Yaqing Ruan, Thomas J. Browning, Zhu Zhu, Chunxue Wang, Haibo Jiang, Ruifeng Zhang
Iron (Fe) is an essential micronutrient for the marine phytoplankton Synechococcus , which is globally distributed and contributes to approximately 17% of global marine net primary production. To investigate how contrasting ecotypes cope with Fe limitation, we compared growth, physiology, and elemental stoichiometry of coastal Synechococcus sp. PCC7002 and oceanic Synechococcus sp. WH7803 under Fe‐replete and Fe‐deplete conditions. The coastal strain PCC7002 maintained stable growth rates under Fe‐deplete conditions whereas the oceanic strain WH7803 demonstrated reduced growth rates. This stability in PCC7002 was supported by reduced cell size, which lowered Fe demand and enhanced surface area‐to‐volume ratios for more efficient nutrient uptake. Light harvesting capacity in PCC7002 was largely preserved under Fe depletion, as indicated by stable pigment : C ratios. Elevated N : P ratios in Fe‐deplete PCC7002 potentially reflected increased N investment in Fe‐response proteins while P demand remained relatively unchanged. In contrast, such flexible morphological and physiological adjustments were not observed in WH7803. Both strains showed shifts in trace element stoichiometry consistent with upregulated divalent metal transporters driving non‐Fe metal uptake under Fe depletion. However, under identical Fe‐replete conditions, PCC7002 exhibited stronger luxury Fe uptake than WH7803. Collectively, these results demonstrate ecotype‐specific Fe acclimation strategies shaped by adaptation to divergent environmental regimes at isolation sites, highlighting the role of Synechococcus diversity in regulating elemental cycling in the ocean.
{"title":"A coastal Synechococcus strain is more resilient to iron limitation than an oceanic strain","authors":"Yaqing Ruan, Thomas J. Browning, Zhu Zhu, Chunxue Wang, Haibo Jiang, Ruifeng Zhang","doi":"10.1002/lno.70353","DOIUrl":"https://doi.org/10.1002/lno.70353","url":null,"abstract":"Iron (Fe) is an essential micronutrient for the marine phytoplankton <jats:italic>Synechococcus</jats:italic> , which is globally distributed and contributes to approximately 17% of global marine net primary production. To investigate how contrasting ecotypes cope with Fe limitation, we compared growth, physiology, and elemental stoichiometry of coastal <jats:italic>Synechococcus</jats:italic> sp. PCC7002 and oceanic <jats:italic>Synechococcus</jats:italic> sp. WH7803 under Fe‐replete and Fe‐deplete conditions. The coastal strain PCC7002 maintained stable growth rates under Fe‐deplete conditions whereas the oceanic strain WH7803 demonstrated reduced growth rates. This stability in PCC7002 was supported by reduced cell size, which lowered Fe demand and enhanced surface area‐to‐volume ratios for more efficient nutrient uptake. Light harvesting capacity in PCC7002 was largely preserved under Fe depletion, as indicated by stable pigment : C ratios. Elevated N : P ratios in Fe‐deplete PCC7002 potentially reflected increased N investment in Fe‐response proteins while P demand remained relatively unchanged. In contrast, such flexible morphological and physiological adjustments were not observed in WH7803. Both strains showed shifts in trace element stoichiometry consistent with upregulated divalent metal transporters driving non‐Fe metal uptake under Fe depletion. However, under identical Fe‐replete conditions, PCC7002 exhibited stronger luxury Fe uptake than WH7803. Collectively, these results demonstrate ecotype‐specific Fe acclimation strategies shaped by adaptation to divergent environmental regimes at isolation sites, highlighting the role of <jats:italic>Synechococcus</jats:italic> diversity in regulating elemental cycling in the ocean.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"1 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147492997","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fabian Lange, Soeren Ahmerkamp, Aman Akeerath Mundanatt, Farooq Moin Jalaluddin, Gesa Schulz, Daniela Voß, Oliver Zielinski, Ulrike Hanz, Gaute Lavik, Hannah K. Marchant, Jan‐Hendrik Hehemann, Timothy G. Ferdelman, Moritz Holtappels, Marcel M. M. Kuypers
Permeable sands on continental shelves host microbial communities that drive organic carbon turnover, oxygen fluxes and nitrogen loss. Advective porewater flow associated with sedimentary bedforms maintains these rates and fluxes. Modeling and laboratory studies suggest that advective porewater flow is tightly coupled to bedform stability. However, the impacts of in situ bedform stability on biogeochemical fluxes in subtidal sands remain unconstrained. We deployed a benthic lander at six stations in the North Sea to measure in situ bedform geometries, oxygen fluxes and primary productivity accompanied with ex situ incubations, glycan extraction and microscopy. We observed bedform migration velocities ranging between 0 and 3.2 cm h −1 , which were only 9–16% of expected values from mechanistic models. Bedform stability may be enhanced by high interstitial colloidal and particulate algal glycans concentrations (2–52 mmol C L −1 ) that are a representative component of extracellular polymeric substances. Benthic primary productivity as a source of carbon was negligible (< 0.003 mmol C m −2 d −1 ). Pore space glycan accumulation was attributed to algal biomass filtered out of the overlying water column by advective flow through the permeable sediment. Benthic glycan concentrations correlated significantly with oxygen consumption rates per volume porewater (17–207 μ mol L −1PW h −1 ), whereas sediment oxygen fluxes (6–17 mmol m −2 d −1 ) significantly correlated with modeled porewater velocities. Overall, the impact of glycans as a proxy for pelagically derived algal biomass was twofold: (1) they drove higher oxygen consumption rates in surface sediments and (2) contributed to stabilization of bedforms, which almost doubled oxygen fluxes into the sediment.
大陆架上可渗透的沙子上有微生物群落，它们驱动有机碳周转、氧通量和氮损失。与沉积河床相关的平流孔隙水维持着这些速率和通量。模拟和实验室研究表明，平流孔隙水流动与河床稳定性密切相关。然而，原位地层稳定性对潮下砂中生物地球化学通量的影响仍然不受限制。我们在北海的六个站点部署了一个底栖着陆器，以测量原位床型几何形状、氧通量和初级生产力，同时进行非原位培养、聚糖提取和显微镜检查。我们观察到的层状迁移速度范围在0到3.2 cm h - 1之间，仅为机制模型预测值的9-16%。作为细胞外聚合物质的代表成分，高间质胶体和颗粒藻聚糖浓度（2-52 mmol C L−1）可增强床型稳定性。底栖生物初级生产力作为碳的来源可以忽略不计（0.003 mmol C m - 2 d - 1）。孔空间聚糖的积累是由于通过可渗透沉积物的平流从上覆水柱中过滤出来的藻类生物量。底栖生物聚糖浓度与每体积孔隙水耗氧量（17-207 μ mol L−1 PW h−1）显著相关，而沉积物氧通量（6-17 mmol m−2 d−1）与模拟孔隙水速度显著相关。总的来说，聚糖作为上层藻类生物量的代表，其影响是双重的：(1)它们提高了表层沉积物的耗氧率；(2)有助于河床的稳定，这几乎使进入沉积物的氧通量增加了一倍。
{"title":"Algal glycans promote microbial turnover of organic matter through stabilization of subtidal permeable sandy sediments","authors":"Fabian Lange, Soeren Ahmerkamp, Aman Akeerath Mundanatt, Farooq Moin Jalaluddin, Gesa Schulz, Daniela Voß, Oliver Zielinski, Ulrike Hanz, Gaute Lavik, Hannah K. Marchant, Jan‐Hendrik Hehemann, Timothy G. Ferdelman, Moritz Holtappels, Marcel M. M. Kuypers","doi":"10.1002/lno.70350","DOIUrl":"https://doi.org/10.1002/lno.70350","url":null,"abstract":"Permeable sands on continental shelves host microbial communities that drive organic carbon turnover, oxygen fluxes and nitrogen loss. Advective porewater flow associated with sedimentary bedforms maintains these rates and fluxes. Modeling and laboratory studies suggest that advective porewater flow is tightly coupled to bedform stability. However, the impacts of in situ bedform stability on biogeochemical fluxes in subtidal sands remain unconstrained. We deployed a benthic lander at six stations in the North Sea to measure in situ bedform geometries, oxygen fluxes and primary productivity accompanied with ex situ incubations, glycan extraction and microscopy. We observed bedform migration velocities ranging between 0 and 3.2 cm h <jats:sup>−1</jats:sup> , which were only 9–16% of expected values from mechanistic models. Bedform stability may be enhanced by high interstitial colloidal and particulate algal glycans concentrations (2–52 mmol C L <jats:sup>−1</jats:sup> ) that are a representative component of extracellular polymeric substances. Benthic primary productivity as a source of carbon was negligible (< 0.003 mmol C m <jats:sup>−2</jats:sup> d <jats:sup>−1</jats:sup> ). Pore space glycan accumulation was attributed to algal biomass filtered out of the overlying water column by advective flow through the permeable sediment. Benthic glycan concentrations correlated significantly with oxygen consumption rates per volume porewater (17–207 <jats:italic>μ</jats:italic> mol L <jats:sup>−1</jats:sup> <jats:sub>PW</jats:sub> h <jats:sup>−1</jats:sup> ), whereas sediment oxygen fluxes (6–17 mmol m <jats:sup>−2</jats:sup> d <jats:sup>−1</jats:sup> ) significantly correlated with modeled porewater velocities. Overall, the impact of glycans as a proxy for pelagically derived algal biomass was twofold: (1) they drove higher oxygen consumption rates in surface sediments and (2) contributed to stabilization of bedforms, which almost doubled oxygen fluxes into the sediment.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"20 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147478056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The ocean is undergoing significant changes, including warming, acidification, and deoxygenation, which pose great challenges to marine biodiversity. However, most models projecting the impacts of climate change on marine species overlook predictor variables critically meaningful for species' ecologies such as pH and dissolved oxygen. The recent release of high‐resolution projections of different future climate‐change scenarios offers the opportunity to explore species redistribution under multiple threats beyond ocean warming. Accordingly, we conducted a global comparative analysis to study the impact of incorporating predictor variables describing pH and dissolved oxygen into marine species distribution models. We used models trained for 268 cold‐water coral species to project potential future distributions for different climate and dispersal scenarios over different time periods. We found that, irrespective of scenario or period, models using pH and dissolved oxygen projected 11.5–21.4% higher impacts of climate change than those without them. For instance, by the end of the century under a high emission scenario, models including pH and oxygen projected an average range contraction of 48.2% for cold‐water corals under a no‐dispersal scenario, compared with a 26.8% contraction projected by models excluding these two predictors. Given the substantial differences in the predicted distribution patterns and the biological importance of these variables, we highlight that researchers should consider more diverse sets of predictor variables when predicting future range shifts for marine biodiversity assessments under climate change.
{"title":"Acidification and deoxygenation matter in assessing redistribution of global cold‐water coral biodiversity induced by climate change","authors":"Shuaishuai Liu, Bingqing Xiao, Ákos Bede‐Fazekas, Stefano Mammola, Jorge García Molinos, Jamie M. Kass, Jorge Assis, Chen Lin, Junmei Qu, Hongwei Huang, Qiang Lin, Zhixin Zhang","doi":"10.1002/lno.70351","DOIUrl":"https://doi.org/10.1002/lno.70351","url":null,"abstract":"The ocean is undergoing significant changes, including warming, acidification, and deoxygenation, which pose great challenges to marine biodiversity. However, most models projecting the impacts of climate change on marine species overlook predictor variables critically meaningful for species' ecologies such as pH and dissolved oxygen. The recent release of high‐resolution projections of different future climate‐change scenarios offers the opportunity to explore species redistribution under multiple threats beyond ocean warming. Accordingly, we conducted a global comparative analysis to study the impact of incorporating predictor variables describing pH and dissolved oxygen into marine species distribution models. We used models trained for 268 cold‐water coral species to project potential future distributions for different climate and dispersal scenarios over different time periods. We found that, irrespective of scenario or period, models using pH and dissolved oxygen projected 11.5–21.4% higher impacts of climate change than those without them. For instance, by the end of the century under a high emission scenario, models including pH and oxygen projected an average range contraction of 48.2% for cold‐water corals under a no‐dispersal scenario, compared with a 26.8% contraction projected by models excluding these two predictors. Given the substantial differences in the predicted distribution patterns and the biological importance of these variables, we highlight that researchers should consider more diverse sets of predictor variables when predicting future range shifts for marine biodiversity assessments under climate change.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"273 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147478060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sacchidanandan V. Pillai, Yayla Sezginer, Adrian Marchetti, Claire P. Till, Emily V. Speciale, Philippe D. Tortell
Iron‐limitation within the California Current System drives changes in phytoplankton taxonomic composition and photo‐physiology over a range of spatial scales. Here we demonstrate how these iron‐dependent signatures can be resolved, with high spatial resolution, using continuous ship‐board optical measurements. Deck‐board incubation experiments, along with discrete measurements of iron and macro nutrient concentrations and molecular diagnostic signatures, demonstrated contrasting levels of iron stress across our study region in the northern California Current System during summer, 2023. Photosynthetic pigment measurements indicated that phytoplankton assemblages were largely dominated by diatoms, but low and high iron waters contained differing relative abundances of phytoplankton genera with different mean cell sizes. High frequency ship‐board measurements of hyperspectral particulate absorption demonstrated the presence of two optically distinct phytoplankton assemblages that were associated with varying levels of iron stress. The distribution of the optical clusters across the cruise track showed strong coherence with a number of oceanographic and physiological variables, including phytoplankton size, nutrient drawdown ratios, photosynthetic efficiency () and absorption cross‐section (), and maximum photosynthetic rates. Notably, optical signatures explained more of the observed photo‐physiological variability than other oceanographic variables, such as sea surface temperature and chlorophyll concentration. Variability in phytoplankton iron stress appeared coupled to the age and source of the upwelling water masses. Our results demonstrate the utility of hyperspectral data to map potential iron‐stress with high spatial resolution in dynamic coastal waters.
{"title":"Hyperspectral optical signatures of iron‐limitation in a coastal upwelling system","authors":"Sacchidanandan V. Pillai, Yayla Sezginer, Adrian Marchetti, Claire P. Till, Emily V. Speciale, Philippe D. Tortell","doi":"10.1002/lno.70344","DOIUrl":"https://doi.org/10.1002/lno.70344","url":null,"abstract":"Iron‐limitation within the California Current System drives changes in phytoplankton taxonomic composition and photo‐physiology over a range of spatial scales. Here we demonstrate how these iron‐dependent signatures can be resolved, with high spatial resolution, using continuous ship‐board optical measurements. Deck‐board incubation experiments, along with discrete measurements of iron and macro nutrient concentrations and molecular diagnostic signatures, demonstrated contrasting levels of iron stress across our study region in the northern California Current System during summer, 2023. Photosynthetic pigment measurements indicated that phytoplankton assemblages were largely dominated by diatoms, but low and high iron waters contained differing relative abundances of phytoplankton genera with different mean cell sizes. High frequency ship‐board measurements of hyperspectral particulate absorption demonstrated the presence of two optically distinct phytoplankton assemblages that were associated with varying levels of iron stress. The distribution of the optical clusters across the cruise track showed strong coherence with a number of oceanographic and physiological variables, including phytoplankton size, nutrient drawdown ratios, photosynthetic efficiency () and absorption cross‐section (), and maximum photosynthetic rates. Notably, optical signatures explained more of the observed photo‐physiological variability than other oceanographic variables, such as sea surface temperature and chlorophyll concentration. Variability in phytoplankton iron stress appeared coupled to the age and source of the upwelling water masses. Our results demonstrate the utility of hyperspectral data to map potential iron‐stress with high spatial resolution in dynamic coastal waters.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"97 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147478107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Urban roadway runoff represents a widespread pollutant in the process of urbanization, and its eco‐evolutionary influence on aquatic organisms remains poorly understood. This study focused on the dominant zooplankton species, Ceriodaphnia cornuta , and systematically investigated the rapid evolution driven by urban roadway runoff, simulated by tire wear particle (TWP) leachate, through multi‐scale spatiotemporal experiments. On a microgeographic spatial scale, sampling sites were established along an urbanization gradient within the Huangpu River basin. The results showed that populations originating from highly urbanized waters exhibited significantly higher population intrinsic rate of increase under TWP stress, revealing a spatial pattern of evolutionary adaptation to the pollutant. On a temporal scale, historical populations were reconstructed by resurrecting dormant eggs from different periods (1980s to 2020s) in sediments. The findings demonstrated that as vehicle ownership and pollution pressure increased in the surrounding areas, contemporary populations exhibited significantly higher tolerance to TWP than historical populations, presenting a clear trajectory of adaptive evolution over time. By employing resurrection ecology and microgeography spatial gradient analysis, this study reveals direct associations between urban pollution‐induced rapid evolution in aquatic organisms. It uncovers the short‐term adaptive mechanisms of zooplankton to urban environmental stressors. These findings advance the understanding of contemporary evolution and enhance predictive capacity for aquatic ecosystem responses to anthropogenic pressures.
{"title":"Rapid evolution of zooplankton linked to urban transportation: Evidence from microgeography and resurrection ecology","authors":"Jianan Li, Jiale Xu, Haoran Zhang, Xiaodong Jiang","doi":"10.1002/lno.70345","DOIUrl":"https://doi.org/10.1002/lno.70345","url":null,"abstract":"Urban roadway runoff represents a widespread pollutant in the process of urbanization, and its eco‐evolutionary influence on aquatic organisms remains poorly understood. This study focused on the dominant zooplankton species, <jats:italic>Ceriodaphnia cornuta</jats:italic> , and systematically investigated the rapid evolution driven by urban roadway runoff, simulated by tire wear particle (TWP) leachate, through multi‐scale spatiotemporal experiments. On a microgeographic spatial scale, sampling sites were established along an urbanization gradient within the Huangpu River basin. The results showed that populations originating from highly urbanized waters exhibited significantly higher population intrinsic rate of increase under TWP stress, revealing a spatial pattern of evolutionary adaptation to the pollutant. On a temporal scale, historical populations were reconstructed by resurrecting dormant eggs from different periods (1980s to 2020s) in sediments. The findings demonstrated that as vehicle ownership and pollution pressure increased in the surrounding areas, contemporary populations exhibited significantly higher tolerance to TWP than historical populations, presenting a clear trajectory of adaptive evolution over time. By employing resurrection ecology and microgeography spatial gradient analysis, this study reveals direct associations between urban pollution‐induced rapid evolution in aquatic organisms. It uncovers the short‐term adaptive mechanisms of zooplankton to urban environmental stressors. These findings advance the understanding of contemporary evolution and enhance predictive capacity for aquatic ecosystem responses to anthropogenic pressures.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"84 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147470898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kendra Turk‐Kubo, Claire Mahaffey, Jo Hopkins, Ruth Hawley, Louisa Norman, Lewis Wrightson, Ben Fisher, Stefanie Rynders, Clive Neil, Maryam Ilyas, Maeve C. Lohan
Nitrogen fixation, the microbial conversion of dinitrogen gas to ammonia, is a key nitrogen source and critical for sustaining marine productivity. We investigated the diversity and activity of nitrogen‐fixers in surface waters of the North Sea and Norwegian coast during July 2023. We detected, for the first time, the presence of Braarudosphaera /UCYN‐A (up to 10 4nifH copies L −1 ) and measurable nitrogen fixation rates (up to 110 nM d −1 ) throughout the North Sea. Nitrogen‐fixing organisms may be transported from the northeast Atlantic across the northern North Sea by southward current systems, via Baltic Sea inflow or be a persistent but overlooked component of the phytoplankton community. We estimate nitrogen fixation may support between 4% and 24% of summertime net primary production. Nitrogen fixation is currently neglected in numerical models of shelf seas, yet may play a critical role in sustaining shelf sea productivity in the contemporary and future ocean.
{"title":"High nitrogen fixation and Braarudosphaera presence in the North Sea","authors":"Kendra Turk‐Kubo, Claire Mahaffey, Jo Hopkins, Ruth Hawley, Louisa Norman, Lewis Wrightson, Ben Fisher, Stefanie Rynders, Clive Neil, Maryam Ilyas, Maeve C. Lohan","doi":"10.1002/lno.70331","DOIUrl":"https://doi.org/10.1002/lno.70331","url":null,"abstract":"Nitrogen fixation, the microbial conversion of dinitrogen gas to ammonia, is a key nitrogen source and critical for sustaining marine productivity. We investigated the diversity and activity of nitrogen‐fixers in surface waters of the North Sea and Norwegian coast during July 2023. We detected, for the first time, the presence of <jats:italic>Braarudosphaera</jats:italic> /UCYN‐A (up to 10 <jats:sup>4</jats:sup> <jats:italic>nifH</jats:italic> copies L <jats:sup>−1</jats:sup> ) and measurable nitrogen fixation rates (up to 110 nM d <jats:sup>−1</jats:sup> ) throughout the North Sea. Nitrogen‐fixing organisms may be transported from the northeast Atlantic across the northern North Sea by southward current systems, via Baltic Sea inflow or be a persistent but overlooked component of the phytoplankton community. We estimate nitrogen fixation may support between 4% and 24% of summertime net primary production. Nitrogen fixation is currently neglected in numerical models of shelf seas, yet may play a critical role in sustaining shelf sea productivity in the contemporary and future ocean.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"55 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147470904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Alba Camacho‐Santamans, Biel Obrador, Camille Minaudo, Lídia Cañas, Yao Wang, Fernanda Mejía‐Peralta, João M. M. Bega, Jorge J. Montes‐Pérez, Daniel von Schiller
Stream hydrological regimes are increasingly altered by water extraction, land‐use change, and climate change, leading to prolonged streambed desiccation in many regions. These alterations significantly impact biogeochemical processes within stream networks. To date, most research on the carbon (C) cycle in aquatic systems has focused on inundated areas, thereby neglecting the potential role of dry streambeds in biogeochemical dynamics. However, some studies have shown that dry streambeds substantially influence C fluxes within fluvial environments, although with limited temporal replication. In this study, we quantify the contribution of dry areas to gaseous C exchange in an intermittent Mediterranean stream. Over 2 yr, we monitored the spatial extent of wet (i.e., inundated) and dry (i.e., air‐exposed) areas and measured carbon dioxide (CO 2 ) and methane (CH 4 ) fluxes along a 100‐m reach using high‐frequency automatic sensors and in‐situ sampling every 2–3 weeks. We found that areal C fluxes were higher in wet compared to dry areas. Fluxes in wet areas displayed strong temporal dynamics, with peaks during phases of rewetting and contraction of the stream. In contrast, fluxes in dry areas were relative stable over time and accounted for 46% of the total reach‐scale C exchange with the atmosphere during the study period. These results emphasize the importance of accounting for inundated and intermittently dry areas when analyzing C exchange dynamics in intermittent streams. This issue is particularly relevant in the current context of climate change, with climate‐driven hydrological changes in many of the world's regions.
{"title":"Unraveling the effects of wet and dry areas on carbon emissions in an intermittent Mediterranean stream","authors":"Alba Camacho‐Santamans, Biel Obrador, Camille Minaudo, Lídia Cañas, Yao Wang, Fernanda Mejía‐Peralta, João M. M. Bega, Jorge J. Montes‐Pérez, Daniel von Schiller","doi":"10.1002/lno.70348","DOIUrl":"https://doi.org/10.1002/lno.70348","url":null,"abstract":"Stream hydrological regimes are increasingly altered by water extraction, land‐use change, and climate change, leading to prolonged streambed desiccation in many regions. These alterations significantly impact biogeochemical processes within stream networks. To date, most research on the carbon (C) cycle in aquatic systems has focused on inundated areas, thereby neglecting the potential role of dry streambeds in biogeochemical dynamics. However, some studies have shown that dry streambeds substantially influence C fluxes within fluvial environments, although with limited temporal replication. In this study, we quantify the contribution of dry areas to gaseous C exchange in an intermittent Mediterranean stream. Over 2 yr, we monitored the spatial extent of wet (i.e., inundated) and dry (i.e., air‐exposed) areas and measured carbon dioxide (CO <jats:sub>2</jats:sub> ) and methane (CH <jats:sub>4</jats:sub> ) fluxes along a 100‐m reach using high‐frequency automatic sensors and in‐situ sampling every 2–3 weeks. We found that areal C fluxes were higher in wet compared to dry areas. Fluxes in wet areas displayed strong temporal dynamics, with peaks during phases of rewetting and contraction of the stream. In contrast, fluxes in dry areas were relative stable over time and accounted for 46% of the total reach‐scale C exchange with the atmosphere during the study period. These results emphasize the importance of accounting for inundated and intermittently dry areas when analyzing C exchange dynamics in intermittent streams. This issue is particularly relevant in the current context of climate change, with climate‐driven hydrological changes in many of the world's regions.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"9 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147447869","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rafael de Carvalho Bueno, Tobias Bleninger, Andreas Lorke
Basin‐scale internal waves are a common phenomenon in thermally stratified water bodies, with important implications for aquatic organisms and biogeochemical cycling. While theoretical analyses of internal seiche generation and their properties are mostly based on idealized (rectangular) basin shapes, several studies have highlighted the influence of basin shape and sloping topography. The results, however, tend to be site‐specific and not widely generalized. Here, we investigate how sloping topography affects the generation of internal seiches in reservoir‐shaped water bodies. We simulated the response of 50 hypothetical basins to wind forcing using a three‐dimensional hydrodynamic model, while systematically varying bottom slope (10 −3 to rectangular basin), basin length (1.5–5 km), and forcing conditions (Wedderburn number 2–20). Our results demonstrate that sloping topography plays a critical role in the generation of internal seiches during the relaxation from wind‐induced upwelling. Upslope‐propagating fronts are formed above the sloping bed and interact with the basin‐scale flows that govern seiche formation. This interaction induces enhanced turbulent mixing and bottom boundary layer separation with transport of water from the slope to the lake interior. We found that the effect of these processes on internal seiche damping could be well described by the slope criticality parameter, a parameter relating the direction of internal wave propagation to bottom slope. These findings suggest that the slope criticality parameter can potentially serve as a predictor of dominant basin‐scale circulation and mixing mechanisms, offering valuable insights into the transport of nutrients, sediments, and organisms in lakes and reservoirs.
{"title":"Internal seiche damping on sloping topography","authors":"Rafael de Carvalho Bueno, Tobias Bleninger, Andreas Lorke","doi":"10.1002/lno.70340","DOIUrl":"https://doi.org/10.1002/lno.70340","url":null,"abstract":"Basin‐scale internal waves are a common phenomenon in thermally stratified water bodies, with important implications for aquatic organisms and biogeochemical cycling. While theoretical analyses of internal seiche generation and their properties are mostly based on idealized (rectangular) basin shapes, several studies have highlighted the influence of basin shape and sloping topography. The results, however, tend to be site‐specific and not widely generalized. Here, we investigate how sloping topography affects the generation of internal seiches in reservoir‐shaped water bodies. We simulated the response of 50 hypothetical basins to wind forcing using a three‐dimensional hydrodynamic model, while systematically varying bottom slope (10 <jats:sup>−3</jats:sup> to rectangular basin), basin length (1.5–5 km), and forcing conditions (Wedderburn number 2–20). Our results demonstrate that sloping topography plays a critical role in the generation of internal seiches during the relaxation from wind‐induced upwelling. Upslope‐propagating fronts are formed above the sloping bed and interact with the basin‐scale flows that govern seiche formation. This interaction induces enhanced turbulent mixing and bottom boundary layer separation with transport of water from the slope to the lake interior. We found that the effect of these processes on internal seiche damping could be well described by the slope criticality parameter, a parameter relating the direction of internal wave propagation to bottom slope. These findings suggest that the slope criticality parameter can potentially serve as a predictor of dominant basin‐scale circulation and mixing mechanisms, offering valuable insights into the transport of nutrients, sediments, and organisms in lakes and reservoirs.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"406 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147373825","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mei Sato, Zachary K. Erickson, Helena McMonagle, Joel K. Llopiz
Mesoscale eddies are ubiquitous features in the world's oceans that create dynamic habitats supporting diverse biological communities. Yet, most studies focus on primary producers and top predators, leaving a key gap at the mid‐trophic level. In this study, we tracked a mode‐water anticyclonic eddy in the North Atlantic for a month during its decay phase using a Lagrangian framework, integrating ship‐based acoustic observations and net sampling with autonomous hydrographic measurements. We found that deep scattering layers, composed primarily of non‐migratory bristlemouths, exhibited temperature‐dependent vertical distributions, avoiding the warmer core waters. In contrast, midwater scattering layers—formed by vertically migrating hatchetfishes and myctophids—were concentrated at the eddy core, with shifts in community composition and size across the eddy. These patterns likely reflect a combination of passive transport and active behavioral responses to eddy‐driven physical forcing. Together, our results demonstrate that eddy life stage and internal structure—not just polarity—shape mesopelagic community organization, offering new mechanistic insight into how mesoscale eddies shape biological structure in the ocean.
{"title":"Mesoscale eddy structure drives spatial variability in mesopelagic fishes","authors":"Mei Sato, Zachary K. Erickson, Helena McMonagle, Joel K. Llopiz","doi":"10.1002/lno.70346","DOIUrl":"https://doi.org/10.1002/lno.70346","url":null,"abstract":"Mesoscale eddies are ubiquitous features in the world's oceans that create dynamic habitats supporting diverse biological communities. Yet, most studies focus on primary producers and top predators, leaving a key gap at the mid‐trophic level. In this study, we tracked a mode‐water anticyclonic eddy in the North Atlantic for a month during its decay phase using a Lagrangian framework, integrating ship‐based acoustic observations and net sampling with autonomous hydrographic measurements. We found that deep scattering layers, composed primarily of non‐migratory bristlemouths, exhibited temperature‐dependent vertical distributions, avoiding the warmer core waters. In contrast, midwater scattering layers—formed by vertically migrating hatchetfishes and myctophids—were concentrated at the eddy core, with shifts in community composition and size across the eddy. These patterns likely reflect a combination of passive transport and active behavioral responses to eddy‐driven physical forcing. Together, our results demonstrate that eddy life stage and internal structure—not just polarity—shape mesopelagic community organization, offering new mechanistic insight into how mesoscale eddies shape biological structure in the ocean.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"89 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147373820","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Willem H. van de Poll, Rebecca Zitoun, Loay J. Jabre, Marieke M. Bos, Anna C. Koek, Wen‐Hsuan Liao, Sharyn Ossebaar, Patrick Laan, Erin M. Bertrand, Rob Middag
High‐latitude North Atlantic currents (60°–70°N) exhibit contrasting nutrient stoichiometries, but the spatial extent of post‐spring bloom iron (Fe) and nitrogen (N) stress on phytoplankton around Iceland remains poorly constrained. Here we pair in situ biogeochemical characteristics with 72 h Fe and N addition experiments in the East Greenland Current (EGC), Irminger Current (IC), Atlantic Current (AC), and East Icelandic Current (EIC) regions. Dissolved iron (dFe) was elevated in the EGC region and depleted in Atlantic surface waters. Unlike dFe, surface nitrate in the EGC region was depleted and elevated in Atlantic waters. Chlorophyll a (Chl a ) and particulate organic carbon standing stocks in the diatom and chlorophyte enriched EGC were ~ 40% lower than in the haptophyte dominated Atlantic waters. Changes in photophysiology during the incubation experiments revealed widespread Fe stress in the IC and in most of the AC stations. Notably, 80% of the experiments with nutrient stoichiometry suggesting Fe limitation (dFe < 0.2 nmol L −1 , N > 0.6 μ mol L −1 ) revealed Fe stress. In contrast, 30% of the experiments with nutrient stoichiometry suggesting N limitation (N < 0.6 μ mol L −1 , dFe > 0.2 nmol L −1 ) showed N stress, mainly in the EGC region. The EIC showed depleted concentrations of nitrate and dFe at the surface. Here, one incubation experiment revealed responses of combined N and Fe stress. The strong summertime density differences between the EGC and Atlantic water masses most likely limits the ability of advected dFe from Greenland and the Arctic to fertilize the Fe‐depleted Atlantic waters.
{"title":"Iron and nitrogen stress controls summertime biogeochemistry in the high‐latitude North Atlantic","authors":"Willem H. van de Poll, Rebecca Zitoun, Loay J. Jabre, Marieke M. Bos, Anna C. Koek, Wen‐Hsuan Liao, Sharyn Ossebaar, Patrick Laan, Erin M. Bertrand, Rob Middag","doi":"10.1002/lno.70341","DOIUrl":"https://doi.org/10.1002/lno.70341","url":null,"abstract":"High‐latitude North Atlantic currents (60°–70°N) exhibit contrasting nutrient stoichiometries, but the spatial extent of post‐spring bloom iron (Fe) and nitrogen (N) stress on phytoplankton around Iceland remains poorly constrained. Here we pair in situ biogeochemical characteristics with 72 h Fe and N addition experiments in the East Greenland Current (EGC), Irminger Current (IC), Atlantic Current (AC), and East Icelandic Current (EIC) regions. Dissolved iron (dFe) was elevated in the EGC region and depleted in Atlantic surface waters. Unlike dFe, surface nitrate in the EGC region was depleted and elevated in Atlantic waters. Chlorophyll <jats:italic>a</jats:italic> (Chl <jats:italic>a</jats:italic> ) and particulate organic carbon standing stocks in the diatom and chlorophyte enriched EGC were ~ 40% lower than in the haptophyte dominated Atlantic waters. Changes in photophysiology during the incubation experiments revealed widespread Fe stress in the IC and in most of the AC stations. Notably, 80% of the experiments with nutrient stoichiometry suggesting Fe limitation (dFe < 0.2 nmol L <jats:sup>−1</jats:sup> , N > 0.6 <jats:italic>μ</jats:italic> mol L <jats:sup>−1</jats:sup> ) revealed Fe stress. In contrast, 30% of the experiments with nutrient stoichiometry suggesting N limitation (N < 0.6 <jats:italic>μ</jats:italic> mol L <jats:sup>−1</jats:sup> , dFe > 0.2 nmol L <jats:sup>−1</jats:sup> ) showed N stress, mainly in the EGC region. The EIC showed depleted concentrations of nitrate and dFe at the surface. Here, one incubation experiment revealed responses of combined N and Fe stress. The strong summertime density differences between the EGC and Atlantic water masses most likely limits the ability of advected dFe from Greenland and the Arctic to fertilize the Fe‐depleted Atlantic waters.","PeriodicalId":18143,"journal":{"name":"Limnology and Oceanography","volume":"12 1","pages":""},"PeriodicalIF":4.5,"publicationDate":"2026-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147373867","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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