Global Biogeochemical Cycles最新文献

{"title":"Carbon and Greenhouse Gas Budgets of Europe: Trends, Interannual and Spatial Variability, and Their Drivers","authors":"Ronny Lauerwald,&nbsp;Ana Bastos,&nbsp;Matthew J. McGrath,&nbsp;Ana Maria Roxana Petrescu,&nbsp;François Ritter,&nbsp;Robbie M. Andrew,&nbsp;Antoine Berchet,&nbsp;Grégoire Broquet,&nbsp;Dominik Brunner,&nbsp;Frédéric Chevallier,&nbsp;Alessandro Cescatti,&nbsp;Sara Filipek,&nbsp;Audrey Fortems-Cheiney,&nbsp;Giovanni Forzieri,&nbsp;Pierre Friedlingstein,&nbsp;Richard Fuchs,&nbsp;Christoph Gerbig,&nbsp;Sander Houweling,&nbsp;Piyu Ke,&nbsp;Bas J. W. Lerink,&nbsp;Wanjing Li,&nbsp;Wei Li,&nbsp;Xiaojun Li,&nbsp;Ingrid Luijkx,&nbsp;Guillaume Monteil,&nbsp;Saqr Munassar,&nbsp;Gert-Jan Nabuurs,&nbsp;Prabir K. Patra,&nbsp;Philippe Peylin,&nbsp;Julia Pongratz,&nbsp;Pierre Regnier,&nbsp;Marielle Saunois,&nbsp;Mart-Jan Schelhaas,&nbsp;Marko Scholze,&nbsp;Stephen Sitch,&nbsp;Rona L. Thompson,&nbsp;Hanqin Tian,&nbsp;Aki Tsuruta,&nbsp;Chris Wilson,&nbsp;Jean-Pierre Wigneron,&nbsp;Yitong Yao,&nbsp;Sönke Zaehle,&nbsp;Philippe Ciais","doi":"10.1029/2024GB008141","DOIUrl":"https://doi.org/10.1029/2024GB008141","url":null,"abstract":"<p>In the framework of the RECCAP2 initiative, we present the greenhouse gas (GHG) and carbon (C) budget of Europe. For the decade of the 2010s, we present a bottom-up (BU) estimate of GHG net-emissions of 3.9 Pg CO₂-eq. yr⁻¹ (using a global warming potential on a 100 years horizon), which are largely dominated by fossil fuel emissions. In this decade, terrestrial ecosystems acted as a net GHG sink of 0.9 Pg CO₂-eq. yr⁻¹, dominated by a CO₂ sink that was partially counterbalanced by net emissions of CH₄ and N₂O. For CH₄ and N₂O, we find good agreement between BU and top-down (TD) estimates from atmospheric inversions. However, our BU land CO₂ sink is significantly higher than the TD estimates. We further show that decadal averages of GHG net-emissions have declined by 1.2 Pg CO₂-eq. yr⁻¹ since the 1990s, mainly due to a reduction in fossil fuel emissions. In addition, based on both data driven BU and TD estimates, we also find that the land CO₂ sink has weakened over the past two decades. A large part of the European CO₂ and C sinks is located in Northern Europe. At the same time, we find a decreasing trend in sink strength in Scandinavia, which can be attributed to an increase in forest management intensity. These are partly offset by increasing CO₂ sinks in parts of Eastern Europe and Northern Spain, attributed in part to land use change. Extensive regions of high CH₄ and N₂O emissions are mainly attributed to agricultural activities and are found in Belgium, the Netherlands and the southern UK. We further analyzed interannual variability in the GHG budgets. The drought year of 2003 shows the highest net-emissions of CO₂ and of all GHGs combined.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 8","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008141","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141967543","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Phosphate Influx and Dust Deposition Create Zonal and Meridional Biogeochemical Gradients in Trichodesmium Abundance","authors":"Shreya Mehta,&nbsp;Rainer Kiko,&nbsp;Helena Hauss,&nbsp;Narendra Ojha,&nbsp;Arvind Singh","doi":"10.1029/2024GB008182","DOIUrl":"https://doi.org/10.1029/2024GB008182","url":null,"abstract":"<p><i>Trichodesmium</i> plays a key role in the biogeochemical cycling of carbon, nitrogen and phosphorus in the Tropical Atlantic Ocean. A complex interplay of physicochemical factors control the growth of <i>Trichodesmium</i>. However, owing to the large spatial and temporal variability, the relative influence of these factors in controlling <i>Trichodesmium</i> distribution and abundance remains unclear. In this study, we examined the basin-scale distribution pattern of <i>Trichodesmium</i> in the upper 200 m water column of the Atlantic Ocean (25°N–30°S and 70°W–20°E) using a large data set (<i>n</i> = 33,235) and tried to constrain the distribution based on various physicochemical parameters. We suggest that the combined effect of warm temperatures and phosphate (PO₄³⁻) availability determines the zonal spatial extent and the abundance of <i>Trichodesmium</i> in the Tropical North Atlantic Ocean. However, the availability of dissolved iron, along with high sea surface temperatures and meteorological parameters such as the wind direction and precipitation, likely govern the meridional distribution of <i>Trichodesmium</i> across the Atlantic Ocean. Excess PO₄³⁻ at the surface rules out the possibility of PO₄³⁻ limitation in regulating the meridional distribution of the <i>Trichodesmium</i>. Depth-integrated nitrogen fixation rates, based on a multiple linear regression, vary from 0.07 to 306 μmol N m⁻² d⁻¹. The presence of <i>Trichodesmium</i> colonies down to a depth of 200 m and the depth-integrated nitrogen fixation rates reflect the pivotal role of <i>Trichodesmium</i> in the nitrogen budget of this region.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 8","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Differential Responses of Soil Phosphorus Fractions to Nitrogen and Phosphorus Fertilization: A Global Meta-Analysis","authors":"Qingshui Yu,&nbsp;Frank Hagedorn,&nbsp;Josep Penuelas,&nbsp;Jordi Sardans,&nbsp;Xiangping Tan,&nbsp;Zhengbing Yan,&nbsp;Chenqi He,&nbsp;Xiaofeng Ni,&nbsp;Yuhao Feng,&nbsp;Jiangling Zhu,&nbsp;Chengjun Ji,&nbsp;Zhiyao Tang,&nbsp;Mai-He Li,&nbsp;Jingyun Fang","doi":"10.1029/2023GB008064","DOIUrl":"https://doi.org/10.1029/2023GB008064","url":null,"abstract":"<p>Anthropogenic inputs of nitrogen (N) and phosphorus (P) to terrestrial ecosystems alter soil nutrient cycling. However, the global-scale responses of soil P fractions to N and P inputs and their underlying mechanisms remain elusive. We conducted a global meta-analysis based on 818 observations of soil P fractions from 99 field N and P addition experiments in forest, grassland, and cropland ecosystems ranging from temperate to tropical zones. Our global meta-analysis revealed distinct responses of soil P fractions to N and P enrichment. For studies using the Chang and Jackson inorganic (Pi) method, we found that high N addition promoted the transformation of immobile Pi fractions into Ferrum/Aluminum-bound Pi and available Pi in surface soils through soil acidification. However, this acid-induced transformation of Pi fractions by N addition was observed only in Calcium-rich soils, while in acidic soils, further acidification led to increase P binding. In contrast, additions of P alone or combined with N significantly increased all soil Pi fractions. Regarding the Hedley P fractions, N addition generally decreased labile organic P by enhancing soil acid phosphatase activity. The responses of other P fractions were influenced by soil pH, fertilization rates, ecosystem type, and other factors. P addition increased most soil P fractions. Overall, both P fractionation methods consistently demonstrate that N inputs deplete soil P and accelerate P cycling, while P inputs increase most soil P fractions, alleviating P limitation. These findings are crucial for predicting the effects of future atmospheric N and P deposition on P cycling processes.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968252","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impacts of Vertical Migrants on Biogeochemistry in an Earth System Model","authors":"Julia Getzlaff,&nbsp;Iris Kriest","doi":"10.1029/2023GB007842","DOIUrl":"10.1029/2023GB007842","url":null,"abstract":"<p>Vertical migrants are a diverse group of organisms, which includes crustaceans, cephalopods and mesopelagic fishes. They play an active role in the biogeochemical cycles but are in general not included in numerical models. In this study we introduce a fully coupled Earth system model that represents vertical migration and with this resolves the key components of the mesopelagic ecosystem, namely migrating zooplankton and mesopelagic fish, including their feedbacks on biogeochemical cycles. The redistribution of nutrients in the water column by vertical migration results in a reduction of the net primary production of 14%–21%, as well as in an asymmetric response in the low oxygenated waters in the tropical Pacific (an increase in the northern and a decrease in the southern oxygen minimum zone). On a global scale, we find the active transport of carbon out of the surface layer to be equivalent to ∼25% of the total export (∼30% relative to passive sinking). In the low latitudes, migration results regionally in a reduction of the shallow export by 2%–10% and an increase of the deep carbon export by 6%–15%. In our simulations, mesopelagic fish, with a biomass of 3–3.4 Gt wet weight, have a slightly larger impact on active carbon flux than migrating zooplankton.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB007842","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141849302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sediment Resuspension Accelerates the Recycling of Terrestrial Organic Carbon at a Large River-Coastal Ocean Interface","authors":"Xueshi Sun,&nbsp;Limin Hu,&nbsp;Dejiang Fan,&nbsp;Houjie Wang,&nbsp;Zuosheng Yang,&nbsp;Zhigang Guo","doi":"10.1029/2024GB008213","DOIUrl":"10.1029/2024GB008213","url":null,"abstract":"<p>Widespread sediment resuspension and transport processes on continental margins can modify deposits and influence the preservation of particulate organic carbon (POC) in marine sediments. However, it remains unclear how post-depositional processes interact with physical mineral protection to affect the transport and fate of terrestrial POC along the river-estuary-shelf paths. Here, we synthesized literature data and newly obtained results from multiple analyses of sedimentology, mineralogy, and inorganic and organic geochemical tracers. Our goal was to quantitatively evaluate the impact of sediment reworking on the redistribution and further transformations of terrestrial POC at the Yangtze River-ocean interface. Our results reveal that sediment resuspension resulting from physical forces along with mineral protection of phyllosilicates plays a crucial role in regulating the recycling and fate of terrestrial POC during its transport across the coastal ocean continuum. Physical processes lead to the resuspension of sequestered POC from suboxic/anoxic muddy sediments into the overlying water column. Concurrently, the interplay of energetic forcing and elevated oxygen levels has the potential to disrupt the organo-mineral associations. The decrease in mineral-carbon stabilization increases the likelihood that reactive POC inclusion/aggregation with minerals becomes accessible to surrounding microorganisms, making it susceptible to microbial/oxidative degradation. Consequently, mostly phyllosilicate-protected ¹⁴C-depleted POC (primarily soil-derived) in &lt;63 μm suspended sediment (&gt;90% of the total mass) remains available for export and reburial in continental shelf sediments. The lateral transport of resuspended sediments from estuaries, previously underestimated, represents a potential contributor to the remobilized millennial-aged POC components involved in active biogeochemical cycling on continental margins.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141843899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon Export in the Subantarctic Zone Revealed by Multi-Year Observations From Biogeochemical-Argo Floats and Sediment Traps","authors":"Xiang Yang,&nbsp;Cathryn A. Wynn-Edwards,&nbsp;Peter G. Strutton,&nbsp;Elizabeth H. Shadwick","doi":"10.1029/2024GB008135","DOIUrl":"10.1029/2024GB008135","url":null,"abstract":"<p>The biological gravitational pump (BGP) and particle injection pumps (PIPs) are significant export pathways for particulate organic carbon from the surface ocean to the interior. Part of this exported carbon fuels remineralization in the mesopelagic ocean and part is sequestered in the deep ocean. Using observations from Biogeochemical-Argo, we characterized the seasonality and magnitude of the BGP and two PIPs: the mixed layer pump (MLP) and eddy subduction pump (ESP), in the Australian sector of the Subantarctic Zone (SAZ sector). For the first time, float-based estimates were rigorously combined with sediment trap flux (<i>F</i>₁₀₀₀) observations from the Southern Ocean Time Series (SOTS), to investigate these pumps' relative and cumulative contributions to carbon export. The BGP exports about 28.6 g C m⁻² year⁻¹, mostly during the productive season and dominates the <i>F</i>₁₀₀₀ seasonality. The MLP exports about 7.6 g C m⁻² year⁻¹, mostly while the mixing layer seasonally shoals; the ESP sporadically exports up to 100 mg C m⁻² day⁻¹, such that these two PIPs have a short but intense impact on the <i>F</i>₁₀₀₀. The carbon transfer efficiency is 3.6% in the SOTS region. An oxygen-based annual net community production estimate (∼50 g C m⁻² year⁻¹) further strengthens this study, and suggests the BGP and MLP make the dominant contribution to the mesopelagic carbon budget. This is representative of the broader SAZ sector in terms of the magnitude and seasonality of carbon export, the consumption of organic material in the mesopelagic, and the organic carbon sequestration in the deep sea.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008135","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141853684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Trends and Drivers of Terrestrial Sources and Sinks of Carbon Dioxide: An Overview of the TRENDY Project","authors":"Stephen Sitch,&nbsp;Michael O’Sullivan,&nbsp;Eddy Robertson,&nbsp;Pierre Friedlingstein,&nbsp;Clément Albergel,&nbsp;Peter Anthoni,&nbsp;Almut Arneth,&nbsp;Vivek K. Arora,&nbsp;Ana Bastos,&nbsp;Vladislav Bastrikov,&nbsp;Nicolas Bellouin,&nbsp;Josep G. Canadell,&nbsp;Louise Chini,&nbsp;Philippe Ciais,&nbsp;Stefanie Falk,&nbsp;Ian Harris,&nbsp;George Hurtt,&nbsp;Akihiko Ito,&nbsp;Atul K. Jain,&nbsp;Matthew W. Jones,&nbsp;Fortunat Joos,&nbsp;Etsushi Kato,&nbsp;Daniel Kennedy,&nbsp;Kees Klein Goldewijk,&nbsp;Erik Kluzek,&nbsp;Jürgen Knauer,&nbsp;Peter J. Lawrence,&nbsp;Danica Lombardozzi,&nbsp;Joe R. Melton,&nbsp;Julia E. M. S. Nabel,&nbsp;Naiqing Pan,&nbsp;Philippe Peylin,&nbsp;Julia Pongratz,&nbsp;Benjamin Poulter,&nbsp;Thais M. Rosan,&nbsp;Qing Sun,&nbsp;Hanqin Tian,&nbsp;Anthony P. Walker,&nbsp;Ulrich Weber,&nbsp;Wenping Yuan,&nbsp;Xu Yue,&nbsp;Sönke Zaehle","doi":"10.1029/2024GB008102","DOIUrl":"https://doi.org/10.1029/2024GB008102","url":null,"abstract":"<p>The terrestrial biosphere plays a major role in the global carbon cycle, and there is a recognized need for regularly updated estimates of land-atmosphere exchange at regional and global scales. An international ensemble of Dynamic Global Vegetation Models (DGVMs), known as the “Trends and drivers of the regional scale terrestrial sources and sinks of carbon dioxide” (TRENDY) project, quantifies land biophysical exchange processes and biogeochemistry cycles in support of the annual Global Carbon Budget assessments and the REgional Carbon Cycle Assessment and Processes, phase 2 project. DGVMs use a common protocol and set of driving data sets. A set of factorial simulations allows attribution of spatio-temporal changes in land surface processes to three primary global change drivers: changes in atmospheric CO₂, climate change and variability, and Land Use and Land Cover Changes (LULCC). Here, we describe the TRENDY project, benchmark DGVM performance using remote-sensing and other observational data, and present results for the contemporary period. Simulation results show a large global carbon sink in natural vegetation over 2012–2021, attributed to the CO₂ fertilization effect (3.8 ± 0.8 PgC/yr) and climate (−0.58 ± 0.54 PgC/yr). Forests and semi-arid ecosystems contribute approximately equally to the mean and trend in the natural land sink, and semi-arid ecosystems continue to dominate interannual variability. The natural sink is offset by net emissions from LULCC (−1.6 ± 0.5 PgC/yr), with a net land sink of 1.7 ± 0.6 PgC/yr. Despite the largest gross fluxes being in the tropics, the largest net land-atmosphere exchange is simulated in the extratropical regions.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2024GB008102","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141730175","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Modeled Seasonal Cycles of Surface N2O Fluxes and Atmospheric N2O","authors":"Qing Sun,&nbsp;Fortunat Joos,&nbsp;Sebastian Lienert,&nbsp;Sarah Berthet,&nbsp;Dustin Carroll,&nbsp;Cheng Gong,&nbsp;Akihiko Ito,&nbsp;Atul K. Jain,&nbsp;Sian Kou-Giesbrecht,&nbsp;Angela Landolfi,&nbsp;Manfredi Manizza,&nbsp;Naiqing Pan,&nbsp;Michael Prather,&nbsp;Pierre Regnier,&nbsp;Laure Resplandy,&nbsp;Roland Séférian,&nbsp;Hao Shi,&nbsp;Parvadha Suntharalingam,&nbsp;Rona L. Thompson,&nbsp;Hanqin Tian,&nbsp;Nicolas Vuichard,&nbsp;Sönke Zaehle,&nbsp;Qing Zhu","doi":"10.1029/2023GB008010","DOIUrl":"https://doi.org/10.1029/2023GB008010","url":null,"abstract":"<p>Nitrous oxide (N₂O) is a greenhouse gas and stratospheric ozone-depleting substance with large and growing anthropogenic emissions. Previous studies identified the influx of N₂O-depleted air from the stratosphere to partly cause the seasonality in tropospheric N₂O (aN₂O), but other contributions remain unclear. Here, we combine surface fluxes from eight land and four ocean models from phase 2 of the Nitrogen/N₂O Model Intercomparison Project with tropospheric transport modeling to simulate aN₂O at eight remote air sampling sites for modern and pre-industrial periods. Models show general agreement on the seasonal phasing of zonal-average N₂O fluxes for most sites, but seasonal peak-to-peak amplitudes differ several-fold across models. The modeled seasonal amplitude of surface aN₂O ranges from 0.25 to 0.80 ppb (interquartile ranges 21%–52% of median) for land, 0.14–0.25 ppb (17%–68%) for ocean, and 0.28–0.77 ppb (23%–52%) for combined flux contributions. The observed seasonal amplitude ranges from 0.34 to 1.08 ppb for these sites. The stratospheric contributions to aN₂O, inferred by the difference between the surface-troposphere model and observations, show 16%–126% larger amplitudes and minima delayed by ∼1 month compared to Northern Hemisphere site observations. Land fluxes and their seasonal amplitude have increased since the pre-industrial era and are projected to grow further under anthropogenic activities. Our results demonstrate the increasing importance of land fluxes for aN₂O seasonality. Considering the large model spread, in situ aN₂O observations and atmospheric transport-chemistry models will provide opportunities for constraining terrestrial and oceanic biosphere models, critical for projecting carbon-nitrogen cycles under ongoing global warming.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008010","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141639631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Physical Mechanisms Sustaining Silica Production Following the Demise of the Diatom Phase of the North Atlantic Spring Phytoplankton Bloom During EXPORTS","authors":"Mark A. Brzezinski,&nbsp;Leah Johnson,&nbsp;Margaret Estapa,&nbsp;Samantha Clevenger,&nbsp;Montserrat Roca-Martí,&nbsp;Elisa Romanelli,&nbsp;Kristen N. Buck,&nbsp;Bethany D. Jenkins,&nbsp;Janice L. Jones","doi":"10.1029/2023GB008048","DOIUrl":"https://doi.org/10.1029/2023GB008048","url":null,"abstract":"<p>Each spring, the North Atlantic experiences one of the largest open-ocean phytoplankton blooms in the global ocean. Diatoms often dominate the initial phase of the bloom with succession driven by exhaustion of silicic acid. The North Atlantic was sampled over 3.5 weeks in spring 2021 following the demise of the main diatom bloom, allowing mechanisms that sustain continued diatom contributions to be examined. Diatom biomass was initially relatively high with biogenic silica concentrations up to 2.25 μmol Si L⁻¹. A low initial silicic acid concentration of 0.1–0.3 μM imposed severe Si limitation of silica production and likely limited the diatom growth rate. Four storms over the next 3.5 weeks entrained silicic acid into the mixed layer, relieving growth limitation, but uptake limitation persisted. Silica production was modest and dominated by the &gt;5.0 μm size fraction although specific rates were highest in the 0.6–5.0 μm size fraction over most of the cruise. Silica dissolution averaged 68% of silica production. The resupply of silicic acid via storm entrainment and silica dissolution supported a cumulative post-bloom silica production that was 32% of that estimated during the main bloom event. Diatoms contributed significantly to new and to primary production after the initial bloom, possibly dominating both. Diatom contribution to organic-carbon export was also significant at 40%–70%. Thus, diatoms can significantly contribute to regional biogeochemistry following initial silicic acid depletion, but that contribution relies on physical processes that resupply the nutrient to surface waters.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2023GB008048","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141631230","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Size-Fractionated Primary Production Dynamics During the Decline Phase of the North Atlantic Spring Bloom","authors":"Meredith G. Meyer,&nbsp;Mark A. Brzezinski,&nbsp;Melanie R. Cohn,&nbsp;Sasha J. Kramer,&nbsp;Nicola Paul,&nbsp;Garrett Sharpe,&nbsp;Alexandria K. Niebergall,&nbsp;Scott Gifford,&nbsp;Nicolas Cassar,&nbsp;Adrian Marchetti","doi":"10.1029/2023GB008019","DOIUrl":"https://doi.org/10.1029/2023GB008019","url":null,"abstract":"<p>The North Atlantic is a region of enhanced biogeochemical and climatological importance for the global ocean as it is the site of one of the largest seasonal phytoplankton blooms on the planet. However, there is a lack of understanding of how phytoplankton size influences bloom dynamics and associated nutrient utilization rates, particularly during the decline phase when export to the deep ocean is especially pronounced. Here, we evaluate trends in size-fractionated carbon, nitrogen, and silicic acid uptake rates in conjunction with environmental parameters to assess these dynamics. In our study, the decline phase of the bloom continued to be highly productive with net primary production (NPP) ranging from 36.4 to 146.6 mmol C m⁻² d⁻¹ and approximately 54% of primary production being driven by large phytoplankton cells (≥5 μm) that were primarily utilizing nitrate (mean <i>f</i>-ratio of 0.77). Entrainment of silicic acid related to deepening of the mixed layer caused by storms increased silicic acid uptake rates to 2.0–5.7 mmol Si m⁻² d⁻¹ without concomitant increases in NPP by large cells (silicic acid to carbon uptake ratios averaged 0.12). A companion study in the North Pacific allowed for paired evaluation of these regions. Our results suggest that in highly productive regions where phytoplankton biomass and productivity is distributed across a broad range of cell sizes, such as the North Atlantic, size itself has a stronger influence on nutrient cycling and potential carbon export relative to regions with lower production and a predominance of small (&lt;5 μm) cells, such as the North Pacific.</p>","PeriodicalId":12729,"journal":{"name":"Global Biogeochemical Cycles","volume":"38 7","pages":""},"PeriodicalIF":5.4,"publicationDate":"2024-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141556574","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}