I. Dunkl, N. Lovenduski, Alessio Collalti, V. Arora, T. Ilyina, V. Brovkin
Abstract. The prediction of atmospheric CO2 concentrations is limited by the high interannual variability (IAV) in terrestrial gross primary productivity (GPP). However, there are large uncertainties in the drivers of GPP IAV among Earth system models (ESMs). Here, we evaluate the impact of these uncertainties on the predictability of atmospheric CO2 in six ESMs. We use regression analysis to determine the role of environmental drivers in (i) the patterns of GPP IAV and (ii) the predictability of GPP. There are large uncertainties in the spatial distribution of GPP IAV. Although all ESMs agree on the high IAV in the tropics, several ESMs have unique hotspots of GPP IAV. The main driver of GPP IAV is temperature in the ESMs using the Community Land Model, whereas it is soil moisture in the ESM developed by the Institute Pierre Simon Laplace (IPSL-CM6A-LR) and in the low-resolution configuration of the Max Planck Earth System Model (MPI-ESM-LR), revealing underlying differences in the source of GPP IAV among ESMs. Between 13 % and 24 % of the GPP IAV is predictable 1 year ahead, with four out of six ESMs showing values of between 19 % and 24 %. Up to 32 % of the GPP IAV induced by soil moisture is predictable, whereas only 7 % to 13 % of the GPP IAV induced by radiation is predictable. The results show that, while ESMs are fairly similar in their ability to predict their own carbon flux variability, these predicted contributions to the atmospheric CO2 variability originate from different regions and are caused by different drivers. A higher coherence in atmospheric CO2 predictability could be achieved by reducing uncertainties in the GPP sensitivity to soil moisture and by accurate observational products for GPP IAV.
{"title":"Gross primary productivity and the predictability of CO2: more uncertainty in what we predict than how well we predict it","authors":"I. Dunkl, N. Lovenduski, Alessio Collalti, V. Arora, T. Ilyina, V. Brovkin","doi":"10.5194/bg-20-3523-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3523-2023","url":null,"abstract":"Abstract. The prediction of atmospheric CO2 concentrations is limited by the high interannual variability (IAV) in terrestrial gross primary\u0000productivity (GPP). However, there are large uncertainties in the drivers of GPP IAV among Earth system models (ESMs). Here, we evaluate the impact\u0000of these uncertainties on the predictability of atmospheric CO2 in six ESMs. We use regression analysis to determine the role of\u0000environmental drivers in (i) the patterns of GPP IAV and (ii) the predictability of GPP. There are large uncertainties in the spatial distribution\u0000of GPP IAV. Although all ESMs agree on the high IAV in the tropics, several ESMs have unique hotspots of GPP IAV. The main driver of GPP IAV is\u0000temperature in the ESMs using the Community Land Model, whereas it is soil moisture in the ESM developed by the Institute Pierre Simon Laplace (IPSL-CM6A-LR) and in the low-resolution configuration of the Max Planck Earth System Model (MPI-ESM-LR), revealing underlying differences in the\u0000source of GPP IAV among ESMs. Between 13 % and 24 % of the GPP IAV is predictable 1 year ahead, with four out of six ESMs showing values of between 19 %\u0000and 24 %. Up to 32 % of the GPP IAV induced by soil moisture is predictable, whereas only 7 % to 13 % of the GPP IAV induced by\u0000radiation is predictable. The results show that, while ESMs are fairly similar in their ability to predict their own carbon flux variability, these predicted contributions to the atmospheric CO2 variability originate from different regions and are caused by different drivers. A higher coherence in atmospheric\u0000CO2 predictability could be achieved by reducing uncertainties in the GPP sensitivity to soil moisture and by accurate observational products\u0000for GPP IAV.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48816060","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}
Marco Fusi, Sylvain Rigaud, Giovanna Guadagnin, Alberto Barausse, Ramona Marasco, Daniele Daffonchio, Julie Régis, Louison Huchet, Capucine Camin, Laura Pettit, Cristina Vina-Herbon, Folco Giomi
Abstract. Oxygen availability is a pivotal factor for ecosystem functioning and the resistance of organisms to the effect of climate change in aquatic habitats. Although extensive work has been done to assess the effect of oxygen on marine and freshwater biota, many studies have not captured the ecological importance of oxygen variations. Overlooking the fluctuating nature of oxygen may cause potential biases in the design and implementation of management policies for aquatic habitats. Conceptual perspectives on the dynamic nature of oxygen fluctuations have been raised in the scientific community in order to enhance the understanding of the effect of oxygen on the physiology and the ecology of aquatic species as well as the biogeochemical functioning of their ecosystems. A growing number of empirical work has been outlining a novel conceptual framework that considers the magnitude of oxygen fluctuation as a key variable that explains adaptation to stress conditions. Oxygen in productive aquatic habitats shows large fluctuations at the diel scale, exposing aquatic species to conditions ranging from extreme supersaturation to anoxia. Recent research has indicated that such a fluctuation tunes the physiological plasticity of the animal in response to thermal stresses. In this paper, we provide compelling evidence based on current research that the fluctuating oxygen landscape, here defined as “oxyscape”, has an important role in aquatic animal physiology and adaptation as well as the ecosystem biogeochemistry. We propose that the oxyscape should be considered in the modelling and managing policies of aquatic ecosystems.
{"title":"Ideas and perspectives: The fluctuating nature of oxygen shapes the ecology of aquatic habitats and their biogeochemical cycles – the aquatic oxyscape","authors":"Marco Fusi, Sylvain Rigaud, Giovanna Guadagnin, Alberto Barausse, Ramona Marasco, Daniele Daffonchio, Julie Régis, Louison Huchet, Capucine Camin, Laura Pettit, Cristina Vina-Herbon, Folco Giomi","doi":"10.5194/bg-20-3509-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3509-2023","url":null,"abstract":"Abstract. Oxygen availability is a pivotal factor for ecosystem functioning and the resistance of organisms to the effect of climate change in aquatic habitats. Although extensive work has been done to assess the effect of oxygen on marine and freshwater biota, many studies have not captured the ecological importance of oxygen variations. Overlooking the fluctuating nature of oxygen may cause potential biases in the design and implementation of management policies for aquatic habitats. Conceptual perspectives on the dynamic nature of oxygen fluctuations have been raised in the scientific community in order to enhance the understanding of the effect of oxygen on the physiology and the ecology of aquatic species as well as the biogeochemical functioning of their ecosystems. A growing number of empirical work has been outlining a novel conceptual framework that considers the magnitude of oxygen fluctuation as a key variable that explains adaptation to stress conditions. Oxygen in productive aquatic habitats shows large fluctuations at the diel scale, exposing aquatic species to conditions ranging from extreme supersaturation to anoxia. Recent research has indicated that such a fluctuation tunes the physiological plasticity of the animal in response to thermal stresses. In this paper, we provide compelling evidence based on current research that the fluctuating oxygen landscape, here defined as “oxyscape”, has an important role in aquatic animal physiology and adaptation as well as the ecosystem biogeochemistry. We propose that the oxyscape should be considered in the modelling and managing policies of aquatic ecosystems.","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135520481","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}
Alessandro Zanchetta, Linda M. J. Kooijmans, S. V. van Heuven, A. Scifo, H. Scheeren, I. Mammarella, U. Karstens, Jin Ma, M. Krol, Huilin Chen
Abstract. Carbonyl sulfide (COS) is a promising tracer for the estimation of terrestrial ecosystem gross primary production (GPP). However, understanding its non-GPP-related sources and sinks, e.g., anthropogenic sources and soil sources and sinks, is also critical to the success of the approach. Here we infer the regional sources and sinks of COS using continuous in situ mole fraction profile measurements of COS along the 60 m tall Lutjewad tower (1 m a.s.l.; 53∘24′ N, 6∘21′ E) in the Netherlands. To identify potential sources that caused the observed enhancements of COS mole fractions at Lutjewad, both discrete flask samples and in situ measurements in the province of Groningen were made from a mobile van using a quantum cascade laser spectrometer (QCLS). We also simulated the COS mole fractions at Lutjewad using the Stochastic Time-Inverted Lagrangian Transport (STILT) model combined with emission inventories and plant uptake fluxes. We determined the nighttime COS fluxes to be -3.0±2.6 pmol m−2 s−1 using the radon-tracer correlation approach and Lutjewad observations. Furthermore, we identified and quantified several COS sources, including biodigesters, sugar production facilities and silicon carbide production facilities in the province of Groningen. Moreover, the simulation results show that the observed COS enhancements can be partially explained by known industrial sources of COS and CS2, in particular from the Ruhr Valley (51.5∘ N, 7.2∘ E) and Antwerp (51.2∘ N, 4.4∘ E) areas. The contribution of likely missing anthropogenic sources of COS and CS2 in the inventory may be significant. The impact of the identified sources in the province of Groningen is estimated to be negligible in terms of the observed COS enhancements. However, in specific conditions, these sources may influence the measurements in Lutjewad. These results are valuable for improving our understanding of the sources and sinks of COS, contributing to the use of COS as a tracer for GPP.
{"title":"Sources and sinks of carbonyl sulfide inferred from tower and mobile atmospheric observations in the Netherlands","authors":"Alessandro Zanchetta, Linda M. J. Kooijmans, S. V. van Heuven, A. Scifo, H. Scheeren, I. Mammarella, U. Karstens, Jin Ma, M. Krol, Huilin Chen","doi":"10.5194/bg-20-3539-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3539-2023","url":null,"abstract":"Abstract. Carbonyl sulfide (COS) is a promising tracer for the estimation of\u0000terrestrial ecosystem gross primary production (GPP). However, understanding\u0000its non-GPP-related sources and sinks, e.g., anthropogenic sources and soil\u0000sources and sinks, is also critical to the success of the approach. Here we\u0000infer the regional sources and sinks of COS using continuous in situ mole fraction\u0000profile measurements of COS along the 60 m tall Lutjewad tower (1 m a.s.l.;\u000053∘24′ N, 6∘21′ E) in the Netherlands. To identify\u0000potential sources that caused the observed enhancements of COS mole\u0000fractions at Lutjewad, both discrete flask samples and in situ measurements\u0000in the province of Groningen were made from a mobile van using a quantum\u0000cascade laser spectrometer (QCLS). We also simulated the COS mole fractions\u0000at Lutjewad using the Stochastic Time-Inverted Lagrangian Transport (STILT)\u0000model combined with emission inventories and plant uptake fluxes. We\u0000determined the nighttime COS fluxes to be -3.0±2.6 pmol m−2 s−1 using the radon-tracer correlation approach and Lutjewad\u0000observations. Furthermore, we identified and quantified several COS sources,\u0000including biodigesters, sugar production facilities and silicon carbide\u0000production facilities in the province of Groningen. Moreover, the simulation\u0000results show that the observed COS enhancements can be partially explained\u0000by known industrial sources of COS and CS2, in particular from the Ruhr\u0000Valley (51.5∘ N, 7.2∘ E) and Antwerp (51.2∘ N,\u00004.4∘ E) areas. The contribution of likely missing anthropogenic\u0000sources of COS and CS2 in the inventory may be significant. The impact\u0000of the identified sources in the province of Groningen is estimated to be\u0000negligible in terms of the observed COS enhancements. However, in specific\u0000conditions, these sources may influence the measurements in Lutjewad. These\u0000results are valuable for improving our understanding of the sources and\u0000sinks of COS, contributing to the use of COS as a tracer for GPP.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47271870","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}
Roxane Tzortzis, A. Doglioli, S. Barrillon, A. Petrenko, Lloyd Izard, Yuan Zhao, F. d’Ovidio, F. Dumas, G. Grégori
Abstract. Numerical simulations have shown that finescale structures such as fronts are often suitable places for the generation of vertical velocities, transporting subsurface nutrients to the euphotic zone and thus modulating phytoplankton abundance and community structure. In these structures, direct in situ estimations of the phytoplankton growth rates are rare; although difficult to obtain, they provide precious information on the ecosystem functioning. Here, we consider the case of a front separating two water masses characterized by several phytoplankton groups with different abundances in the southwestern Mediterranean Sea. In order to estimate possible differences in growth rates, we measured the phytoplankton diurnal cycle in these two water masses as identified by an adaptive and Lagrangian sampling strategy. A size-structured population model was then applied to these data to estimate the growth and loss rates for each phytoplankton group identified by flow cytometry, showing that these two population parameters are significantly different on the two sides of the front and consistent with the relative abundances. Our results introduce a general method for estimating growth rates at frontal systems, paving the way for in situ exploration of finescale biophysical interactions.
{"title":"The contrasted phytoplankton dynamics across a frontal system in the southwestern Mediterranean Sea","authors":"Roxane Tzortzis, A. Doglioli, S. Barrillon, A. Petrenko, Lloyd Izard, Yuan Zhao, F. d’Ovidio, F. Dumas, G. Grégori","doi":"10.5194/bg-20-3491-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3491-2023","url":null,"abstract":"Abstract. Numerical simulations have shown that finescale structures such as fronts are often suitable places for the generation of vertical velocities,\u0000transporting subsurface nutrients to the euphotic zone and thus modulating phytoplankton abundance and community structure. In these structures,\u0000direct in situ estimations of the phytoplankton growth rates are rare; although difficult to obtain, they provide precious information on the\u0000ecosystem functioning. Here, we consider the case of a front separating two water masses characterized by several phytoplankton groups with\u0000different abundances in the southwestern Mediterranean Sea. In order to estimate possible differences in growth rates, we measured the\u0000phytoplankton diurnal cycle in these two water masses as identified by an adaptive and Lagrangian sampling strategy. A size-structured population\u0000model was then applied to these data to estimate the growth and loss rates for each phytoplankton group identified by flow cytometry, showing that\u0000these two population parameters are significantly different on the two sides of the front and consistent with the relative abundances. Our results\u0000introduce a general method for estimating growth rates at frontal systems, paving the way for in situ exploration of finescale biophysical\u0000interactions.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44524485","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}
Yonghong Zheng, Huanfeng Shen, Rory Abernethy, Rob Wilson
Abstract. To investigate the potential value of tree ring blue intensity as a robust climate proxy in central and western China, four species from five sites were assessed. As well as latewood inverted blue intensity, we also examined earlywood blue intensity. To explore the sensitivity of using different extraction parameter settings using the software CooRecorder, seven percentile (P) variant settings for earlywood blue intensity and latewood inverted blue intensity were used, namely P50 : 50, P60 : 40, P70 : 30, P80 : 20, P85 : 15, P90 : 10, and P95 : 5. Age-dependent spline was used for all, and the positive trends were not retained. Correlation analysis was applied between the tree ring parameter chronologies and monthly/seasonal mean temperature, precipitation, and self-calibrated Palmer drought severity index variables. Linear regression was also used to further highlight the potential of developing climate reconstructions using these species. Only subtle differences were found between the different percentile extraction variants. As has been shown for many other Northern Hemisphere studies, latewood inverted blue intensity expresses a strong positive relationship with growing-season temperatures (the two southern sites explain almost 56 % of the temperature variance when combined). However, the low latitude of these sites shows an exciting potential for regions south of 30∘ N that are traditionally not targeted for temperature reconstructions. Earlywood blue intensity also shows good potential to reconstruct hydroclimate parameters in some humid areas.
{"title":"Experiments of the efficacy of tree ring blue intensity as a climate proxy in central and western China","authors":"Yonghong Zheng, Huanfeng Shen, Rory Abernethy, Rob Wilson","doi":"10.5194/bg-20-3481-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3481-2023","url":null,"abstract":"Abstract. To investigate the potential value of tree ring blue intensity as a robust\u0000climate proxy in central and western China, four species from five sites were\u0000assessed. As well as latewood inverted blue intensity, we also examined\u0000earlywood blue intensity. To explore the sensitivity of using different\u0000extraction parameter settings using the software CooRecorder, seven\u0000percentile (P) variant settings for earlywood blue intensity and latewood\u0000inverted blue intensity were used, namely P50 : 50, P60 : 40, P70 : 30, P80 : 20,\u0000P85 : 15, P90 : 10, and P95 : 5. Age-dependent spline was used for all, and the\u0000positive trends were not retained. Correlation analysis was applied between\u0000the tree ring parameter chronologies and monthly/seasonal mean temperature,\u0000precipitation, and self-calibrated Palmer drought severity index variables.\u0000Linear regression was also used to further highlight the potential of\u0000developing climate reconstructions using these species. Only subtle\u0000differences were found between the different percentile extraction variants.\u0000As has been shown for many other Northern Hemisphere studies, latewood\u0000inverted blue intensity expresses a strong positive relationship with\u0000growing-season temperatures (the two southern sites explain almost 56 % of\u0000the temperature variance when combined). However, the low latitude of these\u0000sites shows an exciting potential for regions south of 30∘ N that are\u0000traditionally not targeted for temperature reconstructions. Earlywood blue\u0000intensity also shows good potential to reconstruct hydroclimate parameters\u0000in some humid areas.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41782090","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}
E. Graham, Hyun‐Seob Song, S. Grieger, V. Garayburu-Caruso, J. Stegen, K. Bladon, A. Myers‐Pigg
Abstract. Pyrogenic organic matter (PyOM) from wildfires impacts river corridors globally and is widely regarded as resistant to biological degradation. Though recent work suggests PyOM may be more bioavailable than historically perceived, estimating bioavailability across its chemical spectrum remains elusive. To address this knowledge gap, we assessed potential bioavailability of representative PyOM compounds relative to ubiquitous dissolved organic matter (DOM) with a substrate-explicit model. The range of potential bioavailability of PyOM was greater than natural DOM; however, the predicted thermodynamics, metabolic rates, and carbon use efficiencies (CUEs) overlapped significantly between all OM pools. Compound type (e.g., natural versus PyOM) had approximately 6-fold less impact on predicted respiration rates than simulated carbon and oxygen limitations. Within PyOM, the metabolism of specific chemistries differed strongly between unlimited and oxygen-limited conditions – degradations of anhydrosugars, phenols, and polycyclic aromatic hydrocarbons (PAHs) were more favorable under oxygen limitation than other molecules. Notably, amino sugar-like, protein-like, and lignin-like PyOM had lower carbon use efficiencies relative to natural DOM of the same classes, indicating potential impacts in process-based model representations. Overall, our work illustrates how similar PyOM bioavailability may be to that of natural DOM in the river corridor, furthering our understanding of how PyOM may influence riverine biogeochemical cycling.
{"title":"Potential bioavailability of representative pyrogenic organic matter compounds in comparison to natural dissolved organic matter pools","authors":"E. Graham, Hyun‐Seob Song, S. Grieger, V. Garayburu-Caruso, J. Stegen, K. Bladon, A. Myers‐Pigg","doi":"10.5194/bg-20-3449-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3449-2023","url":null,"abstract":"Abstract. Pyrogenic organic matter (PyOM) from wildfires impacts river\u0000corridors globally and is widely regarded as resistant to biological\u0000degradation. Though recent work suggests PyOM may be more bioavailable than\u0000historically perceived, estimating bioavailability across its chemical\u0000spectrum remains elusive. To address this knowledge gap, we assessed\u0000potential bioavailability of representative PyOM compounds relative to\u0000ubiquitous dissolved organic matter (DOM) with a substrate-explicit model.\u0000The range of potential bioavailability of PyOM was greater than natural DOM;\u0000however, the predicted thermodynamics, metabolic rates, and carbon use\u0000efficiencies (CUEs) overlapped significantly between all OM pools. Compound type\u0000(e.g., natural versus PyOM) had approximately 6-fold less impact on predicted\u0000respiration rates than simulated carbon and oxygen limitations. Within PyOM,\u0000the metabolism of specific chemistries differed strongly between unlimited\u0000and oxygen-limited conditions – degradations of anhydrosugars, phenols, and polycyclic aromatic hydrocarbons (PAHs) were more favorable under oxygen\u0000limitation than other molecules. Notably, amino sugar-like, protein-like, and lignin-like PyOM had lower carbon use efficiencies relative to natural DOM\u0000of the same classes, indicating potential impacts in process-based model\u0000representations. Overall, our work illustrates how similar PyOM\u0000bioavailability may be to that of natural DOM in the river corridor,\u0000furthering our understanding of how PyOM may influence riverine\u0000biogeochemical cycling.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41516535","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}
N. Lehmann, H. Lantuit, M. Böttcher, J. Hartmann, A. Eulenburg, H. Thomas
Abstract. The weathering rate of carbonate minerals is several orders of magnitude higher than for silicate minerals. Therefore, small amounts of carbonate minerals have the potential to control the dissolved weathering loads in silicate-dominated catchments. Both weathering processes produce alkalinity under the consumption of CO2. Given that only alkalinity generation from silicate weathering is thought to be a long-term sink for CO2, a misattributed weathering source could lead to incorrect conclusions about long- and short-term CO2 fixation. In this study, we aimed to identify the weathering sources responsible for alkalinity generation and CO2 fixation across watershed scales in a degrading permafrost landscape in northern Norway, 68.7–70.5∘ N, and on a temporal scale, in a subarctic headwater catchment on the mountainside of Iskorasfjellet, characterized by sporadic permafrost and underlain mainly by silicates as the alkalinity-bearing lithology. By analyzing total alkalinity (AT) and dissolved inorganic carbon (DIC) concentrations, as well as the stable isotope signature of the latter (δ13C-DIC), in conjunction with dissolved cation and anion loads, we found that AT was almost entirely derived from weathering of the sparse carbonate minerals. We propose that in the headwater catchment the riparian zone is a hotspot area of AT generation and release due to its enhanced hydrological connectivity and that the weathering load contribution from the uphill catchment is limited by insufficient contact time of weathering agents and weatherable materials. By using stable water isotopes, it was possible to explain temporal variations in AT concentrations following a precipitation event due to surface runoff. In addition to carbonic acid, sulfuric acid, probably originating from oxidation of pyrite or reduced sulfur in wetlands or from acid deposition, is shown to be a potential corrosive reactant. An increased proportion of sulfuric acid as a potential weathering agent may have resulted in a decrease in AT. Therefore, carbonate weathering in the studied area should be considered not only as a short-term CO2 sink but also as a potential CO2 source. Finally, we found that AT increased with decreasing permafrost probability, and attributed this relation to an increased water storage capacity associated with increasing contact of weathering agent and rock surfaces and enhanced microbial activity. As both soil respiration and permafrost thaw are expected to increase with climate change, increasing the availability of weathering agents in the form of CO2 and water storage capacity, respectively, we suggest that future weathering rates and alkalinity generation will increase concomitantly in the study area.
{"title":"Alkalinity generation from carbonate weathering in a silicate-dominated headwater catchment at Iskorasfjellet, northern Norway","authors":"N. Lehmann, H. Lantuit, M. Böttcher, J. Hartmann, A. Eulenburg, H. Thomas","doi":"10.5194/bg-20-3459-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3459-2023","url":null,"abstract":"Abstract. The weathering rate of carbonate minerals is several\u0000orders of magnitude higher than for silicate minerals. Therefore, small\u0000amounts of carbonate minerals have the potential to control the dissolved\u0000weathering loads in silicate-dominated catchments. Both weathering processes\u0000produce alkalinity under the consumption of CO2. Given that only\u0000alkalinity generation from silicate weathering is thought to be a long-term\u0000sink for CO2, a misattributed weathering source could lead to incorrect\u0000conclusions about long- and short-term CO2 fixation. In this study, we\u0000aimed to identify the weathering sources responsible for alkalinity\u0000generation and CO2 fixation across watershed scales in a degrading\u0000permafrost landscape in northern Norway, 68.7–70.5∘ N, and on\u0000a temporal scale, in a subarctic headwater catchment on the mountainside of\u0000Iskorasfjellet, characterized by sporadic permafrost and underlain mainly by\u0000silicates as the alkalinity-bearing lithology. By analyzing total alkalinity\u0000(AT) and dissolved inorganic carbon (DIC) concentrations, as well as the\u0000stable isotope signature of the latter (δ13C-DIC), in\u0000conjunction with dissolved cation and anion loads, we found that AT was\u0000almost entirely derived from weathering of the sparse carbonate minerals. We\u0000propose that in the headwater catchment the riparian zone is a hotspot area\u0000of AT generation and release due to its enhanced hydrological connectivity\u0000and that the weathering load contribution from the uphill catchment is\u0000limited by insufficient contact time of weathering agents and weatherable\u0000materials. By using stable water isotopes, it was possible to explain\u0000temporal variations in AT concentrations following a precipitation event due\u0000to surface runoff. In addition to carbonic acid, sulfuric acid, probably\u0000originating from oxidation of pyrite or reduced sulfur in wetlands or from\u0000acid deposition, is shown to be a potential corrosive reactant. An increased\u0000proportion of sulfuric acid as a potential weathering agent may have\u0000resulted in a decrease in AT. Therefore, carbonate weathering in the studied\u0000area should be considered not only as a short-term CO2 sink but also\u0000as a potential CO2 source. Finally, we found that AT increased with\u0000decreasing permafrost probability, and attributed this relation to an\u0000increased water storage capacity associated with increasing contact of\u0000weathering agent and rock surfaces and enhanced microbial activity. As both\u0000soil respiration and permafrost thaw are expected to increase with climate\u0000change, increasing the availability of weathering agents in the form of\u0000CO2 and water storage capacity, respectively, we suggest that future\u0000weathering rates and alkalinity generation will increase concomitantly in\u0000the study area.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48359161","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}
Abstract. The oceans are losing oxygen (O2), and oxygen minimum zones are expanding due to climate warming (lower O2 solubility) and eutrophication related to agriculture. This trend is challenging for most marine taxa that are not well adapted to O2 depletion. For other taxa this trend might be advantageous because they can withstand low O2 concentrations or thrive under O2-depleted or even anoxic conditions. Benthic foraminifera are a group of protists that include taxa with adaptations to partly extreme environmental conditions. Several species possess adaptations to O2 depletion that are rare amongst eukaryotes, and these species might benefit from ongoing ocean deoxygenation. In addition, since some foraminifera can calcify even under anoxic conditions, they are important archives for paleoceanographic reconstruction in O2-depleted environments. This paper reviews the current state of knowledge about foraminifera from low-O2 environments. Recent advances in our understanding of specific survival strategies of foraminifera to withstand O2 depletion are summarized and discussed. These adaptations include an anaerobic metabolism, heterotrophic denitrification, symbiosis with bacteria, kleptoplasty and dormancy and have a strong impact on their preferred microhabitat in the sediments, especially the ability of some benthic foraminiferal species to denitrify. Benthic foraminifera also differ regarding their trophic strategies, which has an additional impact on the selection of their microhabitat. For example, some species are strict herbivores that feed exclusively on fresh phytodetritus and live close to the sediment surface, while some species are non-selective detrivores that occupy intermediate to deep infaunal habitats. There is evidence that foraminifers have the capacity to undergo phagocytosis, even under anoxia, and some foraminiferal species which can withstand low-O2 conditions seem to prey on meiofauna. Also, due to their high abundances in O2-depleted environments and their metabolic adaptations, benthic foraminifera are key players in marine nutrient cycling, especially within the marine N and P cycles. This review summarizes the denitrification rates for the species that are known to denitrify and the intracellular nitrate concentrations of the species that are known to intracellularly store nitrate. Finally, equations are provided that can be used to estimate the intracellular nutrient storage and denitrification rates of foraminifera and might be integrated into biogeochemical models.
{"title":"Benthic foraminifera and gromiids from oxygen-depleted environments – survival strategies, biogeochemistry and trophic interactions","authors":"N. Glock","doi":"10.5194/bg-20-3423-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3423-2023","url":null,"abstract":"Abstract. The oceans are losing oxygen (O2), and oxygen minimum zones are\u0000expanding due to climate warming (lower O2 solubility) and\u0000eutrophication related to agriculture. This trend is challenging for most\u0000marine taxa that are not well adapted to O2 depletion. For other taxa\u0000this trend might be advantageous because they can withstand low O2\u0000concentrations or thrive under O2-depleted or even anoxic conditions.\u0000Benthic foraminifera are a group of protists that include taxa with\u0000adaptations to partly extreme environmental conditions. Several species\u0000possess adaptations to O2 depletion that are rare amongst eukaryotes,\u0000and these species might benefit from ongoing ocean deoxygenation. In\u0000addition, since some foraminifera can calcify even under anoxic conditions,\u0000they are important archives for paleoceanographic reconstruction in O2-depleted environments. This paper reviews the current state of knowledge\u0000about foraminifera from low-O2 environments. Recent advances in our\u0000understanding of specific survival strategies of foraminifera to withstand O2\u0000depletion are summarized and discussed. These adaptations include an\u0000anaerobic metabolism, heterotrophic denitrification, symbiosis with\u0000bacteria, kleptoplasty and dormancy and have a strong impact on their\u0000preferred microhabitat in the sediments, especially the ability of some benthic foraminiferal species to denitrify. Benthic foraminifera also differ\u0000regarding their trophic strategies, which has an additional impact on the\u0000selection of their microhabitat. For example, some species are strict\u0000herbivores that feed exclusively on fresh phytodetritus and live close to\u0000the sediment surface, while some species are non-selective detrivores that\u0000occupy intermediate to deep infaunal habitats. There is evidence that\u0000foraminifers have the capacity to undergo phagocytosis, even under anoxia, and some\u0000foraminiferal species which can withstand low-O2 conditions seem to\u0000prey on meiofauna. Also, due to their high abundances in O2-depleted\u0000environments and their metabolic adaptations, benthic foraminifera are key\u0000players in marine nutrient cycling, especially within the marine N and P\u0000cycles. This review summarizes the denitrification rates for the species\u0000that are known to denitrify and the intracellular nitrate concentrations of\u0000the species that are known to intracellularly store nitrate. Finally,\u0000equations are provided that can be used to estimate the intracellular\u0000nutrient storage and denitrification rates of foraminifera and might be\u0000integrated into biogeochemical models.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47682907","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}
R. Mwanake, G. Gettel, E. Wangari, C. Glaser, T. Houska, L. Breuer, K. Butterbach‐Bahl, R. Kiese
Abstract. Anthropogenic activities increase the contributions of inland waters to global greenhouse gas (GHG; CO2, CH4, and N2O) budgets, yet the mechanisms driving these increases are still not well constrained. In this study, we quantified year-long GHG concentrations, fluxes, and water physico-chemical variables from 28 sites contrasted by land use across five headwater catchments in Germany. Based on linear mixed-effects models, we showed that land use was more significant than seasonality in controlling the intra-annual variability of the GHGs. Streams in agriculture-dominated catchments or with wastewater inflows had up to 10 times higher daily CO2, CH4, and N2O emissions and were also more temporally variable (CV > 55 %) than forested streams. Our findings also suggested that nutrient, labile carbon, and dissolved GHG inputs from the agricultural and settlement areas may have supported these hotspots and hot-moments of fluvial GHG emissions. Overall, the annual emission from anthropogenic-influenced streams in CO2 equivalents was up to 20 times higher (∼ 71 kg CO2 m−2 yr−1) than from natural streams (∼ 3 kg CO2 m−2 yr−1), with CO2 accounting for up to 81 % of these annual emissions, while N2O and CH4 accounted for up to 18 % and 7 %, respectively. The positive influence of anthropogenic activities on fluvial GHG emissions also resulted in a breakdown of the expected declining trends of fluvial GHG emissions with stream size. Therefore, future studies should focus on anthropogenically perturbed streams, as their GHG emissions are much more variable in space and time and can potentially introduce the largest uncertainties to fluvial GHG estimates.
摘要人为活动增加了内陆水域对全球温室气体(GHG)的贡献;CO2、CH4和N2O)的预算，但驱动这些增加的机制仍然没有得到很好的约束。在这项研究中，我们量化了28个地点全年的温室气体浓度、通量和水物理化学变量，并与德国五个水源集水区的土地利用进行了对比。基于线性混合效应模型的研究表明，土地利用对温室气体年际变率的控制比季节性更为显著。在以农业为主的集水区或有废水流入的河流中，二氧化碳、甲烷和氧化亚氮的日排放量高达10倍，而且与森林河流相比，它们的时间变化更大(CV值为55%)。我们的研究结果还表明，来自农业和定居地区的养分、不稳定碳和溶解的温室气体输入可能支持了这些河流温室气体排放的热点和热点时刻。总体而言，受人为影响的河流的年排放量(CO2当量为~ 71 kg CO2 m−2 yr−1)比自然河流的年排放量(~ 3 kg CO2 m−2 yr−1)高出20倍，其中CO2占年排放量的81%，而en2o和CH4分别占18%和7%。人类活动对河流温室气体排放的积极影响也导致河流温室气体排放量随河流大小的预期下降趋势被打破。因此，未来的研究应该集中在人为干扰的河流上，因为它们的温室气体排放在空间和时间上的变化更大，并且可能给河流温室气体估算带来最大的不确定性。
{"title":"Anthropogenic activities significantly increase annual greenhouse gas (GHG) fluxes from temperate headwater streams in Germany","authors":"R. Mwanake, G. Gettel, E. Wangari, C. Glaser, T. Houska, L. Breuer, K. Butterbach‐Bahl, R. Kiese","doi":"10.5194/bg-20-3395-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3395-2023","url":null,"abstract":"Abstract. Anthropogenic activities increase the contributions of inland waters to\u0000global greenhouse gas (GHG; CO2, CH4, and N2O) budgets, yet\u0000the mechanisms driving these increases are still not well constrained. In\u0000this study, we quantified year-long GHG concentrations, fluxes, and water\u0000physico-chemical variables from 28 sites contrasted by land use across five\u0000headwater catchments in Germany. Based on linear mixed-effects models, we\u0000showed that land use was more significant than seasonality in controlling\u0000the intra-annual variability of the GHGs. Streams in agriculture-dominated\u0000catchments or with wastewater inflows had up to 10 times higher daily\u0000CO2, CH4, and N2O emissions and were also more temporally\u0000variable (CV > 55 %) than forested streams. Our findings also\u0000suggested that nutrient, labile carbon, and dissolved GHG inputs from the\u0000agricultural and settlement areas may have supported these hotspots and\u0000hot-moments of fluvial GHG emissions. Overall, the annual emission from\u0000anthropogenic-influenced streams in CO2 equivalents was up to 20 times\u0000higher (∼ 71 kg CO2 m−2 yr−1) than from\u0000natural streams (∼ 3 kg CO2 m−2 yr−1), with\u0000CO2 accounting for up to 81 % of these annual emissions, while\u0000N2O and CH4 accounted for up to 18 % and 7 %, respectively. The\u0000positive influence of anthropogenic activities on fluvial GHG emissions also\u0000resulted in a breakdown of the expected declining trends of fluvial GHG\u0000emissions with stream size. Therefore, future studies should focus on\u0000anthropogenically perturbed streams, as their GHG emissions are much more\u0000variable in space and time and can potentially introduce the largest\u0000uncertainties to fluvial GHG estimates.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43133627","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}
Paulina Grigusova, A. Larsen, R. Brandl, Camilo del Río, N. Farwig, D. Kraus, Leandro Paulino, P. Pliscoff, J. Bendix
Abstract. Animal burrowing activity affects soil texture, bulk density, soil water content, and redistribution of nutrients. All of these parameters in turn influence sediment redistribution, which shapes the earth's surface. Hence it is important to include bioturbation into hillslope sediment transport models. However, the inclusion of burrowing animals into hillslope-wide models has thus far been limited and has largely omitted vertebrate bioturbators, which can be major agents of bioturbation, especially in drier areas. Here, we included vertebrate bioturbator burrows into a semi-empirical Morgan–Morgan–Finney soil erosion model to allow a general approach to the assessment of the impacts of bioturbation on sediment redistribution within four sites along the Chilean climate gradient. For this, we predicted the distribution of burrows by applying machine learning techniques in combination with remotely sensed data in the hillslope catchment. Then, we adjusted the spatial model parameters at predicted burrow locations based on field and laboratory measurements. We validated the model using field sediment fences. We estimated the impact of bioturbator burrows on surface processes. Lastly, we analyzed how the impact of bioturbation on sediment redistribution depends on the burrow structure, climate, topography, and adjacent vegetation. Including bioturbation greatly increased model performance and demonstrates the overall importance of vertebrate bioturbators in enhancing both sediment erosion and accumulation along hillslopes, though this impact is clearly staggered according to climatic conditions. Burrowing vertebrates increased sediment accumulation by 137.8 % ± 16.4 % in the arid zone (3.53 kg ha−1 yr−1 vs. 48.79 kg ha−1 yr−1), sediment erosion by 6.5 % ± 0.7 % in the semi-arid zone (129.16 kg ha−1 yr−1 vs. 122.05 kg ha−1 yr−1), and sediment erosion by 15.6 % ± 0.3 % in the Mediterranean zone (4602.69 kg ha−1 yr−1 vs. 3980.96 kg ha−1 yr−1). Bioturbating animals seem to play only a negligible role in the humid zone. Within all climate zones, bioturbation did not uniformly increase erosion or accumulation within the whole hillslope catchment. This depended on adjusting environmental parameters. Bioturbation increased erosion with increasing slope, sink connectivity, and topography ruggedness and decreasing vegetation cover and soil wetness. Bioturbation increased sediment accumulation with increasing surface roughness, soil wetness, and vegetation cover.
{"title":"Mammalian bioturbation amplifies rates of both hillslope sediment erosion and accumulation along the Chilean climate gradient","authors":"Paulina Grigusova, A. Larsen, R. Brandl, Camilo del Río, N. Farwig, D. Kraus, Leandro Paulino, P. Pliscoff, J. Bendix","doi":"10.5194/bg-20-3367-2023","DOIUrl":"https://doi.org/10.5194/bg-20-3367-2023","url":null,"abstract":"Abstract. Animal burrowing activity affects soil texture, bulk density, soil water\u0000content, and redistribution of nutrients. All of these parameters in turn\u0000influence sediment redistribution, which shapes the earth's surface. Hence it\u0000is important to include bioturbation into hillslope sediment transport\u0000models. However, the inclusion of burrowing animals into hillslope-wide\u0000models has thus far been limited and has largely omitted vertebrate\u0000bioturbators, which can be major agents of bioturbation, especially in drier\u0000areas. Here, we included vertebrate bioturbator burrows into a semi-empirical\u0000Morgan–Morgan–Finney soil erosion model to allow a general approach to\u0000the assessment of the impacts of bioturbation on sediment redistribution within four\u0000sites along the Chilean climate gradient. For this, we predicted the\u0000distribution of burrows by applying machine learning techniques in\u0000combination with remotely sensed data in the hillslope catchment. Then, we\u0000adjusted the spatial model parameters at predicted burrow locations based on\u0000field and laboratory measurements. We validated the model using field\u0000sediment fences. We estimated the impact of bioturbator burrows on surface\u0000processes. Lastly, we analyzed how the impact of bioturbation on sediment\u0000redistribution depends on the burrow structure, climate, topography, and\u0000adjacent vegetation. Including bioturbation greatly increased model performance and demonstrates\u0000the overall importance of vertebrate bioturbators in enhancing both sediment\u0000erosion and accumulation along hillslopes, though this impact is clearly\u0000staggered according to climatic conditions. Burrowing vertebrates increased\u0000sediment accumulation by 137.8 % ± 16.4 % in the arid zone (3.53 kg ha−1 yr−1 vs. 48.79 kg ha−1 yr−1), sediment\u0000erosion by 6.5 % ± 0.7 % in the semi-arid zone (129.16 kg ha−1 yr−1 vs. 122.05 kg ha−1 yr−1), and sediment\u0000erosion by 15.6 % ± 0.3 % in the Mediterranean zone (4602.69 kg ha−1 yr−1 vs. 3980.96 kg ha−1 yr−1).\u0000Bioturbating animals seem to play only a negligible role in the humid zone.\u0000Within all climate zones, bioturbation did not uniformly increase erosion or\u0000accumulation within the whole hillslope catchment. This depended on\u0000adjusting environmental parameters. Bioturbation increased erosion with\u0000increasing slope, sink connectivity, and topography ruggedness and decreasing\u0000vegetation cover and soil wetness. Bioturbation increased sediment\u0000accumulation with increasing surface roughness, soil wetness, and vegetation\u0000cover.\u0000","PeriodicalId":8899,"journal":{"name":"Biogeosciences","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42579850","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}
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