Pub Date : 2025-11-01Epub Date: 2025-09-15DOI: 10.1016/j.dsr.2025.104592
Sara Castillo , Ana Ramos , Fran Ramil
The diversity and distribution patterns of molluscs in waters off Guinea-Bissau were investigated alongside their relationships with abiotic factors. Samples were collected using commercial bottom trawls during Spanish Bissau-0810 and three FAO-CCLME expeditions carried out on shelf and continental slope areas, over a depth range of 20–1000 m. A total of 126 species of mollusc were identified (86 gastropods, 39 bivalves and 1 scaphopod). Xenophoridae and Muricidae were the most frequent families, and the gastropod Ponderiana digitata was the most frequent species. Maximum mollusc density occurred between 100 and 200 m depth, with the bivalve Neopycnodonte cochlear dominating. Average diversity by strata decreased with increasing depth, with the maximum in shallow waters (<50 m). Separation of the three main assemblages (continental shelf, upper slope and middle slope) was influenced by a combination of environmental factors including depth, bottom temperature, sediment type and carbonates.
{"title":"Molluscan assemblages from the shelf and upper continental slope off Guinea-Bissau (north-west Africa)","authors":"Sara Castillo , Ana Ramos , Fran Ramil","doi":"10.1016/j.dsr.2025.104592","DOIUrl":"10.1016/j.dsr.2025.104592","url":null,"abstract":"<div><div>The diversity and distribution patterns of molluscs in waters off Guinea-Bissau were investigated alongside their relationships with abiotic factors. Samples were collected using commercial bottom trawls during Spanish <em>Bissau-0810</em> and three <em>FAO-CCLME</em> expeditions carried out on shelf and continental slope areas, over a depth range of 20–1000 m. A total of 126 species of mollusc were identified (86 gastropods, 39 bivalves and 1 scaphopod). Xenophoridae and Muricidae were the most frequent families, and the gastropod <em>Ponderiana digitata</em> was the most frequent species. Maximum mollusc density occurred between 100 and 200 m depth, with the bivalve <em>Neopycnodonte cochlear</em> dominating. Average diversity by strata decreased with increasing depth, with the maximum in shallow waters (<50 m). Separation of the three main assemblages (continental shelf, upper slope and middle slope) was influenced by a combination of environmental factors including depth, bottom temperature, sediment type and carbonates.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"225 ","pages":"Article 104592"},"PeriodicalIF":2.1,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145095493","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 : 2025-11-01Epub Date: 2025-09-01DOI: 10.1016/j.dsr.2025.104579
Hui Zhang , Jing-Chun Feng , Bin Wang , Yongming Shen , Si Zhang
Methane, which is widely present in marine sediments, is not only a potential transitional energy source but also plays a critical role in the global carbon cycle. However, in–depth research on the hydrate phase transition and its effects in porous media under dynamic leakage conditions is still lacking. In this study, X-ray computed tomography was employed to capture the real–time three–dimensional structural evolution of hydrate phase transition. The results indicate that hydrate formation expands and stabilizes gas migration channels, increasing their volume to 6.9 times the original, while also enhancing structural complexity and system permeability. During hydrate dissociation, the combined effects of gravity and released gas and water altered the distribution of gas migration channels, reducing both their volume and permeability. On this basis, the ecological and environmental impacts of hydrate phase transition on the deep–sea methane seepage areas under dynamic seepage conditions were analyzed. Hydrate phase transition playing a crucial role in the biogeochemical processes and the evolution of benthic ecological communities in methane seepage areas. This study demonstrates the role of hydrate phase transitions in reshaping gas migration channels under dynamic leakage, with implications for ecological processes and hydrate resource development in marine sediments.
{"title":"Phase transition and gas migration channels evolutions with methane hydrate system in porous media under dynamic leakage conditions","authors":"Hui Zhang , Jing-Chun Feng , Bin Wang , Yongming Shen , Si Zhang","doi":"10.1016/j.dsr.2025.104579","DOIUrl":"10.1016/j.dsr.2025.104579","url":null,"abstract":"<div><div>Methane, which is widely present in marine sediments, is not only a potential transitional energy source but also plays a critical role in the global carbon cycle. However, in–depth research on the hydrate phase transition and its effects in porous media under dynamic leakage conditions is still lacking. In this study, X-ray computed tomography was employed to capture the real–time three–dimensional structural evolution of hydrate phase transition. The results indicate that hydrate formation expands and stabilizes gas migration channels, increasing their volume to 6.9 times the original, while also enhancing structural complexity and system permeability. During hydrate dissociation, the combined effects of gravity and released gas and water altered the distribution of gas migration channels, reducing both their volume and permeability. On this basis, the ecological and environmental impacts of hydrate phase transition on the deep–sea methane seepage areas under dynamic seepage conditions were analyzed. Hydrate phase transition playing a crucial role in the biogeochemical processes and the evolution of benthic ecological communities in methane seepage areas. This study demonstrates the role of hydrate phase transitions in reshaping gas migration channels under dynamic leakage, with implications for ecological processes and hydrate resource development in marine sediments.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"225 ","pages":"Article 104579"},"PeriodicalIF":2.1,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145266122","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}
Water exchange processes between abyssal basins are a problem of universal interest because they control deep water climate. In this study, structure and variability of deep currents running through the southern gap of the Oki Spur from the Tsushima to Yamato Basins in the southern Japan Sea were investigated using the moored current meters and closely spaced hydrographic observations. Our observations revealed that the deep currents are cold, dense water overflows from the Tsushima Basin. Cold water spilling from the southern gap flows southward on the eastern flank of the spur as cold bottom water. Water mass analyses revealed that cold bottom water mixed with upper warmer water decreased its density during the early movement stages and then increased its density by mixing with lateral saline water. A streamtube model assuming a steady state roughly reproduced the depth, density, and velocity of cold bottom water, suggesting that it was in a near geostrophic balance. A strong southward current event accompanying the cold bottom water was observed from late December 1999 to early February 2000. An ocean reanalysis dataset showed that the event was associated with the Tsushima Current in the upper layer, suggesting that surface current variations promoted abyssal inter-basin water mass exchanges. In addition, current fluctuations of ∼10-day periods prevailed in the overflows, suggesting baroclinic instability.
{"title":"Deep water overflow through the southern gap of the Oki Spur in the Japan Sea","authors":"Tomoharu Senjyu , Satoru Tanimura , Takafumi Aramaki","doi":"10.1016/j.dsr.2025.104578","DOIUrl":"10.1016/j.dsr.2025.104578","url":null,"abstract":"<div><div>Water exchange processes between abyssal basins are a problem of universal interest because they control deep water climate. In this study, structure and variability of deep currents running through the southern gap of the Oki Spur from the Tsushima to Yamato Basins in the southern Japan Sea were investigated using the moored current meters and closely spaced hydrographic observations. Our observations revealed that the deep currents are cold, dense water overflows from the Tsushima Basin. Cold water spilling from the southern gap flows southward on the eastern flank of the spur as cold bottom water. Water mass analyses revealed that cold bottom water mixed with upper warmer water decreased its density during the early movement stages and then increased its density by mixing with lateral saline water. A streamtube model assuming a steady state roughly reproduced the depth, density, and velocity of cold bottom water, suggesting that it was in a near geostrophic balance. A strong southward current event accompanying the cold bottom water was observed from late December 1999 to early February 2000. An ocean reanalysis dataset showed that the event was associated with the Tsushima Current in the upper layer, suggesting that surface current variations promoted abyssal inter-basin water mass exchanges. In addition, current fluctuations of ∼10-day periods prevailed in the overflows, suggesting baroclinic instability.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"225 ","pages":"Article 104578"},"PeriodicalIF":2.1,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144903443","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 : 2025-11-01Epub Date: 2025-09-27DOI: 10.1016/j.dsr.2025.104601
Linghan Meng, Kun Zhang, Haibin Song, Shun Yang
Turbulent mixing is a primary physical process responsible for vertical exchange of materials, heat, momentum, and energy in the ocean, and plays a key role in maintaining the overturning circulation. There are many ways to enhance ocean mixing, one of which is through oceanic eddies. However, sparse in-situ observations cannot accurately describe the structural characteristics of eddies and their contribution to turbulent mixing in the Bering Sea. In this study, we observed numerous subsurface eddies in the deep-sea region of the Bering Sea using high-resolution seismic images. These anticyclonic eddies are primarily oval-shaped or bowl-shaped, with horizontal scales of 7–65 km. The majority fall within the submesoscale range, suggesting they are mainly submesoscale eddies. They generally develop in waters shallower than 250 m, with only a few found below 300 m. Submesoscale filaments are observed on the flanks of these eddies, some of which extend downward from the eddy sides, appearing as inclined filamentous reflections. Using seismic data, we estimated diapycnal mixing and obtained its spatial distribution. The results reveal that diffusivity is significantly enhanced at the edges of eddies, especially along their sides and upper boundaries, with values reaching up to 10−3 m2 s−1. The enhanced diapycnal mixing may be related to submesoscale processes generated during eddy stirring and shear instability caused by eddy-induced velocities. Turbulent mixing induced by eddies promotes the vertical transport of heat, nutrients, and other substances in the ocean, thereby influencing primary productivity in the Bering Sea and significantly impacting the marine environment and ecosystem.
{"title":"Spatial variation of diapycnal mixing estimated from high-resolution seismic images of subsurface eddies, Bering Sea","authors":"Linghan Meng, Kun Zhang, Haibin Song, Shun Yang","doi":"10.1016/j.dsr.2025.104601","DOIUrl":"10.1016/j.dsr.2025.104601","url":null,"abstract":"<div><div>Turbulent mixing is a primary physical process responsible for vertical exchange of materials, heat, momentum, and energy in the ocean, and plays a key role in maintaining the overturning circulation. There are many ways to enhance ocean mixing, one of which is through oceanic eddies. However, sparse in-situ observations cannot accurately describe the structural characteristics of eddies and their contribution to turbulent mixing in the Bering Sea. In this study, we observed numerous subsurface eddies in the deep-sea region of the Bering Sea using high-resolution seismic images. These anticyclonic eddies are primarily oval-shaped or bowl-shaped, with horizontal scales of 7–65 km. The majority fall within the submesoscale range, suggesting they are mainly submesoscale eddies. They generally develop in waters shallower than 250 m, with only a few found below 300 m. Submesoscale filaments are observed on the flanks of these eddies, some of which extend downward from the eddy sides, appearing as inclined filamentous reflections. Using seismic data, we estimated diapycnal mixing and obtained its spatial distribution. The results reveal that diffusivity is significantly enhanced at the edges of eddies, especially along their sides and upper boundaries, with values reaching up to 10<sup>−3</sup> m<sup>2</sup> s<sup>−1</sup>. The enhanced diapycnal mixing may be related to submesoscale processes generated during eddy stirring and shear instability caused by eddy-induced velocities. Turbulent mixing induced by eddies promotes the vertical transport of heat, nutrients, and other substances in the ocean, thereby influencing primary productivity in the Bering Sea and significantly impacting the marine environment and ecosystem.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"225 ","pages":"Article 104601"},"PeriodicalIF":2.1,"publicationDate":"2025-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145219856","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 : 2025-10-01Epub Date: 2025-07-30DOI: 10.1016/j.dsr.2025.104560
Ankur Saini , Santosh Gaikwad , Sabyasachi Sautya , M.A. Sarun Lal , V.B. Subin Raj , N.R. Ramesh , R. Ramesh , S. Ramesh , G.A. Ramadass
The deep-sea harbors a diverse array of organisms playing crucial roles in the ecosystem yet remains largely unexplored. Enteropneusta, commonly known as acorn worms, are a key component of the deep-sea benthos as they play a major role in surficial bioturbation and nutrient cycling. However, knowledge about their distribution, abundance, and behavior in these profound depths is scarce. This study provides the first quantitative assessment of enteropneusta (acorn worms) in the Central Indian Ocean Basin at depths greater than 5200 m. The data were collected using high-resolution seafloor imagery captured by an Autonomous Underwater Vehicle (AUV), which is pre-programmed to carry out surveys independently—unlike Remotely Operated Vehicles (ROVs), which require continuous control by operators aboard the surface vessel. In this study the AUV analyzed an area of 0.5 km2, revealing 2955 enteropneust fecal trails and 13 acorn worms (12 Tergivelum sp. and single Allapasus sp.). The study examined trail characteristics, including shapes, area coverage, and quality, as well as acorn worm morphology. Spiral trails dominated, with no significant preference for rotational direction. Trail quality was ranked from 1° to 3°, with most trails being 2° and 3° quality. This pioneering work provides crucial insights into deep-sea ecosystem functioning in the region, informing responsible decision-making regarding potential PMN exploration activities. This report also a first kind of its quantitative approach of enteropneusta among all the potential PMN sites in the global ocean. The findings contribute to our understanding of deep-sea biodiversity and ecological dynamics in the Indian Ocean.
{"title":"First quantitative assessment of deep-sea acorn worm (Enteropneusta) in PMN-rich zones of the Central Indian Ocean Basin","authors":"Ankur Saini , Santosh Gaikwad , Sabyasachi Sautya , M.A. Sarun Lal , V.B. Subin Raj , N.R. Ramesh , R. Ramesh , S. Ramesh , G.A. Ramadass","doi":"10.1016/j.dsr.2025.104560","DOIUrl":"10.1016/j.dsr.2025.104560","url":null,"abstract":"<div><div>The deep-sea harbors a diverse array of organisms playing crucial roles in the ecosystem yet remains largely unexplored. Enteropneusta, commonly known as acorn worms, are a key component of the deep-sea benthos as they play a major role in surficial bioturbation and nutrient cycling. However, knowledge about their distribution, abundance, and behavior in these profound depths is scarce. This study provides the first quantitative assessment of enteropneusta (acorn worms) in the Central Indian Ocean Basin at depths greater than 5200 m. The data were collected using high-resolution seafloor imagery captured by an Autonomous Underwater Vehicle (AUV), which is pre-programmed to carry out surveys independently—unlike Remotely Operated Vehicles (ROVs), which require continuous control by operators aboard the surface vessel. In this study the AUV analyzed an area of 0.5 km<sup>2</sup>, revealing 2955 enteropneust fecal trails and 13 acorn worms (12 <em>Tergivelum</em> sp. and single <em>Allapasus</em> sp.). The study examined trail characteristics, including shapes, area coverage, and quality, as well as acorn worm morphology. Spiral trails dominated, with no significant preference for rotational direction. Trail quality was ranked from 1° to 3°, with most trails being 2° and 3° quality. This pioneering work provides crucial insights into deep-sea ecosystem functioning in the region, informing responsible decision-making regarding potential PMN exploration activities. This report also a first kind of its quantitative approach of enteropneusta among all the potential PMN sites in the global ocean. The findings contribute to our understanding of deep-sea biodiversity and ecological dynamics in the Indian Ocean.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104560"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144780286","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 : 2025-10-01Epub Date: 2025-07-31DOI: 10.1016/j.dsr.2025.104561
Mengting Zhuo , Yu Hong , Yuhong Zhang , Jiping Liu , Lingqiao Cheng , Guoping Zhu , Song Hu , Yan Du
Polynyas play an important role in climate change by enhancing heat and material exchange between the atmosphere and the ocean in polar regions. This study investigated the influence of strong winds and warm deep water on the Amundsen Sea Polynya (ASP), with a particular focus on ASP events during the winter of 2014. The ASP is located directly above the underwater Bear Ridge, with its shape corresponding to the topography. The ASP is more frequently observed on the eastern side than on the western side, due to the influence of the iceberg chain (fast ice) east of the ASP and prevailing southeast winds. However, we found that the occurrence frequency of the ASP is highest in the shallowest points of the topography, rather than near the iceberg chain on the easternmost side. This is related to the upwelling of warm deep water driven by topography. The upward mixing of warm water with the surface waters inhibits sea ice formation and growth there, helping to maintain the ASP on the east side of the Bear Ridge top. Given the potential for a warmer subsurface ocean around Antarctica in the future, enhanced warm deep water mixing could further impact the thermodynamics of the ASP.
{"title":"Combined influence of strong winds and warm deep water on the formation of Amundsen Sea Polynya in winter","authors":"Mengting Zhuo , Yu Hong , Yuhong Zhang , Jiping Liu , Lingqiao Cheng , Guoping Zhu , Song Hu , Yan Du","doi":"10.1016/j.dsr.2025.104561","DOIUrl":"10.1016/j.dsr.2025.104561","url":null,"abstract":"<div><div>Polynyas play an important role in climate change by enhancing heat and material exchange between the atmosphere and the ocean in polar regions. This study investigated the influence of strong winds and warm deep water on the Amundsen Sea Polynya (ASP), with a particular focus on ASP events during the winter of 2014. The ASP is located directly above the underwater Bear Ridge, with its shape corresponding to the topography. The ASP is more frequently observed on the eastern side than on the western side, due to the influence of the iceberg chain (fast ice) east of the ASP and prevailing southeast winds. However, we found that the occurrence frequency of the ASP is highest in the shallowest points of the topography, rather than near the iceberg chain on the easternmost side. This is related to the upwelling of warm deep water driven by topography. The upward mixing of warm water with the surface waters inhibits sea ice formation and growth there, helping to maintain the ASP on the east side of the Bear Ridge top. Given the potential for a warmer subsurface ocean around Antarctica in the future, enhanced warm deep water mixing could further impact the thermodynamics of the ASP.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104561"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144772323","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 : 2025-10-01Epub Date: 2025-08-08DOI: 10.1016/j.dsr.2025.104573
Audrey M. Pruski, Gilles Vétion, Franck Lartaud, Erwan Peru, Nadine Le Bris
Hydrodynamic and food supply favourable conditions in the Lacaze-Duthiers Canyon (northwestern Mediterranean Sea) have supported the establishment of deep-sea corals, with some of the highest densities recorded in the Mediterranean. However, increasing pressures on these vulnerable habitats raise critical questions about their ecological status and resilience to environmental changes, emphasising the need to understand their trophic ecology. This study provides the most detailed analysis to date of the lipid profiles and fatty acid signatures of two key framework-building cold-water corals, Madrepora oculata and Desmophyllum pertusum (syn. Lophelia pertusa), offering insights into their feeding strategies, dietary requirements, and nutritional condition.
The results reveal that lipid classes exhibit distinct fatty acid compositions based on functional roles (storage vs. structural). Fatty acid trophic markers (FATM) indicative of herbivorous calanoids, carnivorous copepods, and phytodetritus were detected in the storage lipids (waxes and triglycerides) of both species, yet no FATM was specific to either species. This indicates a mixed diet and dietary overlap between the two corals. However, the composition of storage lipids varied significantly across samples, likely reflecting (1) species-specific feeding preferences, with D. pertusum showing greater reliance on overwintering copepods, and (2) the dynamic availability of food resources within the canyon.
Phospholipids were enriched in polyunsaturated fatty acids (PUFA), suggesting that dietary inputs are of sufficiently high quality to meet the metabolic demands of cold-water corals. High levels of storage lipids, primarily long-term reserves (wax esters) enriched in PUFA and zooplankton markers, underscore the good nutritional status of cold-water corals in the Lacaze-Duthiers Canyon.
{"title":"In situ diet patterns and health status of cold-water corals in the Lacaze-Duthiers canyon (NW Mediterranean Sea): insights from fatty acid biomarkers on lipid classes","authors":"Audrey M. Pruski, Gilles Vétion, Franck Lartaud, Erwan Peru, Nadine Le Bris","doi":"10.1016/j.dsr.2025.104573","DOIUrl":"10.1016/j.dsr.2025.104573","url":null,"abstract":"<div><div>Hydrodynamic and food supply favourable conditions in the Lacaze-Duthiers Canyon (northwestern Mediterranean Sea) have supported the establishment of deep-sea corals, with some of the highest densities recorded in the Mediterranean. However, increasing pressures on these vulnerable habitats raise critical questions about their ecological status and resilience to environmental changes, emphasising the need to understand their trophic ecology. This study provides the most detailed analysis to date of the lipid profiles and fatty acid signatures of two key framework-building cold-water corals, <em>Madrepora oculata</em> and <em>Desmophyllum pertusum</em> (syn. <em>Lophelia pertusa</em>), offering insights into their feeding strategies, dietary requirements, and nutritional condition.</div><div>The results reveal that lipid classes exhibit distinct fatty acid compositions based on functional roles (storage vs. structural). Fatty acid trophic markers (FATM) indicative of herbivorous calanoids, carnivorous copepods, and phytodetritus were detected in the storage lipids (waxes and triglycerides) of both species, yet no FATM was specific to either species. This indicates a mixed diet and dietary overlap between the two corals. However, the composition of storage lipids varied significantly across samples, likely reflecting (1) species-specific feeding preferences, with <em>D. pertusum</em> showing greater reliance on overwintering copepods, and (2) the dynamic availability of food resources within the canyon.</div><div>Phospholipids were enriched in polyunsaturated fatty acids (PUFA), suggesting that dietary inputs are of sufficiently high quality to meet the metabolic demands of cold-water corals. High levels of storage lipids, primarily long-term reserves (wax esters) enriched in PUFA and zooplankton markers, underscore the good nutritional status of cold-water corals in the Lacaze-Duthiers Canyon.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104573"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144860889","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 : 2025-10-01Epub Date: 2025-08-05DOI: 10.1016/j.dsr.2025.104571
Chenyu Fan , Zhuangcai Tian , Kai Cui , Jinjian Huang , Sicheng Bian , Liyu Yang , Taiping Zhang
The northeastern South China Sea is characterized by a complex system of submarine canyons, making the study of its sediment “source-to-sink” processes crucial for understanding regional tectonic-climate interactions. This study focuses on two areas: the Taiwan Canyon and northern Manila Trench in the northeastern South China Sea. We used X-ray diffraction to analyze clay minerals. The analysis examined surface and core sediments from seven sampling sites. We studied both composition and sources of these minerals. We quantified the contribution rates from different sources and detailed the transport pathways. The results indicate that clay minerals in the study area are predominantly composed of illite (58.9 %–70.7 %) and chlorite (22.2 %–39.6 %), while smectite (0.3 %–7.4 %) and kaolinite (0.3 %–12.2 %) are present in significantly lower abundances. Taiwan Island is the primary source of clay minerals (47.9–97.7 %), transported to the northern Manila Trench via the Penghu-Gaoping Canyon system and deep-water currents. Luzon Island contributes minimally (<7.4 %), with its materials carried by the Kuroshio Current. The Pearl River catchment serves as a secondary source (1.5–48.2 %). This study proposes that Pearl River sediments in the northern South China Sea are transported via two distinct pathways: (1) shelf sediments are transported through the Taiwan Canyon to the northern Manila Trench, while (2) slope sediments are delivered directly to both the mid-Taiwan Canyon (ZC4) and the northern Manila Trench (YF6). These results offer significant scientific insights into the “source-to-sink” sedimentary processes along the continental margin of the northeastern South China Sea.
{"title":"A new discovery of source contribution and transport mechanism of clay minerals in Taiwan Canyon-Manila Trench","authors":"Chenyu Fan , Zhuangcai Tian , Kai Cui , Jinjian Huang , Sicheng Bian , Liyu Yang , Taiping Zhang","doi":"10.1016/j.dsr.2025.104571","DOIUrl":"10.1016/j.dsr.2025.104571","url":null,"abstract":"<div><div>The northeastern South China Sea is characterized by a complex system of submarine canyons, making the study of its sediment “source-to-sink” processes crucial for understanding regional tectonic-climate interactions. This study focuses on two areas: the Taiwan Canyon and northern Manila Trench in the northeastern South China Sea. We used X-ray diffraction to analyze clay minerals. The analysis examined surface and core sediments from seven sampling sites. We studied both composition and sources of these minerals. We quantified the contribution rates from different sources and detailed the transport pathways. The results indicate that clay minerals in the study area are predominantly composed of illite (58.9 %–70.7 %) and chlorite (22.2 %–39.6 %), while smectite (0.3 %–7.4 %) and kaolinite (0.3 %–12.2 %) are present in significantly lower abundances. Taiwan Island is the primary source of clay minerals (47.9–97.7 %), transported to the northern Manila Trench via the Penghu-Gaoping Canyon system and deep-water currents. Luzon Island contributes minimally (<7.4 %), with its materials carried by the Kuroshio Current. The Pearl River catchment serves as a secondary source (1.5–48.2 %). This study proposes that Pearl River sediments in the northern South China Sea are transported via two distinct pathways: (1) shelf sediments are transported through the Taiwan Canyon to the northern Manila Trench, while (2) slope sediments are delivered directly to both the mid-Taiwan Canyon (ZC4) and the northern Manila Trench (YF6). These results offer significant scientific insights into the “source-to-sink” sedimentary processes along the continental margin of the northeastern South China Sea.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104571"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144827973","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 : 2025-10-01Epub Date: 2025-08-07DOI: 10.1016/j.dsr.2025.104574
Liquan Luo , Haowen Dang , Zhiwei Zeng , Mingyuan Bu , Chen Li , Jianru Li , Yanli Lei , Wei Huang , Zhimin Jian
Cold-water coral (CWC) ecosystems are receiving ever-increasing attention. Here, the distribution of CWC on a single seamount off the northern continental shelf of the South China Sea (SCS) is investigated by combining video footage from manned submersible dives and high-resolution multibeam bathymetric data. An active CWC garden ecosystem, with an average density of 15.11 ± 2.25 individuals per 100 m2, is identified on the seamount. Video footage analysis enabled the classification of CWC into 10 distinct families. The spatial distribution of the CWC on the seamount is significantly influenced by bottom current intensity and substrate type. At the summit of the seamount, dead coral skeletons covering a large area are found on mud substrates. The distribution pattern of the studied CWC garden reveals the important role of the seamount's elevated structure in sustaining benthic ecosystems under high sedimentation-rate conditions. The widespread occurrence of dead scleractinians further indicates the presence of significant environmental stressors that may threaten the long-term viability of the CWC garden, underscoring the need for continued ecological research and conservation efforts on the continental slopes of the South China Sea.
{"title":"Zonation of a cold-water coral garden on the northern continental slope of the South China sea","authors":"Liquan Luo , Haowen Dang , Zhiwei Zeng , Mingyuan Bu , Chen Li , Jianru Li , Yanli Lei , Wei Huang , Zhimin Jian","doi":"10.1016/j.dsr.2025.104574","DOIUrl":"10.1016/j.dsr.2025.104574","url":null,"abstract":"<div><div>Cold-water coral (CWC) ecosystems are receiving ever-increasing attention. Here, the distribution of CWC on a single seamount off the northern continental shelf of the South China Sea (SCS) is investigated by combining video footage from manned submersible dives and high-resolution multibeam bathymetric data. An active CWC garden ecosystem, with an average density of 15.11 ± 2.25 individuals per 100 m<sup>2</sup>, is identified on the seamount. Video footage analysis enabled the classification of CWC into 10 distinct families. The spatial distribution of the CWC on the seamount is significantly influenced by bottom current intensity and substrate type. At the summit of the seamount, dead coral skeletons covering a large area are found on mud substrates. The distribution pattern of the studied CWC garden reveals the important role of the seamount's elevated structure in sustaining benthic ecosystems under high sedimentation-rate conditions. The widespread occurrence of dead scleractinians further indicates the presence of significant environmental stressors that may threaten the long-term viability of the CWC garden, underscoring the need for continued ecological research and conservation efforts on the continental slopes of the South China Sea.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104574"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144809968","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 : 2025-10-01Epub Date: 2025-06-30DOI: 10.1016/j.dsr.2025.104549
Jamael C. Abato , Hiroshi Kajihara
A total of 80 nemertean specimens, representing 30 putative species, were obtained from the trawled material collected along the Japan Trench (JT) and southern Kuril-Kamchatka Trench (KKT) during the KH-22-8 and KH-23-5 cruises of the R/V Hakuho-maru in October 2022 and September 2023, respectively. Samples were collected from the 24 stations along these trenches at depths ranging from 2007 to 7654 m. Molecular and morphological analyses revealed nine species of Palaeonemertea (one in Carininidae, eight in Tubulanidae), seven species of Pilidiophora (six in Lineidae, one in Valenciinidae), and 14 species of Hoplonemertea (six Monostilifera, eight Polystilifera). All palaeonemerteans, six pilidiophorans, and eight hoplonemerteans represented species that are highly likely undescribed and distinct from species known in deep-sea environments globally in the last decade. Two new hadal hoplonemerteans were described in this study: Nemertovema kojimai sp. nov. in JT at 6211 m, and Profundonemertes hakuhoae gen. et sp. nov., found in JT and southern KKT at depths of 6807–7654 m. The phylogeny of the 30 species, including the two newly described, was analyzed using 16S, 18S, and 28S ribosomal RNA, cytochrome c oxidase subunit I (COI), and histone H3 genes. Nemertovema kojimai sp. nov. is closely related to Nemertovema norenburgi Chernyshev and Polyakova, 2019, while Profundonemertes hakuhoae gen. et sp. nov. was nested within Oerstediina, sister to Abyssonemertes kajiharai Chernyshev and Polyakova, 2018a, but with low support. Four previously described species were also reported for the first time in Japanese waters: Baseodiscus profundus Kajihara, Abukawa and Chernyshev, 2022b, in southern KKT; Dinonemertes cf. arctica Korotkevich, 1977 in both trenches; N. norenburgi, in southern KKT; and Phallonemertes murrayi (Brinkmann, 1912), in both trenches as well. The genus Nemertovema Chernyshev and Polyakova, 2018a was reported for the first time in JT, represented by N. kojimai sp. nov. and one additional undescribed species. This study provided the first comprehensive survey of deep-sea nemertean diversity along JT and updated our understanding of species diversity in KKT.
{"title":"Deep-sea nemerteans collected along the Japan Trench and the southern Kuril-Kamchatka Trench onboard the R/V Hakuho-maru with descriptions of two new species in Hoplonemertea","authors":"Jamael C. Abato , Hiroshi Kajihara","doi":"10.1016/j.dsr.2025.104549","DOIUrl":"10.1016/j.dsr.2025.104549","url":null,"abstract":"<div><div>A total of 80 nemertean specimens, representing 30 putative species, were obtained from the trawled material collected along the Japan Trench (JT) and southern Kuril-Kamchatka Trench (KKT) during the KH-22-8 and KH-23-5 cruises of the R/V <em>Hakuho-maru</em> in October 2022 and September 2023, respectively. Samples were collected from the 24 stations along these trenches at depths ranging from 2007 to 7654 m. Molecular and morphological analyses revealed nine species of Palaeonemertea (one in Carininidae, eight in Tubulanidae), seven species of Pilidiophora (six in Lineidae, one in Valenciinidae), and 14 species of Hoplonemertea (six Monostilifera, eight Polystilifera). All palaeonemerteans, six pilidiophorans, and eight hoplonemerteans represented species that are highly likely undescribed and distinct from species known in deep-sea environments globally in the last decade. Two new hadal hoplonemerteans were described in this study: <em>Nemertovema kojimai</em> sp. nov. in JT at 6211 m, and <em>Profundonemertes hakuhoae</em> gen. et sp. nov., found in JT and southern KKT at depths of 6807–7654 m. The phylogeny of the 30 species, including the two newly described, was analyzed using 16S, 18S, and 28S ribosomal RNA, cytochrome <em>c</em> oxidase subunit I (COI), and histone H3 genes. <em>Nemertovema kojimai</em> sp. nov. is closely related to <em>Nemertovema norenburgi</em> Chernyshev and Polyakova, 2019, while <em>Profundonemertes hakuhoae</em> gen. et sp. nov. was nested within Oerstediina, sister to <em>Abyssonemertes kajiharai</em> Chernyshev and Polyakova, 2018a, but with low support. Four previously described species were also reported for the first time in Japanese waters: <em>Baseodiscus profundus</em> Kajihara, Abukawa and Chernyshev, 2022b, in southern KKT; <em>Dinonemertes</em> cf. <em>arctica</em> Korotkevich, 1977 in both trenches; <em>N</em>. <em>norenburgi</em>, in southern KKT; and <em>Phallonemertes murrayi</em> (Brinkmann, 1912), in both trenches as well. The genus <em>Nemertovema</em> Chernyshev and Polyakova, 2018a was reported for the first time in JT, represented by <em>N</em>. <em>kojimai</em> sp. nov. and one additional undescribed species. This study provided the first comprehensive survey of deep-sea nemertean diversity along JT and updated our understanding of species diversity in KKT.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"224 ","pages":"Article 104549"},"PeriodicalIF":2.1,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144772322","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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