Marine Chemistry最新文献

{"title":"Mapping of dissolved black carbon in the Atlantic Ocean","authors":"Nina Davtian ,&nbsp;Nuria Penalva ,&nbsp;Oriol Teruel ,&nbsp;Pau Comes ,&nbsp;Antoni Rosell-Melé ,&nbsp;Joan Villanueva","doi":"10.1016/j.marchem.2025.104568","DOIUrl":"10.1016/j.marchem.2025.104568","url":null,"abstract":"<div><div>Oceanic dissolved black carbon (DBC) is the subject of a conundrum between the dominant riverine inputs in terms of mass flux and its stable and radiogenic carbon isotope composition inconsistent with a predominant riverine origin. Here, we analyzed seawater samples within specific and contrasting water masses along several latitudinal and longitudinal transects across the Atlantic Ocean to quantify DBC and map its latitudinal and water depth changes in this ocean. After comparing latitudinal changes in surface water DBC properties with those in atmospheric pyrogenic carbon inputs from seasonal, massive grass burning events in the African Savanna, we could not demonstrate the significance of atmospheric deposition as a non-riverine source of DBC in the Atlantic Ocean, likely due to the balance by DBC photo-bleaching. We found constant DBC concentrations and increasing trends in the condensation degree of DBC (i.e., B6CA:B5CA molar ratio) from surface to deep Atlantic waters and from the South Atlantic to the North Atlantic within individual shallow to deep water masses. Overall, our mapping of DBC in the Atlantic Ocean highlights the need to explore the following alternative hypotheses in the future to better understand the cycling of oceanic DBC: 1) enhanced regional atmospheric BC deposition from African savanna grassland fires impact particulate rather than dissolved BC in the Atlantic Ocean, 2) oceanic DBC has a predominantly non-pyrogenic origin, and 3) exports of terrigenous DBC across the Atlantic Ocean accompany those of terrigenous humic-like compounds from the North Atlantic via meridional circulation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104568"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266920","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}

{"title":"Relationships between chemical composition of Arctic FeMn formations and their sorption properties for 137Cs and 90Sr radionuclides","authors":"Svetlana Bratskaya ,&nbsp;Andrey Egorin ,&nbsp;Denis Balatskiy ,&nbsp;Marina Palamarchuk ,&nbsp;Natalia Polyakova ,&nbsp;Alexander Ulyantsev","doi":"10.1016/j.marchem.2025.104582","DOIUrl":"10.1016/j.marchem.2025.104582","url":null,"abstract":"<div><div>Shallow-water Fe<img>Mn formations in Arctic are usually not considered as a valuable mineral resource due to sub-economic contents of rare earth and critical metals. However, fast growth rate and unique chemical composition make them interesting candidates for application in environment protection and remediation. Here we have investigated the potential of the Chaun Bay (East Siberian Sea) Fe<img>Mn formations for application as selective sorbents for ¹³⁷Cs and ⁹⁰Sr. Fe<img>Mn formations collected at three stations located inside and nearby submarine groundwater discharge demonstrated highly variable chemical compositions with Fe/Mn ratios (0.058–0.71) and element contents up to 26.65 % (Fe), 17.79 % (Mn), 4.40 % (P), 6.34 % (Al), 15.52 % (Si). Sr contents varied from 880 to 2560 ppm. Akaganeite (β-FeOOH) was identified as the main Fe phase in crusts, while nodules were composed by lepidocrocite (γ-FeOOH) and/or feroxyhite (δ-FeOOH). Sorption properties of Fe<img>Mn formations toward ¹³⁷Cs and ⁹⁰Sr were investigated from low salinity solutions and seawater. The sorption capacity and distribution coefficients <em>(K</em>_d<em>)</em> for ¹³⁷Cs correlated with aluminosilicates contents, while all phases (Fe and Mn oxyhydroxides, phosphates, and silicates) contributed to the ⁹⁰Sr uptake. Fe<img>Mn formations with high P and Mn contents demonstrated an ultimately high selectivity toward ⁹⁰Sr in seawater with K_d up to 517 mL/g for Mn-rich sample that is comparable or better than the selectivity of the most known synthetic sorbents. The results obtained not only confirm the possibility of Fe<img>Mn nodules application for radioactive waste treatment but open up prospects for the nature-inspired design of the composite sorption materials.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104582"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145568513","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}

{"title":"Acid-leachability of metals from suspended particles in the Pacific Ocean","authors":"Yoshiki Sohrin ,&nbsp;Linjie Zheng ,&nbsp;Cheuk-Yin Chan ,&nbsp;Yuzuru Nakaguchi ,&nbsp;Shotaro Takano ,&nbsp;Rumi Sohrin ,&nbsp;Wen-Hsuan Liao ,&nbsp;Tung-Yuan Ho","doi":"10.1016/j.marchem.2025.104571","DOIUrl":"10.1016/j.marchem.2025.104571","url":null,"abstract":"<div><div>Suspended particles are major carriers of trace metals in seawater, while the cycling mechanisms of particulate trace metals remain largely unclear owing to analytical challenges. In this study, we focused on the acid-leachability of particulate trace metals collected from the Pacific Ocean and investigated their compositional features by measuring the total dissolvable metal (tdM) and dissolved metal (dM) concentrations in unfiltered and filtered seawater samples, respectively. We defined the difference between total dissolvable and dissolved metals as the particulate metal (pM). We investigated the pM time course in acidified bottom waters (pH 1.9) over approximately two years. pM increased in two stages and reached equilibrium within a few years. In the field study, we stored acidified seawater samples at least two years before analysis. We compared pM with total particulate metal (tpM) concentrations in the same samples collected from 11 stations in the subarctic Pacific. The tpM concentrations were determined by particle filtration followed by total digestion using strong acids, including HF. The results indicate that pAl and pFe are nearly equivalent to tpAl and tpFe, respectively. Many metals in the suspended particles, including clay minerals, are highly acid-leachable during long-time storage. By compiling our pM data observed in the Pacific Ocean and its marginal seas (approximately 1500 samples), we found that the average pM/dM ratio across the Pacific is 9 for Al and 4 for Fe. Although pAl and pFe exhibit strong linear correlations, their concentrations and regression slopes are spatially variable, reflecting differences in sources and fluxes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104571"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145324731","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}

{"title":"Groundwater modulates nutrient dynamics in a freshened saltmarsh tidal creek","authors":"Jianan Liu ,&nbsp;Xueqing Yu ,&nbsp;Tong Peng ,&nbsp;Xinyi Lin ,&nbsp;Jinzhou Du","doi":"10.1016/j.marchem.2025.104566","DOIUrl":"10.1016/j.marchem.2025.104566","url":null,"abstract":"<div><div>Saltmarsh tidal creeks play a critical role in coastal nutrient cycling, yet submarine groundwater discharge (SGD), as a key driver, remains poorly understood. Research on SGD-derived outwelling of multiple nutrient species is notably scarce in low-salinity estuarine saltmarshes influenced by large rivers. Utilizing long-lived radium isotopes (²²⁶Ra and ²²⁸Ra) combined with high-frequency monitoring encompassing the most comprehensive species of dissolved nutrient to date during both spring and neap tides, we quantified SGD fluxes and their contribution to nutrient outwelling in a low-salinity saltmarsh tidal creek system of the Yangtze River Estuary. Results showed that driven by tidal pumping, SGD flux during spring tides (12 ± 5.9 cm d⁻¹) was significantly greater than during neap tides (0.77 ± 0.42 cm d⁻¹), along with corresponding differences in nutrient transport fluxes. SGD served as a source of dissolved inorganic nitrogen (DIN) and dissolved silicate (DSi) to the tidal creek system. Specifically, NH₄-N contributed approximately 93 % of the outwelling flux, while SGD-derived DSi accounted for 31–36 % of the DSi outwelling. Conversely, SGD functioned as a sink for dissolved phosphorus (inorganic + organic), capable of removing phosphorus in the tidal creek waters. More importantly, due to nitrogen input via SGD and its retention of phosphorus, both groundwater and ebbing tidal creek waters exhibited nitrogen-to‑phosphorus (N/P) ratios significantly exceeding the Redfield ratio. Although the saltmarshes partially mitigated the elevated N/P ratio during the outwelling process, the imbalanced N/P ratio in SGD-driven outwelling still poses risks of inducing coastal eutrophication and harmful algal blooms. This study unveils the crucial regulatory role of SGD in nutrient dynamics within low-salinity saltmarshes, emphasizing the necessity to incorporate groundwater-surface water interactions into coastal nutrient management and ecological conservation.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104566"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145220622","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}

{"title":"Dynamic organic matter sources drive intact polar lipids recently deposited in surface sediments from the Yangtze River Estuary and adjacent sea","authors":"Dayu Duan ,&nbsp;Ke Xu ,&nbsp;Yuxue Yang ,&nbsp;Yue Wu ,&nbsp;Yasong Wang ,&nbsp;Yuli Wei ,&nbsp;Wenjie Xiao ,&nbsp;Zhixuan Feng ,&nbsp;Xueqin Zhao ,&nbsp;Yunping Xu ,&nbsp;Weichao Wu","doi":"10.1016/j.marchem.2025.104574","DOIUrl":"10.1016/j.marchem.2025.104574","url":null,"abstract":"<div><div>Lipids, especially the intact polar lipids, serve as valuable biological information for biogeochemical studies. However, the distributions of sedimentary lipids and their controlling factor in dynamic estuarine systems remain poorly constrained. Here we used an untargeted lipidomics approach to analyze lipid composition in surface sediments across freshwater, turbidity and inner shelf zones in the Yangtze River estuary. A total of 852 lipids from 28,378 molecular features were annotated, covering 35 subclasses based on LIPIDMAPS framework. The most abundant lipids, including subclasses free fatty acids, triacylglycerols, ceramides, diacylglyceryl trimethylhomoserines, and phosphatidylcholines, accounted for up to 71.4 %. Multivariate analysis reveals a significant effect of total organic carbon δ¹³C values (δ¹³C-TOC) and grain size on lipid distribution, suggesting that sedimentary organic matter sources and hydrodynamic conditions are key controlling factors on spatial lipid heterogeneity. An apparent seawards increase in δ¹³C-TOC values (−24.7 − −20.4 ‰) indicates contribution of phytoplankton-derived organic matter to sedimentary TOC from the adjacent sea area. However, most putatively eukaryotic lipids, including phospholipids, glycerolipids and betaine lipids, exhibit no distinct seawards pattern. This pattern is likely attributed to the integrative effect between lipid degradation of riverine phytoplankton and replenishment of marine phytoplankton with the resuspension of sediment. In contrast, most ceramides, especially phytosphingosine-based ceramides, show a substantially decreasing trend seawards and a strongly negative association with δ¹³C-TOC (<em>r</em> &lt; −0.8, <em>p</em> &lt; 0.001), probably indicating a terrestrial origin. This study highlights the lipid diversity under the complex marine dynamics and the potential use of lipids for tracing the biogeochemical cycling of polar lipids in the ocean.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104574"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145465958","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}

{"title":"Submarine groundwater discharge and gas hydrate dissociation fuel organic matter formation in Arctic fjord sediments","authors":"Beata Szymczycha ,&nbsp;Magdalena Diak ,&nbsp;Wei-Li Hong ,&nbsp;Michael Ernst Böttcher ,&nbsp;Aivo Lepland ,&nbsp;Przemysław Makuch ,&nbsp;Sophie ten Hietbrink ,&nbsp;Seyed Reza Saghravani ,&nbsp;Arunima Sen ,&nbsp;Aleksandra Winogradow ,&nbsp;Marc J. Silberberger","doi":"10.1016/j.marchem.2025.104570","DOIUrl":"10.1016/j.marchem.2025.104570","url":null,"abstract":"<div><div>Arctic fjord sediments store significant amounts of organic matter (OM), contributing to the global carbon cycle, but are increasingly influenced by climate change. This study investigates OM distribution and sources in sediments from 24 stations across three West Spitsbergen fjords (Hornsund, Isfjord, and Kongsfjord-Krossfjord), focusing on relationships with porewater chloride concentrations and stable water isotopes. Freshening of porewater indicated by low chlorinity was detected in Isfjord and Hornsund. In Hornsund and Tempelfjord (Isfjord), water isotope signatures point to a meteoric origin, likely via submarine groundwater discharge (SGD). In contrast, Ekmanfjord (Isfjord) shows isotopic evidence of gas hydrate dissociation as the freshening source. Both Isfjord sites contain OM with low δ¹³C_org &lt; –26.8 ‰) and δ¹⁵N_tot (&lt; 3.1 ‰) values, which are inconsistent with known OM sources in Svalbard fjords. We propose that carbon released from SGD and gas hydrate dissociation, along with methane oxidation and nitrogen assimilation by methanotrophic microbes, contribute to OM formation. These findings suggest that Arctic fjord sediments may help mitigate climate change by supporting microbial processes that consume methane, a potent greenhouse gas.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104570"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266922","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}

{"title":"pHT measurements of TRIS buffer solutions in artificial seawater matrix in the salinity range 5–40 and temperature range 5–40 °C. Part 2: Uncertainty of pHT values","authors":"Rieke Schäfer ,&nbsp;Gaëlle Capitaine ,&nbsp;Frank Bastkowski ,&nbsp;Daniela Stoica ,&nbsp;Olivier Pellegrino ,&nbsp;Raquel Quendera ,&nbsp;Eric P. Achterberg ,&nbsp;Simon L. Clegg ,&nbsp;Paola Fisicaro ,&nbsp;Steffen Seitz","doi":"10.1016/j.marchem.2025.104573","DOIUrl":"10.1016/j.marchem.2025.104573","url":null,"abstract":"<div><div>In the first part of this study, we determined a fit function which allows the calculation of the total pH (pH<span><math><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub></math></span>) value of an artificial seawater/2-amino-2-(hydroxymethyl)-1,3-propanediol (TRIS) buffer, extrapolated to 0<!--> <!-->mol<!--> <!-->kg⁻¹ <!-->H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>O TRIS molality (i.e. to a true pH<span><math><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub></math></span> scale), in terms of temperature and practical salinity. In this second part, we present a method to quantify the uncertainty of that function. The uncertainty plays an important role in the characterization of the indicator dye used for the routine spectrophotometric pH<span><math><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub></math></span> measurement in seawater. However, it has not been determined previously. We assigned uncertainties to measured input quantities, and propagated them through the calculation steps described in the first part. Both, analytical uncertainty calculation and Monte Carlo simulations have been applied to adequately consider the various steps of the procedure needed to calculate pH<span><math><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub></math></span> values of artificial seawater. The combined standard uncertainty of pH<span><math><mrow><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub><mrow><mo>(</mo><mi>S</mi><mo>,</mo><mi>T</mi><mo>,</mo><mi>b</mi><mrow><mo>(</mo><mtext>TRIS</mtext><mo>)</mo></mrow><mo>=</mo><mn>0</mn><mtext>mol kg</mtext><msup><mrow></mrow><mrow><mi>−1</mi></mrow></msup><mtext>H</mtext><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub><mtext>O</mtext><mo>)</mo></mrow></mrow></math></span> for artificial seawater/TRIS buffers was 0.0011 over the practical salinity range 5 to 40 and temperature range 5<!--> <!-->°C to 40<!--> <!-->°C. This uncertainty can now be used to determine, the uncertainties of the characterization of the indicator dye used for seawater pH<span><math><msub><mrow></mrow><mrow><mtext>T</mtext></mrow></msub></math></span> measurements.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104573"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145362816","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}

{"title":"Nickel and its isotope in response to differential manganese minerals accumulation in Northwest Pacific sediments","authors":"Hengchao Xu ,&nbsp;Xiaotong Peng ,&nbsp;Shui-Jiong Wang ,&nbsp;Shuangquan Liu ,&nbsp;Jiwei Li ,&nbsp;Hao Yang","doi":"10.1016/j.marchem.2025.104554","DOIUrl":"10.1016/j.marchem.2025.104554","url":null,"abstract":"<div><div>Nickel (Ni) is a biologically essential element in marine systems, yet its oceanic sources and sinks remain incompletely quantified. Micro manganese nodules (MMNs) and particles (MMPs) in marine sediment are major authigenic phase that scavenge critical metals though adsorption or incorporation. The accumulation of these minerals depends strongly on the seawater conditions and diagenetic processes within the sediments. Despite their significance, the influence of different manganese phase on the cycling of polymetallic elements-particularly Ni and its isotopes-has received little attention. This study analyzed MMPs bearing sediments, MMNs, and MMN bearing sediments from the Northwest Pacific Ocean to characterize their geochemical and Ni isotopic signatures. In core JL190, MMNs display Mn/Fe ratio and trace element patterns typical of suboxic-oxic diagenesis. Across all three cores, Ni concentrations track Mn accumulation closely, as shown by strong Mn/Al–Ni/Al correlations. However, core TS01-B10 from the Mariana Trench, which contains diatom-rich clay, yields weaker correlations than the two Philippine Sea cores. Despite these differences, bulk sediment δ⁶⁰Ni values remain light (0.01–0.79 ‰, median 0.27 ‰), consistent with most pelagic sediments. In core B10, declining δ⁶⁰Ni alongside rising Mn/Al ratios imply preferential adsorption of lighter Ni isotopes. In contrast, JL189 show simultaneous increase in Mn/Al and δ⁶⁰Ni, suggesting porewater exchange and isotope fractionation on existing Mn oxides. The heavier Ni isotopic signature in diagenetic MMNs relative to bulk sediments likely reflects prolonged porewater interaction, preserving the porwater's isotopic signature. These results provide the first δ⁶⁰Ni data for MMNs and elucidate their role as Ni carriers. These findings highlight the importance of authigenic Mn oxides in influencing the benthic flux of heavier Ni isotopes, which contributes to balancing the oceanic Ni budget.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104554"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145010744","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}

{"title":"Enhanced microbial consumption of carbon-rich marine organic matter at experimentally elevated temperatures dictated by substrate C:N:P stoichiometry","authors":"Sarah M. Benson ,&nbsp;Robert T. Letscher","doi":"10.1016/j.marchem.2025.104555","DOIUrl":"10.1016/j.marchem.2025.104555","url":null,"abstract":"<div><div>Marine microbes are vital to oceanic ecosystems and influence the global climate through their paramount role in Earth's biogeochemical cycles. With this intricate role in ecosystems, it is important to understand the effect of increasing ocean temperatures on the cycling of organic matter (OM), which is hypothesized to contribute a positive feedback to future warming via an acceleration in microbial respiration of OM to CO₂. We experimentally investigated the temperature sensitivity of microbial consumption of marine particulate OM (POM) focused in the rapidly warming Gulf of Maine during the 2019 and 2020 fall phytoplankton bloom. The overall rate and quantity of microbial POM (C, N, and P pools) consumption at in situ versus elevated temperatures were quantified within bottle incubations over the course of two weeks. POM incubated at warmer temperatures (+5 to 6 °C) was generally consumed at a faster rate with an overall larger quantity consumed compared to cooler temperatures (12 to 14 °C). Significant interannual variability in consumption rates and temperature sensitivity (Q₁₀ parameter) across elemental pools was found and linked to the initial POM C:N:P stoichiometry. More nitrogen-rich POM was preferentially consumed at in situ temperatures, whereas carbon-rich POM, likely containing a terrigenous component, was preferentially consumed at warmer experimental temperatures. The empirically estimated temperature sensitivity (Q₁₀) ranged from 2.7 to 3.4 in 2019 versus 1.0–1.2 in 2020, variable between and amongst POM elemental pools, suggesting both temperature and organic matter substrate stoichiometry (composition) play an important role in dictating the microbial POM remineralization response to warming ocean temperatures.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104555"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019275","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}

{"title":"Unraveling sedimentary organic matter in the Oiapoque estuarine-marine ecosystem: Insights from elemental composition and isotopic fingerprints on the Amazon coast","authors":"Yasmym Schütz de Vincenzi Weirich ,&nbsp;Carlos Eduardo de Rezende ,&nbsp;Fernanda Maria de Souza ,&nbsp;Valdenira Ferreira dos Santos ,&nbsp;César C. Martins","doi":"10.1016/j.marchem.2025.104565","DOIUrl":"10.1016/j.marchem.2025.104565","url":null,"abstract":"<div><div>The Oiapoque River estuary, located on the border between Brazil and French Guiana, is an understudied Amazon region characterized by intense discharge of fluvial sediment and terrestrial organic matter (OM). Influenced by environmental factors such as temperature, salinity, tides, and currents, the sedimentary OM composition reflects both autochthonous production and adjacent land biomass. This study aimed to identify and differentiate primary sources of sedimentary OM in the Amazon coastal zone using geochemical parameters such as total organic carbon (TOC), total nitrogen (TN), their relative atomic ratio (expressed as C/N), and carbon and nitrogen isotopic ratios (δ¹³C and δ¹⁵N). Two surface sediment sampling campaigns were conducted in 2018 during the wet and dry seasons. The sediments showed a strong correlation between TOC and TN across both campaigns (R² = 0.98 and 0.94); however, results suggested the contribution of inorganic nitrogen forms (e.g., NH₄⁺). The C/N ratio indicated predominant OM from terrigenous input (∼24) at upstream sites and marine input (∼5 and ∼ 9) at downstream ones. The δ¹³C analysis revealed low variability along the estuary, with values around −27 ‰ upstream and near the mouth (typical of land or C3 plant contributions), intermediate values around −24 ‰ in the central portion (mixed sources), and higher values around −22 ‰ near the mouth (marine inputs). The δ¹⁵N values (∼3 ‰) were primarily found in the inner region, at the center of the estuary, and near the mouth where river discharges occur, associated with terrestrial plants. The elemental and isotopic composition of the sedimentary OM indicates a predominance of terrigenous OM, particularly near areas influenced by the Uáça and Ouanary rivers, reflecting land use and human occupation. Estuarine dynamics, influenced by rainfall and tidal currents, affect the distribution of marine inputs and the mixture of allochthonous and autochthonous sources throughout the estuary.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"273 ","pages":"Article 104565"},"PeriodicalIF":2.5,"publicationDate":"2025-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145096881","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}