Pub Date : 2025-02-01DOI: 10.1016/j.csr.2024.105389
Birane Ndom , Siny Ndoye , Bamol Ali Sow , Vincent Echevin
The Casamance estuary, located in southern Senegal, is a region of remarkable ecological, tourist and economic significance. It undergoes strong seasonal variations of salinity due to its reverse estuary nature during the dry season. This study aims to characterize tidal dynamics in the western part of the Casamance estuary, spanning from the river mouth to the town of Ziguinchor, during the dry season. Utilizing a three-dimensional, non-linear model with a high spatial resolution, we focused on simulating the tidal elevations and currents and evaluating them with sea level and current measurements both within the estuary and at its mouth. Whereas modelled tidal elevations agreed with observations, revealing eastward tidal propagation within the estuary, tidal currents near the river mouth and into the estuary were underestimated. The Eulerian residual circulation was mainly seaward whereas the Lagrangian residual circulation was significantly weaker due to compensation by the Stokes drift. This modeling study marks a crucial first step towards conducting comprehensive environmental impact assessments in the Casamance estuary, paving the way for a deeper understanding and preservation of this region.
{"title":"Tides in the Casamance estuary: A modeling study","authors":"Birane Ndom , Siny Ndoye , Bamol Ali Sow , Vincent Echevin","doi":"10.1016/j.csr.2024.105389","DOIUrl":"10.1016/j.csr.2024.105389","url":null,"abstract":"<div><div>The Casamance estuary, located in southern Senegal, is a region of remarkable ecological, tourist and economic significance. It undergoes strong seasonal variations of salinity due to its reverse estuary nature during the dry season. This study aims to characterize tidal dynamics in the western part of the Casamance estuary, spanning from the river mouth to the town of Ziguinchor, during the dry season. Utilizing a three-dimensional, non-linear model with a high spatial resolution, we focused on simulating the tidal elevations and currents and evaluating them with sea level and current measurements both within the estuary and at its mouth. Whereas modelled tidal elevations agreed with observations, revealing eastward tidal propagation within the estuary, tidal currents near the river mouth and into the estuary were underestimated. The Eulerian residual circulation was mainly seaward whereas the Lagrangian residual circulation was significantly weaker due to compensation by the Stokes drift. This modeling study marks a crucial first step towards conducting comprehensive environmental impact assessments in the Casamance estuary, paving the way for a deeper understanding and preservation of this region.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105389"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145166","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}
Pub Date : 2025-02-01DOI: 10.1016/j.csr.2024.105385
Jiajia Yao , Rujun Yang , Yingying Zhang , Minghan Zhu , Mengqi Bi , Kunyu Ma , Yuan Liu , He Xie , Yao Wu
Iron (Fe) is an essential trace element for the growth and metabolism of marine plankton. Fe(II), the reduced form of iron, is highly soluble and more labile in seawater, contributing significantly to iron bioavailability in marine environments. This study investigates the temporal and spatial distributions of Fe(II) and dissolved iron (DFe) during autumn (October 11–22, 2018), spring (March 4–14, 2019), and summer (July 9–17, 2019) in the Yangtze River estuary. Fe(II) concentrations decreased from nearshore to offshore, with higher levels predominantly in areas influenced by Yangtze River water, indicating that terrestrial input from the river is the main source of Fe(II). Seasonal variations in Fe(II) concentrations were observed, with the highest levels in summer and the lowest in autumn. Median Fe(II) concentrations in autumn, spring and summer were 0.60 nM, 0.81 nM, and 1.33 nM, respectively. DFe concentrations generally decreased from nearshore to offshore, except in summer. The concentration of DFe exhibits seasonal variations. Median DFe concentrations in autumn, spring and summer were 16.10 nM, 44.65 nM, and 22.41 nM, respectively. Both Fe(II) concentrations and Fe(II)/DFe ratios peaked in summer surface waters. Significant correlations were found between Fe(II)/DFe ratios and NH4-N/DIN or NO3-N/DIN ratios in summer.
{"title":"Temporal and spatial distribution of Fe(II) and dissolved iron and their influencing factors in the Yangtze River estuary","authors":"Jiajia Yao , Rujun Yang , Yingying Zhang , Minghan Zhu , Mengqi Bi , Kunyu Ma , Yuan Liu , He Xie , Yao Wu","doi":"10.1016/j.csr.2024.105385","DOIUrl":"10.1016/j.csr.2024.105385","url":null,"abstract":"<div><div>Iron (Fe) is an essential trace element for the growth and metabolism of marine plankton. Fe(II), the reduced form of iron, is highly soluble and more labile in seawater, contributing significantly to iron bioavailability in marine environments. This study investigates the temporal and spatial distributions of Fe(II) and dissolved iron (DFe) during autumn (October 11–22, 2018), spring (March 4–14, 2019), and summer (July 9–17, 2019) in the Yangtze River estuary. Fe(II) concentrations decreased from nearshore to offshore, with higher levels predominantly in areas influenced by Yangtze River water, indicating that terrestrial input from the river is the main source of Fe(II). Seasonal variations in Fe(II) concentrations were observed, with the highest levels in summer and the lowest in autumn. Median Fe(II) concentrations in autumn, spring and summer were 0.60 nM, 0.81 nM, and 1.33 nM, respectively. DFe concentrations generally decreased from nearshore to offshore, except in summer. The concentration of DFe exhibits seasonal variations. Median DFe concentrations in autumn, spring and summer were 16.10 nM, 44.65 nM, and 22.41 nM, respectively. Both Fe(II) concentrations and Fe(II)/DFe ratios peaked in summer surface waters. Significant correlations were found between Fe(II)/DFe ratios and NH<sub>4</sub>-N/DIN or NO<sub>3</sub>-N/DIN ratios in summer.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105385"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145167","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 : 2025-02-01DOI: 10.1016/j.csr.2024.105397
Filipe Vieira , Alexsandra S. Lima , Geórgenes H. Cavalcante
This study presents a spectral wave model developed and validated for the Alagoas State in NE Brazil using satellite altimeter data. The model, spanning 32 years from 1979 to 2010, driven by CFSR wind forcing, captures the wave climate dynamics across seasons and regions. Energetic waves dominate winter and spring, contrasting with milder conditions in summer. Spatially, heightened wave activity is concentrated in the southern border with Sergipe, notably near the São Francisco River mouth, gradually tapering off towards the northern coast. Trends in significant wave height (Hm0) reveal seasonal fluctuations, with winter and spring exhibiting positive trends, while summer trends are predominantly negative. Notably, winter trends peak at 0.6% per year along the central to southern coastal stretch. Conversely, summer witnesses a maximum negative trend of 0.4% per year nearshore. Over the 32-year span, the annual mean shows a general negative trend (∼0.2% per year) across most of the study area, albeit with minor positive trends in the northern region. Particularly noteworthy is the accelerated increase (∼0.4% per year) in extreme conditions (P99) nearshore where Hm0 reached 2.7 m on Maceió coast potentially exacerbating erosion and should be the object of further considerations for coastal management design.
{"title":"Characterization of wave climate and trends for Alagoas State, NE Brazil","authors":"Filipe Vieira , Alexsandra S. Lima , Geórgenes H. Cavalcante","doi":"10.1016/j.csr.2024.105397","DOIUrl":"10.1016/j.csr.2024.105397","url":null,"abstract":"<div><div>This study presents a spectral wave model developed and validated for the Alagoas State in NE Brazil using satellite altimeter data. The model, spanning 32 years from 1979 to 2010, driven by CFSR wind forcing, captures the wave climate dynamics across seasons and regions. Energetic waves dominate winter and spring, contrasting with milder conditions in summer. Spatially, heightened wave activity is concentrated in the southern border with Sergipe, notably near the São Francisco River mouth, gradually tapering off towards the northern coast. Trends in significant wave height (H<sub>m0</sub>) reveal seasonal fluctuations, with winter and spring exhibiting positive trends, while summer trends are predominantly negative. Notably, winter trends peak at 0.6% per year along the central to southern coastal stretch. Conversely, summer witnesses a maximum negative trend of 0.4% per year nearshore. Over the 32-year span, the annual mean shows a general negative trend (∼0.2% per year) across most of the study area, albeit with minor positive trends in the northern region. Particularly noteworthy is the accelerated increase (∼0.4% per year) in extreme conditions (P99) nearshore where H<sub>m0</sub> reached 2.7 m on Maceió coast potentially exacerbating erosion and should be the object of further considerations for coastal management design.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105397"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145174","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 : 2025-02-01DOI: 10.1016/j.csr.2024.105374
K.H. Brink
Idealized primitive equation numerical model experiments are used to investigate the coastal downwelling driven by an alongshore wind stress of limited alongshore extent.
Within the forced region, results are qualitatively as expected from previous two-dimensional studies: a nearshore pool of light, homogeneous water is formed, and there is a distinct front separating this pool from ambient stratified waters farther offshore. The front, given sufficient time, extends alongshore from the forcing region hundreds of kilometers “downwave” (in the sense of long coastal trapped wave propagation). Expressions are developed to predict the offshore location of the downwelling front as a function alongshore distance. The key to these scalings is to assume that the total (integrated alongshore) volume of water downwelled per unit time is balanced by a strictly alongshore flow in the “downwave” direction.
{"title":"Determining the cross-shelf scales of coastal downwelling","authors":"K.H. Brink","doi":"10.1016/j.csr.2024.105374","DOIUrl":"10.1016/j.csr.2024.105374","url":null,"abstract":"<div><div>Idealized primitive equation numerical model experiments are used to investigate the coastal downwelling driven by an alongshore wind stress of limited alongshore extent.</div><div>Within the forced region, results are qualitatively as expected from previous two-dimensional studies: a nearshore pool of light, homogeneous water is formed, and there is a distinct front separating this pool from ambient stratified waters farther offshore. The front, given sufficient time, extends alongshore from the forcing region hundreds of kilometers “downwave” (in the sense of long coastal trapped wave propagation). Expressions are developed to predict the offshore location of the downwelling front as a function alongshore distance. The key to these scalings is to assume that the total (integrated alongshore) volume of water downwelled per unit time is balanced by a strictly alongshore flow in the “downwave” direction.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105374"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145098","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 : 2025-02-01DOI: 10.1016/j.csr.2024.105388
J. Ibarra-Romero , E. Mateos , S.G. Marinone
The wind breeze effect on the Todos Santos Bay, Baja California summer currents were analyzed through various numerical experiments, including the coupling of an oceanic and atmospheric model. It was found that the average currents and their variability are modified by the sea breeze, mainly in the shallow region (<40 m) and in the superficial layers (>5 m). The bay average circulation was found to be cyclonic in all the experiments. However, in the presence of sea breeze, the cyclonic circulation was less intense. The lower intensity was due to the breeze-synoptic wind interaction that inhibits the positive curl wind stress in shallow regions of the bay. Consequently, the Ekman pumping was suppressed, and the mixing of surface layers was promoted. Numerical evidence shows that the breeze was the main factor for the variability of the current above 5 m depth. A possible mechanism that explains the breezes' importance in the current's variability is that the diurnal wind-driven currents resonate with the bay inertial currents.
{"title":"The effects of summer breeze on Todos Santos Bay current, Ensenada, B.C., Mexico","authors":"J. Ibarra-Romero , E. Mateos , S.G. Marinone","doi":"10.1016/j.csr.2024.105388","DOIUrl":"10.1016/j.csr.2024.105388","url":null,"abstract":"<div><div>The wind breeze effect on the Todos Santos Bay, Baja California summer currents were analyzed through various numerical experiments, including the coupling of an oceanic and atmospheric model. It was found that the average currents and their variability are modified by the sea breeze, mainly in the shallow region (<40 m) and in the superficial layers (>5 m). The bay average circulation was found to be cyclonic in all the experiments. However, in the presence of sea breeze, the cyclonic circulation was less intense. The lower intensity was due to the breeze-synoptic wind interaction that inhibits the positive curl wind stress in shallow regions of the bay. Consequently, the Ekman pumping was suppressed, and the mixing of surface layers was promoted. Numerical evidence shows that the breeze was the main factor for the variability of the current above 5 m depth. A possible mechanism that explains the breezes' importance in the current's variability is that the diurnal wind-driven currents resonate with the bay inertial currents.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105388"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145145","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}
Algal reefs are unique and valuable yet poorly understood marine ecosystems. The causal relationships between environmental driving forces and biotic community distributions in an algal reef ecosystem were assessed to fill large scientific gaps. Using a structural equation model (SEM) coupled with factor analysis, we established a well-fitted algal reef SEM. This model revealed that there were two subsystems, one operating primarily above the reef laminated substratum and the other beneath the surface. The crustose coralline algae (CCA) and non-CCA cover areas were affected, with an inverse trend between the two, by river inputs, as indicated by NH3-N concentrations, and by the seasonal rhythm of riverine NO3-N concentrations. The trends revealed spatial competition between the two algal groups. The CCA coverage and epifaunal gastropod density responded positively to the presence of pebble habitat. Notably, sand coverage and its variation did not hinder the coverage of the two macrophytes. However, the epifaunal gastropod and arthropod densities were negatively regulated by the sand coverage variability. The infaunal arthropod density was positively influenced by the sediment heavy metal content. Among the biotic communities, the non-CCA cover area negatively affected the infaunal polychaeta density. Furthermore, the increasing infaunal polychaete density increased those of sipunculans, bivalves, and arthropods, implying co-occurrence. This SEM revealed that riverine nutrients, pebble habitat type and sand coverage variability were significant environmental drivers in organizing the biotic communities in an algal reef ecosystem.
{"title":"Exploring the causal relationships between environmental factors and benthos distributions in an intertidal algal reef ecosystem via a structural equation model","authors":"Chun-Wei Wu , Shih-wei Liao , Showe-Mei Lin , Shou-Chung Huang , Chang-Po Chen , Po-Kang Shih , Hwey-Lian Hsieh","doi":"10.1016/j.csr.2024.105382","DOIUrl":"10.1016/j.csr.2024.105382","url":null,"abstract":"<div><div>Algal reefs are unique and valuable yet poorly understood marine ecosystems. The causal relationships between environmental driving forces and biotic community distributions in an algal reef ecosystem were assessed to fill large scientific gaps. Using a structural equation model (SEM) coupled with factor analysis, we established a well-fitted algal reef SEM. This model revealed that there were two subsystems, one operating primarily above the reef laminated substratum and the other beneath the surface. The crustose coralline algae (CCA) and non-CCA cover areas were affected, with an inverse trend between the two, by river inputs, as indicated by NH<sub>3</sub>-N concentrations, and by the seasonal rhythm of riverine NO<sub>3</sub>-N concentrations. The trends revealed spatial competition between the two algal groups. The CCA coverage and epifaunal gastropod density responded positively to the presence of pebble habitat. Notably, sand coverage and its variation did not hinder the coverage of the two macrophytes. However, the epifaunal gastropod and arthropod densities were negatively regulated by the sand coverage variability. The infaunal arthropod density was positively influenced by the sediment heavy metal content. Among the biotic communities, the non-CCA cover area negatively affected the infaunal polychaeta density. Furthermore, the increasing infaunal polychaete density increased those of sipunculans, bivalves, and arthropods, implying co-occurrence. This SEM revealed that riverine nutrients, pebble habitat type and sand coverage variability were significant environmental drivers in organizing the biotic communities in an algal reef ecosystem.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105382"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145097","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}
Pub Date : 2025-02-01DOI: 10.1016/j.csr.2024.105370
Ahmed I. Rushdi , Hattan A. Alharbi , Najeeb Rasul , Abdulqader Bazeyad , Bernd R.T. Simoneit , Miguel A. Goni , Khalid F. Al-Mutlaq
Samples from the upper surface sediments of Obhur Lagoon, located north of Jeddah, were collected to analyze the concentrations, spatial distribution, and origins of natural lipids. The lagoon was segmented into three zones based on their surrounding ecosystems: Z I (adjacent to inland areas), Z II (the transitional region between Z I and the coastal Z III), and Z III (the coastal region). The primary natural biogenic lipid compounds found in the total extractable organic matter (TEOM) included n-alkanes (partial), fatty acids, fatty alcohols, and steroids. The n-alkanes of biogenic origin were primarily derived from terrestrial higher plant wax, decreasing from approximately 38% in Z I to 12% in Z III. Conversely, contributions from aquatic algae and diatoms increased from about 1% to 8% from Z I to Z III, while microbial inputs declined from roughly 3%–0.5% over the same zones. The relative concentrations of fatty acids from higher plants varied, accounting for about 6% in Z I, 4% in Z II, and 5% in Z III. Aquatic algae sources contributed approximately 80% in all regions, and microbial inputs slightly decreased from 14% to 12% from Z I to Z III. Terrestrial inputs of fatty n-alcohols declined from around 32% in Z I to 11% in Z III, while contributions from aquatic algae and diatoms decreased from about 62% to 45% from Z I to Z III, with microbial inputs remaining around 10%. Steroid inputs from terrestrial plants decreased from 37% in Z I to 16% in Z III, while those from aquatic biota increased from 58% in Z I to 76% in Z III. The microbial inputs of steroids were highest in Z III (11.5%), followed by Z II (9.9%) and Z I (9.4%). The total natural lipid contributions from terrestrial sources decreased from 42.8% in Z I to 19.2% in Z III, while the aquatic source component increased from 53.0% in Z I to 77.4% in Z III. These results suggest that the lagoon's biogeochemistry is influenced by the surrounding ecosystems, lagoon hydrodynamics, and local human and social activities.
{"title":"Concentrations, spatial distributions, and origins of natural aliphatic lipids and sterols in sediments of Obhur Lagoon, Red Sea Coast, Saudi Arabia","authors":"Ahmed I. Rushdi , Hattan A. Alharbi , Najeeb Rasul , Abdulqader Bazeyad , Bernd R.T. Simoneit , Miguel A. Goni , Khalid F. Al-Mutlaq","doi":"10.1016/j.csr.2024.105370","DOIUrl":"10.1016/j.csr.2024.105370","url":null,"abstract":"<div><div>Samples from the upper surface sediments of Obhur Lagoon, located north of Jeddah, were collected to analyze the concentrations, spatial distribution, and origins of natural lipids. The lagoon was segmented into three zones based on their surrounding ecosystems: Z I (adjacent to inland areas), Z II (the transitional region between Z I and the coastal Z III), and Z III (the coastal region). The primary natural biogenic lipid compounds found in the total extractable organic matter (TEOM) included <u>n</u>-alkanes (partial), fatty acids, fatty alcohols, and steroids. The <u>n</u>-alkanes of biogenic origin were primarily derived from terrestrial higher plant wax, decreasing from approximately 38% in Z I to 12% in Z III. Conversely, contributions from aquatic algae and diatoms increased from about 1% to 8% from Z I to Z III, while microbial inputs declined from roughly 3%–0.5% over the same zones. The relative concentrations of fatty acids from higher plants varied, accounting for about 6% in Z I, 4% in Z II, and 5% in Z III. Aquatic algae sources contributed approximately 80% in all regions, and microbial inputs slightly decreased from 14% to 12% from Z I to Z III. Terrestrial inputs of fatty <u>n</u>-alcohols declined from around 32% in Z I to 11% in Z III, while contributions from aquatic algae and diatoms decreased from about 62% to 45% from Z I to Z III, with microbial inputs remaining around 10%. Steroid inputs from terrestrial plants decreased from 37% in Z I to 16% in Z III, while those from aquatic biota increased from 58% in Z I to 76% in Z III. The microbial inputs of steroids were highest in Z III (11.5%), followed by Z II (9.9%) and Z I (9.4%). The total natural lipid contributions from terrestrial sources decreased from 42.8% in Z I to 19.2% in Z III, while the aquatic source component increased from 53.0% in Z I to 77.4% in Z III. These results suggest that the lagoon's biogeochemistry is influenced by the surrounding ecosystems, lagoon hydrodynamics, and local human and social activities.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105370"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145104","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 : 2025-02-01DOI: 10.1016/j.csr.2024.105394
Chunyan Li
Transient weather systems are often associated with alternating warm and cold advections of air masses and changing wind directions, which drive coastal ocean and estuarine waters to oscillate quasi-periodically. Quantifying water transport under these meteorologically induced oscillations — between inland waterways and the coastal ocean — helps to interpret land-ocean interactions, sediment transport, and other effects of migrating weather systems. The challenge lies in the difficulty of obtaining continuous, long-term direct measurements of transport due to logistical constraints. Here, we apply a method to determine the meteorological tide-induced volume transport of water using an intensive survey. We correlate transport values measured by a boat-mounted ADCP with vertically averaged velocities from a bottom-mounted ADCP, which recorded a much longer time series. The correlation is then used to compute transport over the period of the bottom-mounted ADCP deployment. Observations were conducted at Belle Pass, Port Fourchon. The transport data revealed the impact of weather systems, including four cold fronts. A model of volume transport, accounting for rotary cold front wind variations, was applied, where both along-channel and along-coastline wind components contribute to the remote wind effect, leading to a more complex response to passing weather systems. The local wind effect is much smaller than the remote wind effect, and transport is primarily controlled by water level fluctuations resulting from open boundary input. Finally, the channel orientation relative to the coastline is found to be critical in determining both the magnitude and phase of the transport.
{"title":"Determining meteorological tidal transport through a channel on the coast","authors":"Chunyan Li","doi":"10.1016/j.csr.2024.105394","DOIUrl":"10.1016/j.csr.2024.105394","url":null,"abstract":"<div><div>Transient weather systems are often associated with alternating warm and cold advections of air masses and changing wind directions, which drive coastal ocean and estuarine waters to oscillate quasi-periodically. Quantifying water transport under these meteorologically induced oscillations — between inland waterways and the coastal ocean — helps to interpret land-ocean interactions, sediment transport, and other effects of migrating weather systems. The challenge lies in the difficulty of obtaining continuous, long-term direct measurements of transport due to logistical constraints. Here, we apply a method to determine the meteorological tide-induced volume transport of water using an intensive survey. We correlate transport values measured by a boat-mounted ADCP with vertically averaged velocities from a bottom-mounted ADCP, which recorded a much longer time series. The correlation is then used to compute transport over the period of the bottom-mounted ADCP deployment. Observations were conducted at Belle Pass, Port Fourchon. The transport data revealed the impact of weather systems, including four cold fronts. A model of volume transport, accounting for rotary cold front wind variations, was applied, where both along-channel and along-coastline wind components contribute to the remote wind effect, leading to a more complex response to passing weather systems. The local wind effect is much smaller than the remote wind effect, and transport is primarily controlled by water level fluctuations resulting from open boundary input. Finally, the channel orientation relative to the coastline is found to be critical in determining both the magnitude and phase of the transport.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105394"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145169","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}
Hypoxia in the mesopelagic and demersal realms of marine ecosystems directly or indirectly affects fish population structure, community composition and ecosystem functioning. This may result in excess mortality or the emigration of organisms from the area, resulting in dead zones. The present study reports on a dead zone on the north-western Bay of Bengal's continental margin with no discernible fish catch. The phenomenon is associated with stratification, small residence time of suspended matter in the water column and weak vertical/horizontal mixing due to a retention area (and increased biological flux) observed in the region as a result of cooccurring warm and cold core eddies, resulting intense decompose activities in the regional bottom. As with similar ocean zones globally, dominance of a single species (Parascombrops pellucidus) around the zone's periphery (edge effect) is also reported which is attributed to their feeding patterns, locomotory characteristics, prey preferences and availability. The dead zone's seasonal occurrence indicates the influence of natural or anthropogenically induced climatic variability can even affect demersal/bottom-dwelling organisms. The present work discusses the drivers and implications of dead zones using in situ oceanographic and fishery data, remote sensing observations and model outputs.
{"title":"A dead zone on the north-western Bay of Bengal's continental margin and its alarming impact on the distribution of demersal fishes","authors":"Manjebrayakath Hashim, B.R. Smitha, K.V. Aneesh Kumar","doi":"10.1016/j.csr.2024.105398","DOIUrl":"10.1016/j.csr.2024.105398","url":null,"abstract":"<div><div>Hypoxia in the mesopelagic and demersal realms of marine ecosystems directly or indirectly affects fish population structure, community composition and ecosystem functioning. This may result in excess mortality or the emigration of organisms from the area, resulting in <em>dead zones</em>. The present study reports on a <em>dead zone</em> on the north-western Bay of Bengal's continental margin with no discernible fish catch. The phenomenon is associated with stratification, small residence time of suspended matter in the water column and weak vertical/horizontal mixing due to a retention area (and increased biological flux) observed in the region as a result of cooccurring warm and cold core eddies, resulting intense decompose activities in the regional bottom. As with similar ocean zones globally, dominance of a single species (<em>Parascombrops pellucidus</em>) around the zone's periphery (<em>edge effect</em>) is also reported which is attributed to their feeding patterns, locomotory characteristics, prey preferences and availability. The <em>dead zone</em>'s seasonal occurrence indicates the influence of natural or anthropogenically induced climatic variability can even affect demersal/bottom-dwelling organisms. The present work discusses the drivers and implications of <em>dead zones</em> using in situ oceanographic and fishery data, remote sensing observations and model outputs.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105398"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145281","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 : 2025-02-01DOI: 10.1016/j.csr.2024.105362
Giuliana Andrea Díaz-Mendoza , Knut Krämer , Gitta Ann von Rönn , Christoph Heinrich , Klaus Schwarzer , Hans-Christian Reimers , Christian Winter
The Southwestern Baltic Sea is a notable example of intense human impact on the seafloor in a confined shallow marine environment. Various marks left by dredging, dumping, fishing, anchoring, among others, reflect the different pressures on the seafloor. These activities represent cumulative stressors for marine ecosystems, potentially leading to habitat modification or loss. Characterizing and quantifying the extent of the different pressures is essential for understanding the system and evaluating the environmental status outlined by different legal frameworks. Here, the effects of different human activities on the seafloor in exemplary hotspots in the SW Baltic Sea are visualized and assessed. Actual anthropogenic marks are compared with assessments based on commonly accessible regional and local information from remote sensing data and institutional sources. About 36% of the seafloor of the investigated area is influenced, mainly by bottom trawling, propeller scouring, anchoring, and dumping. More than 91% of the human footprint corresponds to trawl marks, mainly affecting soft substrates. In addition, from 15% to 47% of the seafloor is disturbed in selected ‘detail areas' within the hotspots. Comparisons with indirect data used for regional pressure estimation demonstrate how hydroacoustic data can enhance assessments of seabed physical pressures. However, quantitative comparisons are challenging, especially when information on human activities is limited or when seafloor recovery rates in relation to the frequency of anthropogenic pressures are unknown.
{"title":"Hotspots of human impact on the seafloor in the Southwestern Baltic Sea","authors":"Giuliana Andrea Díaz-Mendoza , Knut Krämer , Gitta Ann von Rönn , Christoph Heinrich , Klaus Schwarzer , Hans-Christian Reimers , Christian Winter","doi":"10.1016/j.csr.2024.105362","DOIUrl":"10.1016/j.csr.2024.105362","url":null,"abstract":"<div><div>The Southwestern Baltic Sea is a notable example of intense human impact on the seafloor in a confined shallow marine environment. Various marks left by dredging, dumping, fishing, anchoring, among others, reflect the different pressures on the seafloor. These activities represent cumulative stressors for marine ecosystems, potentially leading to habitat modification or loss. Characterizing and quantifying the extent of the different pressures is essential for understanding the system and evaluating the environmental status outlined by different legal frameworks. Here, the effects of different human activities on the seafloor in exemplary hotspots in the SW Baltic Sea are visualized and assessed. Actual anthropogenic marks are compared with assessments based on commonly accessible regional and local information from remote sensing data and institutional sources. About 36% of the seafloor of the investigated area is influenced, mainly by bottom trawling, propeller scouring, anchoring, and dumping. More than 91% of the human footprint corresponds to trawl marks, mainly affecting soft substrates. In addition, from 15% to 47% of the seafloor is disturbed in selected ‘detail areas' within the hotspots. Comparisons with indirect data used for regional pressure estimation demonstrate how hydroacoustic data can enhance assessments of seabed physical pressures. However, quantitative comparisons are challenging, especially when information on human activities is limited or when seafloor recovery rates in relation to the frequency of anthropogenic pressures are unknown.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"285 ","pages":"Article 105362"},"PeriodicalIF":2.1,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143145101","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}
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