Pub Date : 2025-07-28DOI: 10.1016/j.dsr2.2025.105524
Kamalodin Kor, Hamid Ershadifar, Abolfazl Saleh
Phosphorus is a vital macronutrient that regulates marine biogeochemical cycles and ecosystem production. This is the first thorough investigation of phosphorus geochemistry in surface sediments of the Persian Gulf (PG) and the Gulf of Oman (GO), quantifying its fractions, potential ecological risks and potential bioavailability. Five forms of phosphorus were quantified using a sequential extraction technique. TP ranged from 636.0 to 1341.3 μg/g and 599.6–1354.1 μg/g in the summer and winter, respectively. Calcium-bound phosphorus (Ca-P) and detrital phosphorus (De-P) were the dominant forms of TP in surface sediments, with following descending order to other forms: O-P > Fe-P > Ad-P. Inorganic phosphorus (P) comprised over 83 % of the TP in the study area's sediments, indicating a low contribution from organic phosphorus. A mean of 29.1 % and 25.3 % of TP was found to be bioavailable phosphorus during the summer and winter sampling periods, respectively. Phosphorus pollution index exceeded one at most stations in both seasons, indicating sediment phosphorus pollution. Effective management of phosphorus inputs and maintenance of phosphorus balance are recommended to prevent eutrophication and HABs in the PG and GO.
{"title":"Sedimentary phosphorus in the Persian Gulf and the Gulf of Oman: Geochemical fractionation, seasonal variations, potential bioavailability, and ecological risk","authors":"Kamalodin Kor, Hamid Ershadifar, Abolfazl Saleh","doi":"10.1016/j.dsr2.2025.105524","DOIUrl":"10.1016/j.dsr2.2025.105524","url":null,"abstract":"<div><div>Phosphorus is a vital macronutrient that regulates marine biogeochemical cycles and ecosystem production. This is the first thorough investigation of phosphorus geochemistry in surface sediments of the Persian Gulf (PG) and the Gulf of Oman (GO), quantifying its fractions, potential ecological risks and potential bioavailability. Five forms of phosphorus were quantified using a sequential extraction technique. TP ranged from 636.0 to 1341.3 μg/g and 599.6–1354.1 μg/g in the summer and winter, respectively. Calcium-bound phosphorus (Ca-P) and detrital phosphorus (De-P) were the dominant forms of TP in surface sediments, with following descending order to other forms: O-P > Fe-P > Ad-P. Inorganic phosphorus (P) comprised over 83 % of the TP in the study area's sediments, indicating a low contribution from organic phosphorus. A mean of 29.1 % and 25.3 % of TP was found to be bioavailable phosphorus during the summer and winter sampling periods, respectively. Phosphorus pollution index exceeded one at most stations in both seasons, indicating sediment phosphorus pollution. Effective management of phosphorus inputs and maintenance of phosphorus balance are recommended to prevent eutrophication and HABs in the PG and GO.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105524"},"PeriodicalIF":3.0,"publicationDate":"2025-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739307","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}
Despite the relatively low probability of tsunamis in the Persian Gulf, the region's strategic importance necessitate a comprehensive risk assessment. This study evaluates both near-field and far-field tsunami sources affecting the Persian Gulf using numerical modeling based on nonlinear shallow-water equations. The Kazerun Fault system, recently identified as extending into the Gulf, is analyzed as a local tsunami source, while the maximum probable earthquake of the Makran subduction zone is considered the primary distant threat. Bathymetric influences are assessed by simulating near-field scenarios with both actual depth data and artificially deepened basin configurations.
Simulations reveal that for an Mw 7.9 earthquake, pure thrust faulting along the Kazerun Fault generates a tsunami with wave heights of up to 3 m, whereas purely strike-slip mechanisms yield negligible amplitudes (<0.3 m). While most coastal zones under actual bathymetry exhibit lower wave heights than deepened scenarios, localized areas show comparable or greater amplitudes. These findings challenge the assumption that shallow bathymetry inherently limits tsunami impacts in the Persian Gulf, demonstrating that depth-related attenuation alone cannot ensure immunity. Far-field modeling indicates that, despite precise modeling using nested bathymetry grids and accounting for non-uniform slip distributions to capture worst-case scenarios, Makran tsunami waves entering the Persian Gulf remain below 0.5 m, aligning with prior studies. This suggests that the Gulf's interior shores are largely protected against tsunamis originating from the Makran subduction zone. However, this work underscores the necessity of reevaluating local tsunami sources, particularly the offshore segments of the Kazerun Fault.
{"title":"Tsunami hazard assessment in the Persian Gulf: Evaluating near-field and far-field sources","authors":"Ehsan Rastgoftar, Seyed Masoud Mahmoudof, Jafar Azizpour, Mohammad Hossein Kazeminezhad, Mahmood Reza Akbarpour Jannat","doi":"10.1016/j.dsr2.2025.105519","DOIUrl":"10.1016/j.dsr2.2025.105519","url":null,"abstract":"<div><div>Despite the relatively low probability of tsunamis in the Persian Gulf, the region's strategic importance necessitate a comprehensive risk assessment. This study evaluates both near-field and far-field tsunami sources affecting the Persian Gulf using numerical modeling based on nonlinear shallow-water equations. The Kazerun Fault system, recently identified as extending into the Gulf, is analyzed as a local tsunami source, while the maximum probable earthquake of the Makran subduction zone is considered the primary distant threat. Bathymetric influences are assessed by simulating near-field scenarios with both actual depth data and artificially deepened basin configurations.</div><div>Simulations reveal that for an Mw 7.9 earthquake, pure thrust faulting along the Kazerun Fault generates a tsunami with wave heights of up to 3 m, whereas purely strike-slip mechanisms yield negligible amplitudes (<0.3 m). While most coastal zones under actual bathymetry exhibit lower wave heights than deepened scenarios, localized areas show comparable or greater amplitudes. These findings challenge the assumption that shallow bathymetry inherently limits tsunami impacts in the Persian Gulf, demonstrating that depth-related attenuation alone cannot ensure immunity. Far-field modeling indicates that, despite precise modeling using nested bathymetry grids and accounting for non-uniform slip distributions to capture worst-case scenarios, Makran tsunami waves entering the Persian Gulf remain below 0.5 m, aligning with prior studies. This suggests that the Gulf's interior shores are largely protected against tsunamis originating from the Makran subduction zone. However, this work underscores the necessity of reevaluating local tsunami sources, particularly the offshore segments of the Kazerun Fault.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105519"},"PeriodicalIF":3.0,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144771647","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}
The Persian Gulf is a shallow, semi-enclosed marginal sea basin characterized by a distinct geological history, harsh environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Brachyuran crabs constitute a diverse component of the Persian Gulf fauna, distributed unevenly in the various habitats. The biodiversity and regional biogeographic data for the Persian Gulf and Gulf of Oman crab fauna are still poorly understood and rarely incorporated into global biodiversity databases. Here, we have addressed this shortfall by mapping the regional distributions of 262 species of brachyuran crabs in the Persian Gulf and the Gulf of Oman and incorporating the data with open-access biodiversity databases. We used QGIS 3.24.3 and R 4.2.2 packages for mapping and analyzing the distribution records. Our analyses revealed that the Persian Gulf exhibits proportionally higher diversity metrics than the Gulf of Oman for brachyuran crabs. Cluster analysis revealed that the Iranian coasts are relatively differentiated from the Arabian coasts of the Persian Gulf and the Gulf of Oman. The distribution and alpha species richness patterns per hexagonal cells were higher in the Iranian coastal waters, particularly around the Strait of Hormuz and Qeshm Island. Furthermore, the distribution and species richness of the Persian Gulf brachyuran crabs were positively correlated with temperature (°C) and calcite (mol.m-3), while negatively correlated with dissolved oxygen (mol.m-3). Although our analyses did not recognize the Persian Gulf as a center of endemism, but highlighted it as an important peripheral region with significant influences on the present-day diversity and distribution of northwestern Indian Ocean brachyuran crabs. We believe that the present results reveal new insights to be considered in conservation actions to protect marine biodiversity in underrepresented and ecologically unique regions such as the Persian Gulf.
{"title":"Species richness patterns of brachyuran crabs in the Persian Gulf and the Gulf of Oman","authors":"Nima Hashemian , Reza Naderloo , Adnan Shahdadi , Hanieh Saeedi","doi":"10.1016/j.dsr2.2025.105508","DOIUrl":"10.1016/j.dsr2.2025.105508","url":null,"abstract":"<div><div>The Persian Gulf is a shallow, semi-enclosed marginal sea basin characterized by a distinct geological history, harsh environmental conditions, and intermittent connection with the Indian Ocean during the Pleistocene glacial periods. Brachyuran crabs constitute a diverse component of the Persian Gulf fauna, distributed unevenly in the various habitats. The biodiversity and regional biogeographic data for the Persian Gulf and Gulf of Oman crab fauna are still poorly understood and rarely incorporated into global biodiversity databases. Here, we have addressed this shortfall by mapping the regional distributions of 262 species of brachyuran crabs in the Persian Gulf and the Gulf of Oman and incorporating the data with open-access biodiversity databases. We used QGIS 3.24.3 and R 4.2.2 packages for mapping and analyzing the distribution records. Our analyses revealed that the Persian Gulf exhibits proportionally higher diversity metrics than the Gulf of Oman for brachyuran crabs. Cluster analysis revealed that the Iranian coasts are relatively differentiated from the Arabian coasts of the Persian Gulf and the Gulf of Oman. The distribution and alpha species richness patterns per hexagonal cells were higher in the Iranian coastal waters, particularly around the Strait of Hormuz and Qeshm Island. Furthermore, the distribution and species richness of the Persian Gulf brachyuran crabs were positively correlated with temperature (°C) and calcite (mol.m-3), while negatively correlated with dissolved oxygen (mol.m-3). Although our analyses did not recognize the Persian Gulf as a center of endemism, but highlighted it as an important peripheral region with significant influences on the present-day diversity and distribution of northwestern Indian Ocean brachyuran crabs. We believe that the present results reveal new insights to be considered in conservation actions to protect marine biodiversity in underrepresented and ecologically unique regions such as the Persian Gulf.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105508"},"PeriodicalIF":3.0,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739308","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 : 2025-07-25DOI: 10.1016/j.dsr2.2025.105523
A.L. Volkova, S.S. Dautov, T.N. Dautova
Data on brittle stars from the Emperor Seamount Chain (ESC) are presented, including their distribution across the seamounts of the region, characteristics of their vertical distributions, biogeographical characters, and dominance in macrobenthic communities. This study is based on the results of work with a collection of more than 100 samples and the analysis of more than 70 h of video material obtained during two expeditions on the R/V Akademik Lavrentyev (2019 and 2021) using the ROV Comanche 18. Representatives of 29 species, 17 families, and 21 genera of the class Ophiuroidea have been identified, and their association with different types of substrate (sandy sediment with silt and outcrops of the underlying rock, solidified lava and rocky bottom) on the ESC have been revealed. Dominant species found on different seamounts are Ophiocreas sp., Ophiocten hastatum, Ophiura leptoctenia, Ophiomusa lymani, Ophiopholis aculeata, Ophiura ooplax. The benthos of the ESC was found to contain a large number of brittle star taxa, which were dominant or significant components of the communities. A correlation between different brittle star taxa and specific substrate types was identified. Due to the spatial extent of the ESC, communities contain groups of brittle stars with very different biogeographical characteristics. The Bray-Curtis similarity analysis confirmed the presence of a biogeographical boundary around 37°N, where the North Pacific ophiuroid set of species intersects with that of Central Pacific origin.
本文介绍了黄帝海底山链（ESC）海蛇尾的分布特征、垂直分布特征、生物地理特征和大型底栖生物群落优势度。这项研究是基于收集了100多个样本的工作结果，并分析了R/V Akademik Lavrentyev（2019年和2021年）使用ROV Comanche 18进行的两次探险中获得的70多个小时的视频材料。目前已鉴定出蛇总纲17科21属29种，并揭示了它们与ESC上不同类型基质（含粉砂和下伏岩石露头的砂质沉积物、凝固熔岩和岩底）的关系。在不同海山上发现的优势种为蛇麻、蛇麻、细纹蛇麻、麻麻、细纹蛇麻、黄纹蛇麻、黄纹蛇麻。ESC底栖生物中含有大量的海蛇尾类群，是群落的优势或重要组成部分。不同的海蛇尾分类群与特定的底物类型之间存在相关性。由于ESC的空间范围，群落中包含了具有非常不同生物地理特征的海蛇尾群落。Bray-Curtis相似性分析证实了在37°N附近存在一个生物地理边界，在那里北太平洋蛇属与中太平洋起源的蛇属相交。
{"title":"Ophiuroidea of the Emperor Seamount Chain – diversity, distribution and biogeography","authors":"A.L. Volkova, S.S. Dautov, T.N. Dautova","doi":"10.1016/j.dsr2.2025.105523","DOIUrl":"10.1016/j.dsr2.2025.105523","url":null,"abstract":"<div><div>Data on brittle stars from the Emperor Seamount Chain (ESC) are presented, including their distribution across the seamounts of the region, characteristics of their vertical distributions, biogeographical characters, and dominance in macrobenthic communities. This study is based on the results of work with a collection of more than 100 samples and the analysis of more than 70 h of video material obtained during two expeditions on the R/V <em>Akademik Lavrentyev</em> (2019 and 2021) using the ROV Comanche 18. Representatives of 29 species, 17 families, and 21 genera of the class Ophiuroidea have been identified, and their association with different types of substrate (sandy sediment with silt and outcrops of the underlying rock, solidified lava and rocky bottom) on the ESC have been revealed. Dominant species found on different seamounts are <em>Ophiocreas</em> sp.<em>, Ophiocten hastatum</em>, <em>Ophiura leptoctenia</em>, <em>Ophiomusa lymani, Ophiopholis aculeata</em>, <em>Ophiura ooplax.</em> The benthos of the ESC was found to contain a large number of brittle star taxa, which were dominant or significant components of the communities. A correlation between different brittle star taxa and specific substrate types was identified. Due to the spatial extent of the ESC, communities contain groups of brittle stars with very different biogeographical characteristics. The Bray-Curtis similarity analysis confirmed the presence of a biogeographical boundary around 37°N, where the North Pacific ophiuroid set of species intersects with that of Central Pacific origin.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105523"},"PeriodicalIF":3.0,"publicationDate":"2025-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739294","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 : 2025-07-22DOI: 10.1016/j.dsr2.2025.105517
Lopamudra Roy , Amit K. Ghosh , Ajoy Kumar Bhaumik
An in-depth analysis on the calcareous nannofossil content in the Miocene to Pleistocene sediments from the offshore of northeast Indian Ocean has been carried out. The sediments of the NGHP core (NGHP-01-17A) drilled at Andaman-Nicobar Basin are characterized by significant biostratigraphically marker/index taxa of calcareous nannofossils. The calcareous nannofossil biohorizons/zones are assignable to NN9─NN19 zones of Martini (1971) that correspond to CNM13─CNPL7 zones of Backman et al. (2012). The significant calcareous nannofossil bio-events indicate an age from late Miocene i.e., Tortonian (9.81 Ma) to early Pleistocene i.e., Gelasian (1.81 Ma) for the studied samples. The calcareous nannofossil assemblages recorded herein are closely comparable to the assemblages described from other deep sea drilling sites (DSDP, ODP and IODP) located at lower mid latitudes. In the context of palaeoecology, the important and dominant calcareous nannofossils include species of Discoaster, Helicosphaera, Reticulofenestra (small < 3 μm), Reticulofenestra (large > 3 μm) and Sphenolithus, whereas, the subdominant species are Calcidiscus leptoporus and Coccolithus pelagicus. Using the significant calcareous nannofossil biohorizons the sedimentation rate from late Miocene (Tortonian) to early Pleistocene (Gelasian) has been reconstructed. The estimated average sedimentation rates during Tortonian and Messinian are ∼208 m/Ma and ∼64 m/Ma respectively. However, the sedimentation rate during the Pliocene substantially declined. During the Pliocene and Pleistocene (Gelasian) the sedimentation rates have been estimated ∼34 m/Ma and ∼14 m/Ma respectively.
{"title":"High resolution Miocene to Pleistocene calcareous nannofossil biostratigraphy from northeast Indian Ocean: A comprehensive analysis on biohorizons, global correlation, palaeogeography, palaeoecology and sedimentation rate","authors":"Lopamudra Roy , Amit K. Ghosh , Ajoy Kumar Bhaumik","doi":"10.1016/j.dsr2.2025.105517","DOIUrl":"10.1016/j.dsr2.2025.105517","url":null,"abstract":"<div><div>An in-depth analysis on the calcareous nannofossil content in the Miocene to Pleistocene sediments from the offshore of northeast Indian Ocean has been carried out. The sediments of the NGHP core (NGHP-01-17A) drilled at Andaman-Nicobar Basin are characterized by significant biostratigraphically marker/index taxa of calcareous nannofossils. The calcareous nannofossil biohorizons/zones are assignable to NN9─NN19 zones of Martini (1971) that correspond to CNM13─CNPL7 zones of Backman et al. (2012). The significant calcareous nannofossil bio-events indicate an age from late Miocene i.e., Tortonian (9.81 Ma) to early Pleistocene i.e., Gelasian (1.81 Ma) for the studied samples. The calcareous nannofossil assemblages recorded herein are closely comparable to the assemblages described from other deep sea drilling sites (DSDP, ODP and IODP) located at lower mid latitudes. In the context of palaeoecology, the important and dominant calcareous nannofossils include species of <em>Discoaster</em>, <em>Helicosphaera</em>, <em>Reticulofenestra</em> (small < 3 μm), <em>Reticulofenestra</em> (large > 3 μm) and <em>Sphenolithus,</em> whereas, the subdominant species are <em>Calcidiscus leptoporus</em> and <em>Coccolithus pelagicus</em>. Using the significant calcareous nannofossil biohorizons the sedimentation rate from late Miocene (Tortonian) to early Pleistocene (Gelasian) has been reconstructed. The estimated average sedimentation rates during Tortonian and Messinian are ∼208 m/Ma and ∼64 m/Ma respectively. However, the sedimentation rate during the Pliocene substantially declined. During the Pliocene and Pleistocene (Gelasian) the sedimentation rates have been estimated ∼34 m/Ma and ∼14 m/Ma respectively.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105517"},"PeriodicalIF":3.0,"publicationDate":"2025-07-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144878599","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}
Carbon is a common element on Earth, found in various molecular forms. However, the excessive release of carbon dioxide (CO2) into the atmosphere from burning fossil fuels is a major concern due to its greenhouse potential. The oceans help remove a significant amount of atmospheric CO2 through organic (Corg) and inorganic carbon (CaCO3) sequestration, burying it in sediments for a long time. The ocean's ability to store carbon varies with time, depending on several factors, making it challenging to predict the future fate of atmospheric CO2. The northeast Indian Ocean is particularly vulnerable to human activities that could alter its potential to store carbon in the bottom sediments. Therefore, it is crucial to understand how carbon burial has changed in this region over time. We provide basin scale changes in carbon burial in the northeast Indian Ocean by using organic carbon (Corg %), calcium carbonate (CaCO3 %), total carbon (TC), organic carbon to nitrogen ratio (Corg/N), stable carbon (δ13C) and, nitrogen (δ15N) isotopic ratio data from a total of 19 cores (3 new and 16 previously published). We report a significant change in carbon burial in both the marginal marine and open ocean regions of the northeast Indian Ocean during glacial-interglacial intervals. Additionally, different regions of the ocean stored varying amounts of carbon, indicating a strong spatial heterogeneity in carbon burial since the last deglaciation. During the last glacial maximum (LGM), sediments' CaCO3 content decreased in the deep sea but increased on the shelf. The opposite was true for Corg burial patterns, with values higher than recent throughout the LGM, and the highest Corg content during LGM. The basin-wide lowest CaCO3 and Corg content was during the Greenlandian and Northgrippian. Marginal seas' carbon burial changes were mainly influenced by monsoon-induced productivity, sedimentation rate, sediment texture, and dissolved oxygen concentration. On the other hand, water mass changes primarily drove carbon burial in deeper regions. The findings will help in assessing the carbon burial potential of this region in the warming world.
{"title":"A large glacial-interglacial shift in carbon burial in the northeast Indian Ocean during the Late Quaternary","authors":"Rajeev Saraswat , Rinu Fathima , Thejasino Suokhrie , Sujata R. Kurtarkar","doi":"10.1016/j.dsr2.2025.105518","DOIUrl":"10.1016/j.dsr2.2025.105518","url":null,"abstract":"<div><div>Carbon is a common element on Earth, found in various molecular forms. However, the excessive release of carbon dioxide (CO<sub>2</sub>) into the atmosphere from burning fossil fuels is a major concern due to its greenhouse potential. The oceans help remove a significant amount of atmospheric CO<sub>2</sub> through organic (C<sub>org</sub>) and inorganic carbon (CaCO<sub>3</sub>) sequestration, burying it in sediments for a long time. The ocean's ability to store carbon varies with time, depending on several factors, making it challenging to predict the future fate of atmospheric CO<sub>2</sub>. The northeast Indian Ocean is particularly vulnerable to human activities that could alter its potential to store carbon in the bottom sediments. Therefore, it is crucial to understand how carbon burial has changed in this region over time. We provide basin scale changes in carbon burial in the northeast Indian Ocean by using organic carbon (C<sub>org</sub> %), calcium carbonate (CaCO<sub>3</sub> %), total carbon (TC), organic carbon to nitrogen ratio (C<sub>org</sub>/N), stable carbon (δ<sup>13</sup>C) and, nitrogen (δ<sup>15</sup>N) isotopic ratio data from a total of 19 cores (3 new and 16 previously published). We report a significant change in carbon burial in both the marginal marine and open ocean regions of the northeast Indian Ocean during glacial-interglacial intervals. Additionally, different regions of the ocean stored varying amounts of carbon, indicating a strong spatial heterogeneity in carbon burial since the last deglaciation. During the last glacial maximum (LGM), sediments' CaCO<sub>3</sub> content decreased in the deep sea but increased on the shelf. The opposite was true for C<sub>org</sub> burial patterns, with values higher than recent throughout the LGM, and the highest C<sub>org</sub> content during LGM. The basin-wide lowest CaCO<sub>3</sub> and C<sub>org</sub> content was during the Greenlandian and Northgrippian. Marginal seas' carbon burial changes were mainly influenced by monsoon-induced productivity, sedimentation rate, sediment texture, and dissolved oxygen concentration. On the other hand, water mass changes primarily drove carbon burial in deeper regions. The findings will help in assessing the carbon burial potential of this region in the warming world.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105518"},"PeriodicalIF":3.0,"publicationDate":"2025-07-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144739306","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 : 2025-07-10DOI: 10.1016/j.dsr2.2025.105507
Pavel E. Mikhailik , Irina A. Vishnevskaya , Liang Yi , Evgeniy V. Mikhailik
We studied the morphology, mineral composition, and chemical composition of ferromanganese (Fe-Mn) crusts from the central segment of the Emperor Chain Guyots (Jingū, Ōjin, and Nintoku). These Fe-Mn crusts are characterized by a 10 Å manganese phase, amalgamated with vernadite (δ-MnO2), exhibiting significant variation in their mineralogical composition when compared to those associated with other Pacific seamounts. Notably, these Co-rich crusts are highly enriched in lead, with concentrations reaching up to 5303 ppm and an average of 3029 ppm. They show elevated levels of molybdenum (up to 1429 ppm, with an average of 879 ppm) and tungsten (up to 287 ppm), approximately double those found in other global ocean regions. A remarkable enrichment of rare earth elements and yttrium (REY) was also observed, with a cumulative level of 5431 ppm. The concentrations of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), and nickel (Ni), in combination with the REY distribution patterns, suggest that these Fe-Mn crusts are primarily of hydrogenic origin. Nonetheless, there is evidence of a hydrothermal contribution, particularly linked to the Late Pliocene volcanic rejuvenation phase (3.97–3.21 million years ago) of the Pacific Plate.
{"title":"Compositional variation and genesis of ferromanganese crusts in the central segment of Emperor Chain Guyots, Pacific Ocean","authors":"Pavel E. Mikhailik , Irina A. Vishnevskaya , Liang Yi , Evgeniy V. Mikhailik","doi":"10.1016/j.dsr2.2025.105507","DOIUrl":"10.1016/j.dsr2.2025.105507","url":null,"abstract":"<div><div>We studied the morphology, mineral composition, and chemical composition of ferromanganese (Fe-Mn) crusts from the central segment of the Emperor Chain Guyots (Jingū, Ōjin, and Nintoku). These Fe-Mn crusts are characterized by a 10 Å manganese phase, amalgamated with vernadite (δ-MnO<sub>2</sub>), exhibiting significant variation in their mineralogical composition when compared to those associated with other Pacific seamounts. Notably, these Co-rich crusts are highly enriched in lead, with concentrations reaching up to 5303 ppm and an average of 3029 ppm. They show elevated levels of molybdenum (up to 1429 ppm, with an average of 879 ppm) and tungsten (up to 287 ppm), approximately double those found in other global ocean regions. A remarkable enrichment of rare earth elements and yttrium (REY) was also observed, with a cumulative level of 5431 ppm. The concentrations of manganese (Mn), iron (Fe), cobalt (Co), copper (Cu), and nickel (Ni), in combination with the REY distribution patterns, suggest that these Fe-Mn crusts are primarily of hydrogenic origin. Nonetheless, there is evidence of a hydrothermal contribution, particularly linked to the Late Pliocene volcanic rejuvenation phase (3.97–3.21 million years ago) of the Pacific Plate.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105507"},"PeriodicalIF":2.3,"publicationDate":"2025-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144632665","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 : 2025-07-06DOI: 10.1016/j.dsr2.2025.105505
Hamid Ershadifar, Abolfazl Saleh, Kamalodin Kor
The present research study is intended to assess the probable sources of suspended particulate matter (SPM) in the Persian Gulf. SPM was collected at three to four depth resolutions: surface, 10 and/or 25 m, and 2–3 m above the seabed over three research cruises: PGE1901 (May 2019), PGE1902 (November 2019), and PGE2101 (March 2021). The SPM concentration exhibits several maxima along the northern coastline and is higher in winter than spring and autumn. SPM consisted of calcium carbonate (CaCO3), opaline silica (SiO2), organic matter, detrital matter from the upper continental crust (UCC), and contaminants derived from industrial activities (e.g., leaking or combustion of fossil fuels). Particulate organic matter (POM) is the major fraction in offshore samples, accounting for up to 84 % of the particulate mass, while the contribution of MnO2 is lower than 0.1 % during the three seasons. The particulate CaCO3 content varied more than other major components, being lowest in the northern Strait of Hormuz and up to 40 % in the region near the southern carbonate shelf. Strong coupling among the biochemical parameters Chl-a, bSi, TPP, and TPN was observed during the winter, likely reflecting higher autotrophic contributions to the particulate organic matter (POM). The decrease in TPN from autumn to winter, along with increases in Chl-a and TPP, resulted in three- and two-fold drops in N:Chl-a and N:P ratios, respectively. The concentrations of metal elements decrease in the general order of Ca > Fe > Al > Zn > Ti > Mn > Cr > Cu > Ni > Pb > V > Mo > Cd. Most of the elements exhibit enrichment levels ranging from 50 to 5000 times higher than the values found in the upper continental crust, with notable exceptions for titanium (Ti) and manganese (Mn). Except for cadmium, with a Me/P ratio close to the reported intracellular values, phytoplankton's contribution to the particulate pool of other bioactive trace elements barely exceeds 15 %. The predominant fraction of particulate Pb, Zn, Cu, and Ni is beyond the dust and phytoplankton contribution, possibly from the long-term accumulation of these elements, with some signs of local anthropogenic input.
{"title":"The behavior of particulate matter in the Persian Gulf: biogeochemical proxies for source identification","authors":"Hamid Ershadifar, Abolfazl Saleh, Kamalodin Kor","doi":"10.1016/j.dsr2.2025.105505","DOIUrl":"10.1016/j.dsr2.2025.105505","url":null,"abstract":"<div><div>The present research study is intended to assess the probable sources of suspended particulate matter (SPM) in the Persian Gulf. SPM was collected at three to four depth resolutions: surface, 10 and/or 25 m, and 2–3 m above the seabed over three research cruises: PGE1901 (May 2019), PGE1902 (November 2019), and PGE2101 (March 2021). The SPM concentration exhibits several maxima along the northern coastline and is higher in winter than spring and autumn. SPM consisted of calcium carbonate (CaCO<sub>3</sub>), opaline silica (SiO<sub>2</sub>), organic matter, detrital matter from the upper continental crust (UCC), and contaminants derived from industrial activities (e.g., leaking or combustion of fossil fuels). Particulate organic matter (POM) is the major fraction in offshore samples, accounting for up to 84 % of the particulate mass, while the contribution of MnO<sub>2</sub> is lower than 0.1 % during the three seasons. The particulate CaCO<sub>3</sub> content varied more than other major components, being lowest in the northern Strait of Hormuz and up to 40 % in the region near the southern carbonate shelf. Strong coupling among the biochemical parameters Chl-a, bSi, TPP, and TPN was observed during the winter, likely reflecting higher autotrophic contributions to the particulate organic matter (POM). The decrease in TPN from autumn to winter, along with increases in Chl-a and TPP, resulted in three- and two-fold drops in N:Chl-a and N:P ratios, respectively. The concentrations of metal elements decrease in the general order of Ca > Fe > Al > Zn > Ti > Mn > Cr > Cu > Ni > Pb > V > Mo > Cd. Most of the elements exhibit enrichment levels ranging from 50 to 5000 times higher than the values found in the upper continental crust, with notable exceptions for titanium (Ti) and manganese (Mn). Except for cadmium, with a Me/P ratio close to the reported intracellular values, phytoplankton's contribution to the particulate pool of other bioactive trace elements barely exceeds 15 %. The predominant fraction of particulate Pb, Zn, Cu, and Ni is beyond the dust and phytoplankton contribution, possibly from the long-term accumulation of these elements, with some signs of local anthropogenic input.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105505"},"PeriodicalIF":2.3,"publicationDate":"2025-07-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595795","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 : 2025-07-05DOI: 10.1016/j.dsr2.2025.105506
Kirstin S. Meyer-Kaiser , Kharis Schrage , Melanie Bergmann
Hard-bottom habitats, including dropstones and rocky reefs, increase habitat heterogeneity and host unique communities in the Fram Strait. This manuscript synthesizes research on the composition and dynamics of hard-bottom communities over HAUSGARTEN's 25 years, combining known patterns with previously unpublished data. Our research reveals that hard-bottom communities have high biodiversity, including taxa that have not yet been identified or described. Research on reproduction in hard-bottom taxa has been limited. For the most common hard-bottom species, which include sponges, soft corals, and anemones, larvae tend to settle near their parents. Hydroids have much broader-range dispersal and serve as pioneer species in the deep Fram Strait. Results from two novel recruitment experiments (2015–2024, 2019–2024), combined with results from two previous studies, show the process of succession in hard-bottom communities. Initial recruitment of hydroids was followed by tube worms, sponges, and cnidarians, leading to a strong increase in rarefied species richness and differences in species composition over time. Tracking of the hard-bottom fauna on marked stones showed negligible growth and 0–23 % mortality over 5 years (2019–2024). In summary, our research indicates that hard-bottom taxa in the deep Fram Strait have short-range larval dispersal, low recruitment, and slow growth. These characteristics suggest that hard-bottom communities have limited resilience to anthropogenic disturbance.
{"title":"Hard-bottom communities in the deep Fram Strait: patterns, processes, and looming questions","authors":"Kirstin S. Meyer-Kaiser , Kharis Schrage , Melanie Bergmann","doi":"10.1016/j.dsr2.2025.105506","DOIUrl":"10.1016/j.dsr2.2025.105506","url":null,"abstract":"<div><div>Hard-bottom habitats, including dropstones and rocky reefs, increase habitat heterogeneity and host unique communities in the Fram Strait. This manuscript synthesizes research on the composition and dynamics of hard-bottom communities over HAUSGARTEN's 25 years, combining known patterns with previously unpublished data. Our research reveals that hard-bottom communities have high biodiversity, including taxa that have not yet been identified or described. Research on reproduction in hard-bottom taxa has been limited. For the most common hard-bottom species, which include sponges, soft corals, and anemones, larvae tend to settle near their parents. Hydroids have much broader-range dispersal and serve as pioneer species in the deep Fram Strait. Results from two novel recruitment experiments (2015–2024, 2019–2024), combined with results from two previous studies, show the process of succession in hard-bottom communities. Initial recruitment of hydroids was followed by tube worms, sponges, and cnidarians, leading to a strong increase in rarefied species richness and differences in species composition over time. Tracking of the hard-bottom fauna on marked stones showed negligible growth and 0–23 % mortality over 5 years (2019–2024). In summary, our research indicates that hard-bottom taxa in the deep Fram Strait have short-range larval dispersal, low recruitment, and slow growth. These characteristics suggest that hard-bottom communities have limited resilience to anthropogenic disturbance.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105506"},"PeriodicalIF":2.3,"publicationDate":"2025-07-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144595793","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}
The recent roadmap IndOOS-2 has stressed the need to expand the biogeochemical-Argo observing system in the Indian Ocean. The Monaco Explorations Indian Ocean expedition offered a unique opportunity to meet this goal in the southwestern sector which was, in this regard and at that time, one of the least covered oceanic regions. We designed a deployment strategy for the biogeochemical float array grounded on past experiences, existing knowledge, and the analysis of historical datasets to cover the contrasting biophysical regimes from the Seychelles Chagos Thermocline Ridge to the subtropical gyre. Aligning with IndOOS-2 recommendations, a denser float distribution was set in the tropical band to enhance biogeochemical observations in upwelling zones. Following this strategy, a fleet of seventeen biogeochemical floats was successfully deployed during the expedition in October–November 2022. After two years of operations, the spatio-temporal distribution covered by the fleet confirmed that the goals of the deployment strategy have been reached, revealing seasonal modulations of the meridional trophic gradient with respect to phytoplankton biomass from tropical mesotrophy to subtropical oligotrophy.
{"title":"Biogeochemical float deployment strategy in the Southwestern Indian ocean","authors":"Wilhem Riom , Vincent Taillandier , Céline Dimier , Fabrizio D'Ortenzio , Hervé Claustre","doi":"10.1016/j.dsr2.2025.105504","DOIUrl":"10.1016/j.dsr2.2025.105504","url":null,"abstract":"<div><div>The recent roadmap <em>IndOOS-2</em> has stressed the need to expand the biogeochemical-Argo observing system in the Indian Ocean. The Monaco Explorations Indian Ocean expedition offered a unique opportunity to meet this goal in the southwestern sector which was, in this regard and at that time, one of the least covered oceanic regions. We designed a deployment strategy for the biogeochemical float array grounded on past experiences, existing knowledge, and the analysis of historical datasets to cover the contrasting biophysical regimes from the Seychelles Chagos Thermocline Ridge to the subtropical gyre. Aligning with IndOOS-2 recommendations, a denser float distribution was set in the tropical band to enhance biogeochemical observations in upwelling zones. Following this strategy, a fleet of seventeen biogeochemical floats was successfully deployed during the expedition in October–November 2022. After two years of operations, the spatio-temporal distribution covered by the fleet confirmed that the goals of the deployment strategy have been reached, revealing seasonal modulations of the meridional trophic gradient with respect to phytoplankton biomass from tropical mesotrophy to subtropical oligotrophy.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105504"},"PeriodicalIF":2.3,"publicationDate":"2025-06-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144517962","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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