Pub Date : 2025-01-01DOI: 10.1016/j.marchem.2024.104482
Xuan Ji , Ming-Liang Zhao , Jie Ni , Gao-Bin Xu , Jing Zhang , Gui-Peng Yang
The carbon monoxide (CO) cycle in the marine mixed layer determines its emissions to the atmosphere and subsequently affects atmospheric chemistry and climate change. However, the contributions of oceanic CO transformation pathways and their impacting factors remain inadequately understood. Therefore, we investigated the distribution and cycle processes of CO in the Eastern Indian Ocean (EIO) and developed a CO budget model for the mixed layer. Surface seawater CO concentrations presented a diurnal variation due to periodic variations in solar radiation and rapid microbial consumption. The spatial distribution of CO in seawater was dominated by chromophoric dissolved organic matter (CDOM) and solar radiation. The EIO was a source of atmospheric CO and its daily CO emissions produced increases in the CO mixing ratio and hydroxyl radical consumption rate in the overlying atmosphere by 74.03 pptv and 6.48 pptv d−1, respectively. Additionally, the budget model findings indicated that photoproduction (CDOM plus particulate organic matter), dark production, and phytoplankton emission accounted for about 67 %, 30 %, and 3 % of total CO production. The microbial consumption (94 %) and sea-air exchange (6 %) were the primary and secondary sink for CO within the mixed layer, respectively. Moreover, the photo-mineralization of dissolved organic carbon was estimated using CO as a proxy for CO2 photoproduction. This study deepens our understanding of the oceanic CO cycle and the impact of photo-mineralization on the carbon cycle and is vital for refining global oceanic CO source-sink budgets and modelling studies.
{"title":"Distribution, emission, and cycling processes of carbon monoxide in the tropical open ocean","authors":"Xuan Ji , Ming-Liang Zhao , Jie Ni , Gao-Bin Xu , Jing Zhang , Gui-Peng Yang","doi":"10.1016/j.marchem.2024.104482","DOIUrl":"10.1016/j.marchem.2024.104482","url":null,"abstract":"<div><div>The carbon monoxide (CO) cycle in the marine mixed layer determines its emissions to the atmosphere and subsequently affects atmospheric chemistry and climate change. However, the contributions of oceanic CO transformation pathways and their impacting factors remain inadequately understood. Therefore, we investigated the distribution and cycle processes of CO in the Eastern Indian Ocean (EIO) and developed a CO budget model for the mixed layer. Surface seawater CO concentrations presented a diurnal variation due to periodic variations in solar radiation and rapid microbial consumption. The spatial distribution of CO in seawater was dominated by chromophoric dissolved organic matter (CDOM) and solar radiation. The EIO was a source of atmospheric CO and its daily CO emissions produced increases in the CO mixing ratio and hydroxyl radical consumption rate in the overlying atmosphere by 74.03 pptv and 6.48 pptv d<sup>−1</sup>, respectively. Additionally, the budget model findings indicated that photoproduction (CDOM plus particulate organic matter), dark production, and phytoplankton emission accounted for about 67 %, 30 %, and 3 % of total CO production. The microbial consumption (94 %) and sea-air exchange (6 %) were the primary and secondary sink for CO within the mixed layer, respectively. Moreover, the photo-mineralization of dissolved organic carbon was estimated using CO as a proxy for CO<sub>2</sub> photoproduction. This study deepens our understanding of the oceanic CO cycle and the impact of photo-mineralization on the carbon cycle and is vital for refining global oceanic CO source-sink budgets and modelling studies.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104482"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178167","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.marchem.2024.104485
Anna Hughes, Clare E. Reimers, Kristen E. Fogaren , Yvan Alleau
{"title":"Corrigendum to “Spatiotemporal variability in benthic-pelagic coupling on the Oregon-Washington Shelf” [Marine Chemistry Volume 268 (2025) Article number 104473]","authors":"Anna Hughes, Clare E. Reimers, Kristen E. Fogaren , Yvan Alleau","doi":"10.1016/j.marchem.2024.104485","DOIUrl":"10.1016/j.marchem.2024.104485","url":null,"abstract":"","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104485"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.marchem.2024.104484
Mitsuhide Sato , Shigenobu Takeda
To test the possibility of nickel (Ni) limitation and nickel‑nitrogen (Ni-N) colimitation on phytoplankton growth, seven urea/Ni enrichment experiments were conducted in the subtropical and subarctic Pacific Ocean. Effects of additions of urea, nickel, and combination of urea and nickel were examined by monitoring the growth of the whole phytoplankton community and three different phytoplankton populations, Synechococcus, Prochlorococcus, and eukaryotes. In all the experiments in the subtropical regions, urea addition significantly increased the total chlorophyll a concentration as compared to the unamended control after two days of incubation, confirming widespread nitrogen limitation and high accessibility of the urea‑nitrogen to phytoplankton in the subtropical Pacific. In contrast, Ni addition did not affect the total chlorophyll a concentration, whether it was added alone or in combination with urea. To elucidate population-level responses to urea and/or Ni addition, cellular and population chlorophyll content and carbon content were estimated using flow cytometric parameters. Synechococcus and Prochlorococcus mainly responded to the urea enrichment. The addition of Ni alone did not show a significant effect on the chlorophyll or carbon content of any phytoplankton population in most of the experiments. Ni-N colimitation was evident only for Synechococcus, and not for Prochlorococcus or eukaryotic phytoplankton. Ni-N colimitation was evident in the urea drawdown rates only for one experiment out of the six experiments. In contrast, in the subarctic region, urea drawdown decreased with Ni addition, although the reason for this was unclear. The present study demonstrates that Ni bioavailability in the subtropical Pacific can evoke Ni-N colimitation in the pico-sized cyanobacteria Synechococcus, but it does not seem to affect phytoplankton biomass at the community level.
{"title":"Examining nickel limitation on urea utilization by phytoplankton communities in the subtropical Pacific Ocean","authors":"Mitsuhide Sato , Shigenobu Takeda","doi":"10.1016/j.marchem.2024.104484","DOIUrl":"10.1016/j.marchem.2024.104484","url":null,"abstract":"<div><div>To test the possibility of nickel (Ni) limitation and nickel‑nitrogen (Ni-N) colimitation on phytoplankton growth, seven urea/Ni enrichment experiments were conducted in the subtropical and subarctic Pacific Ocean. Effects of additions of urea, nickel, and combination of urea and nickel were examined by monitoring the growth of the whole phytoplankton community and three different phytoplankton populations, <em>Synechococcus</em>, <em>Prochlorococcus</em>, and eukaryotes. In all the experiments in the subtropical regions, urea addition significantly increased the total chlorophyll <em>a</em> concentration as compared to the unamended control after two days of incubation, confirming widespread nitrogen limitation and high accessibility of the urea‑nitrogen to phytoplankton in the subtropical Pacific. In contrast, Ni addition did not affect the total chlorophyll <em>a</em> concentration, whether it was added alone or in combination with urea. To elucidate population-level responses to urea and/or Ni addition, cellular and population chlorophyll content and carbon content were estimated using flow cytometric parameters. <em>Synechococcus</em> and <em>Prochlorococcus</em> mainly responded to the urea enrichment. The addition of Ni alone did not show a significant effect on the chlorophyll or carbon content of any phytoplankton population in most of the experiments. Ni-N colimitation was evident only for <em>Synechococcus</em>, and not for <em>Prochlorococcus</em> or eukaryotic phytoplankton. Ni-N colimitation was evident in the urea drawdown rates only for one experiment out of the six experiments. In contrast, in the subarctic region, urea drawdown decreased with Ni addition, although the reason for this was unclear. The present study demonstrates that Ni bioavailability in the subtropical Pacific can evoke Ni-N colimitation in the pico-sized cyanobacteria <em>Synechococcus</em>, but it does not seem to affect phytoplankton biomass at the community level.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104484"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-01DOI: 10.1016/j.marchem.2024.104481
Prayna P.P. Maharaj , Pamela M. Barrett , Michael J. Ellwood
Copper (Cu) is an important micronutrient that is involved in multiple metabolic processes in marine phytoplankton. However, Cu concentrations that exceed an organism-specific tolerance level can be toxic. The measurement of stable Cu isotopic composition in seawater is an effective tool to better understand the biogeochemical cycling of this micronutrient in the marine environment. Here, we report the dissolved Cu (dCu) concentration and isotope composition of waters of the East Australian Current (EAC), the western boundary current in the south Pacific. The voyage was undertaken in 2018 during the austral spring as GEOTRACES process study GPpr13 consisting of a north-south transect categorised by the transition from warm, salty subtropical (ST) waters to the cold, fresh subantarctic (SA) waters in the Pacific sector of the Southern Ocean. The average dCu isotope composition (δ65dCu) of the upper water column increased by ∼0.3 ‰ from north to south. The northern EAC stations generally had isotopically lighter dCu in surface waters, with mixed layer δ65dCu values ranging from 0.25 ‰ to 0.31 ‰. Mixed layer δ65dCu values ranged from 0.20 ‰ to 0.47 ‰ at the southern extension of the EAC and from 0.54 ‰ to 0.63 ‰ in the subantarctic zone. Generally, δ65dCu profiles showed significant variability in the upper water column (200 m). The δ65dCu composition was heavier at depths of chlorophyll a maxima, particularly for the high productivity stations, which can be attributed to either biological uptake and/or scavenging. A heavier surface δ65dCu isotopic signature relative to deeper waters was also observed at stations with low chlorophyll a concentrations due to strong organic complexation of the heavy isotope in the upper water column. The deep ocean (≥2000 m) δ65dCu at one of the subantarctic stations (station 10) was considerably lighter (0.25 ± 0.06 ‰), indicating a possible benthic supply of isotopically light Cu. This study provides a high-resolution δ65Cu dataset, affording new insights into the biogeochemical cycling of Cu in the ocean.
铜（Cu）是一种重要的微量元素，参与了海洋浮游植物的多种代谢过程。然而，铜浓度超过生物体特异性耐受水平可能是有毒的。测定海水中稳定Cu同位素组成是更好地了解海洋环境中微量元素生物地球化学循环的有效工具。本文报道了南太平洋西边界流东澳大利亚流（EAC）水体中溶解铜（dCu）的浓度和同位素组成。这次航行是在2018年的南方春季进行的，GEOTRACES过程研究GPpr13由南北样带组成，由南大洋太平洋部分从温暖、咸的亚热带（ST）水域到寒冷、新鲜的亚南极（SA）水域的过渡分类。上层水柱平均dCu同位素组成（δ65dCu）自北向南增加~ 0.3‰。EAC北部台站地表水δ65dCu总体同位素较轻，混合层δ65dCu值在0.25‰~ 0.31‰之间。混合层δ65dCu值在东太平洋南缘为0.20‰~ 0.47‰，在亚南极带为0.54‰~ 0.63‰。总体而言，δ65dCu剖面在上层水柱（200 m）表现出显著的变化，δ65dCu组成在叶绿素a最大深度更重，特别是在高生产力站，这可能归因于生物吸收和/或清除。在叶绿素A浓度较低的站点，由于上层水体中重同位素的有机络合作用较强，地表δ65dCu同位素特征相对较深。其中一个亚南极站（10站）的深海(≥2000 m) δ65dCu较轻（0.25±0.06‰），表明可能存在轻同位素Cu的底栖补给。该研究提供了高分辨率的δ65Cu数据集，为Cu在海洋中的生物地球化学循环提供了新的见解。
{"title":"Biogeochemical cycling of dissolved Cu along the East Australian Current","authors":"Prayna P.P. Maharaj , Pamela M. Barrett , Michael J. Ellwood","doi":"10.1016/j.marchem.2024.104481","DOIUrl":"10.1016/j.marchem.2024.104481","url":null,"abstract":"<div><div>Copper (Cu) is an important micronutrient that is involved in multiple metabolic processes in marine phytoplankton. However, Cu concentrations that exceed an organism-specific tolerance level can be toxic. The measurement of stable Cu isotopic composition in seawater is an effective tool to better understand the biogeochemical cycling of this micronutrient in the marine environment. Here, we report the dissolved Cu (dCu) concentration and isotope composition of waters of the East Australian Current (EAC), the western boundary current in the south Pacific. The voyage was undertaken in 2018 during the austral spring as GEOTRACES process study GPpr13 consisting of a north-south transect categorised by the transition from warm, salty subtropical (ST) waters to the cold, fresh subantarctic (SA) waters in the Pacific sector of the Southern Ocean. The average dCu isotope composition (δ<sup>65</sup>dCu) of the upper water column increased by ∼0.3 ‰ from north to south. The northern EAC stations generally had isotopically lighter dCu in surface waters, with mixed layer δ<sup>65</sup>dCu values ranging from 0.25 ‰ to 0.31 ‰. Mixed layer δ<sup>65</sup>dCu values ranged from 0.20 ‰ to 0.47 ‰ at the southern extension of the EAC and from 0.54 ‰ to 0.63 ‰ in the subantarctic zone. Generally, δ<sup>65</sup>dCu profiles showed significant variability in the upper water column (200 m). The δ<sup>65</sup>dCu composition was heavier at depths of chlorophyll <em>a</em> maxima, particularly for the high productivity stations, which can be attributed to either biological uptake and/or scavenging. A heavier surface δ<sup>65</sup>dCu isotopic signature relative to deeper waters was also observed at stations with low chlorophyll <em>a</em> concentrations due to strong organic complexation of the heavy isotope in the upper water column. The deep ocean (≥2000 m) δ<sup>65</sup>dCu at one of the subantarctic stations (station 10) was considerably lighter (0.25 ± 0.06 ‰), indicating a possible benthic supply of isotopically light Cu. This study provides a high-resolution δ<sup>65</sup>Cu dataset, affording new insights into the biogeochemical cycling of Cu in the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104481"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143177296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-26DOI: 10.1016/j.marchem.2024.104473
Anna Hughes , Clare E. Reimers, Kristen E. Fogaren, Yvan Alleau
Continental shelf sediments are sinks for dissolved oxygen (DO) and sources of many major and minor nutrients required for oceanic surface primary production resulting in a strong coupling between benthic and pelagic biogeochemical cycling. In this study, we present paired benthic flux and bottom water biogeochemical data collected from two Oregon shelf sites sampled approximately quarter-annually between 2017 and 2019, and from nine other shelf sites, located off central Oregon to southern Washington, and sampled in either July or September 2022. The benthic fluxes were determined using a novel set-up for ex situ core incubations. When fluxes were normalized to the respective measured sediment DO flux, ratios aligned well with ratios of past flux estimates from the region which were determined using in situ benthic chambers; however, the ex situ flux magnitudes are generally lower. Our findings demonstrate sediments acting as net sinks for DO and nitrate, and sources for phosphate, silicate, and ammonium. Shelf-wide estimates of the relative contribution of sediment-remineralized phosphate and silicate to surface waters on the Oregon shelf, indicate that shelf sediments supplied at least 5 ± 7 % and 37 ± 7 % of the available phosphate and silicate during recent summer upwelling seasons, with similar, respective estimates of 2 ± 9 % and 35 ± 11 % during the spring. Remineralization ratios of C:N:P:O2 corroborate increased denitrification during the summer and weak denitrification during the winter due to a more oxygenated water column in support of previous studies. A multi-tracer water mass analysis also exhibited an increased water-column nitrate deficit during the summer and fall. Benthic denitrification rates, estimated from benthic fluxes, were between 0.2 and 1.8 mmol N m-2 day-1 and in the range of past assessments during the upwelling season. A simple model, applied to further constrain the contributions to bottom water fixed nitrogen (N) loss under assumptions of benthic boundary layer height and residence time, showed that although sediment denitrification could readily account for total bottom water N losses during the summer, additional water-column denitrification is indicated by the strength of early fall deficits at some stations. Constraining water-column and benthic contributions to fixed N deficits is important for understanding how N-limited primary productivity in this region will respond to projected ocean deoxygenation under anticipated global warming. These results demonstrate the interplay of sediment and water-column remineralization processes across the OR-WA shelf. As in most shallow marine systems, the two are integral to the ecosystem dynamics and responses to environmental change.
大陆架沉积物是溶解氧（DO）的汇，也是海洋表面初级生产所需的许多主要和次要营养物质的来源，导致底栖生物和远洋生物地球化学循环之间的强烈耦合。在这项研究中，我们提供了配对的底栖生物通量和底水生物地球化学数据，这些数据收集于2017年至2019年期间大约每季度取样一次的两个俄勒冈州大陆架地点，以及位于俄勒冈州中部至华盛顿州南部的其他九个大陆架地点，并于2022年7月或9月取样。底栖生物通量是用一种新的装置来确定的，用于非原位核心孵育。当通量归一化到各自测量的沉积物DO通量时，比率与该地区过去使用原位底栖生物室确定的通量估计比率吻合得很好；然而，非原位通量通常较低。我们的研究结果表明，沉积物是DO和硝酸盐的净汇，也是磷酸盐、硅酸盐和铵的来源。对俄勒冈大陆架表层水沉积物再矿化磷酸盐和硅酸盐相对贡献的估计表明，在最近的夏季上升流季节，大陆架沉积物提供了至少5±7%和37±7%的可用磷酸盐和硅酸盐，在春季分别为2±9%和35±11%。C:N:P:O2的再矿化比率证实了夏季反硝化作用增加，冬季反硝化作用减弱，这是由于水柱含氧量较高，支持了先前的研究。多示踪水质量分析也显示夏季和秋季水柱硝酸盐亏缺增加。根据底栖生物通量估算的底栖生物反硝化速率在0.2至1.8 mmol N m-2 day-1之间，在上升流季节的过去评估范围内。采用一个简单的模型，在假定底栖边界层高度和停留时间的情况下，进一步限制了对底水固定氮(N)损失的贡献，结果表明，尽管沉积物反硝化可以很容易地解释夏季底水的总氮损失，但在一些站点，早期秋季赤字的强度表明了额外的水柱反硝化作用。限制水柱和底栖生物对固定氮赤字的贡献对于了解该地区氮限制初级生产力在预期的全球变暖下如何响应预测的海洋脱氧非常重要。这些结果证明了沉积物和水柱再矿化过程在整个OR-WA大陆架上的相互作用。与大多数浅海系统一样，这两者是生态系统动态和对环境变化的反应的组成部分。
{"title":"Spatiotemporal variability in benthic-pelagic coupling on the Oregon-Washington shelf","authors":"Anna Hughes , Clare E. Reimers, Kristen E. Fogaren, Yvan Alleau","doi":"10.1016/j.marchem.2024.104473","DOIUrl":"10.1016/j.marchem.2024.104473","url":null,"abstract":"<div><div>Continental shelf sediments are sinks for dissolved oxygen (DO) and sources of many major and minor nutrients required for oceanic surface primary production resulting in a strong coupling between benthic and pelagic biogeochemical cycling. In this study, we present paired benthic flux and bottom water biogeochemical data collected from two Oregon shelf sites sampled approximately quarter-annually between 2017 and 2019, and from nine other shelf sites, located off central Oregon to southern Washington, and sampled in either July or September 2022. The benthic fluxes were determined using a novel set-up for <em>ex situ</em> core incubations. When fluxes were normalized to the respective measured sediment DO flux, ratios aligned well with ratios of past flux estimates from the region which were determined using <em>in situ</em> benthic chambers; however, the <em>ex situ</em> flux magnitudes are generally lower. Our findings demonstrate sediments acting as net sinks for DO and nitrate, and sources for phosphate, silicate, and ammonium. Shelf-wide estimates of the relative contribution of sediment-remineralized phosphate and silicate to surface waters on the Oregon shelf, indicate that shelf sediments supplied at least 5 ± 7 % and 37 ± 7 % of the available phosphate and silicate during recent summer upwelling seasons, with similar, respective estimates of 2 ± 9 % and 35 ± 11 % during the spring. Remineralization ratios of C:N:P:O<sub>2</sub> corroborate increased denitrification during the summer and weak denitrification during the winter due to a more oxygenated water column in support of previous studies. A multi-tracer water mass analysis also exhibited an increased water-column nitrate deficit during the summer and fall. Benthic denitrification rates, estimated from benthic fluxes, were between 0.2 and 1.8 mmol N m<sup>-2</sup> day<sup>-1</sup> and in the range of past assessments during the upwelling season. A simple model, applied to further constrain the contributions to bottom water fixed nitrogen (N) loss under assumptions of benthic boundary layer height and residence time, showed that although sediment denitrification could readily account for total bottom water N losses during the summer, additional water-column denitrification is indicated by the strength of early fall deficits at some stations. Constraining water-column and benthic contributions to fixed N deficits is important for understanding how N-limited primary productivity in this region will respond to projected ocean deoxygenation under anticipated global warming. These results demonstrate the interplay of sediment and water-column remineralization processes across the OR-WA shelf. As in most shallow marine systems, the two are integral to the ecosystem dynamics and responses to environmental change.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104473"},"PeriodicalIF":3.0,"publicationDate":"2024-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142759097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.marchem.2024.104467
J. Sánchez-Rodríguez , A. Sierra , S. Moreno , J. Forja , T. Ortega
The Guadalquivir Estuary is the largest estuary in the southwest basin of the Iberian Peninsula, which is subject to strong anthropogenic influence such as the damming or the multitude of crop fields on its margins. Nitrous Oxide (N2O) variability is analysed considering the influence of temperature, salinity, water-atmosphere fluxes, benthic fluxes, reactivity and lateral inputs. N2O increases along the salinity gradient, with values ranging from 5.9 to 103.3 nmol L−1. Thus, values of N2O concentration are very close to equilibrium with the atmosphere at the mouth, while in the inner zone the fluxes to the atmosphere are higher, showing the greatest variability of N2O in the estuary (74.26 ± 7.41 μmol m−2 d−1). Sediments act as a source of N2O to the water column, with benthic fluxes presenting a wide range from 2 to 20 μmol m−2 d−1. Denitrification processes in the sediments may be important in the inner part of the estuary, where negative benthic fluxes of nitrate have been observed. Production rates of N2O in the water column are estimated from incubation experiments, resulting in higher production with temperature, and lower with salinity. Lateral inputs are calculated by balance of the different processes characterized and seems to be an important factor influencing N2O variability in the inner zone of the estuary.
{"title":"Nitrous oxide variability along an estuary influenced by agricultural land use (Guadalquivir estuary, SW Spain)","authors":"J. Sánchez-Rodríguez , A. Sierra , S. Moreno , J. Forja , T. Ortega","doi":"10.1016/j.marchem.2024.104467","DOIUrl":"10.1016/j.marchem.2024.104467","url":null,"abstract":"<div><div>The Guadalquivir Estuary is the largest estuary in the southwest basin of the Iberian Peninsula, which is subject to strong anthropogenic influence such as the damming or the multitude of crop fields on its margins. Nitrous Oxide (N<sub>2</sub>O) variability is analysed considering the influence of temperature, salinity, water-atmosphere fluxes, benthic fluxes, reactivity and lateral inputs. N<sub>2</sub>O increases along the salinity gradient, with values ranging from 5.9 to 103.3 nmol L<sup>−1</sup>. Thus, values of N<sub>2</sub>O concentration are very close to equilibrium with the atmosphere at the mouth, while in the inner zone the fluxes to the atmosphere are higher, showing the greatest variability of N<sub>2</sub>O in the estuary (74.26 ± 7.41 μmol m<sup>−2</sup> d<sup>−1</sup>). Sediments act as a source of N<sub>2</sub>O to the water column, with benthic fluxes presenting a wide range from 2 to 20 μmol m<sup>−2</sup> d<sup>−1</sup>. Denitrification processes in the sediments may be important in the inner part of the estuary, where negative benthic fluxes of nitrate have been observed. Production rates of N<sub>2</sub>O in the water column are estimated from incubation experiments, resulting in higher production with temperature, and lower with salinity. Lateral inputs are calculated by balance of the different processes characterized and seems to be an important factor influencing N<sub>2</sub>O variability in the inner zone of the estuary.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104467"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.marchem.2024.104472
Rodrigo Kerr , Thiago Monteiro , Iole Beatriz M. Orselli , Virginia Maria Tavano , Carlos Rafael B. Mendes
Hydrographic properties and carbon dioxide partial pressure (pCO2) were measured through underway survey of surface waters during spring 2014, mainly along the Surface Haline Front in the continental shelf-break domain in the southwestern South Atlantic Ocean margin. Additionally, discrete seawater surface samples were collected along the ship track to identify the phytoplankton community and measure seawater chemical properties. This study aims to identify the drivers of the marine CO2‑carbonate chemistry and the role played by the phytoplankton composition on changes in the surface marine carbonate properties and the sea-air CO2 exchanges in two biogeochemical provinces (i.e., South Brazil Bight – SBB, and Southern Brazilian Shelf – SBS) governed by the dynamics of the Brazil Current system in the South Atlantic Ocean. The water masses identified on the surface of the region were Tropical Water (mostly present at offshore regions), Subtropical Shelf Water (mostly present over the continental shelf and slope), and Plata Plume Water (present in the south coastal domain of the SBS). On average, the study area behaved as a weak net CO2 outgassing zone of 1.2 ± 2.3 mmol m−2 d−1 during the spring, despite some subregions behaving as CO2 ingassing zones. The CO2 uptake verified in the SBB was related with mesoscale activity bringing cold waters in the region while CO2 uptake in the continental shelf domain of SBS was associated with the presence of cooler and fresher Plata Plume Water. Changes in total alkalinity and dissolved inorganic carbon at surface were mainly governed by CaCO3 production in SBB and seawater dilution in SBS, although other processes may also have influenced on their spatial variability. The dominant phytoplankton groups were haptophytes (31 %), Trichodesmium (21 %), and picocyanobateria (28 %), corresponding to Synechococcus (17 %) and Prochlorococcus (11 %). The dominance of the diatom group was associated with a decrease in sea surface pCO2 (mainly at coastal zones at southern areas), although the sea-air CO2 exchanges were regulated by cooling process due the presence of Plata Plume Water in that region. Changes in surface pH were related to high concentration of Trichodesmium slicks at offshore zones with the highest microalgae concentration, leading to pH drops of up to 0.4. Trichodesmium slicks likely allowed the development of haptophytes in offshore oligotrophic waters due to its role on N2 fixation. An increase of ∼20 % in the dominance of haptophytes contribution was verified in that situation, which was likely in a post-bloom development stage, since an increased dissolved inorganic carbon content was observed, associated with a prevalence of net respiration processes.
{"title":"Sea-air CO2 exchanges, pCO2 drivers and phytoplankton communities in the southwestern South Atlantic Ocean during spring","authors":"Rodrigo Kerr , Thiago Monteiro , Iole Beatriz M. Orselli , Virginia Maria Tavano , Carlos Rafael B. Mendes","doi":"10.1016/j.marchem.2024.104472","DOIUrl":"10.1016/j.marchem.2024.104472","url":null,"abstract":"<div><div>Hydrographic properties and carbon dioxide partial pressure (<em>p</em>CO<sub>2</sub>) were measured through underway survey of surface waters during spring 2014, mainly along the Surface Haline Front in the continental shelf-break domain in the southwestern South Atlantic Ocean margin. Additionally, discrete seawater surface samples were collected along the ship track to identify the phytoplankton community and measure seawater chemical properties. This study aims to identify the drivers of the marine CO<sub>2</sub>‑carbonate chemistry and the role played by the phytoplankton composition on changes in the surface marine carbonate properties and the sea-air CO<sub>2</sub> exchanges in two biogeochemical provinces (i.e., South Brazil Bight – SBB, and Southern Brazilian Shelf – SBS) governed by the dynamics of the Brazil Current system in the South Atlantic Ocean. The water masses identified on the surface of the region were Tropical Water (mostly present at offshore regions), Subtropical Shelf Water (mostly present over the continental shelf and slope), and Plata Plume Water (present in the south coastal domain of the SBS). On average, the study area behaved as a weak net CO<sub>2</sub> outgassing zone of 1.2 ± 2.3 mmol m<sup>−2</sup> d<sup>−1</sup> during the spring, despite some subregions behaving as CO<sub>2</sub> ingassing zones. The CO<sub>2</sub> uptake verified in the SBB was related with mesoscale activity bringing cold waters in the region while CO<sub>2</sub> uptake in the continental shelf domain of SBS was associated with the presence of cooler and fresher Plata Plume Water. Changes in total alkalinity and dissolved inorganic carbon at surface were mainly governed by CaCO<sub>3</sub> production in SBB and seawater dilution in SBS, although other processes may also have influenced on their spatial variability. The dominant phytoplankton groups were haptophytes (31 %), <em>Trichodesmium</em> (21 %), and picocyanobateria (28 %), corresponding to <em>Synechococcus</em> (17 %) and <em>Prochlorococcus</em> (11 %). The dominance of the diatom group was associated with a decrease in sea surface <em>p</em>CO<sub>2</sub> (mainly at coastal zones at southern areas), although the sea-air CO<sub>2</sub> exchanges were regulated by cooling process due the presence of Plata Plume Water in that region. Changes in surface pH were related to high concentration of <em>Trichodesmium</em> slicks at offshore zones with the highest microalgae concentration, leading to pH drops of up to 0.4. <em>Trichodesmium</em> slicks likely allowed the development of haptophytes in offshore oligotrophic waters due to its role on N<sub>2</sub> fixation. An increase of ∼20 % in the dominance of haptophytes contribution was verified in that situation, which was likely in a post-bloom development stage, since an increased dissolved inorganic carbon content was observed, associated with a prevalence of net respiration processes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104472"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142722482","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.marchem.2024.104469
Shou-En Tsao , Po-Yen Shen , Chun-Mao Tseng
The partial pressure of CO2 (pCO2) and associated CO2 air-sea flux exhibit highly heterogeneous temporal and spatial patterns in ocean margins. In this study, we analyzed a three-year time-series of data sampled during 2011–2014 along the Kuroshio Current within the East China Sea (ECS) to investigate the seasonal pattern of carbonate chemistry and CO2 air-sea fluxes. Annually, the Kuroshio within the ECS operates as a net CO2 sink at approximately 1.3 mol C m−2 yr−1, less than estimates over the ECS shelf (∼1.8 mol C m−2 yr−1). The thermal control of pCO2 makes the Kuroshio a strong CO2 sink in winter, with a transition to net-neutral, or a weak CO2 source in summer. On an interannual basis, however, the seasonal CO2 air-sea fluxes in the Kuroshio may undergo shifts if warming conditions continue.
大洋边缘的二氧化碳分压（pCO2）和相关的二氧化碳海气通量呈现出高度异质性的时空模式。在本研究中，我们分析了 2011-2014 年中国东海（ECS）黑潮沿岸三年的时间序列数据，研究了碳酸盐化学和二氧化碳海气通量的季节模式。每年，东海海域内黑潮的二氧化碳净吸收汇约为 1.3 mol C m-2 yr-1，低于东海大陆架的估计值（1.8 mol C m-2 yr-1）。对 pCO2 的热控制使黑潮在冬季成为一个强大的二氧化碳汇，在夏季过渡到净中性或弱二氧化碳源。不过，如果气候继续变暖，黑潮的季节性二氧化碳海气通量可能会发生变化。
{"title":"Seasonal variation of CO2 air-sea flux and effects of warming in the Kuroshio Current of the East China Sea","authors":"Shou-En Tsao , Po-Yen Shen , Chun-Mao Tseng","doi":"10.1016/j.marchem.2024.104469","DOIUrl":"10.1016/j.marchem.2024.104469","url":null,"abstract":"<div><div>The partial pressure of CO<sub>2</sub> (<em>p</em>CO<sub>2</sub>) and associated CO<sub>2</sub> air-sea flux exhibit highly heterogeneous temporal and spatial patterns in ocean margins. In this study, we analyzed a three-year time-series of data sampled during 2011–2014 along the Kuroshio Current within the East China Sea (ECS) to investigate the seasonal pattern of carbonate chemistry and CO<sub>2</sub> air-sea fluxes. Annually, the Kuroshio within the ECS operates as a net CO<sub>2</sub> sink at approximately 1.3 mol C m<sup>−2</sup> yr<sup>−1</sup>, less than estimates over the ECS shelf (∼1.8 mol C m<sup>−2</sup> yr<sup>−1</sup>). The thermal control of <em>p</em>CO<sub>2</sub> makes the Kuroshio a strong CO<sub>2</sub> sink in winter, with a transition to net-neutral, or a weak CO<sub>2</sub> source in summer. On an interannual basis, however, the seasonal CO<sub>2</sub> air-sea fluxes in the Kuroshio may undergo shifts if warming conditions continue.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104469"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656458","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Trace element analyses in brackish waters are challenging for many elements at ppb/ppt levels and analytical methods. In this work, we compare two methods using inductively coupled plasma mass spectrometry (ICP-MS) for quantifying antimony (Sb). Results of a previous study along the salinity gradient in a macrotidal estuary (i.e., the Gironde Estuary, France) using isotopic dilution via single quadrupole ICP-MS are compared to reanalyzed aliquots of the same samples. Direct analyses of estuarine water samples via standard additions (N = 52) were performed with a QQQ-ICP-MS (new generation, iCAP TQ Thermo®) to determine dissolved (< 0.2 μm filtered and UV-irradiated replicates) Sb concentrations during two contrasting hydrological conditions (low vs high freshwater discharges). Despite following good analytical practices on both studies, the use of the new analytical device provides more robust results and highlighted a characteristic 121Sb isotopic interference in estuarine samples at S > 20, efficiently eliminated by the QQQ-ICP-MS performance. This means that Sb reactivity shows an additive, non-conservative behavior in the Gironde Estuary, with a more defined bell-shaped profile in low discharge compared to high discharge conditions. This approach allows to quantify for the first time in the literature Sb dissolved net fluxes from the Gironde Estuary to the Atlantic coast and provides an updated value for the seawater endmember. This study opens future applications of QQQ-ICP-MS for quantifying on a more routine basis dissolved trace elements in brackish waters, providing guidelines and good practices for field studies regarding Sb determination in estuarine systems.
{"title":"Reactivity and fluxes of antimony in a macrotidal estuarine salinity gradient: Insights from single and triple quadrupole ICP-MS performances","authors":"Teba Gil-Díaz , Frédérique Pougnet , Lionel Dutruch , Jörg Schäfer , Alexandra Coynel","doi":"10.1016/j.marchem.2024.104465","DOIUrl":"10.1016/j.marchem.2024.104465","url":null,"abstract":"<div><div>Trace element analyses in brackish waters are challenging for many elements at ppb/ppt levels and analytical methods. In this work, we compare two methods using inductively coupled plasma mass spectrometry (ICP-MS) for quantifying antimony (Sb). Results of a previous study along the salinity gradient in a macrotidal estuary (i.e., the Gironde Estuary, France) using isotopic dilution via single quadrupole ICP-MS are compared to reanalyzed aliquots of the same samples. Direct analyses of estuarine water samples via standard additions (<em>N</em> = 52) were performed with a QQQ-ICP-MS (new generation, iCAP TQ Thermo®) to determine dissolved (< 0.2 μm filtered and UV-irradiated replicates) Sb concentrations during two contrasting hydrological conditions (low vs high freshwater discharges). Despite following good analytical practices on both studies, the use of the new analytical device provides more robust results and highlighted a characteristic <sup>121</sup>Sb isotopic interference in estuarine samples at S > 20, efficiently eliminated by the QQQ-ICP-MS performance. This means that Sb reactivity shows an additive, non-conservative behavior in the Gironde Estuary, with a more defined bell-shaped profile in low discharge compared to high discharge conditions. This approach allows to quantify for the first time in the literature Sb dissolved net fluxes from the Gironde Estuary to the Atlantic coast and provides an updated value for the seawater endmember. This study opens future applications of QQQ-ICP-MS for quantifying on a more routine basis dissolved trace elements in brackish waters, providing guidelines and good practices for field studies regarding Sb determination in estuarine systems.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104465"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142656455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-11-01DOI: 10.1016/j.marchem.2024.104466
Jessalyn E. Davis , Rebecca S. Robinson , Emily R. Estes , Veronique E. Oldham , Evan A. Solomon , Roger P. Kelly , Katherine E. Bell , Joseph A. Resing , Randelle M. Bundy
Transport processes along the river-ocean continuum influence delivery of nutrients, carbon and trace metals from terrestrial systems to the marine environment, impacting coastal primary productivity and water quality. Although trace metal transformations have been studied extensively in the Mississippi River Delta region of the Northern Gulf of Mexico, investigations of manganese (Mn) and the presence of ligand-stabilized, dissolved manganese (Mn(III)-L) and its role in the transformation of trace elements and organic matter during riverine transport and estuarine mixing have not been considered. This study examined the chemical speciation of dissolved and particulate Mn in the water column and sediment porewaters in the Mississippi River and Northern Gulf of Mexico in March of 2021 to explore transformations in Mn speciation along the river-ocean continuum and the impact of different processes on the distribution of Mn. Total dissolved Mn concentrations were highest in the Mississippi River and decreased offshore, while Mn(III)-L contributed most to the dissolved Mn pool in near-shore waters. Porewater profiles indicated that ligand stabilization prevented dissolved Mn(III) reduction below the depth of oxygen penetration and in the presence of equimolar dissolved iron(II). Dissolved Mn(III)-L was enriched in bottom waters at all Northern Gulf of Mexico stations, and diffusive flux modelling of porewater dissolved Mn suggested that reducing sediments were a source of dissolved Mn to the overlying water column in the form of both reduced Mn(II) and Mn(III)-L. A simple box model of the Mn cycle in the Northern Gulf of Mexico indicates that Mn(III)-L is required to balance the Mn budget in this region and is an integral, and previously unconsidered, piece of the Mn cycle in the Northern Gulf of Mexico. The presence of Mn(III)-L in this system likely has an outsized impact on trace element scavenging rates, oxidative capacity, and the carbon cycle that have not been previously appreciated.
{"title":"Dynamic manganese cycling in the northern Gulf of Mexico","authors":"Jessalyn E. Davis , Rebecca S. Robinson , Emily R. Estes , Veronique E. Oldham , Evan A. Solomon , Roger P. Kelly , Katherine E. Bell , Joseph A. Resing , Randelle M. Bundy","doi":"10.1016/j.marchem.2024.104466","DOIUrl":"10.1016/j.marchem.2024.104466","url":null,"abstract":"<div><div>Transport processes along the river-ocean continuum influence delivery of nutrients, carbon and trace metals from terrestrial systems to the marine environment, impacting coastal primary productivity and water quality. Although trace metal transformations have been studied extensively in the Mississippi River Delta region of the Northern Gulf of Mexico, investigations of manganese (Mn) and the presence of ligand-stabilized, dissolved manganese (Mn(III)-L) and its role in the transformation of trace elements and organic matter during riverine transport and estuarine mixing have not been considered. This study examined the chemical speciation of dissolved and particulate Mn in the water column and sediment porewaters in the Mississippi River and Northern Gulf of Mexico in March of 2021 to explore transformations in Mn speciation along the river-ocean continuum and the impact of different processes on the distribution of Mn. Total dissolved Mn concentrations were highest in the Mississippi River and decreased offshore, while Mn(III)-L contributed most to the dissolved Mn pool in near-shore waters. Porewater profiles indicated that ligand stabilization prevented dissolved Mn(III) reduction below the depth of oxygen penetration and in the presence of equimolar dissolved iron(II). Dissolved Mn(III)-L was enriched in bottom waters at all Northern Gulf of Mexico stations, and diffusive flux modelling of porewater dissolved Mn suggested that reducing sediments were a source of dissolved Mn to the overlying water column in the form of both reduced Mn(II) and Mn(III)-L. A simple box model of the Mn cycle in the Northern Gulf of Mexico indicates that Mn(III)-L is required to balance the Mn budget in this region and is an integral, and previously unconsidered, piece of the Mn cycle in the Northern Gulf of Mexico. The presence of Mn(III)-L in this system likely has an outsized impact on trace element scavenging rates, oxidative capacity, and the carbon cycle that have not been previously appreciated.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"267 ","pages":"Article 104466"},"PeriodicalIF":3.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142703071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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