Journal of Geophysical Research: Biogeosciences最新文献

{"title":"Groundwater-Derived Carbon Promotes Hypoxia and Acidification in a Large Tropical Estuary","authors":"Zhenyan Wang,&nbsp;Yan Zhang,&nbsp;Isaac R. Santos,&nbsp;Clare E. Robinson,&nbsp;Xuejing Wang,&nbsp;Kai Xiao,&nbsp;Xiaolang Zhang,&nbsp;Wei Wang,&nbsp;Zhaoxi Liu,&nbsp;Hailong Li","doi":"10.1029/2025JG009366","DOIUrl":"10.1029/2025JG009366","url":null,"abstract":"<p>Submarine groundwater discharge (SGD) derived nutrient inputs have been extensively documented. However, SGD-derived carbon fluxes remain largely unconstrained, representing a critical gap in most coastal carbon budgets. Here, we resolve SGD and dissolved carbon budgets in the Pearl River Estuary (PRE), the largest estuary in Southern China surrounded by the world's largest urban conglomerate. Broadly-defined SGD contributes 89%–96% of the dissolved inorganic carbon (DIC) pool (2–4 times riverine inputs) and 20%–70% of the dissolved organic carbon (DOC) fluxes of the PRE. SGD transports DIC exceeding total alkalinity (TAlk) by 2.7–7 times, potentially driving pH decline and acidification of nearshore waters. Groundwater <i>p</i>CO₂ values are 10–36 times higher than estuarine waters. SGD-derived DOC mineralization can decrease estuary water pH by 0.04–0.16 units and increase CO₂ by 6.0–90.0 μmol L⁻¹, affecting local coral populations and benthic organisms. SGD also reduces seawater dissolved oxygen (DO) by 12–150 μmol L⁻¹ and fuels the development of hypoxic zones. Overall, SGD regionally intensifies seawater hypoxia and acidification, creating challenging conditions for coral reef survival in an already stressed ecosystem. Our findings demonstrate that SGD should be integrated into carbon budgets and ecological assessments of the land-ocean continuum.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147564679","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":"Groundwater-Derived Carbon Promotes Hypoxia and Acidification in a Large Tropical Estuary","authors":"Zhenyan Wang,&nbsp;Yan Zhang,&nbsp;Isaac R. Santos,&nbsp;Clare E. Robinson,&nbsp;Xuejing Wang,&nbsp;Kai Xiao,&nbsp;Xiaolang Zhang,&nbsp;Wei Wang,&nbsp;Zhaoxi Liu,&nbsp;Hailong Li","doi":"10.1029/2025JG009366","DOIUrl":"https://doi.org/10.1029/2025JG009366","url":null,"abstract":"<p>Submarine groundwater discharge (SGD) derived nutrient inputs have been extensively documented. However, SGD-derived carbon fluxes remain largely unconstrained, representing a critical gap in most coastal carbon budgets. Here, we resolve SGD and dissolved carbon budgets in the Pearl River Estuary (PRE), the largest estuary in Southern China surrounded by the world's largest urban conglomerate. Broadly-defined SGD contributes 89%–96% of the dissolved inorganic carbon (DIC) pool (2–4 times riverine inputs) and 20%–70% of the dissolved organic carbon (DOC) fluxes of the PRE. SGD transports DIC exceeding total alkalinity (TAlk) by 2.7–7 times, potentially driving pH decline and acidification of nearshore waters. Groundwater <i>p</i>CO₂ values are 10–36 times higher than estuarine waters. SGD-derived DOC mineralization can decrease estuary water pH by 0.04–0.16 units and increase CO₂ by 6.0–90.0 μmol L⁻¹, affecting local coral populations and benthic organisms. SGD also reduces seawater dissolved oxygen (DO) by 12–150 μmol L⁻¹ and fuels the development of hypoxic zones. Overall, SGD regionally intensifies seawater hypoxia and acidification, creating challenging conditions for coral reef survival in an already stressed ecosystem. Our findings demonstrate that SGD should be integrated into carbon budgets and ecological assessments of the land-ocean continuum.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147564742","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":"Declines in Conifer Forest Recovery and Forest Loss From Four Decades of Wildfire in California","authors":"Ved N. Bhoot,&nbsp;Jinhyuk E. Kim,&nbsp;James T. Randerson,&nbsp;Michael L. Goulden","doi":"10.1029/2025JG009105","DOIUrl":"10.1029/2025JG009105","url":null,"abstract":"<p>California's forests are increasingly being exposed to intense wildfires. Past research has tracked wildfires' impact on these natural lands, yet there remains a critical gap in tracking post-fire vegetation recovery and its trends, particularly for the extent of different forest types. Here, we developed annual maps of discrete vegetation classes using seasonal satellite surface reflectance and a random forest classifier. We first used our maps to track changes in vegetation cover in the study area from 1985 to 2022. For burned areas between 1985 and 2022, conifer and hardwood forests declined by 14.9% and 22.4%, respectively, but shrublands expanded 22.4%. Next, we quantified vegetation extent recovery in wildfire affected areas as the ratio of the observed post-fire area to a calculated control area for each vegetation type. We compared recovery fractions for 15 years post-fire burned in 1986–1996 and 1997–2007 wildfires and found hardwood forest recovery to be stable but with a greater interquartile range (median 99% [IQR: 92%–105%] and 100% [IQR: 77%–106%], respectively), and conifer forest recovery to be significantly declining (87% [IQR: 82%–95%] and 71% [IQR: 65%–82%], respectively). Even though hardwood forests fared better recovery-wise, recent large and severe wildfire seasons led to a decline of 4.7% in hardwood forests from 2017 to 2022 for the study area. These results depict natural lands in California that are rapidly changing, risking continuation of these trends given large, severe wildfire and climate warming.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147564378","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":"Declines in Conifer Forest Recovery and Forest Loss From Four Decades of Wildfire in California","authors":"Ved N. Bhoot,&nbsp;Jinhyuk E. Kim,&nbsp;James T. Randerson,&nbsp;Michael L. Goulden","doi":"10.1029/2025JG009105","DOIUrl":"https://doi.org/10.1029/2025JG009105","url":null,"abstract":"<p>California's forests are increasingly being exposed to intense wildfires. Past research has tracked wildfires' impact on these natural lands, yet there remains a critical gap in tracking post-fire vegetation recovery and its trends, particularly for the extent of different forest types. Here, we developed annual maps of discrete vegetation classes using seasonal satellite surface reflectance and a random forest classifier. We first used our maps to track changes in vegetation cover in the study area from 1985 to 2022. For burned areas between 1985 and 2022, conifer and hardwood forests declined by 14.9% and 22.4%, respectively, but shrublands expanded 22.4%. Next, we quantified vegetation extent recovery in wildfire affected areas as the ratio of the observed post-fire area to a calculated control area for each vegetation type. We compared recovery fractions for 15 years post-fire burned in 1986–1996 and 1997–2007 wildfires and found hardwood forest recovery to be stable but with a greater interquartile range (median 99% [IQR: 92%–105%] and 100% [IQR: 77%–106%], respectively), and conifer forest recovery to be significantly declining (87% [IQR: 82%–95%] and 71% [IQR: 65%–82%], respectively). Even though hardwood forests fared better recovery-wise, recent large and severe wildfire seasons led to a decline of 4.7% in hardwood forests from 2017 to 2022 for the study area. These results depict natural lands in California that are rapidly changing, risking continuation of these trends given large, severe wildfire and climate warming.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009105","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147564309","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":"Constraining Greenhouse Gas Cycling and Emissions in Africa's Largest Humic Lake","authors":"M. Barthel,&nbsp;T. W. Drake,&nbsp;A. de Clippele,&nbsp;L. W. de Groot,&nbsp;M. Engelhardt,&nbsp;N. Haghipour,&nbsp;Y. Hou,&nbsp;N. Kueter,&nbsp;D. Lewicka-Szczebak,&nbsp;A. Ludjwera Bahati,&nbsp;C. L. Tschumbu,&nbsp;K. Van Oost,&nbsp;J. N. Wabakanghanzi,&nbsp;R. A. Werner,&nbsp;J. Zambo Mandea,&nbsp;J. Six,&nbsp;J. D. Hemingway","doi":"10.1029/2025JG009218","DOIUrl":"https://doi.org/10.1029/2025JG009218","url":null,"abstract":"&lt;p&gt;Humic tropical lakes and wetlands are globally important sources of atmospheric greenhouse gases (GHGs). However, mechanistic insight into GHG cycling in such systems remains limited—especially in understudied central Africa. To address this, here we measured high-, falling-, and low-water seasonal concentrations and isotopic compositions of the major dissolved GHGs &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CH&lt;/mtext&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CH}}_{4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}mathrm{O}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; in Africa's largest humic lake: Mai Ndombe, Democratic Republic of Congo. We find that the water column is weakly to non-stratified and is highly supersaturated with respect to atmospheric equilibrium for all GHGs across all seasons, sampling stations, and water depths. Additionally, all GHG concentrations increase steadily with increasing water depth, reflecting atmospheric gas exchange due to physical mixing in the upper water column as well as biological processes. Extrapolating these results—combined with field measurements such as temperature and wind speed—we estimate that Lake Mai Ndombe emits 375 ± 32 Gg C yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, 623 ± 136 Mg C yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CH&lt;/mtext&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CH}}_{4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and 223 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 20 Mg N yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009218","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563910","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":"Different Mechanisms Underlie Plant-Mediated Methane Transport in a Tidal Salt Marsh Versus an Impounded Brackish Wetland","authors":"Georgia S. Seyfried,&nbsp;Barbara J. Campbell,&nbsp;Nichole Giani,&nbsp;Dustin G. Gannon,&nbsp;Thomas L. O’Halloran","doi":"10.1029/2025JG008987","DOIUrl":"10.1029/2025JG008987","url":null,"abstract":"<p>Wetlands are a significant source of methane (CH₄), but their contributions to the global CH₄ budget remain uncertain. Wetland CH₄ production may be better constrained by addressing uncertainty in plant-mediated CH₄ transport, which is highly variable, motivating the current work. We measured whole-plant, plant-adjacent and non-vegetated carbon dioxide (CO₂) and CH₄ fluxes throughout the day approximately monthly for 1 yr in a euhaline tidal salt marsh and a mesohaline, non-tidal impounded wetland. To assess mechanisms, gas fluxes were accompanied by measurements of environmental variables and soil chemical and biological properties. We found that plants facilitated greater CH₄ fluxes across diurnal and seasonal scales but via distinct mechanisms at our two study sites. We observed daytime peaks in whole-plant and plant-adjacent CH₄ fluxes at the salt marsh, but no diurnal patterns in any CH₄ fluxes at the impounded wetland. Daytime peaks could indicate more efficient pressurized flow of CH₄ through plant biomass or greater sensitivity of aboveground fluxes to temperature or plant productivity. At the annual scale, peak whole-plant CH₄ fluxes were greater at the impounded wetland than at the salt marsh, while peak plant-adjacent CH₄ fluxes were greater at the salt marsh than at the impounded wetland. Differences between sites were attributed to plant-soil-microbe interactions and abiotic conditions such as temperature, water column depth and salinity that determine root-adjacent porewater CH₄ concentrations and the potential for plant-mediated CH₄ transport. These results increase our understanding of plant-mediated CH₄ transport and the mechanisms underlying high variability in these fluxes across coastal wetlands.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563879","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":"Double-Peaked Hyperspectral Features at 710 and 800 nm for Monitoring Coastal Chlorophyll-α Concentrations From Space","authors":"Satoru Yamamoto,&nbsp;Masaru Mizuyama,&nbsp;Moe Matsuoka,&nbsp;Ayame Ikeda,&nbsp;Hiroki Mizuochi,&nbsp;Akira Iguchi","doi":"10.1029/2025JG009443","DOIUrl":"10.1029/2025JG009443","url":null,"abstract":"&lt;p&gt;The concentration of chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; has been estimated from sea color, primarily based on the reflectance ratio between the blue and green spectral bands in multiband images obtained by satellite optical sensors. However, this method is only effective in open, clear water and cannot be reliably applied to shallow coastal waters. In this study, we propose the potential use of double-peaked features at wavelengths of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;710&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $710,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;800&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $800,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm in hyperspectral reflectance data as indicators of the chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; concentration in shallow coastal waters. We conducted data mining to identify spectra exhibiting the double-peaked features in reflectance data obtained by the Hyperspectral Imager Suite (HISUI) over coastal regions of Okinawa Island, Japan. Our analysis revealed that the detection points with the double-peaked features are clustered in specific shallow coastal areas, such as reefs and coves, where biological activity is expected to be high, especially around Maeda and Yakata. For these detection points, the spectral relationship between peak strengths at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;710&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $710,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;800&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $800,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm can be categorized into distinct trends, which appear to depend on local variations in the chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; concentration. In addition, in situ measurements using FieldSpec confirmed the presence of double-peaked features at Yakata and Maeda, whereas such fea","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009443","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563946","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":"Constraining Greenhouse Gas Cycling and Emissions in Africa's Largest Humic Lake","authors":"M. Barthel,&nbsp;T. W. Drake,&nbsp;A. de Clippele,&nbsp;L. W. de Groot,&nbsp;M. Engelhardt,&nbsp;N. Haghipour,&nbsp;Y. Hou,&nbsp;N. Kueter,&nbsp;D. Lewicka-Szczebak,&nbsp;A. Ludjwera Bahati,&nbsp;C. L. Tschumbu,&nbsp;K. Van Oost,&nbsp;J. N. Wabakanghanzi,&nbsp;R. A. Werner,&nbsp;J. Zambo Mandea,&nbsp;J. Six,&nbsp;J. D. Hemingway","doi":"10.1029/2025JG009218","DOIUrl":"10.1029/2025JG009218","url":null,"abstract":"&lt;p&gt;Humic tropical lakes and wetlands are globally important sources of atmospheric greenhouse gases (GHGs). However, mechanistic insight into GHG cycling in such systems remains limited—especially in understudied central Africa. To address this, here we measured high-, falling-, and low-water seasonal concentrations and isotopic compositions of the major dissolved GHGs &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CH&lt;/mtext&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CH}}_{4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mi&gt;N&lt;/mi&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;mi&gt;O&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${mathrm{N}}_{2}mathrm{O}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; in Africa's largest humic lake: Mai Ndombe, Democratic Republic of Congo. We find that the water column is weakly to non-stratified and is highly supersaturated with respect to atmospheric equilibrium for all GHGs across all seasons, sampling stations, and water depths. Additionally, all GHG concentrations increase steadily with increasing water depth, reflecting atmospheric gas exchange due to physical mixing in the upper water column as well as biological processes. Extrapolating these results—combined with field measurements such as temperature and wind speed—we estimate that Lake Mai Ndombe emits 375 ± 32 Gg C yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CO&lt;/mtext&gt;\u0000 &lt;mn&gt;2&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CO}}_{2}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, 623 ± 136 Mg C yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;msub&gt;\u0000 &lt;mtext&gt;CH&lt;/mtext&gt;\u0000 &lt;mn&gt;4&lt;/mn&gt;\u0000 &lt;/msub&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; ${text{CH}}_{4}$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;, and 223 &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mo&gt;±&lt;/mo&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $pm $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; 20 Mg N yr&lt;sup&gt;−1&lt;/sup&gt; as &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009218","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563881","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":"Seasonal Hydrology at the Salt Marsh-Upland Interface","authors":"Amirhossein Noori,&nbsp;Giovanna Nordio,&nbsp;Dannielle Pratt,&nbsp;Tyler Messerschmidt,&nbsp;Sean Fettrow,&nbsp;Angelia L. Seyfferth,&nbsp;Matthew Kirwan,&nbsp;Holly A. Michael,&nbsp;Sergio Fagherazzi","doi":"10.1029/2025JG009297","DOIUrl":"10.1029/2025JG009297","url":null,"abstract":"<p>Sea level rise and storm surges are salinizing coastal areas, transforming forests and agricultural fields into salt marshes. This study examines seasonal variations in soil and groundwater hydrology at the transition zone between salt marshes and upland areas along the Mid-Atlantic coast of the USA. We apply Linear Discriminant Analysis to data sets of soil moisture, soil conductivity, soil temperature, water table depth, groundwater salinity, and groundwater temperature to identify and categorize patterns within hydrological data. We further used Canonical Correlation Analysis to determine relationships between vegetation characteristics (greenness and Basal Area (BA)), soil composition (fraction of clay and sand), and hydrological parameters (groundwater level, groundwater specific conductivity, soil water content, and soil conductivity). Our analysis indicates that storm surges increase spatial variations in seasonal subsurface hydrological conditions among sites, as each location responds differently to disturbance. This heightened inter-site variability contrasts with previous findings of storm-driven homogenization within individual sites. By summer, sites become more homogeneous as hydrological variability decreases, indicating that vegetation gradients along the marsh–forest ecotone are mainly governed by winter and spring conditions. Vegetation characteristics (BA and greenness) are more strongly associated with soil water than with groundwater characteristics. Vegetation greenness also correlates closely with soil water conditions in fall and winter, when site differences are more pronounced. Groundwater salinity and water table depth are related to clay content in the soil. This regional-scale comparison highlights the hydrological variability of the marsh-upland boundary, how it is influenced by soil characteristics, and its relation to vegetation cover, offering insights for effective adaptation strategies to mitigate salinization and preserve coastal biodiversity.</p>","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563912","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":"Double-Peaked Hyperspectral Features at 710 and 800 nm for Monitoring Coastal Chlorophyll-α Concentrations From Space","authors":"Satoru Yamamoto,&nbsp;Masaru Mizuyama,&nbsp;Moe Matsuoka,&nbsp;Ayame Ikeda,&nbsp;Hiroki Mizuochi,&nbsp;Akira Iguchi","doi":"10.1029/2025JG009443","DOIUrl":"https://doi.org/10.1029/2025JG009443","url":null,"abstract":"&lt;p&gt;The concentration of chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; has been estimated from sea color, primarily based on the reflectance ratio between the blue and green spectral bands in multiband images obtained by satellite optical sensors. However, this method is only effective in open, clear water and cannot be reliably applied to shallow coastal waters. In this study, we propose the potential use of double-peaked features at wavelengths of &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;710&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $710,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;800&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $800,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm in hyperspectral reflectance data as indicators of the chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; concentration in shallow coastal waters. We conducted data mining to identify spectra exhibiting the double-peaked features in reflectance data obtained by the Hyperspectral Imager Suite (HISUI) over coastal regions of Okinawa Island, Japan. Our analysis revealed that the detection points with the double-peaked features are clustered in specific shallow coastal areas, such as reefs and coves, where biological activity is expected to be high, especially around Maeda and Yakata. For these detection points, the spectral relationship between peak strengths at &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;710&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $710,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm and &lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mn&gt;800&lt;/mn&gt;\u0000 &lt;mspace&gt;&lt;/mspace&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $800,$&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt;nm can be categorized into distinct trends, which appear to depend on local variations in the chlorophyll-&lt;span&gt;&lt;/span&gt;&lt;math&gt;\u0000 &lt;semantics&gt;\u0000 &lt;mrow&gt;\u0000 &lt;mi&gt;α&lt;/mi&gt;\u0000 &lt;/mrow&gt;\u0000 &lt;annotation&gt; $alpha $&lt;/annotation&gt;\u0000 &lt;/semantics&gt;&lt;/math&gt; concentration. In addition, in situ measurements using FieldSpec confirmed the presence of double-peaked features at Yakata and Maeda, whereas such fea","PeriodicalId":16003,"journal":{"name":"Journal of Geophysical Research: Biogeosciences","volume":"131 3","pages":""},"PeriodicalIF":3.5,"publicationDate":"2026-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/2025JG009443","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147563906","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}