Marine Chemistry最新文献

{"title":"Surface macro- and micro-nutrients within the Copper River plume region respond to along-shore winds","authors":"E.L.S. Ortega,&nbsp;I. Reister,&nbsp;S.L. Danielson,&nbsp;A.M. Aguilar-Islas","doi":"10.1016/j.marchem.2025.104508","DOIUrl":"10.1016/j.marchem.2025.104508","url":null,"abstract":"<div><div>The Copper River is a major source of freshwater to the Northern Gulf of Alaska (NGA) shelf with a seasonal cycle that reaches peak discharge in summer. This glacially-fed river also provides a large input of dissolved chemicals to the NGA, and because of its large particle load, it impacts the distribution of particle-reactive elements. Summertime sampling of shelf water properties was carried out within the Copper River plume region during two years: first during a period of upwelling-favorable winds and higher river discharge (4–7 July 2019) and later during lower river discharge and more typical downwelling conditions (11–13 July 2020). Although these wind conditions were observed in separate years, both can occur over the course of a single summer. We found that the export of most nutrients to surface shelf waters was enhanced under upwelling-favorable winds accompanied by higher river discharge compared to downwelling conditions and lower discharge. For example, greater cross-shelf plume transport in 2019 resulted in higher mid-shelf surface inventories for nitrate + nitrite (N + N), silicic acid (H₄SiO₄), phosphate (PO₄³⁻), dissolved Fe (dFe), and dissolved Cu (dCu) compared to 2020. Entrainment of relatively macronutrient-rich subsurface waters under upwelling conditions may also have contributed to the enhancement of these mid-shelf nutrient inventories. The observed high N:P ratios in plume waters were likely driven by the scavenging of P within particle-laden plume waters. Similarly, we observed lower than expected [dFe] (1.58 to 6.12 nM) in particle-laden plume waters, likely a result of enhanced scavenging combined with low concentrations of dissolved Fe-binding ligands. Although dNi and dZn have a river source, we observed lower concentrations in surface shelf waters under upwelling conditions, suggesting enhanced dilution by relatively micronutrient-poor subsurface waters. Results highlight the influence of sub-seasonal variations in atmospheric forcing on nutrient distributions and suggest that this forcing also impacts the location and timing of primary production hotspots during summer, adding to the ecological mosaic of the NGA across a range of temporal and spatial scales.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104508"},"PeriodicalIF":3.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143510835","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}

{"title":"Dissolved iron release by sediment and dust particles in Antarctic seawater greater than glacial flour and sea-ice particles","authors":"Matthew Corkill ,&nbsp;Klaus Martin Meiners ,&nbsp;Pat Wongpan ,&nbsp;Pier van der Merwe ,&nbsp;Layla Creac'h ,&nbsp;Sandrin Feig ,&nbsp;Talitha Nelson ,&nbsp;Abigail Jessica Rose Smith ,&nbsp;Ashley T. Townsend ,&nbsp;Samantha Twiname ,&nbsp;Delphine Lannuzel","doi":"10.1016/j.marchem.2025.104509","DOIUrl":"10.1016/j.marchem.2025.104509","url":null,"abstract":"<div><div>Primary productivity by phytoplankton in the Southern Ocean can be limited by low iron concentrations. Iron limitation in the surface ocean around Antarctica may be alleviated by particle dissolution of dust from exposed rock, glacial flour, resuspended marine sediment, and sea ice. Ligands, which are ubiquitous in seawater, chelate some metals and keep them in solution. Ligands are thereby thought to increase metal solubility, including iron. Leaching studies of Antarctic particles from various sources are rare but important due to observed and predicted changes occurring around Antarctica, e.g., changes in sea ice and ice-free areas on the continent. Here, we quantified the solubility of iron in different particle types using vertical flow-through leaching experiments that simulated sinking through the water column and ran for 78 min of flow at 4 °C under trace metal-clean conditions. Both unaltered and ultraviolet-irradiated seawater leaching solution treatments were used to test the effect of organic ligands on iron dissolution, which was found to be non-significant. Sediment and dust released the most dissolved iron to seawater, followed by glacial flour, and then sea-ice particles (9.00 ± 9.92 × 10⁻² and 3.18 ± 3.79 × 10⁻², 1.97 ± 1.79 × 10⁻⁴, 1.37 ± 0.90 × 10⁻⁹ g DFe/100 g material, respectively). We discuss these laboratory results in relation to particle availability and how this may affect the supply of dissolved iron to Antarctic surface waters.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104509"},"PeriodicalIF":3.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143510834","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}

{"title":"Comparative study of dissolved copper speciation using DGT and CLE-AdSV in a contaminated urban river estuary and marina","authors":"Billie G.B. Benedict ,&nbsp;Rebecca Zitoun ,&nbsp;Keith A. Hunter ,&nbsp;Sylvia G. Sander","doi":"10.1016/j.marchem.2025.104500","DOIUrl":"10.1016/j.marchem.2025.104500","url":null,"abstract":"<div><div>A comprehensive study was conducted in a river estuary and marina in Auckland, New Zealand, to examine the <em>in-situ</em> speciation of copper (Cu) complexes across freshwater, estuarine, and marine environments using the diffusive gradient in thin films (DGT) technique. The study employed both open-pore (OP) and restrictive-pore (RP) diffusive gels of varying thicknesses to assess the effectiveness of DGT hydrogels and the role of the apparent diffusive boundary layer (ADBL) in determining the lability of Cu complexes in natural waters. The DGT findings were compared with results from competing ligand exchange–adsorptive stripping voltammetry (CLE-AdSV) and a speciation prediction model (WHAM/Model-VII). The study highlighted the critical importance of accounting for the ADBL, as its exclusion led to an average underestimation of Cu-complex lability by approximately 50 %. Given the minimal difference in outcomes between DGT-OP and DGT-RP, the use of standard DGT-OP is recommended. Further analysis revealed a strong correlation between DGT-labile Cu (CuDGT-lab), the weaker Cu-L₂ complexes detected by CLE-AdSV, and the inorganic Cu species predicted by WHAM/Model-VII, the latter two based on discrete samples. A strong relationship was also noted between Cu_DGT-lab and the inorganic Cu measured by CLE-AdSV. The study provided compelling evidence that the <em>in-situ</em> ligand pool consists of a mixture of terrestrial humic substances and marine-derived organic ligands. These marine ligands form highly stable Cu-L₁ complexes along the salinity gradient, which were mostly DGT-inert. The DGT results indicated that the lability of <em>in-situ</em> Cu complexes decreased with increasing salinity, with over 60 % of Cu in freshwater being DGT-labile. Overall, the study demonstrates that the DGT technique is a robust and straightforward method for environmental monitoring and risk assessment across diverse physico-chemical water conditions.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"270 ","pages":"Article 104500"},"PeriodicalIF":3.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143508084","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}

{"title":"Excess alkalinity and its impacts on pCO2 estimation in coastal and estuarine waters of the Yellow Sea","authors":"Young Ho Ko ,&nbsp;Seung-Hee Shin ,&nbsp;Seong-Gil Kim ,&nbsp;Mi-Ok Park ,&nbsp;Min-Woo Seok ,&nbsp;Min-Soo Kim ,&nbsp;Kitack Lee ,&nbsp;Tae-Wook Kim","doi":"10.1016/j.marchem.2025.104499","DOIUrl":"10.1016/j.marchem.2025.104499","url":null,"abstract":"<div><div>Excess alkalinity (TA_EX) represents an uncharacterized component of total alkalinity (TA), which can introduce significant uncertainty in the estimation of other carbonate parameters. This effect is particularly pronounced in productive coastal regions, where the use of measured TA as an input parameter may lead to inaccurate assessment. In this study, we evaluated the seasonal variability of TA_EX along the western coast of South Korea by applying an overdetermination method, which allows for the quantification of discrepancies (i.e., TA_EX) between measured TA and values calculated from pH and dissolved inorganic carbon (DIC). Samples with salinity below 20 were excluded due to difficulties in accurately quantifying uncertainties in TA_EX calculations, which increase significantly below this threshold. Elevated TA_EX concentrations were found in waters with salinity below 25, with some instances exhibiting TA_EX values reaching up to 50 μmol kg⁻¹, suggesting riverine influence. Additionally, elevated TA_EX values (&gt; 20 μmol kg⁻¹) were also observed in locations markedly undersaturated with respect to atmospheric CO₂, indicating contributions from in-situ biological production. The high TA_EX values associated with increased water transparency during autumn and winter months suggested that light penetration may significantly enhance biological activity, subsequently increasing TA_EX levels. These findings highlight the importance of riverine inputs and biological processes in shaping the spatial and temporal distribution of TA_EX. In the study area, TA_EX should be accounted for in seawater partial pressure of CO₂ (<em>p</em>CO₂) calculations using the DIC–TA pair, as TA_EX significantly influences these calculations compared to the pH–TA and pH–DIC pair.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104499"},"PeriodicalIF":3.0,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427906","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":"Achieving measurement comparability in mercury speciation analysis in seawater: Key requirements and best practices","authors":"Igor Živković ,&nbsp;Lars-Eric Heimbürger-Boavida ,&nbsp;Mariia V. Petrova ,&nbsp;Aurélie Dufour ,&nbsp;Ermira Begu ,&nbsp;Milena Horvat","doi":"10.1016/j.marchem.2025.104498","DOIUrl":"10.1016/j.marchem.2025.104498","url":null,"abstract":"<div><div>The comparability of measurement results is an important issue in contemporary mercury (Hg) speciation in seawater. Sampling campaigns must be properly designed to determine significant differences on spatial and temporal scales, considering two major parameters: the variability of expected data at a given sampling point/transect and variability in the results due to the intrinsic properties of specific analytical methods, particularly the measurement uncertainty. This study assessed the required sample size, considering several aspects of data variability when determining total Hg, dissolved gaseous Hg, and methylated Hg species in seawater. The required sample sizes were calculated using (1) the measurement uncertainty of a single-laboratory measurement of analytical methods used; (2) performance of the laboratories in interlaboratory comparison exercises; and (3) natural variability in Hg species/fractions in a selected case study in the Central Adriatic Sea. It was shown that the measurement uncertainty of a particular method and interlaboratory variability among laboratories have significant influence on data interpretation in case natural variability of Hg fractions is relatively small, such as for example the open seawater depth profiles. In contrary, in areas with large natural variability of Hg contractions, such as coastal and contaminated sites, their influence on data interpretation is negligible. The present paper introduces the importance of proper estimation of measurement uncertainty in international programs, such as GEOTRACES, where data comparability is of fundamental importance to assess temporal and spatial trends of Hg measurements in the marine environment.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104498"},"PeriodicalIF":3.0,"publicationDate":"2025-02-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143350669","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}

{"title":"Physical-biological processes regulating summer sea-air CO2 exchanges along the Drake Passage and northern Antarctic Peninsula","authors":"Rodrigo Kerr ,&nbsp;Thiago Monteiro ,&nbsp;Matheus S. Batista ,&nbsp;Brendon Yuri Damini","doi":"10.1016/j.marchem.2025.104497","DOIUrl":"10.1016/j.marchem.2025.104497","url":null,"abstract":"<div><div>We determined the sea-air carbon dioxide (CO₂) exchanges and investigated the main physical-biological processes responsible for regulating the sea surface partial pressure of CO₂. This was done through the analysis of continuous and discrete measurements of oceanographic and atmospheric variables measured during the NAUTILUS V cruise (January 2019) crossing the main fronts along the Drake Passage and several distinct biogeochemical provinces along the northern Antarctic Peninsula. The main findings indicated that the Drake Passage acted as a weak net CO₂ outgassing area (∼0.1 mmol m⁻² d⁻¹), although contrasting regions with close sea-air CO₂ fluxes magnitudes of ∼3 mmol m⁻² d⁻¹ were identified north (a net CO₂ sink zone regulated by net photosynthesis) and south (a net CO₂ source zone regulated by net respiration) of the Polar Front. On the other hand, the northern Antarctic Peninsula areas demonstrated a more heterogeneous sea-air CO₂ exchanges behaviour varying from moderate net CO₂ outgassing of ∼1.3 mmol m⁻² d⁻¹ (Bransfield Strait, western Antarctic Peninsula and Weddell Sea continental shelves) to a moderate (∼ −2.4 mmol m⁻² d⁻¹) or weak (∼ −0.1 mmol m⁻² d⁻¹) net CO₂ ingassing in Antarctic Sound surroundings and Gerlache Strait, respectively. It is interesting to note that a huge intensification of the net CO₂ outgassing of ∼5 mmol m⁻² d⁻¹ was identified in the area under the influence of the Antarctic Slope Front bifurcation eddy south of Clarence Island. The CO₂ outgassing is expected in this stationary and anticyclonic feature, but its magnitude was ∼75 % higher than the known estimate, which was associated with strengthen winds and eddy dynamics. Net respiration was the leading biological process occurring in the study area, except north of Polar Front where net photosynthesis prevailed. The patchy distribution of sea-air CO₂ exchanges behaviour along the Drake Passage and northern Antarctic Peninsula reinforced the needs for better understanding and focus on finer resolution of the CO₂ chemistry and processes at regional and local investigations, especially in a region suffering with multiple climate stressors, located in a transition zone of warm and cold environments, and key to connect the Southern Ocean ecosystems in a circumpolar way.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104497"},"PeriodicalIF":3.0,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143222704","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":"Vertical biochemical composition of particulate organic matter in the Seychelles-Chagos Thermocline Ridge (SCTR), southwestern Indian Ocean","authors":"Sanghoon Park ,&nbsp;Yejin Kim ,&nbsp;Jaesoon Kim ,&nbsp;Jae Ha Jeon ,&nbsp;Inhee Lee ,&nbsp;Doshik Hahm ,&nbsp;Dong-Jin Kang ,&nbsp;Sang Heon Lee","doi":"10.1016/j.marchem.2025.104496","DOIUrl":"10.1016/j.marchem.2025.104496","url":null,"abstract":"<div><div>The Seychelles-Chagos Thermocline Ridge (SCTR) in the southwestern Indian Ocean is characterized by upwelling-driven nutrient enrichment and enhanced biological activity compared to adjacent non-SCTR regions. This study investigated the vertical distribution and biochemical composition of particulate organic matter (POM) within these contrasting environments. The SCTR featured a shallower thermocline and cooler sea surface temperatures, indicative of upwelling, which correlated with significantly higher chlorophyll-<em>a</em> concentrations (<em>t</em>-test, <em>p</em> &lt; 0.05). A notable dominance of micro-sized phytoplankton was observed in the SCTR, contributing 13.6 ± 3.0 % of the total phytoplankton biomass, compared to 5.6 ± 1.6 % in the non-SCTR. CHEMTAX analysis revealed distinct phytoplankton communities, with diatoms being approximately four times more abundant in the SCTR (16.5 ± 4.5 %) than in the non-SCTR (4.2 ± 1.2 %). Meanwhile, <em>Prochlorococcus</em> dominated both regions but contributed less in the SCTR (25.2 ± 3.9 %) than non-SCTR (46.8 ± 7.1 %). The biological macromolecular composition of POM showed clear regional differences, with lipid concentrations in the SCTR's photic layer significantly higher (61.3 μg L⁻¹) than in the non-SCTR (23.4 μg L⁻¹). Total biological macromolecule concentrations in the SCTR's photic zone was more than double that of the non-SCTR (96.3 μg L⁻¹ vs. 40.9 μg L⁻¹), reflecting enhanced biological productivity. Elevated macromolecule concentrations were also detected in the aphotic layer of the SCTR. Notably, the less pronounced decline in the protein-to-carbohydrate ratio from photic to aphotic layers in the SCTR suggests that POM sinking to the deep ocean in this region is relatively fresher and less degraded, indicating a more efficient biological carbon pump and enhanced potential for carbon sequestration. These findings highlight the SCTR as a key region of elevated biological productivity and distinct environmental mechanisms driving biogeochemical cycling, providing critical insights into organic matter preservation and carbon export processes in tropical upwelling systems and their role in global marine ecosystems.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104496"},"PeriodicalIF":3.0,"publicationDate":"2025-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092363","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":"Influence of the Mackenzie River plume dispersal on the dissolved barium concentrations in the upper Canada Basin waters","authors":"M. Gamrani ,&nbsp;S. Zimmermann ,&nbsp;W.J. Williams ,&nbsp;C. Guéguen","doi":"10.1016/j.marchem.2025.104495","DOIUrl":"10.1016/j.marchem.2025.104495","url":null,"abstract":"<div><div>Dissolved barium has been shown to have the potential to track river runoff in marine waters. In this study, the distribution of dissolved barium was determined in the upper 450 m waters of the Canada Basin along the Joint Ocean Ice Study 140°W transect in August/September 2019–2021. In these highly stratified Canada Basin waters, the dBa concentrations increased from 42.51 nmol kg⁻¹ in the Atlantic waters to 128.91 nmol kg⁻¹ in the polar mixed layer. The dispersal of Ba-rich surface waters found over the slope and outer shelves is attributed to the Mackenzie River plume. These waters were either confined nearshore with northwest winds (2019 and 2020) or entrained into the Beaufort Gyre interior under easterly winds (2021). In the subsurface layers, the vertical variation in barium concentration in the Pacific Winter Water and Atlantic Halocline waters showed evidence of mixing. Dissolved Ba dynamics provide a window into the complex interplay between physical, biological, and chemical processes in Arctic waters, making it a valuable tracer for understanding ocean circulation, nutrient transport, and ecosystem functioning in the rapidly changing Arctic region.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104495"},"PeriodicalIF":3.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143092362","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}

{"title":"Carbonate and isotope chemistry in the outer Yellow River Estuary and beyond: Effects of flood and cold wave on interannnual variations in coastal stable carbon isotope","authors":"Zi-chen Liu ,&nbsp;Wei-dong Zhai","doi":"10.1016/j.marchem.2025.104486","DOIUrl":"10.1016/j.marchem.2025.104486","url":null,"abstract":"<div><div>The stable carbon isotope composition (δ¹³C) of dissolved inorganic carbon (DIC) traces many biogeochemical processes in large river estuaries and adjacent coastal seas. To better understand the dynamics of DIC and its isotope composition (δ¹³C_DIC) responding to floods and cold waves in the outer Yellow River Estuary and adjacent Laizhou Bay and central Bohai Sea, seven field surveys were conducted in summer and autumn of 2021 and 2022. Interannual variations in carbonate chemistry and δ¹³C_DIC were investigated. In the outer Yellow River Estuary, distributions of DIC and δ¹³C_DIC had little difference before and after an artificial flood, although water mixing dominates spatial variations of carbonate chemistry and stable isotopic composition in summer. The excess carbonate relative to a simplified two-endmember water-mixing was likely caused by the release of bicarbonate ions from the sediment and/or coastal wetlands over the Yellow River Estuary. In contrast, metabolic processes significantly affected the changes in DIC and δ¹³C_DIC in the adjacent central Bohai Sea. In 2022, δ¹³C_DIC in Laizhou Bay was lighter than that in 2021, while δ¹³C_DIC in the central Bohai Sea was heavier than that in 2021. This can be attributed to the wintertime super cold waves at the beginning of 2021 that affects the Bohai Sea and an unusual autumnal flood in 2021 that affects the Laizhou Bay. Both events make δ¹³C_DIC lighter (over half a year later) at given salinity with negligible changes in DIC concentrations. Our results also revealed that the lower reach of the Yellow River Estuary was a source of atmospheric CO₂ in summer. Although the quick transport of terrestrial nutrients caused by the artificial water-sediment regulation did not promote net community production soon, likely owing to high turbidity and relatively short residence time before our July cruises, the unusual autumnal flood likely transported much more nutrients into the Estuary and triggered algal blooms and turned it into a sink area of the atmospheric CO₂ in autumn. These findings provide fundamental information and new insights that support better understanding the complexity of the carbonate chemistry and isotope geochemistry dynamics in this ocean margin.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"269 ","pages":"Article 104486"},"PeriodicalIF":3.0,"publicationDate":"2025-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143128304","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":"Advanced deep learning technique for estimating global surface ocean calcium carbonate saturation (Ωcal)","authors":"Ibrahim Shaik ,&nbsp;P.V. Nagamani ,&nbsp;Sandesh Yadav ,&nbsp;Yash Manmode ,&nbsp;G. Srinivasa Rao","doi":"10.1016/j.marchem.2024.104483","DOIUrl":"10.1016/j.marchem.2024.104483","url":null,"abstract":"<div><div>The accurate estimation of surface ocean calcium carbonate saturation (Ω_<em>cal</em>) is crucial for understanding the impacts of ocean acidification (OA) on marine ecosystems, particularly for calcifying organisms. This study investigates the estimation of global surface ocean Ω_<em>cal</em> using machine learning (ML) models and satellite-derived data. Three ML models such as feed-forward neural networks (FFNN), random forests (RF), and Tabularnet (TabNet) were employed to estimate Ω_<em>cal</em>, utilizing in-situ and satellite measurements of sea surface temperature (SST), sea surface salinity (SSS), and Chlorophyll-a concentration (Chla). Among these, the TabNet model exhibited superior performance, with a root-mean-square error (RMSE) of 0.39, mean relative error (MRE) of 0.019, mean normalized bias (MNB) of 0.0058 and coefficient of determination (R²) of 0.96. SST showed a strong positive correlation with Ω_<em>cal</em> (<em>r</em> = 0.95), while SSS and Chla exhibited moderate positive (<em>r</em> = 0.49) and weak negative (<em>r</em> = −0.27) correlations, respectively. The study revealed significant spatiotemporal variability in Ω_<em>cal</em>, driven by seasonal changes and ocean circulation patterns. Sensitivity analysis highlighted the robustness of the TabNet model, maintaining high predictive capability despite variations in SST, SSS, and Chla. The TabNet model high accuracy provides a valuable tool for monitoring and forecasting changes in ocean chemistry, informing conservation efforts and policy-making. This study emphasizes the importance of advanced ML models in marine science and their potential for enhancing our understanding of global oceanic processes.</div></div>","PeriodicalId":18219,"journal":{"name":"Marine Chemistry","volume":"268 ","pages":"Article 104483"},"PeriodicalIF":3.0,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143178166","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}