Continental Shelf Research最新文献

{"title":"Upwelling processes variability and water circulation along the northern margin of the Gulf of Cadiz","authors":"","doi":"10.1016/j.csr.2024.105310","DOIUrl":"10.1016/j.csr.2024.105310","url":null,"abstract":"<div><p>The present study investigates the contributions of upwelling mechanisms (coastal upwelling from boundary divergence and Ekman pumping from spatially variable wind) at the northern margin of the Gulf of Cadiz (NMGoC) based on high-resolution wind. The effects of the spatiotemporal upwelling mechanisms variability are then explored using current observations along with sea surface temperature and sea level anomaly. Upwelling favourable conditions occur throughout the year along the NMGoC, with the strongest intensity near Cape São Vicente due to a persistent positive wind stress curl. In winter, the surface water divergence is restricted to the coastal boundary due to strong coastal upwelling events that result in a cross-shore sea-level gradient close to the coast. Towards the summer, the gradient increases and extends further offshore (over the slope) at the western region due to the intensification of the Ekman pumping. Therefore, the seasonal and spatial variability of coastal upwelling and Ekman pumping contributes significantly to the offshore position of the geostrophic Gulf of Cadiz Current over the western shelf slope. Furthermore, a permanent sea level depression corresponds to the location of the strongest Ekman pumping, near Cape São Vicente. The dynamic adjustment of this feature may drive the cyclonic cell and alongshore poleward currents often observed in the area.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0278434324001407/pdfft?md5=0a56a13336abbc5b4cd13c91f8d1d149&pid=1-s2.0-S0278434324001407-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142075860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Copepod community in the coastal waters off Kochi (India) signify the enhanced estuarine flushing during the Southwest Monsoon","authors":"","doi":"10.1016/j.csr.2024.105309","DOIUrl":"10.1016/j.csr.2024.105309","url":null,"abstract":"<div><p>Even though many studies refer to copepods as potential indicators of hydrographical settings and/or water masses, focused studies on this aspect are very scarce in Indian waters. Hence, this study assesses the hydrography and the copepod composition in a cross-shore transect (7–30 m depth zone) off Kochi along the southwest coast of India during different seasons to understand how seasonal hydrography alters the composition of copepods. The copepod community in the study area was found to consist of 36 species (26 dominant) during the Southwest Monsoon [(SWM) June to September], 31 species (16 dominant) during the Northeast Monsoon [(NEM) November to February], and 39 species (26 dominant) during the Pre-Monsoon [(PRM) March to May]. The salient observations in this study are (a) a higher contribution of cyclopoids (45–50%) during the oligotrophic PRM when the microbial food web was dominant; (b) the dominance of several truly estuarine copepods (<em>Acartia plumosa</em>, <em>Acartiella keralensis</em>, <em>Pseudodiaptomous annandalei</em>, and <em>P. serricaudatus</em>) during the SWM when the flushing of the adjacent estuarine system (Kochi backwaters) was the seasonal highest; and (c) the dominant occurrence of <em>Temora turbinata</em>, commonly referred to as an indicator of coastal upwelling, during both the SWM and the NEM indicates their conducive conditions in the study area during both seasons and (d) the occurrence of copepods <em>Acartia danae</em>, <em>A. erythraea</em>, <em>Acrocalanus gibber</em>, <em>A</em>. <em>gracilis</em>, <em>Centropages orsinii</em>, <em>C. tenuiremis</em>, <em>Corycaeus catus</em>, <em>C. speciosus</em>, <em>Oithona similis</em>, <em>O. spinirostris</em>, <em>Oncaea venusta</em>, <em>Paracalanus parvus</em>, and <em>Undinula vulgaris</em> in the study area regardless of seasons. The study concludes that, while the presence of truly estuarine copepods in the study area can be attributed to estuarine watermass indicators, the presence of several other dominant species found regardless of the season cannot, as their occurrence is widespread in the eastern Arabian Sea and the western Bay of Bengal, owing to seasonal water mass exchange between the two regions.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141993768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ecological assessment of macrobenthic communities in Chabahar Bay, the Gulf of Oman","authors":"","doi":"10.1016/j.csr.2024.105308","DOIUrl":"10.1016/j.csr.2024.105308","url":null,"abstract":"<div><h3>Aim</h3><p>Assessing the potential of the Chabahar Bay coasts for classification as marine and coastal protected areas.</p></div><div><h3>Location</h3><p>Chabahar Bay, northeast of the Gulf of Oman.</p></div><div><h3>Period</h3><p>Two seasons from 2017 to 2019.</p></div><div><h3>Major taxa studied</h3><p>Macrobenthic invertebrates.</p></div><div><h3>Methods</h3><p>The evaluation was based on the 2008 International Union for Conservation of Nature (IUCN) ecological model categories and criteria/sub-criteria. The study investigated criteria such as biodiversity, naturalness, dependency, representativeness, uniqueness, productivity, vulnerability, and integrity; the study was conducted at four zones of three stations within three regions.</p></div><div><h3>Results</h3><p>The northern region of Chabahar Bay showed significant differences in community structure compared to the other two regions. The highest abundance of macrobenthic invertebrates was observed in the northern area of Chabahar Bay, whereas the lowest abundance was observed in Konarak. Macrobenthic abundance, salinity, and electrical conductivity (EC) were found to influence the community structure of macrobenthic organisms; each region was assigned a score, categorizing it as an IUCN Category II protected area.</p></div><div><h3>Main conclusions</h3><p>The AMBI analysis revealed that some ecosystems in the studied regions were alarmingly disturbed, indicating the need for management attention to protect and conserve these ecosystems.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141951017","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical and Isotopic evidence for volcanism on the Alleppey Terrace, southwest Indian continental margin","authors":"","doi":"10.1016/j.csr.2024.105301","DOIUrl":"10.1016/j.csr.2024.105301","url":null,"abstract":"<div><p>The Arabian Sea consists of prominent undersea bathymetric highs whose genesis is often attributed to volcanism either related to the 90-85 Ma Marion or the 70-65 Ma Reunion hot spot activity on the Indian Plate. The enigmatic Alleppey Terrace (AT) is one such significant bathymetric high in the southwestern continental margin of India. We studied the siliciclastic sediments deposited on the AT and the adjacent shelf region using major/trace element, and Sr-Nd isotope geochemistry to decipher their provenances and implications of the findings for the origin of the Terrace. Geochemical data suggest that the AT sediments are chemically distinct from the adjacent shelf sediments, with the former having been sourced from juvenile mafic rocks and the latter from significantly older, felsic continental crustal rocks. Although currently located at a water depth of ∼300 m, AT was likely exposed above the sea level in the past and had undergone subaerial weathering and lateritization. The ε_Nd of AT sediments (−17.1 to −10.9), which is much radiogenic than that of the shelf sediments (−26.4 to −22.2), indicates significant presence of a juvenile basaltic component - likely derived from <em>in situ</em> weathering of the local seafloor/basement. The common component in both the terrace and shelf sediments appears to be terrigenous, deposited by the local rivers draining the Western Ghats. Conspicuous similarities of trace element ratios and isotopic compositions of the terrace sediments with those of the volcanic rocks temporally and spatially related to the Deccan volcanism suggest that the AT may contain traces of the end Cretaceous Reunion-Deccan plume/hotspot activity on the India subcontinent.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141951652","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical characteristics and provenance of metals in surface sediments of hydrate area, northern south China sea","authors":"","doi":"10.1016/j.csr.2024.105298","DOIUrl":"10.1016/j.csr.2024.105298","url":null,"abstract":"<div><p>Geochemical characteristics and provenance of metals in surface sediments of hydrate area, northern South China Sea has not been reported yet, therefore this paper aimed to reveal metals' distribution, assess the pollution of potentially hazradous metals (Cu, Pb, Zn, Cd, Cr, As, Hg), and inferred provenance of metals using principal component analysis. Twenty-five surface sediments were collected by box sampler from 2014 to 2015 in the national special project on gas hydrate. The concentration of MnO and Hg varied greatly. Most of metals were higher in the north of study area. The sediment was mainly polluted by Hg either pollution status or ecological risk, while it's also moderately polluted by Cr and moderately ecological polluted by Cd. The metals were mainly related to terrigenous detrital, biological source, some volcanic activities, and also little atmospheric deposition. Our findings would further improve the understanding of metals and their related biogeochemical process.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141950254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The influence of seabed geology on the nature and preservation of bottom trawl marks in the Bornholm Basin, southern Baltic Sea","authors":"","doi":"10.1016/j.csr.2024.105297","DOIUrl":"10.1016/j.csr.2024.105297","url":null,"abstract":"<div><p>This study investigates six areas in a historically heavily trawled region of the southern Baltic Sea. Using acoustic geophysical mapping data and sediment cores from three field campaigns (2019, 2020, 2023), we evaluate and quantify the cumulative physical impacts from bottom trawling and the influence of seabed geology on mapped trawl tracks. The results are compared with fishing intensity data over three periods; 2012–2016, 2017–2019 and after the fishery closed. A correlation between fishing intensity and density of mapped trawl tracks exists in the soft sediments of the northern part of the area, while this link is weak in the less trawled southern part, where the seabed is characterized by more consolidated glacial clays and the high density of mapped trawl tracks reflects the preservation of tracks &gt;8 years old. Four years after the closure of the fishery there were no signs of trawl-track degradation in any of the areas. In summary, mapped track densities alone are not a suitable measure of trawling intensity, considering the influence of seabed geology and the persistence of trawl tracks over time. Sediment deformation, observed by CT-scanning, indicates extensive remoulding and coarsening of the upper 20–40 cm of sediments in the trawled areas.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0278434324001274/pdfft?md5=7450df5b121bf3fabbefdac824536e3d&pid=1-s2.0-S0278434324001274-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141844468","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effect of fortnightly and seasonal changes in estuarine physical variables on phytoplankton distribution in a macrotidal monsoon estuary","authors":"","doi":"10.1016/j.csr.2024.105292","DOIUrl":"10.1016/j.csr.2024.105292","url":null,"abstract":"<div><p>Seasonal and neap-spring tidal changes in estuarine physical variables and their effect on the phytoplankton distribution in the macrotidal Tanintharyi River estuary (TRE), Myanmar were studied in 2019. During the dry season, the saltwater intrudes upstream while only until the mid-estuary during the wet season due to the hindering of saltwater by the strong river flow. The turbidity variations driven by enhanced mixing and neap-spring transition influenced the light required for phytoplankton growth during both seasons. The diversity index was higher (2.57–3.07) in the dry season with low evenness (0.64–0.79) compared to the low diversity index (2.16–2.73) with high evenness (0.75–0.90) in the wet season. The peak diatom density was observed under low turbidity (6 FTU) and a salinity of 25, and their distribution were correlated positively with salinity, mean light intensity in the mixed layer (I_m) and euphotic depth (Z_e) while negatively with light attenuation (K) and turbidity. Among diatoms species, <em>Thalassionema frauenfeldii</em>, <em>Thalassionema nitzschioides</em> and <em>Pseudonitzschia seriata</em> were found as dominant species (positively correlated with salinity and I_m whereas negatively with turbidity and K) during the dry season whereas <em>Thalassiosira eccentrica</em> and <em>Coscinodiscus granii</em> were dominant with low salinity in the wet season. The dinoflagellates were more sensitive to strong mixing condition than diatoms and their distribution were positively influenced by I_m and Z_e. Therefore, the neap-spring tidal and seasonal variations in saltwater intrusion, mixing, turbidity, and light availability are the major factors that maintained the phytoplankton diversity in the tropical TRE.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141705816","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The coalescence of two mangrove-lined river plumes and consequences for sediment transport and deposition in a coastal environment","authors":"","doi":"10.1016/j.csr.2024.105280","DOIUrl":"10.1016/j.csr.2024.105280","url":null,"abstract":"<div><p>We employed idealized numerical experiments using Delft3D to investigate how the interactions of coalescing buoyant river plumes with mangrove vegetation affect sediment transport and deposition in the coastal zone. Our model system, based on the Firth of Thames in the North Island of New Zealand, is designed to represent two mangrove-lined rivers debouching into a coastal bay. Sediment transport patterns into the three adjacent mangrove forest regions (central, western, and eastern) were assessed by quantifying the sediment fluxes over a tidal cycle. The interactions between the buoyant river plumes resulted in a coalesced river plume that flowed along the central mangrove forest between the rivers. The dominant contributors to the total sediment transport into the mangrove forests varied with both the total and the relative flows through the two rivers. When both rivers were forced with their respective flows at the 50th percentile of observed flow, the analysis of sediment transport fluxes along the central forest revealed sediment deposition inside the mangrove forests lining the river mouth nearly four times greater than in the intermediate regions along the central forest; consistent with satellite imagery of the Firth of Thames. Winds of 5<!--> <!-->m s⁻¹ modify the overall sediment transport patterns by deflecting the river plume in the direction of the wind. The magnitude of sediment flux is the highest (nearly 80% compared to the no-wind scenario) in the case of an easterly wind scenario as the alongshore transport is enhanced by Coriolis deflection and wind direction aligned with the alongshore flows of the larger plume.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141846020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Role of phytoplankton composition on exudation of dissolved organic carbon in the Bay of Bengal","authors":"","doi":"10.1016/j.csr.2024.105296","DOIUrl":"10.1016/j.csr.2024.105296","url":null,"abstract":"<div><p>Phytoplankton in the marine environment exudates part of the primary production as dissolved organic carbon (DOC) into the surrounding waters. The rate of exudation of DOC is depended on the hydrographic condition, nutrient availability, phytoplankton composition, and their size structure. To examine this, samples were collected from the coastal and offshore regions where different hydrographic conditions exists in the Bay of Bengal. The coastal waters were relatively low saline, rich in inorganic nutrients, high phytoplankton biomass (Chl-a) and primary production in the coastal compared to offshore regions. The photic zone integrated Chl-a displayed insignificant difference between coastal and offshore regions whereas higher photic zone integrated primary production was observed in the former than latter region. Dominance of microplankton was observed in the coastal waters associating with high inorganic nitrogen concentrations, in contrast, picoplankton dominated in the offshore region associating with low inorganic nitrogen but high organic nitrogen concentrations. Due to high surface-to-volume ratio of picoplankton, ∼45% of the primary production exudated as DOC in the offshore compared to the coastal region (∼12%) due to dominance of microplankton. The sum of primary production and DOC exudation, called total primary production, was almost equal in the coastal and offshore regions. The mean phytoplankton biomass normalized primary production (pB) in the Bay of Bengal was low (17 ± 8 mgC mgChl-a⁻¹ d⁻¹) compared to Arabian Sea (37 ± 5 mgC mgChl-a⁻¹ d⁻¹). In contrast pB estimated based on total primary production is close (30 ± 16 mgC mgChla⁻¹ d⁻¹) to that of the Arabian Sea (37 ± 5 mgC mgChl-a⁻¹ d⁻¹) suggesting that the Bay of Bengal is equally productive compared to that of Arabian Sea than hitherto hypothesized due to strong stratification and less nutrients input in the former basin. The low sinking carbon flux observed below the photic zone is attributed to the release of primary production as DOC. The released DOC from the phytoplankton may support heterotrophic activity as evidenced by the existence of strong net heterotrophy in the Bay of Bengal. This may lead to the time lag between primary and export productions. None of these processes were incorporated into the numerical models resulting in inaccurate simulations of carbon cycling in the northern Indian Ocean. Modifications in the models by incorporating these processes may improve model simulations for a better understanding the modifications in biogeochemical processes due to climate change in the Bay of Bengal.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141960313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"High-resolution organic and black carbon records in the South Yellow Sea over the last century","authors":"","doi":"10.1016/j.csr.2024.105300","DOIUrl":"10.1016/j.csr.2024.105300","url":null,"abstract":"<div><p>The mud depositional area (\"mud area\") of the South Yellow Sea serves as a prominent carbon sink within the Eastern Continental Shelf of China, offering crucial insights into human activities and climate fluctuations and its relationship with carbon cycle. This study investigates variations in total organic carbon (TOC) and black carbon (BC) concentrations in South Yellow Sea sediments. By combining ²¹⁰Pb isotope analysis with grain-size profiling, the study distinguishes organic carbon origins, revealing the complex interplay between human activities and environmental shifts since the Industrial Revolution. The reasons for discrepancies between TOC and BC contents are analyzed, yielding the following results: (1) Sediment core QY-2 predominantly contains terrestrial-sourced organic carbon, primarily derived from the Yellow River and the Yangtze River. (2) Temporal fluctuations of BC in core QY-2 show distinct trends, periodic responses to human activities, particularly peaks in 1937 and 1945, linked to large-scale wars in China. (3) Relaxed carbon emission regulations in China, coupled with industrial growth spurred by the “reform and opening up” policy, led to a continuous rise in BC content from the mid-1960s to the 1980s, peaking in 1980. Subsequently, reduced BC values during the 1990s correlated with emission control policies and the shift from highly polluting domestic coal stoves to cleaner alternatives like liquefied petroleum gas or natural gas stoves. (4) BC content was influenced by the East Asian monsoon and Pacific Decadal Oscillation (PDO), with higher BC accumulation rates occurring in summer and depletion in winter. (5) Interestingly, changes in BC and TOC content exhibited a negative correlation. While grain size and material sources minimally influenced these discrepancies, the primary driver lay in the water's redox environment, impacting other TOC components and thereby causing variations in both TOC and BC content. This study of black carbon sources to sinks in the South Yellow Sea Mud Area holds significant implications for the broader Yellow Sea sedimentary system and provides support for understanding carbon cycle and marine environments.</p></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":null,"pages":null},"PeriodicalIF":2.1,"publicationDate":"2024-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141997376","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}