, soil mobility, and hydrology; however, few studies have monitored long-term changes in DOM composition to investigate links with climate. Here, we characterized 17-year trends in DOC and DOM in 48 streams across a land use gradient and modeled patterns therein with climatic and hydrological conditions. Across streams, Mann-Kendall trend analyses showed that DOC decreased through time, while DOM became fresher, more aromatic, and contained an increased proportion of urban-derived DOM from the terrestrial catchment. Using generalized additive models, we observed significant linear, unimodal, and multimodal patterns in DOM composition with precipitation and soil temperature. Generally, precipitation increased terrestrial DOM, whereas soil temperature increased urban-derived DOM, particularly in catchments characterized by increasing levels of urbanization. Our study highlights the importance of long-term monitoring in understanding dynamic interactions between terrestrial—fluvial carbon transfer and biogeochemical effects of global climate change and urbanization. Altogether, our results show that interactions between climate change and urbanization will shape future DOM dynamics in streams.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"39 8","pages":""},"PeriodicalIF":5.5,"publicationDate":"2025-08-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025GB008534","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144897385","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}