This study evaluates the hydrodynamic and tidal dynamics of the Persian Gulf using the Finite Volume Community Ocean Model (FVCOM) under two distinct forcing configurations: wind-and-tide and tide-only. A comprehensive statistical assessment was conducted to validate the model's performance in replicating tidal elevation and flow velocity against in-situ data as well as TPXO10 tidal predictions. Co-tidal maps revealed that semi-diurnal constituents (e.g., M2, S2) exhibit pronounced phase transitions, particularly at the Strait of Hormuz, highlighting the influence of regional bathymetry on tidal propagation. Diurnal constituents (e.g., K1, O1) showed more uniform phase distributions, suggesting reduced sensitivity to topographic constraints. The analysis of tidal amplitudes underscored the dominance of the M2 and K1 constituents. Vertical analyses of current speeds revealed distinct patterns of tidal attenuation between diurnal and semi-diurnal constituents. The diurnal constituents undergo greater amplitude reductions with depth compared to semi-diurnal constituents, indicating stronger bottom interaction processes for longer-period tides. While the M2 constituent demonstrated minimal sensitivity to wind forcing, diurnal constituents like K1 showed significant attenuation influenced by seasonal stratification and atmospheric conditions. These findings underscore the critical interplay between wind forcing, tidal dynamics, and seasonal variability in shaping the hydrodynamics of the Persian Gulf.
{"title":"The vertical profiles of the tidal constituents and bed-induced dissipation of tidal signals in the Persian Gulf","authors":"Morteza Keshtgar , Seyed Mostafa Siadatmousavi , Jafar Azizpour","doi":"10.1016/j.dsr2.2025.105528","DOIUrl":"10.1016/j.dsr2.2025.105528","url":null,"abstract":"<div><div>This study evaluates the hydrodynamic and tidal dynamics of the Persian Gulf using the Finite Volume Community Ocean Model (FVCOM) under two distinct forcing configurations: wind-and-tide and tide-only. A comprehensive statistical assessment was conducted to validate the model's performance in replicating tidal elevation and flow velocity against in-situ data as well as TPXO10 tidal predictions. Co-tidal maps revealed that semi-diurnal constituents (e.g., M2, S2) exhibit pronounced phase transitions, particularly at the Strait of Hormuz, highlighting the influence of regional bathymetry on tidal propagation. Diurnal constituents (e.g., K1, O1) showed more uniform phase distributions, suggesting reduced sensitivity to topographic constraints. The analysis of tidal amplitudes underscored the dominance of the M2 and K1 constituents. Vertical analyses of current speeds revealed distinct patterns of tidal attenuation between diurnal and semi-diurnal constituents. The diurnal constituents undergo greater amplitude reductions with depth compared to semi-diurnal constituents, indicating stronger bottom interaction processes for longer-period tides. While the M2 constituent demonstrated minimal sensitivity to wind forcing, diurnal constituents like K1 showed significant attenuation influenced by seasonal stratification and atmospheric conditions. These findings underscore the critical interplay between wind forcing, tidal dynamics, and seasonal variability in shaping the hydrodynamics of the Persian Gulf.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105528"},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144826357","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 : 2025-09-01Epub 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":"2025-09-01","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}
Understanding mesozooplankton (MSP) dynamics in nursery habitats is crucial for assessing ecosystem health and trophic interactions, particularly in anthropogenically stressed yet ecologically significant areas, such as Sulaibikhat Bay – home to Kuwait's first Marine Protected Area (MPA) in the northwestern Arabian/Persian Gulf (NWG). This study examines MSP community dynamics and environmental interactions over 26 months (October 2018–March 2021) across five fixed stations, including sites influenced by desalination and sewage outfalls. Seasonal fluctuations in water temperature, salinity, and nutrients significantly influenced MSP community structure. Copepods dominated, with cyclopoids (Oithona spp.) peaking in summer and fall, while calanoids (Parvocalanus crassirostris, Acartia spp.) were more prevalent in winter and spring. The cyclopoid-to-calanoid ratio, a potential indicator of trophic shifts, varied significantly across seasons, with cyclopoids prevailing in warmer months. Diversity and dispersion patterns, assessed through Venn diagrams and PERMDISP analysis, revealed higher species turnover near polluted sites and greater stability within the MPA. Taxonomic relatedness indices (AvTD, VarTD) indicated reduced diversity in chronically stressed areas. BIOENV and RELATE analyses identified temperature, dissolved oxygen, turbidity, and nanophytoplankton chlorophyll a as key drivers of the MSP community. Significant negative correlations between fish larvae and cyclopoids near the Al-Ghazali sewer outlet suggested potential prey-predator interactions, reinforcing the ecological implications of MSP composition shifts in this nursery habitat. While the MPA supports high MSP diversity, ongoing stressors, such as brine discharge and sewage, continue to shape the MSP community and trophic interactions. This study provides critical insights for ecosystem-based management of marine resources in and around Kuwait's first MPA in the NWG.
{"title":"Mesozooplankton community responses to environmental stressors in Kuwait's first marine protected area","authors":"Rakhesh Madhusoodhanan, Turki Al-Said, Faiza Al-Yamani, Gopikrishna Mantha, Takahiro Yamamoto, Loreta Fernandes, Ayaz Ahmed, Nithyanandan Manickam, Amit Sarkar, Sabeena Habeebullah Koduvayur Habeebullah, Fathima Thuslim, Waleed Al-Zekri, Jessy Sebastian, Maryam Al-Enezi","doi":"10.1016/j.dsr2.2025.105533","DOIUrl":"10.1016/j.dsr2.2025.105533","url":null,"abstract":"<div><div>Understanding mesozooplankton (MSP) dynamics in nursery habitats is crucial for assessing ecosystem health and trophic interactions, particularly in anthropogenically stressed yet ecologically significant areas, such as Sulaibikhat Bay – home to Kuwait's first Marine Protected Area (MPA) in the northwestern Arabian/Persian Gulf (NWG). This study examines MSP community dynamics and environmental interactions over 26 months (October 2018–March 2021) across five fixed stations, including sites influenced by desalination and sewage outfalls. Seasonal fluctuations in water temperature, salinity, and nutrients significantly influenced MSP community structure. Copepods dominated, with cyclopoids (<em>Oithona</em> spp.) peaking in summer and fall, while calanoids (<em>Parvocalanus crassirostris</em>, <em>Acartia</em> spp.) were more prevalent in winter and spring. The cyclopoid-to-calanoid ratio, a potential indicator of trophic shifts, varied significantly across seasons, with cyclopoids prevailing in warmer months. Diversity and dispersion patterns, assessed through Venn diagrams and PERMDISP analysis, revealed higher species turnover near polluted sites and greater stability within the MPA. Taxonomic relatedness indices (AvTD, VarTD) indicated reduced diversity in chronically stressed areas. BIOENV and RELATE analyses identified temperature, dissolved oxygen, turbidity, and nanophytoplankton chlorophyll <em>a</em> as key drivers of the MSP community. Significant negative correlations between fish larvae and cyclopoids near the Al-Ghazali sewer outlet suggested potential prey-predator interactions, reinforcing the ecological implications of MSP composition shifts in this nursery habitat. While the MPA supports high MSP diversity, ongoing stressors, such as brine discharge and sewage, continue to shape the MSP community and trophic interactions. This study provides critical insights for ecosystem-based management of marine resources in and around Kuwait's first MPA in the NWG.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105533"},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144890809","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 : 2025-09-01Epub Date: 2025-08-20DOI: 10.1016/j.dsr2.2025.105532
Mehrshad Taheri , Mohammad Ali Hamzeh , Abolfazl Saleh , Maryam Yazdani Foshtomi , Ahmad Radmanesh
Understanding the drivers of nematode community structure in subtidal ecosystems is critical for assessing marine biodiversity and ecosystem health. As sensitive bioindicators of environmental change, marine nematodes provide crucial insights into ecosystem dynamics; however, their spatial distribution patterns in the Persian Gulf's subtidal zones remain poorly understood. This study investigates the spatial variability of free–living nematode communities across five distinct transects in this understudied region. A total of 2189 specimens, representing 60 different genera, were identified. Nematode density showed significant variation, ranging from 16.7 to 92.6 individuals in 10 cm2, with the highest densities typically found at the shallowest stations. The average number of genera per sample ranged from 1 to 18.67. The Shannon diversity indices varied significantly, with a maximum of 2.58 and a minimum of 0, while evenness scores ranged from 0.76 to 1. Notable differences in nematode community structure were observed across the various transects and stations. The overall nematode community was dominated by genera such as Actinonema, Axonolaimus, Dorylaimopsis, Gnomoxyala, Halalaimus, Hopperia, Marylynnia, Pierrickia, Sabatieria, Subsphaerolaimus, and Terschellingia across different transects. According to DistLM analysis, depth, salinity, mean grain size, pH, and temperature together explained 22.9 % of the total variance in the nematode community, with depth accounting for 9.3 % and the other significant variables contributing an additional 13.6 %. Further research is essential to clarify the relationship between nematode communities and environmental conditions in underexplored ecosystems like this region.
{"title":"Distribution of free–Living marine nematodes along environmental gradients in the strait of hormuz","authors":"Mehrshad Taheri , Mohammad Ali Hamzeh , Abolfazl Saleh , Maryam Yazdani Foshtomi , Ahmad Radmanesh","doi":"10.1016/j.dsr2.2025.105532","DOIUrl":"10.1016/j.dsr2.2025.105532","url":null,"abstract":"<div><div>Understanding the drivers of nematode community structure in subtidal ecosystems is critical for assessing marine biodiversity and ecosystem health. As sensitive bioindicators of environmental change, marine nematodes provide crucial insights into ecosystem dynamics; however, their spatial distribution patterns in the Persian Gulf's subtidal zones remain poorly understood. This study investigates the spatial variability of free–living nematode communities across five distinct transects in this understudied region. A total of 2189 specimens, representing 60 different genera, were identified. Nematode density showed significant variation, ranging from 16.7 to 92.6 individuals in 10 cm<sup>2</sup>, with the highest densities typically found at the shallowest stations. The average number of genera per sample ranged from 1 to 18.67. The Shannon diversity indices varied significantly, with a maximum of 2.58 and a minimum of 0, while evenness scores ranged from 0.76 to 1. Notable differences in nematode community structure were observed across the various transects and stations. The overall nematode community was dominated by genera such as <em>Actinonema</em>, <em>Axonolaimus</em>, <em>Dorylaimopsis</em>, <em>Gnomoxyala</em>, <em>Halalaimus</em>, <em>Hopperia</em>, <em>Marylynnia</em>, <em>Pierrickia</em>, <em>Sabatieria</em>, <em>Subsphaerolaimus</em>, and <em>Terschellingia</em> across different transects. According to DistLM analysis, depth, salinity, mean grain size, pH, and temperature together explained 22.9 % of the total variance in the nematode community, with depth accounting for 9.3 % and the other significant variables contributing an additional 13.6 %. Further research is essential to clarify the relationship between nematode communities and environmental conditions in underexplored ecosystems like this region.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105532"},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144889520","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 : 2025-09-01Epub Date: 2025-08-13DOI: 10.1016/j.dsr2.2025.105529
Amir Ghazilou
The Persian Gulf forms a natural geographic barrier to coral reef communities. This study employs MaxEnt modeling with environmental data from Bio-ORACLE to assess the potential distributions of coral/algae and microalgal mats under present conditions and future (2090–2100) scenarios for SSP1, SSP3, and SSP5. Maximum temperature and mixed layer depth were found as the key environmental variables defining habitat suitability. Present-day suitable habitat for coral/algae totals approximately 94,161 km2. Under SSP1, a moderate decline of 2.29 % (to ∼92,002 km2) in habitat area is projected. SSP3 scenario shows an increase of 14.32 % (up to ∼107,651 km2), potentially due to local adaptation. In comparison, SSP5 projects a severe 18.14 % decrease (∼77,072 km2) with fragmentation and isolation characterized by a 40 % drop in effective mesh size and 130 % increase in edge density. Microalgal mats exhibited an increasing area and connectivity under more severe scenarios, with the total core area rising from ∼5.2 million to over 16.7 million square units. The largest patch index exceeded 82 %, and the aggregation index peaked near 95 %. Biotic velocity metrics suggested that microalgal mats require movements exceeding 1400 m/year, which is higher than those of coral/algae. North-south direction dominates patterns of change in distribution. These results underscore the need for targeted conservation that prioritizes connectivity and scenario-sensitive management actions in response to climate change in the Persian Gulf.
{"title":"MaxEnt modeling for predicting the present-day and future potential geographical distribution of coral/algae in the Persian Gulf under climate change","authors":"Amir Ghazilou","doi":"10.1016/j.dsr2.2025.105529","DOIUrl":"10.1016/j.dsr2.2025.105529","url":null,"abstract":"<div><div>The Persian Gulf forms a natural geographic barrier to coral reef communities. This study employs MaxEnt modeling with environmental data from Bio-ORACLE to assess the potential distributions of coral/algae and microalgal mats under present conditions and future (2090–2100) scenarios for SSP1, SSP3, and SSP5. Maximum temperature and mixed layer depth were found as the key environmental variables defining habitat suitability. Present-day suitable habitat for coral/algae totals approximately 94,161 km<sup>2</sup>. Under SSP1, a moderate decline of 2.29 % (to ∼92,002 km<sup>2</sup>) in habitat area is projected. SSP3 scenario shows an increase of 14.32 % (up to ∼107,651 km<sup>2</sup>), potentially due to local adaptation. In comparison, SSP5 projects a severe 18.14 % decrease (∼77,072 km<sup>2</sup>) with fragmentation and isolation characterized by a 40 % drop in effective mesh size and 130 % increase in edge density. Microalgal mats exhibited an increasing area and connectivity under more severe scenarios, with the total core area rising from ∼5.2 million to over 16.7 million square units. The largest patch index exceeded 82 %, and the aggregation index peaked near 95 %. Biotic velocity metrics suggested that microalgal mats require movements exceeding 1400 m/year, which is higher than those of coral/algae. North-south direction dominates patterns of change in distribution. These results underscore the need for targeted conservation that prioritizes connectivity and scenario-sensitive management actions in response to climate change in the Persian Gulf.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"223 ","pages":"Article 105529"},"PeriodicalIF":3.0,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144841760","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 : 2025-09-01Epub 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":"2025-09-01","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}
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":"2025-08-01","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}
Pub Date : 2025-08-01Epub 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.
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Pub Date : 2025-08-01Epub Date: 2025-05-22DOI: 10.1016/j.dsr2.2025.105486
Tatiana N. Dautova
Seamounts are of interest to the scientific community as they occupy a significant part of the ocean floor area and are areas of high biodiversity and productivity. The Hawaiian-Emperor Chain, formed by the Hawaiian mantle plume, is crucial for understanding of the lithospheric plates’ movement in the past. The chain is the longest contiguous chain of islands, guyots and seamounts in the world, whose edges are located in contrasting climatic and biogeographic zones. It may provide stepping stones for dispersal of deep-sea fauna and serve as their refugia, as well as containing commercial resources. The geological features, plankton and fish stocks of this area have been studied since the 1970s, but bottom systems are poorly studied. With the development of deep-sea surveys and the use of ROVs, the bottom communities of the seamounts in the North Pacific and the Emperor Chain have been studied over the last 10 years.
Results
of three research cruises to the area performed in 2019 and 2021 are presented. Numerous new faunistic and biogeographic findings, including the biogeographic boundary between North Pacific and Central Pacific assemblages of species, are made. The feeding modes of the deep-sea corals in the Emperor Chain were surveyed. New data regarding high vertical mixing rates in the area (using Sr isotopes ratio) and possible influence of Aeolian dust input from Asia into the area were obtained. Although seamounts were not previously considered important regions for methane production, substantial methane generation at the Emperor Chain area was discovered. Given the large number of seamounts in the ocean, the global methane budget should be reconsidered.
{"title":"Introduction to the Emperor Seamount Chain studies","authors":"Tatiana N. Dautova","doi":"10.1016/j.dsr2.2025.105486","DOIUrl":"10.1016/j.dsr2.2025.105486","url":null,"abstract":"<div><div>Seamounts are of interest to the scientific community as they occupy a significant part of the ocean floor area and are areas of high biodiversity and productivity. The Hawaiian-Emperor Chain, formed by the Hawaiian mantle plume, is crucial for understanding of the lithospheric plates’ movement in the past. The chain is the longest contiguous chain of islands, guyots and seamounts in the world, whose edges are located in contrasting climatic and biogeographic zones. It may provide stepping stones for dispersal of deep-sea fauna and serve as their refugia, as well as containing commercial resources. The geological features, plankton and fish stocks of this area have been studied since the 1970s, but bottom systems are poorly studied. With the development of deep-sea surveys and the use of ROVs, the bottom communities of the seamounts in the North Pacific and the Emperor Chain have been studied over the last 10 years.</div></div><div><h3>Results</h3><div>of three research cruises to the area performed in 2019 and 2021 are presented. Numerous new faunistic and biogeographic findings, including the biogeographic boundary between North Pacific and Central Pacific assemblages of species, are made. The feeding modes of the deep-sea corals in the Emperor Chain were surveyed. New data regarding high vertical mixing rates in the area (using Sr isotopes ratio) and possible influence of Aeolian dust input from Asia into the area were obtained. Although seamounts were not previously considered important regions for methane production, substantial methane generation at the Emperor Chain area was discovered. Given the large number of seamounts in the ocean, the global methane budget should be reconsidered.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105486"},"PeriodicalIF":2.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144185103","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 : 2025-08-01Epub Date: 2025-06-17DOI: 10.1016/j.dsr2.2025.105502
Elyas Soleimani , Moslem Daliri , Ali Salarpouri , Hossein Zamani
Enhancing the efficiency of small pelagic purse-seine fisheries is essential for promoting responsible fisheries management in the Persian Gulf. Therefore, this study forecasts the spatiotemporal catch variations of Sind sardinella (Sardinella sindensis) and Buccaneer anchovy (Encrasicholina punctifer) caught by double-boat purse seiners in the northern Persian Gulf, Qeshm Island. To achieve this, a dataset comprising fishing records from 314 purse seine operations, along with associated environmental parameters obtained from satellite imagery—including sea surface temperature (SST), chlorophyll-a concentration, photosynthetically active radiation (PAR), wind speed, wind direction, depth, and distance—was compiled and analyzed using an advanced machine learning methodology covering the period from September 2014 to October 2023. The evaluation of the regression models used to predict sardine and anchovy catches—including Random Forest (RF), Boosting, and Support Vector Regression (SVR)—revealed varying levels of predictive performance across both species and model types. In the case of sardine, the Boosting Regression model yielded the highest predictive accuracy, characterized by a relatively low error (RMSE = 395.5) and moderate explanatory power (R2 = 0.41). Conversely, for anchovies, the SVR model with a radial basis function (RBF) kernel demonstrated superior performance relative to the other models, with an RMSE of 437 and an R2 of 0.35. The results suggest that anchovy catch prediction was more challenging and potentially influenced by additional unmodeled variables. The CPUE of sardine increases with rising chlorophyll-a concentrations up to approximately 2 mg/m3, but declines beyond this point. The optimal SST range was between 22 °C and 26 °C, whereas sardine catches declined at temperatures exceeding 30 °C. Because anchovy was consistently present across all sampling sets, distance from the shoreline emerged as the most influential parameter contributing to successful net captures. A negative relationship was observed between this factor and anchovy CPUE. As the second most important variable, the optimal SST range for anchovy was similar to that of sardine. Given the substantial fishing effort in the northern Persian Gulf, the findings of this study may help enhance regional fishing strategies by promoting the integration of climate change considerations into operational planning.
{"title":"Prediction of sardine and anchovy catches by double-boat purse seiners in the northern Persian Gulf using machine learning models","authors":"Elyas Soleimani , Moslem Daliri , Ali Salarpouri , Hossein Zamani","doi":"10.1016/j.dsr2.2025.105502","DOIUrl":"10.1016/j.dsr2.2025.105502","url":null,"abstract":"<div><div>Enhancing the efficiency of small pelagic purse-seine fisheries is essential for promoting responsible fisheries management in the Persian Gulf. Therefore, this study forecasts the spatiotemporal catch variations of Sind sardinella (<em>Sardinella sindensis</em>) and Buccaneer anchovy (<em>Encrasicholina punctifer</em>) caught by double-boat purse seiners in the northern Persian Gulf, Qeshm Island. To achieve this, a dataset comprising fishing records from 314 purse seine operations, along with associated environmental parameters obtained from satellite imagery—including sea surface temperature (SST), chlorophyll-a concentration, photosynthetically active radiation (PAR), wind speed, wind direction, depth, and distance—was compiled and analyzed using an advanced machine learning methodology covering the period from September 2014 to October 2023. The evaluation of the regression models used to predict sardine and anchovy catches—including Random Forest (RF), Boosting, and Support Vector Regression (SVR)—revealed varying levels of predictive performance across both species and model types. In the case of sardine, the Boosting Regression model yielded the highest predictive accuracy, characterized by a relatively low error (RMSE = 395.5) and moderate explanatory power (R<sup>2</sup> = 0.41). Conversely, for anchovies, the SVR model with a radial basis function (RBF) kernel demonstrated superior performance relative to the other models, with an RMSE of 437 and an R<sup>2</sup> of 0.35. The results suggest that anchovy catch prediction was more challenging and potentially influenced by additional unmodeled variables. The CPUE of sardine increases with rising chlorophyll-a concentrations up to approximately 2 mg/m<sup>3</sup>, but declines beyond this point. The optimal SST range was between 22 °C and 26 °C, whereas sardine catches declined at temperatures exceeding 30 °C. Because anchovy was consistently present across all sampling sets, distance from the shoreline emerged as the most influential parameter contributing to successful net captures. A negative relationship was observed between this factor and anchovy CPUE. As the second most important variable, the optimal SST range for anchovy was similar to that of sardine. Given the substantial fishing effort in the northern Persian Gulf, the findings of this study may help enhance regional fishing strategies by promoting the integration of climate change considerations into operational planning.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"222 ","pages":"Article 105502"},"PeriodicalIF":2.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144312892","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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