Pub Date : 2025-07-07DOI: 10.1016/j.marchem.2025.104544
Lorena S. Nascimento , Felipe R. Santos , Pollyana C.V. Morais , Allyne F. Gama , Márcia C. Bícego , Satie Taniguchi , Rafael A. Lourenço , César C. Martins , Lucas B. Moreira , Rivelino M. Cavalcante
Surface sediments from the Jaguaribe River, in a Brazilian semi-arid region, were investigated for the presence of traditional and emerging organic contaminants to identify the multiple pollution sources in the area. Aliphatic and polycyclic aromatic hydrocarbons were linked to phytoplankton, microbiological species, specific vegetation, and minimal petroleum and pyrolysis compounds. Regarding sterols, higher contributions from stigmasterol and cholesterol were associated with higher plants and zooplankton, respectively. However, coprostanol levels suggested fecal contamination from large mammals, corroborated by the predominance of synthetic over natural hormones. The main origins found for pesticides were their use in health campaigns, agriculture, and domestic use. The toxicity assessment revealed that all stations presented a high risk to biota, especially from hormone and pesticide compounds. This multimolecular approach allowed the identification and differentiation of pollution sources from urban and rural activities and the potential risk for the biota in an important region of Brazil.
{"title":"Pollution assessment and ecological risk of organic contaminants in a river-estuary of the northeastern Brazilian semi-arid: Traditional and emerging contaminants unraveling rural and urban activities","authors":"Lorena S. Nascimento , Felipe R. Santos , Pollyana C.V. Morais , Allyne F. Gama , Márcia C. Bícego , Satie Taniguchi , Rafael A. Lourenço , César C. Martins , Lucas B. Moreira , Rivelino M. Cavalcante","doi":"10.1016/j.marchem.2025.104544","DOIUrl":"10.1016/j.marchem.2025.104544","url":null,"abstract":"<div><div>Surface sediments from the Jaguaribe River, in a Brazilian semi-arid region, were investigated for the presence of traditional and emerging organic contaminants to identify the multiple pollution sources in the area. Aliphatic and polycyclic aromatic hydrocarbons were linked to phytoplankton, microbiological species, specific vegetation, and minimal petroleum and pyrolysis compounds. Regarding sterols, higher contributions from stigmasterol and cholesterol were associated with higher plants and zooplankton, respectively. However, coprostanol levels suggested fecal contamination from large mammals, corroborated by the predominance of synthetic over natural hormones. The main origins found for pesticides were their use in health campaigns, agriculture, and domestic use. The toxicity assessment revealed that all stations presented a high risk to biota, especially from hormone and pesticide compounds. This multimolecular approach allowed the identification and differentiation of pollution sources from urban and rural activities and the potential risk for the biota in an important region of Brazil.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"272 ","pages":"Article 104544"},"PeriodicalIF":3.0,"publicationDate":"2025-07-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144596476","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 : 2025-07-01DOI: 10.1016/j.marchem.2025.104531
Rianne J.M. van Kaam, Martin Kölling, Marcus Elvert, Kai-Uwe Hinrichs, Matthias Zabel
Dust deposition to the ocean plays an indirect role in the carbon cycle due to stimulating the primary production by fertilisation. Additionally, it transports carbon to the ocean floor by acting as ballast for marine aggregates. Despite these recognized impacts, the direct influence of dust-seawater interactions on the carbon cycle remains poorly understood. Here, we study the effects of mineral dust on the dissolved organic carbon (DOC) concentration in seawater by performing sorption experiments through time series and stable carbon isotope analysis. We added two different amounts of dust to a solution of artificial seawater and 13C-labelled dissolved organic matter from Spirulina extract, creating a low and high dust-seawater ratio system. After 72 h, we observe a decrease in DOC for both systems, indicating the adsorption of DOC from the Spirulina extract onto dust particles. Analysis of the stable carbon isotope ratios of total organic carbon on the dust samples, before and after the sorption experiments, confirms these findings. Furthermore, our study shows that the net uptake of DOC on dust depends on the relative importance of adsorption, release and degradation of organic carbon. DOC release can become the dominant process based on the dust-seawater ratio and the initial organic carbon present on the dust, demonstrating that dust can act as both a sink and a source of organic carbon in the near-surface waters.
{"title":"Dust deposition directly affects the concentration of dissolved organic carbon in the ocean","authors":"Rianne J.M. van Kaam, Martin Kölling, Marcus Elvert, Kai-Uwe Hinrichs, Matthias Zabel","doi":"10.1016/j.marchem.2025.104531","DOIUrl":"10.1016/j.marchem.2025.104531","url":null,"abstract":"<div><div>Dust deposition to the ocean plays an indirect role in the carbon cycle due to stimulating the primary production by fertilisation. Additionally, it transports carbon to the ocean floor by acting as ballast for marine aggregates. Despite these recognized impacts, the direct influence of dust-seawater interactions on the carbon cycle remains poorly understood. Here, we study the effects of mineral dust on the dissolved organic carbon (DOC) concentration in seawater by performing sorption experiments through time series and stable carbon isotope analysis. We added two different amounts of dust to a solution of artificial seawater and <sup>13</sup>C-labelled dissolved organic matter from <em>Spirulina</em> extract, creating a low and high dust-seawater ratio system. After 72 h, we observe a decrease in DOC for both systems, indicating the adsorption of DOC from the <em>Spirulina</em> extract onto dust particles. Analysis of the stable carbon isotope ratios of total organic carbon on the dust samples, before and after the sorption experiments, confirms these findings. Furthermore, our study shows that the net uptake of DOC on dust depends on the relative importance of adsorption, release and degradation of organic carbon. DOC release can become the dominant process based on the dust-seawater ratio and the initial organic carbon present on the dust, demonstrating that dust can act as both a sink and a source of organic carbon in the near-surface waters.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104531"},"PeriodicalIF":3.0,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144557449","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 : 2025-07-01DOI: 10.1016/j.marchem.2025.104533
Qixian Chen , Yifan Li , Chen-Tung Arthur Chen , Zong-Pei Jiang , Wei-Jun Cai , Hongwen Pan , Yunwen Shen , Zesheng Ding , Yanan Di , Chenba Zhu , Nianzhi Jiao , Yiwen Pan
Diatoms play a pivotal role in the ocean, contributing approximately 40 % of marine primary production, with nearly half of the particulate organic carbon being exported. The recent discovery of a novel diatom-induced calcification pathway has attracted significant attention due to its implications for marine carbon, calcium, and silicon cycling. Despite its potential, the lack of a quantitative initiation threshold and comparative analysis with known calcifying organisms limit our ability to predict its ecological impact, particularly on carbon sequestration. This study addresses these gaps by cultivating the common diatom species, Skeletonema costatum, under simulated marine conditions to evaluate its CaCO3 precipitation potential and define the biogeochemical threshold for calcification. The experimental results showed that S. costatum can induce calcification across a range of environmental conditions, including varying dissolved inorganic carbon (DIC 1837 to 2709 μmol·kg−1), nitrogen sources (NH4+ or NO3−), and cell densities (104 to 105 cells·mL−1). Calcification was initiated when the aragonite saturation state (Ωarag) exceeded ∼8. The calcification rate exhibits a linear correlation with Ωarag in the bulk solution, categorizing it as a “biologically induced” process. Our findings highlight similarities between the calcification mechanisms of S. costatum and other calcifying organisms, revealing the common ality of environmental drivers. This study advances our understanding of diatom-induced calcification, offering insights into its role in the marine carbon cycle and potential contributions to carbon sequestration strategies.
{"title":"Diatom-induced calcification in coastal marine environments: Biomineralization threshold and mechanism","authors":"Qixian Chen , Yifan Li , Chen-Tung Arthur Chen , Zong-Pei Jiang , Wei-Jun Cai , Hongwen Pan , Yunwen Shen , Zesheng Ding , Yanan Di , Chenba Zhu , Nianzhi Jiao , Yiwen Pan","doi":"10.1016/j.marchem.2025.104533","DOIUrl":"10.1016/j.marchem.2025.104533","url":null,"abstract":"<div><div>Diatoms play a pivotal role in the ocean, contributing approximately 40 % of marine primary production, with nearly half of the particulate organic carbon being exported. The recent discovery of a novel diatom-induced calcification pathway has attracted significant attention due to its implications for marine carbon, calcium, and silicon cycling. Despite its potential, the lack of a quantitative initiation threshold and comparative analysis with known calcifying organisms limit our ability to predict its ecological impact, particularly on carbon sequestration. This study addresses these gaps by cultivating the common diatom species, <em>Skeletonema costatum</em>, under simulated marine conditions to evaluate its CaCO<sub>3</sub> precipitation potential and define the biogeochemical threshold for calcification. The experimental results showed that <em>S. costatum</em> can induce calcification across a range of environmental conditions, including varying dissolved inorganic carbon (DIC 1837 to 2709 μmol·kg<sup>−1</sup>), nitrogen sources (NH<sub>4</sub><sup>+</sup> or NO<sub>3</sub><sup>−</sup>), and cell densities (10<sup>4</sup> to 10<sup>5</sup> cells·mL<sup>−1</sup>). Calcification was initiated when the aragonite saturation state (Ω<sub>arag</sub>) exceeded ∼8. The calcification rate exhibits a linear correlation with Ω<sub>arag</sub> in the bulk solution, categorizing it as a “biologically induced” process. Our findings highlight similarities between the calcification mechanisms of <em>S. costatum</em> and other calcifying organisms, revealing the common ality of environmental drivers. This study advances our understanding of diatom-induced calcification, offering insights into its role in the marine carbon cycle and potential contributions to carbon sequestration strategies.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104533"},"PeriodicalIF":3.0,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144524021","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 : 2025-06-23DOI: 10.1016/j.marchem.2025.104532
Wiwit , Kuo Hong Wong , Chia-Jung Lu , Hideki Fukuda , Hiroshi Ogawa , Shigenobu Takeda , Kazutaka Takahashi , Asami S. Mashio , Hajime Obata
Although copper (Cu) is necessary for phytoplankton growth, it becomes toxic at high concentrations. The bioavailability and toxicity of Cu are governed by its chemical speciation, with free inorganic Cu2+ being the most toxic species. In this study, we estimated free Cu2+ concentrations in Japanese coastal waters to evaluate the effects of Cu toxicity on phytoplankton growth. Incubation experiments were conducted using natural phytoplankton assemblages in seawater collected from Otsuchi Bay, northeastern Japan, and Goto-nada in the East China Sea. The cells were incubated for 14 days with Cu additions of up to 100 nM. Copper speciation parameters were determined using the reverse titration methods with competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV). Chlorophyll-a concentrations increased with the addition of <10 nM Cu but decreased at 100 nM Cu due to Cu toxicity. We found that phytoplankton growth caused negligible increases in Cu-binding organic ligand concentrations. Free Cu2+ concentrations were simulated using the initial Cu speciation parameters obtained from the reverse titration method under varying Cu concentrations. When assuming the presence of only one class of organic ligands, the estimated Cu2+ concentrations were inconsistent with the incubation results. In contrast, by considering two classes of ligands, the increase in the concentration of Cu2+ closely matched the incubation data. This suggests that the resolution of the weaker class of organic ligands is crucial for evaluating Cu toxicity in seawater.
{"title":"Copper-binding organic ligands and phytoplankton growth in Japanese coastal waters","authors":"Wiwit , Kuo Hong Wong , Chia-Jung Lu , Hideki Fukuda , Hiroshi Ogawa , Shigenobu Takeda , Kazutaka Takahashi , Asami S. Mashio , Hajime Obata","doi":"10.1016/j.marchem.2025.104532","DOIUrl":"10.1016/j.marchem.2025.104532","url":null,"abstract":"<div><div>Although copper (Cu) is necessary for phytoplankton growth, it becomes toxic at high concentrations. The bioavailability and toxicity of Cu are governed by its chemical speciation, with free inorganic Cu<sup>2+</sup> being the most toxic species. In this study, we estimated free Cu<sup>2+</sup> concentrations in Japanese coastal waters to evaluate the effects of Cu toxicity on phytoplankton growth. Incubation experiments were conducted using natural phytoplankton assemblages in seawater collected from Otsuchi Bay, northeastern Japan, and Goto-nada in the East China Sea. The cells were incubated for 14 days with Cu additions of up to 100 nM. Copper speciation parameters were determined using the reverse titration methods with competitive ligand exchange adsorptive cathodic stripping voltammetry (CLE-AdCSV). Chlorophyll-<em>a</em> concentrations increased with the addition of <10 nM Cu but decreased at 100 nM Cu due to Cu toxicity. We found that phytoplankton growth caused negligible increases in Cu-binding organic ligand concentrations. Free Cu<sup>2+</sup> concentrations were simulated using the initial Cu speciation parameters obtained from the reverse titration method under varying Cu concentrations. When assuming the presence of only one class of organic ligands, the estimated Cu<sup>2+</sup> concentrations were inconsistent with the incubation results. In contrast, by considering two classes of ligands, the increase in the concentration of Cu<sup>2+</sup> closely matched the incubation data. This suggests that the resolution of the weaker class of organic ligands is crucial for evaluating Cu toxicity in seawater.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104532"},"PeriodicalIF":3.0,"publicationDate":"2025-06-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144501772","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 : 2025-06-02DOI: 10.1016/j.marchem.2025.104530
Hojong Seo , Guebuem Kim
We investigated particulate organic carbon (POC) transport across the shelf to the basin bottom in the East/Japan Sea, using Aluminum (Al) and 210Pb as tracers. Our results show that the sedimentary deposition of 210Pb in the basin (2327 m) is comparable with the scavenging removal flux from the water column (117 ± 15 %), whereas it increases threefold in the shelf (296 ± 50 %) (200 m), suggesting substantial lateral inputs of land- and shelf-origin sediments. We also show that conventionally used excess 210Pb-derived sedimentation rates without considering mixing can be overestimated by 3–8 times in continental margin sediments, where sedimentation rates are low (< 0.15 cm yr−1), leading to significant overestimation of POC burial fluxes. Sedimentation rates based on an Al mass balance with sedimentary 210Pb budgets align more closely with those from 14C and tephra analyses in this region. A POC box model using the refined sedimentation rate indicates that POC burial fluxes in the East Sea are 0.3–1.0 % of primary production. These values are four times lower than previous estimates based on 210Pb-derived sedimentation rates in the same region, but consistent with those observed in similar oceanic settings. Additionally, the POC box model suggests that sediment resuspensions can significantly contribute (34–70 %) to sinking POC fluxes in the bottom sediments. Thus, our results highlight that in continental margins, where 210Pb decay and mixing are difficult to distinguish due to slow sedimentation rates, traditional 210Pb dating methods can significantly overestimate sedimentation rates and associated material fluxes.
以铝（Al）和210Pb为示踪剂，研究了东/日本海陆架到海盆底部的颗粒有机碳（POC）运输。研究结果表明，210Pb在盆地（2327 m）的沉积沉积量与水柱的清除去除通量（117±15%）相当，而在陆架（200 m）的沉积沉积量增加了3倍（296±50%），表明陆架源沉积物有大量的侧向输入。我们还表明，在沉积速率较低的大陆边缘沉积物中，常规使用的不考虑混合的过量210pb沉积速率可能被高估3-8倍(<；0.15 cm yr - 1)，导致对POC埋藏通量的严重高估。基于Al质量平衡和沉积210Pb收支的沉积速率与14C和tephra分析的沉积速率更接近。利用精细化沉降速率建立的POC盒模型表明，东海POC埋藏通量为初级产量的0.3 ~ 1.0%。这些值比以前根据同一地区210pb沉积速率估算的值低4倍，但与在类似海洋环境中观测到的值一致。此外，POC箱型模型表明，沉积物再悬浮对底部沉积物POC通量的下降有显著贡献（34 - 70%）。因此，我们的研究结果表明，在大陆边缘，由于沉积速率缓慢，210Pb的衰变和混合难以区分，传统的210Pb测年方法可能会显著高估沉积速率和相关物质通量。
{"title":"Tracing cross-shelf transport and accumulation of particulate organic carbon in the continental margin bottom sediments using Aluminum and 210Pb","authors":"Hojong Seo , Guebuem Kim","doi":"10.1016/j.marchem.2025.104530","DOIUrl":"10.1016/j.marchem.2025.104530","url":null,"abstract":"<div><div>We investigated particulate organic carbon (POC) transport across the shelf to the basin bottom in the East/Japan Sea, using Aluminum (Al) and <sup>210</sup>Pb as tracers. Our results show that the sedimentary deposition of <sup>210</sup>Pb in the basin (2327 m) is comparable with the scavenging removal flux from the water column (117 ± 15 %), whereas it increases threefold in the shelf (296 ± 50 %) (200 m), suggesting substantial lateral inputs of land- and shelf-origin sediments. We also show that conventionally used excess <sup>210</sup>Pb-derived sedimentation rates without considering mixing can be overestimated by 3–8 times in continental margin sediments, where sedimentation rates are low (< 0.15 cm yr<sup>−1</sup>), leading to significant overestimation of POC burial fluxes. Sedimentation rates based on an Al mass balance with sedimentary <sup>210</sup>Pb budgets align more closely with those from <sup>14</sup>C and tephra analyses in this region. A POC box model using the refined sedimentation rate indicates that POC burial fluxes in the East Sea are 0.3–1.0 % of primary production. These values are four times lower than previous estimates based on <sup>210</sup>Pb-derived sedimentation rates in the same region, but consistent with those observed in similar oceanic settings. Additionally, the POC box model suggests that sediment resuspensions can significantly contribute (34–70 %) to sinking POC fluxes in the bottom sediments. Thus, our results highlight that in continental margins, where <sup>210</sup>Pb decay and mixing are difficult to distinguish due to slow sedimentation rates, traditional <sup>210</sup>Pb dating methods can significantly overestimate sedimentation rates and associated material fluxes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104530"},"PeriodicalIF":3.0,"publicationDate":"2025-06-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144230867","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 : 2025-05-31DOI: 10.1016/j.marchem.2025.104529
Thiago Monteiro , Matheus Batista , Rodrigo Kerr
The influence of physical and biogeochemical processes on the variability of the carbonate system in the Southern Ocean remains poorly constrained. Understanding this influence is crucial to distinguish natural variations from anthropogenic impacts and accurately interpret observed trends. Here, we investigate how physical and biogeochemical processes influence the spatial distribution of summer carbonate system variables along the Drake Passage and northern Antarctic Peninsula. Continuous, high-frequency surface partial pressure of CO2 (pCO2), dissolved oxygen (O2) and essential hydrographic variables were collected during the austral summer of 2019, whereas other carbonate system variables were estimated after the reconstruction and evaluation of total alkalinity. Our findings show that in the Drake Passage, Circumpolar Deep Water upwelling increases the pCO2 (> 400 μatm) and dissolved inorganic carbon (> 2175 μmol kg−1), leading to reduced pH (< 7.99) south of the Polar Front. North of the Polar Front, photosynthesis lowers pCO2 (< 390 μatm), while increasing pH (> 8.00) and carbonate ions (> 110 μmol kg−1), with enrichment occurring in the Subantarctic coccolithophore growth region. Along the northern Antarctic Peninsula, including Gerlache Strait, Antarctic Sound, and Admiralty Bay, photosynthesis and sea ice/glacial melt are the main drivers of pCO2 reductions to levels below 350 μatm. The mixing of Circumpolar Deep Water with Weddell Sea Dense Shelf Water can naturally and anthropogenically raise pCO2 and decrease pH in northern Antarctic Peninsula waters, where pH is generally lower (as low as 7.90) compared to adjacent areas. Nevertheless, most environments remain supersaturated with respect to carbonate minerals calcite and aragonite, although signs of aragonite undersaturation have occur in surface waters influenced by Dense Shelf Water. These findings offer new insights into carbonate system processes across a large Southern Ocean region, improving understanding of spatial variability in marine carbon dynamics.
{"title":"Spatial variability of marine carbonate system along the Drake Passage and northern Antarctic Peninsula during the austral summer","authors":"Thiago Monteiro , Matheus Batista , Rodrigo Kerr","doi":"10.1016/j.marchem.2025.104529","DOIUrl":"10.1016/j.marchem.2025.104529","url":null,"abstract":"<div><div>The influence of physical and biogeochemical processes on the variability of the carbonate system in the Southern Ocean remains poorly constrained. Understanding this influence is crucial to distinguish natural variations from anthropogenic impacts and accurately interpret observed trends. Here, we investigate how physical and biogeochemical processes influence the spatial distribution of summer carbonate system variables along the Drake Passage and northern Antarctic Peninsula. Continuous, high-frequency surface partial pressure of CO<sub>2</sub> (<em>p</em>CO<sub>2</sub>), dissolved oxygen (O<sub>2</sub>) and essential hydrographic variables were collected during the austral summer of 2019, whereas other carbonate system variables were estimated after the reconstruction and evaluation of total alkalinity. Our findings show that in the Drake Passage, Circumpolar Deep Water upwelling increases the <em>p</em>CO<sub>2</sub> (> 400 μatm) and dissolved inorganic carbon (> 2175 μmol kg<sup>−1</sup>), leading to reduced pH (< 7.99) south of the Polar Front. North of the Polar Front, photosynthesis lowers <em>p</em>CO<sub>2</sub> (< 390 μatm), while increasing pH (> 8.00) and carbonate ions (> 110 μmol kg<sup>−1</sup>), with enrichment occurring in the Subantarctic coccolithophore growth region. Along the northern Antarctic Peninsula, including Gerlache Strait, Antarctic Sound, and Admiralty Bay, photosynthesis and sea ice/glacial melt are the main drivers of <em>p</em>CO<sub>2</sub> reductions to levels below 350 μatm. The mixing of Circumpolar Deep Water with Weddell Sea Dense Shelf Water can naturally and anthropogenically raise <em>p</em>CO<sub>2</sub> and decrease pH in northern Antarctic Peninsula waters, where pH is generally lower (as low as 7.90) compared to adjacent areas. Nevertheless, most environments remain supersaturated with respect to carbonate minerals calcite and aragonite, although signs of aragonite undersaturation have occur in surface waters influenced by Dense Shelf Water. These findings offer new insights into carbonate system processes across a large Southern Ocean region, improving understanding of spatial variability in marine carbon dynamics.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104529"},"PeriodicalIF":3.0,"publicationDate":"2025-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144205285","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 : 2025-05-01DOI: 10.1016/j.marchem.2025.104521
Kevin Diaz , David Point , Wilson Carhuapoma , Astrid Avellan , Maricarmen Igarza , Jesús Ledesma , Fanny Rioual , Michelle Graco
The diffusive gradient in thin film technique (DGT) represents an in situ passive sampling method designed to preconcentrate various compounds, including sulfides, for detection at low concentrations. While DGT applications for sulfides have been studied in freshwater, this research extends its use to marine environments. A detailed methodology is presented for synthesizing, assembling, calibrating, and field-deploying DGT samplers to measure sulfides in the low micromolar range in marine waters. The in-house DGT samplers developed in this study demonstrated improved performance, with more homogeneous binding gels and smaller silver iodide particles (0.51 ± 0.34 μm) compared to commercial alternatives. Grayscale imaging enabled accurate quantification of sulfide accumulation in the gels, confirming the method's reliability for detecting trace-level sulfides in marine environments. Comparative analysis showed in-house and commercial samplers performed similarly in estimating sulfide concentrations. Field deployments along the Peruvian coast revealed significant vertical and spatial sulfide gradients. In the Callao coastal area (12°S) (July–August 2022), concentrations ranged from 0.03 to 0.45 μM across a 35 m depth profile. In Paracas bay (13.8°S) (March–April 2023), a shallower coastal station, concentrations ranged from 1.17 to 6.46 μM, reflecting increased benthic production. These results highlight the utility of DGT samplers as cost-effective tools for biogeochemical monitoring, enabling studies of the ocean sulfur cycle. The findings emphasize the growing application of DGTs in marine and coastal water column research.
{"title":"In situ measurement of trace sulfide concentrations in marine coastal waters using diffusive gradient in thin film passive samplers","authors":"Kevin Diaz , David Point , Wilson Carhuapoma , Astrid Avellan , Maricarmen Igarza , Jesús Ledesma , Fanny Rioual , Michelle Graco","doi":"10.1016/j.marchem.2025.104521","DOIUrl":"10.1016/j.marchem.2025.104521","url":null,"abstract":"<div><div>The diffusive gradient in thin film technique (DGT) represents an <em>in situ</em> passive sampling method designed to preconcentrate various compounds, including sulfides, for detection at low concentrations. While DGT applications for sulfides have been studied in freshwater, this research extends its use to marine environments. A detailed methodology is presented for synthesizing, assembling, calibrating, and field-deploying DGT samplers to measure sulfides in the low micromolar range in marine waters. The in-house DGT samplers developed in this study demonstrated improved performance, with more homogeneous binding gels and smaller silver iodide particles (0.51 ± 0.34 μm) compared to commercial alternatives. Grayscale imaging enabled accurate quantification of sulfide accumulation in the gels, confirming the method's reliability for detecting trace-level sulfides in marine environments. Comparative analysis showed in-house and commercial samplers performed similarly in estimating sulfide concentrations. Field deployments along the Peruvian coast revealed significant vertical and spatial sulfide gradients. In the Callao coastal area (12°S) (July–August 2022), concentrations ranged from 0.03 to 0.45 μM across a 35 m depth profile. In Paracas bay (13.8°S) (March–April 2023), a shallower coastal station, concentrations ranged from 1.17 to 6.46 μM, reflecting increased benthic production. These results highlight the utility of DGT samplers as cost-effective tools for biogeochemical monitoring, enabling studies of the ocean sulfur cycle. The findings emphasize the growing application of DGTs in marine and coastal water column research.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"271 ","pages":"Article 104521"},"PeriodicalIF":3.0,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917536","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 : 2025-04-16DOI: 10.1016/j.marchem.2025.104520
Claris N. Sunjo , Eliot A. Atekwana , Hendratta N. Ali , Henry M. Agbogun , Isaac K. Njilah
Tidal creeks are conduits for tide-driven processing and exchange of water and dissolved inorganic carbon (DIC) between the open estuary and mangrove forests. Yet, the sources of DIC, and the role of tidal creeks in the cycling of DIC and its transport to the open water of mangrove estuaries is poorly understood. This study was conducted in a tidal creek in the freshwater tidal zone at the land-estuary boundary of a tropical mangrove estuary. We made 177 measurements of salinity and 80 measurements of geogenic solutes (silica, Ca, Mg), DIC components (partial pressure of CO2 (pCO2), alkalinity and total DIC) and stable isotopes of water (δ18O and δD) and DIC (δ13CDIC). We aimed to determine the sources and the timing of water input into the tidal creek, how the different water sources control input of DIC, and how DIC is cycled through semidiurnal mixed tides and over a diel cycle. The salinity-δ18O relationship indicates two sources of water, while the relationships for salinity-DO, salinity-solute, and salinity-DIC implicated submarine groundwater discharge (SGD) as the source providing the DIC processed and transported to the open estuary. Normalized water level vs. salinity reveals that SGD sourced DIC dominates the water column during tidal ebbing and halfway through tidal flooding. In contrast, freshwater from the open estuary mainly dilutes the solutes and DIC from halfway during tidal flooding to peak high tide. The photocycle, heterotrophic and autotrophic processes are unable to explain the more than 5 times greater than atmospheric pCO2 recorded during the daytime and at low tide. These findings demonstrate that SGD is a significant DIC source in tidal creeks at the land-estuary transition zone which indicate the important role of SGD in the cycling of carbon in the freshwater tidal zones of mangrove estuaries.
{"title":"The role of tidal creeks in carbon processing and export to the freshwater tidal zone at the land-estuary boundary of tropical mangrove estuaries","authors":"Claris N. Sunjo , Eliot A. Atekwana , Hendratta N. Ali , Henry M. Agbogun , Isaac K. Njilah","doi":"10.1016/j.marchem.2025.104520","DOIUrl":"10.1016/j.marchem.2025.104520","url":null,"abstract":"<div><div>Tidal creeks are conduits for tide-driven processing and exchange of water and dissolved inorganic carbon (DIC) between the open estuary and mangrove forests. Yet, the sources of DIC, and the role of tidal creeks in the cycling of DIC and its transport to the open water of mangrove estuaries is poorly understood. This study was conducted in a tidal creek in the freshwater tidal zone at the land-estuary boundary of a tropical mangrove estuary. We made 177 measurements of salinity and 80 measurements of geogenic solutes (silica, Ca, Mg), DIC components (partial pressure of CO<sub>2</sub> (pCO<sub>2</sub>), alkalinity and total DIC) and stable isotopes of water (δ<sup>18</sup>O and δD) and DIC (δ<sup>13</sup>C<sub>DIC</sub>). We aimed to determine the sources and the timing of water input into the tidal creek, how the different water sources control input of DIC, and how DIC is cycled through semidiurnal mixed tides and over a diel cycle. The salinity-δ<sup>18</sup>O relationship indicates two sources of water, while the relationships for salinity-DO, salinity-solute, and salinity-DIC implicated submarine groundwater discharge (SGD) as the source providing the DIC processed and transported to the open estuary. Normalized water level vs. salinity reveals that SGD sourced DIC dominates the water column during tidal ebbing and halfway through tidal flooding. In contrast, freshwater from the open estuary mainly dilutes the solutes and DIC from halfway during tidal flooding to peak high tide. The photocycle, heterotrophic and autotrophic processes are unable to explain the more than 5 times greater than atmospheric pCO<sub>2</sub> recorded during the daytime and at low tide. These findings demonstrate that SGD is a significant DIC source in tidal creeks at the land-estuary transition zone which indicate the important role of SGD in the cycling of carbon in the freshwater tidal zones of mangrove estuaries.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104520"},"PeriodicalIF":3.0,"publicationDate":"2025-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143863748","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 : 2025-04-10DOI: 10.1016/j.marchem.2025.104518
J. Sánchez-Rodríguez , V. Amaral , S. Sirviente , A. Sierra , M. Bruno , J. Forja , T. Ortega
The Guadalquivir Estuary is the largest in the southwest Iberian Peninsula and is influenced by various anthropic activities, such as damming and rice farming, which regulate river flow and provide lateral inputs to the system. Despite its role as a major source of freshwater and dissolved organic matter (DOM) to the Gulf of Cadiz, there has been limited research on the seasonal distribution of DOM and dissolved organic carbon (DOC) export. This study chemically characterizes DOM using its optical properties along the salinity gradient and during tidal sampling cycles conducted from 2018 to 2022, improving the understanding of DOM dynamics in the estuary. Results show that the DOM in the estuary is predominantly allochthonous, with humic-like components accounting for 85.8 ± 5.8 % of fluorescent DOM (FDOM), while protein-like components, associated with autochthonous processes, account for only 14.2 ± 5.9 %. Mixing and biogeochemical reactivity are the main processes controlling DOM distribution, with mixing being the most significant. Lateral inputs from marshes and rice crops play an important role, particularly in the intermediate zone. Autochthonous DOM is more prominent during the dry season, especially in Summer. The estuary exports 5.8 g C m−2 yr−1 of DOC, along with substantial amounts of humic-like and protein-like FDOM, especially during extreme rainfall events that increase river flow, and therefore, discharge. DOC transport from the Guadalquivir Estuary is low if we consider the dimensions of its watershed area, highlighting the impact of damming on DOC transport.
瓜达尔基维尔河口是伊比利亚半岛西南部最大的河口，受到各种人为活动的影响，如筑坝和种植水稻，这些活动调节河流流量并为该系统提供横向输入。尽管它是加的斯湾淡水和溶解有机物质（DOM）的主要来源，但对DOM和溶解有机碳（DOC）出口的季节性分布研究有限。本研究利用DOM在盐度梯度和2018 - 2022年潮汐采样周期中的光学特性对其进行化学表征，提高了对河口DOM动态的理解。结果表明，河口DOM以异源性为主，腐殖质样成分占荧光DOM （FDOM）的85.8±5.8%，而与本地过程相关的蛋白样成分仅占14.2±5.9%。混合和生物地球化学反应是控制DOM分布的主要过程，其中混合作用最为显著。来自沼泽和水稻作物的横向投入发挥了重要作用，特别是在中间地带。原生DOM在旱季尤其在夏季更为突出。河口输出5.8 g C m−2 yr−1的DOC，以及大量腐殖质样和蛋白质样FDOM，特别是在极端降雨事件期间，增加了河流流量，从而增加了流量。如果考虑到瓜达尔基维尔河口流域面积的大小，从该河口的DOC运输量很低，这突出了筑坝对DOC运输的影响。
{"title":"Drivers of dissolved organic matter transport in the Guadalquivir estuary (SW, Spain)","authors":"J. Sánchez-Rodríguez , V. Amaral , S. Sirviente , A. Sierra , M. Bruno , J. Forja , T. Ortega","doi":"10.1016/j.marchem.2025.104518","DOIUrl":"10.1016/j.marchem.2025.104518","url":null,"abstract":"<div><div>The Guadalquivir Estuary is the largest in the southwest Iberian Peninsula and is influenced by various anthropic activities, such as damming and rice farming, which regulate river flow and provide lateral inputs to the system. Despite its role as a major source of freshwater and dissolved organic matter (DOM) to the Gulf of Cadiz, there has been limited research on the seasonal distribution of DOM and dissolved organic carbon (DOC) export. This study chemically characterizes DOM using its optical properties along the salinity gradient and during tidal sampling cycles conducted from 2018 to 2022, improving the understanding of DOM dynamics in the estuary. Results show that the DOM in the estuary is predominantly allochthonous, with humic-like components accounting for 85.8 ± 5.8 % of fluorescent DOM (FDOM), while protein-like components, associated with autochthonous processes, account for only 14.2 ± 5.9 %. Mixing and biogeochemical reactivity are the main processes controlling DOM distribution, with mixing being the most significant. Lateral inputs from marshes and rice crops play an important role, particularly in the intermediate zone. Autochthonous DOM is more prominent during the dry season, especially in Summer. The estuary exports 5.8 g C m<sup>−2</sup> yr<sup>−1</sup> of DOC, along with substantial amounts of humic-like and protein-like FDOM, especially during extreme rainfall events that increase river flow, and therefore, discharge. DOC transport from the Guadalquivir Estuary is low if we consider the dimensions of its watershed area, highlighting the impact of damming on DOC transport.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104518"},"PeriodicalIF":3.0,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143828860","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 : 2025-04-10DOI: 10.1016/j.marchem.2025.104519
Tal Benaltabet , Gil Lapid , Ronen Alkalay , Yishai Weinstein , Tim Steffens , Eric P. Achterberg , Adi Torfstein
Continental margins support marine primary productivity by transferring nutrients and micro-nutrients (trace metals) from the coast to the oceans. Yet, the mechanisms governing the delivery of trace metals across the land-sea continuum, and how they vary temporally, are still poorly constrained. Here, we report high spatial resolution depth profiles of dissolved trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb), rare earth elements (REEs), nutrients (PO4, TON, and SiOH4) and Pb isotopes from two transect cruises in the oligotrophic eastern Mediterranean Sea.
Varying anthropogenic inputs resulted in inter-cruise variations in Zn and Pb concentrations and Pb isotopes. In contrast, low temporal variability was registered for PO4, SiOH4, Cu, and Co. The isotopic composition of Pb in the eastern Mediterranean Sea (206Pb/207Pb = 1.161–1.173 and 208Pb/206Pb = 2.085–2.101) is controlled by advected Atlantic surface water and anthropogenic inputs delivered via continental runoff (terrestrial) or atmospheric shuttles. The deep-water inventory of Pb is partially controlled by historical anthropogenic sources. An enrichment in Zn and Cd (81 and 17 %, respectively) and a 50 % depletion in Pb relative to open-waters was observed in Intermediate Levantine Waters, in tandem with terrestrial Pb isotopic signatures, light REE depletion (shale-normalized Nd/Yb < 0.22) and a strong Ce anomaly (Ce/Ce* < 0.20). These are driven by intermediate nepheloid layers from the margins, which act as both a source and a sink for trace metals through release and scavenging, evident 300–500 km away from the shore. This study highlights the dynamic role of continental margins in modulating terrestrial and anthropogenic inputs to the oceans.
{"title":"Dynamics of dissolved trace metals, rare earth elements and Pb isotopes across the eastern margins of the Mediterranean Sea","authors":"Tal Benaltabet , Gil Lapid , Ronen Alkalay , Yishai Weinstein , Tim Steffens , Eric P. Achterberg , Adi Torfstein","doi":"10.1016/j.marchem.2025.104519","DOIUrl":"10.1016/j.marchem.2025.104519","url":null,"abstract":"<div><div>Continental margins support marine primary productivity by transferring nutrients and micro-nutrients (trace metals) from the coast to the oceans. Yet, the mechanisms governing the delivery of trace metals across the land-sea continuum, and how they vary temporally, are still poorly constrained. Here, we report high spatial resolution depth profiles of dissolved trace metals (Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb), rare earth elements (REEs), nutrients (PO<sub>4</sub>, TON, and SiOH<sub>4</sub>) and Pb isotopes from two transect cruises in the oligotrophic eastern Mediterranean Sea.</div><div>Varying anthropogenic inputs resulted in inter-cruise variations in Zn and Pb concentrations and Pb isotopes. In contrast, low temporal variability was registered for PO<sub>4</sub>, SiOH<sub>4</sub>, Cu, and Co. The isotopic composition of Pb in the eastern Mediterranean Sea (<sup>206</sup>Pb/<sup>207</sup>Pb = 1.161–1.173 and <sup>208</sup>Pb/<sup>206</sup>Pb = 2.085–2.101) is controlled by advected Atlantic surface water and anthropogenic inputs delivered via continental runoff (terrestrial) or atmospheric shuttles. The deep-water inventory of Pb is partially controlled by historical anthropogenic sources. An enrichment in Zn and Cd (81 and 17 %, respectively) and a 50 % depletion in Pb relative to open-waters was observed in Intermediate Levantine Waters, in tandem with terrestrial Pb isotopic signatures, light REE depletion (shale-normalized Nd/Yb < 0.22) and a strong Ce anomaly (Ce/Ce* < 0.20). These are driven by intermediate nepheloid layers from the margins, which act as both a source and a sink for trace metals through release and scavenging, evident 300–500 km away from the shore. This study highlights the dynamic role of continental margins in modulating terrestrial and anthropogenic inputs to the oceans.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104519"},"PeriodicalIF":3.0,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143851335","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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