Pub Date : 2025-12-24DOI: 10.1016/j.csr.2025.105631
Jochen Kämpf
Using a coupled physical-biological model, this work investigates the spreading of an unprecedented harmful algal bloom (HAB) that since March 2025 has been causing massive kills of marine animals in Gulf St. Vincent, which alongside Spencer Gulf is one of the two South Australian gulfs. The gulfs are large inverse estuaries with limited physical connectivity to the ambient coastal ocean. The biological model accounts for algal growth, mortality due to turbulent shear rate, a sink term representing other effects like zooplankton grazing, and diel vertical migration. The growth rate is based on the known physiology of Karenia mikimotoi, initially thought to dominate the algal bloom. For simplicity, limitations of algal growth due to lack of nutrients or oxygen are ignored. The model hindcast reproduces the initial spreading of the HAB, which started in mid-March 2025 just outside Gulf St. Vincent, from where it spread across this entire gulf within 2–3 months, not affecting Spencer Gulf. Seasonal cooling of gulf waters during winter reduces the growth rate and hence the cell densities of K. mikimotoi. The worst-case model scenario predicts both the spreading of the algal bloom through Spencer Gulf and its future resurgence in warmer waters in both gulfs. Surprisingly and in contrast to the model prediction, high cell counts >1000 cells mL−1 of Karenia species still persisted in Gulf St. Vincent throughout the winter months. Moreover. a recent laboratory analysis of water samples revealed that, while K. mikimotoi had the expected low cell densities in colder water, another Karenia species, known as K. cristata, dominated the algal bloom mix during winter. Additional model simulations address this missing Karenia species under the assumption that it grows well in cold water.
{"title":"Prediction of the spreading of an unprecedented harmful algal bloom in South Australian gulfs","authors":"Jochen Kämpf","doi":"10.1016/j.csr.2025.105631","DOIUrl":"10.1016/j.csr.2025.105631","url":null,"abstract":"<div><div>Using a coupled physical-biological model, this work investigates the spreading of an unprecedented harmful algal bloom (HAB) that since March 2025 has been causing massive kills of marine animals in Gulf St. Vincent, which alongside Spencer Gulf is one of the two South Australian gulfs. The gulfs are large inverse estuaries with limited physical connectivity to the ambient coastal ocean. The biological model accounts for algal growth, mortality due to turbulent shear rate, a sink term representing other effects like zooplankton grazing, and diel vertical migration. The growth rate is based on the known physiology of <em>Karenia mikimotoi</em>, initially thought to dominate the algal bloom. For simplicity, limitations of algal growth due to lack of nutrients or oxygen are ignored. The model hindcast reproduces the initial spreading of the HAB, which started in mid-March 2025 just outside Gulf St. Vincent, from where it spread across this entire gulf within 2–3 months, not affecting Spencer Gulf. Seasonal cooling of gulf waters during winter reduces the growth rate and hence the cell densities of <em>K. mikimotoi</em>. The worst-case model scenario predicts both the spreading of the algal bloom through Spencer Gulf and its future resurgence in warmer waters in both gulfs. Surprisingly and in contrast to the model prediction, high cell counts >1000 cells mL<sup>−1</sup> of <em>Karenia</em> species still persisted in Gulf St. Vincent throughout the winter months. Moreover. a recent laboratory analysis of water samples revealed that, while <em>K. mikimotoi</em> had the expected low cell densities in colder water, another <em>Karenia</em> species, known as <em>K. cristata</em>, dominated the algal bloom mix during winter. Additional model simulations address this missing <em>Karenia</em> species under the assumption that it grows well in cold water.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105631"},"PeriodicalIF":2.2,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840264","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}
Magnetic minerals are ubiquitous in estuarine, coastal, and shelf systems and potential recorders of geological, climatic and sedimentary processes. Sediments in the tropical sedimentary system of Goa have been extensively studied to reconstruct the paleoenvironment changes, sedimentation, and diagenetic history. However, a dedicated source-to-sink analysis of sediments delivered to the Arabian Sea (off Goa, India) using a magnetic and sedimentological approach was so far lacking. Such analysis is crucial for the development of environmental magnetism based mineralogical proxies. The present study sets out to identify environmental fingerprints of magnetic minerals originating from diverse sources and depositional environments, and assess their relative magnetic contribution to the bedload sediments in a complex tropical estuarine and marine shelf system of Goa, India. Compilation of magnetic and grain size properties of catchment rocks, riverbank soils, and bedload (fluvial, estuarine, marine) sediments of Goa, India showed large variations in the composition of magnetic mineral and distribution pattern. A clear N-S magnetic contrast in estuaries of Goa, India showing a decline in ferrimagnetic minerals content, followed by subsequent increase in high coercivity minerals and volume of coarser clastic size sediments suggest a marked change in sediment provenance. Grain size distribution of the studied estuarine sediments revealed two distinct patterns, which seems to be controlled by contrasting sediment provenance, changing detrital input, riverine morphology, and hydro-and sediment dynamics. A noticeable source-to-sink trend of loss of fluvial-derived fine silt-size bedload sediments and selective retention of coarser sediments within the south Goa estuaries can be reconciled with the efficient sediment partitioning regime driven by regional hydrodynamics, which restricted the settling of finer fluvial sediment fraction and therefore got regularly exported out to the Arabian Sea. Poor linkage between magnetic susceptibility and organic carbon content in estuaries of Goa suggest that early diagenesis had minimal impact on the bulk sediment magnetic signal. Our study provide full spectrum of magnetic properties of rocks, soils, and modern sediments, which helped in establishing the magnetic mineral inventory of the tropical estuarine system of Goa. Interpretation of rock magnetic and grain size data of bedload sediments provide crucial insights on sedimentary processes constraining the transport and depositional of magnetic particles and clastic sediment grain size fractions during their transit from source-to-sink. We demonstrate that magnetomineralogical approach presented in this study bears the potential and can be easily applied to trace the modern source-to-sink processes in other larger tropical sedimentary system around the world.
{"title":"Magnetic mineralogical and sedimentological approach for tracing source-to-sink processes in a tropical fluvial, estuarine, and marine system","authors":"Firoz Badesab , Nitin Kadam , Prashila Pednekar , Shazia Shaheen , Omkar Sagavekar , Sriram Gullapalli , Mamilla Venkateshwarlu , T. Vijaya Kumar , A.V. Satyakumar , K. Mohan , Virsen Gaikwad , Satish J. Sangode , Shubham Waghmare , Anish Varma , E.V.S.S.K. Babu , Sakshi Raikar","doi":"10.1016/j.csr.2025.105630","DOIUrl":"10.1016/j.csr.2025.105630","url":null,"abstract":"<div><div>Magnetic minerals are ubiquitous in estuarine, coastal, and shelf systems and potential recorders of geological, climatic and sedimentary processes. Sediments in the tropical sedimentary system of Goa have been extensively studied to reconstruct the paleoenvironment changes, sedimentation, and diagenetic history. However, a dedicated source-to-sink analysis of sediments delivered to the Arabian Sea (off Goa, India) using a magnetic and sedimentological approach was so far lacking. Such analysis is crucial for the development of environmental magnetism based mineralogical proxies. The present study sets out to identify environmental fingerprints of magnetic minerals originating from diverse sources and depositional environments, and assess their relative magnetic contribution to the bedload sediments in a complex tropical estuarine and marine shelf system of Goa, India. Compilation of magnetic and grain size properties of catchment rocks, riverbank soils, and bedload (fluvial, estuarine, marine) sediments of Goa, India showed large variations in the composition of magnetic mineral and distribution pattern. A clear N-S magnetic contrast in estuaries of Goa, India showing a decline in ferrimagnetic minerals content, followed by subsequent increase in high coercivity minerals and volume of coarser clastic size sediments suggest a marked change in sediment provenance. Grain size distribution of the studied estuarine sediments revealed two distinct patterns, which seems to be controlled by contrasting sediment provenance, changing detrital input, riverine morphology, and hydro-and sediment dynamics. A noticeable source-to-sink trend of loss of fluvial-derived fine silt-size bedload sediments and selective retention of coarser sediments within the south Goa estuaries can be reconciled with the efficient sediment partitioning regime driven by regional hydrodynamics, which restricted the settling of finer fluvial sediment fraction and therefore got regularly exported out to the Arabian Sea. Poor linkage between magnetic susceptibility and organic carbon content in estuaries of Goa suggest that early diagenesis had minimal impact on the bulk sediment magnetic signal. Our study provide full spectrum of magnetic properties of rocks, soils, and modern sediments, which helped in establishing the magnetic mineral inventory of the tropical estuarine system of Goa. Interpretation of rock magnetic and grain size data of bedload sediments provide crucial insights on sedimentary processes constraining the transport and depositional of magnetic particles and clastic sediment grain size fractions during their transit from source-to-sink. We demonstrate that magnetomineralogical approach presented in this study bears the potential and can be easily applied to trace the modern source-to-sink processes in other larger tropical sedimentary system around the world.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"298 ","pages":"Article 105630"},"PeriodicalIF":2.2,"publicationDate":"2025-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145886054","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 : 2025-12-19DOI: 10.1016/j.csr.2025.105626
Carlos A.F. Schettini , Nils E. Asp
The hydrodynamics of the inner shelf east of the Amazon River mouth in the Southeastern Amazon Coastal Zone (SACZ) are examined based on 1.5 years of observations of wind and currents. A meteorological station was established onshore to record the wind data, while an acoustic Doppler current profiler was moored offshore at a depth of 22 m. This is the first observational dataset of such length and quality east of the Amazon River mouth off SACZ. The results reveal two primary modes of hydrodynamic variation associated with the zonal migration of the Intertropical Convergence Zone (ITCZ), which significantly influences the regional wind regime. The first mode, termed “wet”, occurs when the ITCZ shifts southward, leading to brief periods (hours to days) of wind relaxation. In contrast, the second mode, referred to as “dry”, is characterized by a northward displacement of the ITCZ, resulting in more intense and consistent wind conditions. Throughout the year, the hydrodynamics are predominantly controlled by semidiurnal meso (neap) and macro (spring) tidal regimes, accounting for more than 98 % of the variance in cross-shelf currents and more than 90 % of longitudinal currents. This dominance is especially pronounced during the dry mode. In the wet mode, the current regime exhibits greater vertical variability, with low-frequency currents near the surface potentially dominating (>80 %). These low-frequency currents are associated with periods of wind relaxation and the eastward advance of the Amazon River plume. During the dry mode, low-frequency currents are influenced primarily by wind action, with a secondary contribution from the synodic modulation of tidal amplitude.
{"title":"Hydrodynamics of the inner shelf east of the Amazon River mouth","authors":"Carlos A.F. Schettini , Nils E. Asp","doi":"10.1016/j.csr.2025.105626","DOIUrl":"10.1016/j.csr.2025.105626","url":null,"abstract":"<div><div>The hydrodynamics of the inner shelf east of the Amazon River mouth in the Southeastern Amazon Coastal Zone (SACZ) are examined based on 1.5 years of observations of wind and currents. A meteorological station was established onshore to record the wind data, while an acoustic Doppler current profiler was moored offshore at a depth of 22 m. This is the first observational dataset of such length and quality east of the Amazon River mouth off SACZ. The results reveal two primary modes of hydrodynamic variation associated with the zonal migration of the Intertropical Convergence Zone (ITCZ), which significantly influences the regional wind regime. The first mode, termed “wet”, occurs when the ITCZ shifts southward, leading to brief periods (hours to days) of wind relaxation. In contrast, the second mode, referred to as “dry”, is characterized by a northward displacement of the ITCZ, resulting in more intense and consistent wind conditions. Throughout the year, the hydrodynamics are predominantly controlled by semidiurnal meso (neap) and macro (spring) tidal regimes, accounting for more than 98 % of the variance in cross-shelf currents and more than 90 % of longitudinal currents. This dominance is especially pronounced during the dry mode. In the wet mode, the current regime exhibits greater vertical variability, with low-frequency currents near the surface potentially dominating (>80 %). These low-frequency currents are associated with periods of wind relaxation and the eastward advance of the Amazon River plume. During the dry mode, low-frequency currents are influenced primarily by wind action, with a secondary contribution from the synodic modulation of tidal amplitude.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105626"},"PeriodicalIF":2.2,"publicationDate":"2025-12-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790317","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 : 2025-12-18DOI: 10.1016/j.csr.2025.105628
Rafał Nawrot , Melita Peharda , Saskia Macharia , Hana Uvanović , Adam Tomašových , Martin Zuschin
Changes in life history of marine species in response to harvesting and human-induced environmental changes are frequently observed in modern ecosystems, but the true magnitude of these shifts is difficult to evaluate without robust information on the pre-impact state of the affected populations. The edible bivalve Noah's Ark shell (Arca noae L.) was extensively harvested in the eastern Adriatic Sea in the late 19th and early 20th century until its fishery collapsed following mass mortality in the late 1940s. The lack of data on growth parameters of this species prior to that event biases our understanding of its life history and complicates establishing sustainable levels of harvesting. To provide a baseline for assessment of the current state of populations of A. noae in the Adriatic Sea, we compared growth rates and lifespan, estimated based on annual shell growth lines, between live-collected individuals and fossil (Holocene) specimens sampled from sediment cores. The maximum age observed in our modern samples was 35 years whereas the ontogenetically oldest fossil specimen lived for at least 85 years, extending the longest recorded lifespan for the Arcidae family by over three decades. Our results indicate that individuals of A. noae collected in the 21st century grow faster and have much shorter lifespan compared to their Holocene counterparts, suggesting that intensive harvesting in the past combined with increasing water temperatures and eutrophication of the northern Adriatic Sea had a significant impact on the population dynamics of this species.
{"title":"Fossil evidence for accelerated growth and shorter lifespan in the harvested bivalve Arca noae in the Adriatic Sea","authors":"Rafał Nawrot , Melita Peharda , Saskia Macharia , Hana Uvanović , Adam Tomašových , Martin Zuschin","doi":"10.1016/j.csr.2025.105628","DOIUrl":"10.1016/j.csr.2025.105628","url":null,"abstract":"<div><div>Changes in life history of marine species in response to harvesting and human-induced environmental changes are frequently observed in modern ecosystems, but the true magnitude of these shifts is difficult to evaluate without robust information on the pre-impact state of the affected populations. The edible bivalve Noah's Ark shell (<em>Arca noae</em> L.) was extensively harvested in the eastern Adriatic Sea in the late 19th and early 20th century until its fishery collapsed following mass mortality in the late 1940s. The lack of data on growth parameters of this species prior to that event biases our understanding of its life history and complicates establishing sustainable levels of harvesting. To provide a baseline for assessment of the current state of populations of <em>A. noae</em> in the Adriatic Sea, we compared growth rates and lifespan, estimated based on annual shell growth lines, between live-collected individuals and fossil (Holocene) specimens sampled from sediment cores. The maximum age observed in our modern samples was 35 years whereas the ontogenetically oldest fossil specimen lived for at least 85 years, extending the longest recorded lifespan for the Arcidae family by over three decades. Our results indicate that individuals of <em>A. noae</em> collected in the 21st century grow faster and have much shorter lifespan compared to their Holocene counterparts, suggesting that intensive harvesting in the past combined with increasing water temperatures and eutrophication of the northern Adriatic Sea had a significant impact on the population dynamics of this species.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105628"},"PeriodicalIF":2.2,"publicationDate":"2025-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840263","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 : 2025-12-16DOI: 10.1016/j.csr.2025.105627
Julia Abrao Teixeira , Piero L.F. Mazzini , Xun Cai , Manuel Colombo , Qubin Qin , Meredith Evans Seeley , Y. Joseph Zhang
Estuaries play a critical role in mediating the flux of land-derived microplastics to the ocean, where they pose a threat to marine ecosystems. This study investigates the fate of microplastic particles exported from the Chesapeake Bay (CB) to the Mid-Atlantic Bight (MAB), using an offline Lagrangian particle-tracking approach coupled with a 3D hydrodynamic model (SCHISM). Particles were released hourly from 17 locations at the mouth of Chesapeake Bay, totaling 148,920 particles over one year. Ten sensitivity experiments were conducted, exploring how polymer type (polyethylene, polypropylene), particle size (0.001 mm, 5 mm), and biofouling influenced their distribution patterns. All scenarios showed high frequency of particles reaching Virginia and North Carolina bays. Unfouled buoyant microplastics were mainly transported southward along the Virginia and North Carolina shelves, with limited northward movement restricted to the outer shelf and offshore. When biofouling was included, particle distribution broadened and extended northward to the Gulf of Maine. As biofouled microplastics sank, interactions with cross-shelf circulation enhanced transport into inner-shelf and estuarine regions in the MAB. While polymer type had negligible effects on transport, particle size played a major role. Larger biofouled microplastics (5 mm) did not sink during the one-year simulation and followed distribution patterns similar to unfouled microplastics. Their residence time on the MAB shelf ranged between 17 and 19 days, whereas smaller biofouled microplastics (0.001 mm) had residence time nearly twice as long, between 31 and 34 days. These results underscore the importance of incorporating biofouling into predictive transport models to better assess microplastic fate in coastal systems.
{"title":"Distribution and fate of microplastics from the Chesapeake Bay to the Mid-Atlantic Bight: A Lagrangian particle tracking approach","authors":"Julia Abrao Teixeira , Piero L.F. Mazzini , Xun Cai , Manuel Colombo , Qubin Qin , Meredith Evans Seeley , Y. Joseph Zhang","doi":"10.1016/j.csr.2025.105627","DOIUrl":"10.1016/j.csr.2025.105627","url":null,"abstract":"<div><div>Estuaries play a critical role in mediating the flux of land-derived microplastics to the ocean, where they pose a threat to marine ecosystems. This study investigates the fate of microplastic particles exported from the Chesapeake Bay (CB) to the Mid-Atlantic Bight (MAB), using an offline Lagrangian particle-tracking approach coupled with a 3D hydrodynamic model (SCHISM). Particles were released hourly from 17 locations at the mouth of Chesapeake Bay, totaling 148,920 particles over one year. Ten sensitivity experiments were conducted, exploring how polymer type (polyethylene, polypropylene), particle size (0.001 mm, 5 mm), and biofouling influenced their distribution patterns. All scenarios showed high frequency of particles reaching Virginia and North Carolina bays. Unfouled buoyant microplastics were mainly transported southward along the Virginia and North Carolina shelves, with limited northward movement restricted to the outer shelf and offshore. When biofouling was included, particle distribution broadened and extended northward to the Gulf of Maine. As biofouled microplastics sank, interactions with cross-shelf circulation enhanced transport into inner-shelf and estuarine regions in the MAB. While polymer type had negligible effects on transport, particle size played a major role. Larger biofouled microplastics (5 mm) did not sink during the one-year simulation and followed distribution patterns similar to unfouled microplastics. Their residence time on the MAB shelf ranged between 17 and 19 days, whereas smaller biofouled microplastics (0.001 mm) had residence time nearly twice as long, between 31 and 34 days. These results underscore the importance of incorporating biofouling into predictive transport models to better assess microplastic fate in coastal systems.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105627"},"PeriodicalIF":2.2,"publicationDate":"2025-12-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790316","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}
As one of the most prominent marine ranches in southern China, the waters around Nan'ao Island are influenced by multiple stressors, including coastal currents, summer upwelling, river discharge, and aquaculture activities. To elucidate the phytoplankton succession dynamic under multiple stressors, phytoplankton community and key environmental factors were seasonally investigated in the waters around Nan'ao Island during 2022. A total of 159 species of phytoplankton were recorded, and 14 dominant species were identified across the four seasons. Pseudonitzschia delicatissima was dominant year-round and distributed throughout the study area. In spring, some phytoplankton species, such as Prorocentrum micans and Skeletonema spp., experienced explosive growth under the impact of river discharge. The abundance of phytoplankton generally declined from inshore to the offshore region, with the highest value occurring in the summer. The horizontal distributions of phytoplankton communities were mainly regulated by the salinity, nutrient concentration and N/P ratio, which greatly determined by the river discharge. While, the seasonal succession of phytoplankton community was mainly driven by the temporal variations in water temperature and hydrodynamic conditions (mainly summer upwelling and winter Zhe-Min Coastal Current). Additionally, the phytoplankton abundance and chlorophyll a concentration generally showed lower values in the shellfish-seaweed aquaculture zone, suggesting the present marine farming model might have effectively reduced the risk of harmful algal blooms and improved the water quality. This study provided valuable insights for the succession mechanism of phytoplankton community, contributing to the sustainable development of coastal ecosystems.
{"title":"Spatial and seasonal variations of the phytoplankton community under multiple stressors in the area around Nan'ao Island, northern South China Sea","authors":"Zhixi Zhou , Yujiao Chen , Huijuan Tang , Guohong Xiao , Haochen Huang , Zhixin Ke","doi":"10.1016/j.csr.2025.105625","DOIUrl":"10.1016/j.csr.2025.105625","url":null,"abstract":"<div><div>As one of the most prominent marine ranches in southern China, the waters around Nan'ao Island are influenced by multiple stressors, including coastal currents, summer upwelling, river discharge, and aquaculture activities. To elucidate the phytoplankton succession dynamic under multiple stressors, phytoplankton community and key environmental factors were seasonally investigated in the waters around Nan'ao Island during 2022. A total of 159 species of phytoplankton were recorded, and 14 dominant species were identified across the four seasons. <em>Pseudonitzschia delicatissima</em> was dominant year-round and distributed throughout the study area. In spring, some phytoplankton species, such as <em>Prorocentrum micans</em> and <em>Skeletonema</em> spp., experienced explosive growth under the impact of river discharge. The abundance of phytoplankton generally declined from inshore to the offshore region, with the highest value occurring in the summer. The horizontal distributions of phytoplankton communities were mainly regulated by the salinity, nutrient concentration and N/P ratio, which greatly determined by the river discharge. While, the seasonal succession of phytoplankton community was mainly driven by the temporal variations in water temperature and hydrodynamic conditions (mainly summer upwelling and winter Zhe-Min Coastal Current). Additionally, the phytoplankton abundance and chlorophyll <em>a</em> concentration generally showed lower values in the shellfish-seaweed aquaculture zone, suggesting the present marine farming model might have effectively reduced the risk of harmful algal blooms and improved the water quality. This study provided valuable insights for the succession mechanism of phytoplankton community, contributing to the sustainable development of coastal ecosystems.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105625"},"PeriodicalIF":2.2,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737343","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 : 2025-12-12DOI: 10.1016/j.csr.2025.105624
Mohammad Sadman Alam , Subrata Sarker , Nabanita Das , Shashowti Chowdhury Riya , Myung Hwangbo , Jongsun Kim
The Bay of Bengal (BoB) receives significant amounts of discharge from river runoff as the largest delta in the world, which affects the dynamic of coastal and estuarine systems. Thus, Saint Martin Island (SMI), located in the northeastern part of the BoB, faces a significant influx of sediments and numerous contaminants from upstream sources, which are affecting the biogeochemistry of SMI. It is hypothesized that both river influx and frequent tropical cyclones that occur in the BoB significantly influence the coastal ecosystem of the Island. Therefore, to understand the coastal ecosystem of SMI, the spatiotemporal variability of nutrients and chl-a (July 2022–June 2023) was explored. This study identified the northeast (NE) monsoon as an important season for primary productivity with the concentration of chl-a, inorganic nitrogen, phosphate, and silicate as 1.03 μg L-1, 64.09 μmol L-1, 3.86 μmol L-1, 86.17 μmol L-1, respectively. Seasonal and regional nutrient ratios were near-Redfield (N:P:Si ≈ 17–18:1:17–18), with modest monsoonal shifts and comparatively stronger N-Si supply toward the estuary. The correlation of rain, wind stress, river discharge, Ekman transport, salinity, nutrients, temperature, chl-a, and dissolved oxygen was evaluated by using a coast-normal wind and Ekman framework together with structural equation modelling (SEM). SEM indicated positive effects of discharge, rainfall, and Ekman transport on nutrients. Especially, chl-a was positively associated with salinity and DIP and negatively with DIN and temperature, while the direct Ekman-to-chl-a path was not significant. After the cyclone Sitrang, the mixed-layer was deepened (∼1.33 m), and a narrowed temperature-salinity pattern toward higher salinity, DIP, and DIN increases in the upper 50 m was observed. During the southwest (SW) monsoon, river discharge dominated nutrient supply, whereas the reduced rainfall was correlated with wind- and eddy-assisted vertical inputs that sustained productivity near the estuary during the NE monsoon. This study highlighted monthly horizontal and vertical variations of hydrological parameters and their interrelationship with algal growth and nutrient dynamics.
{"title":"Drivers of nutrient dynamics and chlorophyll-a variability: The role of freshwater input, upwelling, and tropical cyclones near Saint Martin's Island, Bangladesh","authors":"Mohammad Sadman Alam , Subrata Sarker , Nabanita Das , Shashowti Chowdhury Riya , Myung Hwangbo , Jongsun Kim","doi":"10.1016/j.csr.2025.105624","DOIUrl":"10.1016/j.csr.2025.105624","url":null,"abstract":"<div><div>The Bay of Bengal (BoB) receives significant amounts of discharge from river runoff as the largest delta in the world, which affects the dynamic of coastal and estuarine systems. Thus, Saint Martin Island (SMI), located in the northeastern part of the BoB, faces a significant influx of sediments and numerous contaminants from upstream sources, which are affecting the biogeochemistry of SMI. It is hypothesized that both river influx and frequent tropical cyclones that occur in the BoB significantly influence the coastal ecosystem of the Island. Therefore, to understand the coastal ecosystem of SMI, the spatiotemporal variability of nutrients and chl-a (July 2022–June 2023) was explored. This study identified the northeast (NE) monsoon as an important season for primary productivity with the concentration of chl-a, inorganic nitrogen, phosphate, and silicate as 1.03 μg L-1, 64.09 μmol L-1, 3.86 μmol L-1, 86.17 μmol L-1, respectively. Seasonal and regional nutrient ratios were near-Redfield (N:P:Si ≈ 17–18:1:17–18), with modest monsoonal shifts and comparatively stronger N-Si supply toward the estuary. The correlation of rain, wind stress, river discharge, Ekman transport, salinity, nutrients, temperature, chl-a, and dissolved oxygen was evaluated by using a coast-normal wind and Ekman framework together with structural equation modelling (SEM). SEM indicated positive effects of discharge, rainfall, and Ekman transport on nutrients. Especially, chl-a was positively associated with salinity and DIP and negatively with DIN and temperature, while the direct Ekman-to-chl-a path was not significant. After the cyclone Sitrang, the mixed-layer was deepened (∼1.33 m), and a narrowed temperature-salinity pattern toward higher salinity, DIP, and DIN increases in the upper 50 m was observed. During the southwest (SW) monsoon, river discharge dominated nutrient supply, whereas the reduced rainfall was correlated with wind- and eddy-assisted vertical inputs that sustained productivity near the estuary during the NE monsoon. This study highlighted monthly horizontal and vertical variations of hydrological parameters and their interrelationship with algal growth and nutrient dynamics.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105624"},"PeriodicalIF":2.2,"publicationDate":"2025-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790320","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 : 2025-12-06DOI: 10.1016/j.csr.2025.105622
Paula Birocchi , Marcelo Dottori , Leticia Fabre-Lima , Carine de Godoi Rezende Costa , José Roberto Bairão Leite , Dalton Kei Sasaki , Robert James Chant
<div><div>Climate change has the potential to alter the rainfall regimes in South America (SA), which can affect the local river discharge and disturb estuarine environments. Thus, understanding the water flux variability under climate change and the influence of extreme events in a complex estuary is relevant to prevent and mitigate future negative impacts. Here we quantified the water flux to understand potential changes in estuaries and focus on investigating the variability of river discharge under both present and future climate projections, while also considering the effects of extreme events such as storm tides and atmospheric blocking. The Cananéia-Iguape estuarine-lagoon complex (CIELC), situated in the South Brazil Bight (SBB), was chosen as an example to apply the method. It has two inlets, a dominant source of river discharge (Valo Grande Channel, VGC), and smaller tributaries. The water flux was calculated with numerical simulations for three estuarine cross-sections by integrating the fluxes through them. The experiments were performed using a hydrodynamic numerical model and its results were validated. Validation parameter values ranged from 0.80 to 0.94 for salinity, 0.57 to 0.84 for currents, and 0.93 for total sea level. The modeled sea level was used to classify the area of study as hypersynchronous, with tidal amplitudes increasing upstream. For the climate change scenarios, we found that a decrease in precipitation of 5% (September SSP126) and 25% (September SSP585), and an increase of 5% (June SSP126) and 15% (June SSP585) in the rainfall, and consequently, in the river discharge, caused statistically significant changes in the water flux. Higher water fluxes were found during periods of stronger river discharge, particularly during the anomalous storm tide of August 2016, when intense rainfall was present. Since this estuary dynamics is dominated by tides, we compared the future scenarios of water fluxes considering neap and spring, and between ebb and flood tides. Water flow increased during the spring in comparison to the neap tide by approximately 7%, 5%, and 1%, in the northern, southern inlets, and the VGC cross-sections, respectively. The ebb tidal fluxes, with a mean value of approximately 163 m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> s<span><math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> were 24% significantly stronger (<span><math><mi>p</mi></math></span>-value <span><math><mo><</mo></math></span>0.05) than the flood, which presented a mean value of 124 m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> s<span><math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>. Both inlets showed faster ebb periods, with mean values of 6.14 and 5.98 h, in comparison to the flood of 6.25 and 6.41 h, respectively. We quantified the water flux percentage in each tributary connected to the main estuarine channel,
气候变化有可能改变南美洲（SA）的降雨制度，这可能影响当地河流流量并扰乱河口环境。因此，了解气候变化和极端事件对复杂河口水通量的影响对预防和减轻未来的负面影响具有重要意义。在这里，我们量化了水通量以了解河口的潜在变化，并重点研究了当前和未来气候预测下河流流量的变异性，同时也考虑了极端事件（如风暴潮和大气阻塞）的影响。位于南巴西湾（SBB）的canan - iguape河口-泻湖综合体（CIELC）被选为应用该方法的例子。它有两个入口，一个主要的河流排放源（Valo Grande Channel， VGC）和较小的支流。对三个河口断面的水流通量进行了数值模拟，计算了水流通量。利用水动力数值模型进行了实验，并对实验结果进行了验证。盐度验证参数值为0.80 ~ 0.94，海流验证参数值为0.57 ~ 0.84，总海平面验证参数值为0.93。利用模拟的海平面将研究区域划分为超同步，潮汐振幅在上游增加。在气候变化情景下，降水量减少5%（9月SSP126）和25%(9月SSP585)，降雨量增加5%（6月SSP126）和15%(6月SSP585)，从而引起河流量的显著变化。在河流流量较强的时期，特别是2016年8月异常风暴潮期间，发现了较高的水通量，当时出现了强降雨。由于该河口动态受潮汐控制，我们比较了考虑小潮和大潮以及退潮和涨潮的未来水通量情景。与小潮相比，春季北部、南部入海口和VGC断面的水流量分别增加了约7%、5%和1%。退潮通量均值约为163 m3 s - 1，比洪潮通量均值124 m3 s - 1强24% （p值<；0.05）。两个进水口的平均退潮时间分别为6.14和5.98 h，而洪水的平均退潮时间分别为6.25和6.41 h。考虑到所有研究情景，我们量化了与主要河口通道相连的每条支流的水通量百分比。总体而言，北部入口被确定为主要的水运通道，约占整个河口的总流量的68.2%。该研究揭示了亚热带河口-泻湖综合体水通量动态的未来和极端条件，对气候变化条件下的可持续水管理战略至关重要。
{"title":"Water flux quantification in a subtropical estuary through numerical modeling","authors":"Paula Birocchi , Marcelo Dottori , Leticia Fabre-Lima , Carine de Godoi Rezende Costa , José Roberto Bairão Leite , Dalton Kei Sasaki , Robert James Chant","doi":"10.1016/j.csr.2025.105622","DOIUrl":"10.1016/j.csr.2025.105622","url":null,"abstract":"<div><div>Climate change has the potential to alter the rainfall regimes in South America (SA), which can affect the local river discharge and disturb estuarine environments. Thus, understanding the water flux variability under climate change and the influence of extreme events in a complex estuary is relevant to prevent and mitigate future negative impacts. Here we quantified the water flux to understand potential changes in estuaries and focus on investigating the variability of river discharge under both present and future climate projections, while also considering the effects of extreme events such as storm tides and atmospheric blocking. The Cananéia-Iguape estuarine-lagoon complex (CIELC), situated in the South Brazil Bight (SBB), was chosen as an example to apply the method. It has two inlets, a dominant source of river discharge (Valo Grande Channel, VGC), and smaller tributaries. The water flux was calculated with numerical simulations for three estuarine cross-sections by integrating the fluxes through them. The experiments were performed using a hydrodynamic numerical model and its results were validated. Validation parameter values ranged from 0.80 to 0.94 for salinity, 0.57 to 0.84 for currents, and 0.93 for total sea level. The modeled sea level was used to classify the area of study as hypersynchronous, with tidal amplitudes increasing upstream. For the climate change scenarios, we found that a decrease in precipitation of 5% (September SSP126) and 25% (September SSP585), and an increase of 5% (June SSP126) and 15% (June SSP585) in the rainfall, and consequently, in the river discharge, caused statistically significant changes in the water flux. Higher water fluxes were found during periods of stronger river discharge, particularly during the anomalous storm tide of August 2016, when intense rainfall was present. Since this estuary dynamics is dominated by tides, we compared the future scenarios of water fluxes considering neap and spring, and between ebb and flood tides. Water flow increased during the spring in comparison to the neap tide by approximately 7%, 5%, and 1%, in the northern, southern inlets, and the VGC cross-sections, respectively. The ebb tidal fluxes, with a mean value of approximately 163 m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> s<span><math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span> were 24% significantly stronger (<span><math><mi>p</mi></math></span>-value <span><math><mo><</mo></math></span>0.05) than the flood, which presented a mean value of 124 m<span><math><msup><mrow></mrow><mrow><mn>3</mn></mrow></msup></math></span> s<span><math><msup><mrow></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></math></span>. Both inlets showed faster ebb periods, with mean values of 6.14 and 5.98 h, in comparison to the flood of 6.25 and 6.41 h, respectively. We quantified the water flux percentage in each tributary connected to the main estuarine channel,","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105622"},"PeriodicalIF":2.2,"publicationDate":"2025-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145790240","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 : 2025-12-05DOI: 10.1016/j.csr.2025.105623
Maciej Chelchowski, Piotr Balazy, Piotr Kuklinski
The incessantly disturbed Antarctic intertidal zone is currently facing additional challenges associated with climate change, such as warming and increased meltwater runoff. However, long-term biological data that would enable quantification of how these environmental changes affect the intertidal zone and its ecosystem functioning are still lacking. Therefore, the main goal of this study was to evaluate the interannual variability in the structure of an intertidal macrobenthos assemblage in maritime Antarctica (Admiralty Bay, King George Island 62° S). Sampling was carried out in 2011, 2017 and 2019, in early January, at three intertidal levels: low, mid and high. The results clearly show that the intertidal zone remained relatively rich and abundant over the investigated period. The interannual pattern of diversity and species richness was as follows: 2019 > 2017 > 2011. Each studied year was dominated, to varying degrees, by the bivalve Altenaeum charcoti, the gastropods Laevilacunaria antarctica, Laevilitorina caliginosa and Onoba sp., along with the amphipod Paramoera edouardi. The primary driver of interannual variability seems to be random physical disturbances, such as temperature anomalies, ice activity, and wind force. In addition, year-to-year temperature changes may further affect the state and development of intertidal assemblages in a given year. The interannual variation documented here provides a stronger basis for assessing how Antarctic intertidal assemblages may respond to the rapid environmental changes projected for this region.
不断受到干扰的南极潮间带目前正面临着与气候变化有关的额外挑战，例如变暖和融水径流增加。然而，能够量化这些环境变化如何影响潮间带及其生态系统功能的长期生物学数据仍然缺乏。因此，本研究的主要目的是评估南极海洋（Admiralty Bay, King George Island 62°S）潮间带大型底栖动物群落结构的年际变化。在2011年、2017年和2019年1月初，在低、中、高三个潮间带进行了采样。结果清楚地表明，在调查期间，潮间带保持相对丰富和丰富。多样性和物种丰富度的年际格局为：2019 >； 2017 > 2011。在每一年的研究中，双壳类动物Altenaeum charcoti、腹足类动物Laevilacunaria antarctica、Laevilitorina caliginosa和Onoba sp.以及片足类动物paroera edouardi都在不同程度上占主导地位。年际变化的主要驱动因素似乎是随机的物理干扰，如温度异常、冰活动和风力。此外，温度的年际变化可能进一步影响某一年潮间带组合的状态和发展。这里记录的年际变化为评估南极潮间带组合如何响应该地区预计的快速环境变化提供了更有力的基础。
{"title":"Interannual variability in the structure of macrobenthic assemblages in the maritime Antarctic intertidal zone","authors":"Maciej Chelchowski, Piotr Balazy, Piotr Kuklinski","doi":"10.1016/j.csr.2025.105623","DOIUrl":"10.1016/j.csr.2025.105623","url":null,"abstract":"<div><div>The incessantly disturbed Antarctic intertidal zone is currently facing additional challenges associated with climate change, such as warming and increased meltwater runoff. However, long-term biological data that would enable quantification of how these environmental changes affect the intertidal zone and its ecosystem functioning are still lacking. Therefore, the main goal of this study was to evaluate the interannual variability in the structure of an intertidal macrobenthos assemblage in maritime Antarctica (Admiralty Bay, King George Island 62° S). Sampling was carried out in 2011, 2017 and 2019, in early January, at three intertidal levels: low, mid and high. The results clearly show that the intertidal zone remained relatively rich and abundant over the investigated period. The interannual pattern of diversity and species richness was as follows: 2019 > 2017 > 2011. Each studied year was dominated, to varying degrees, by the bivalve <em>Altenaeum charcoti</em>, the gastropods <em>Laevilacunaria antarctica</em>, <em>Laevilitorina caliginosa</em> and <em>Onoba</em> sp., along with the amphipod <em>Paramoera edouardi</em>. The primary driver of interannual variability seems to be random physical disturbances, such as temperature anomalies, ice activity, and wind force. In addition, year-to-year temperature changes may further affect the state and development of intertidal assemblages in a given year. The interannual variation documented here provides a stronger basis for assessing how Antarctic intertidal assemblages may respond to the rapid environmental changes projected for this region.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105623"},"PeriodicalIF":2.2,"publicationDate":"2025-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737342","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 : 2025-11-27DOI: 10.1016/j.csr.2025.105620
A. Prajith , Reji Srinivas , M.K. Sreeraj , N. Sreejith , S. Suja , A.V. Sijinkumar
Seamounts and bathymetric highs are prominent features of the southwestern continental margin of India, yet their influence on sediment transport and deposition remains poorly understood. This study investigates the Alleppey Terrace (AT) and adjacent shelf using sediment texture, clay mineralogy, microfossil assemblages, suspended particulate matter fluxes, and regional circulation data to elucidate depositional dynamics and environmental controls. Grain-size analysis reveals a clear contrast between the sand-dominated outer shelf and the clay-rich AT sediments, indicating distinct depositional settings. Clay mineralogy signatures suggest that shelf sediments are primarily riverine in origin, whereas AT sediments derive largely from in situ weathering of local basaltic basement rocks. Microfossil assemblages indicate low surface productivity and minimal sediment reworking over the AT. Seasonal suspended particulate matter flux measurements using a submersible particle-size analyzer (LISST) confirm that land-derived material does not reach the AT regions. Overall, the interplay between limited sediment sources, bathymetric controls, and hydrodynamic processes has created a unique low-energy depositional environment in the AT, contrasting with the more dynamic adjacent shelf. These findings highlight the critical role of bathymetric highs in modulating sediment flux, preserving relic deposits, and influencing paleoenvironmental conditions along the continental margin.
{"title":"The role of bathymetry in shaping sediment deposition: a case study from the Alleppey Terrace and adjacent shelf, southwestern India","authors":"A. Prajith , Reji Srinivas , M.K. Sreeraj , N. Sreejith , S. Suja , A.V. Sijinkumar","doi":"10.1016/j.csr.2025.105620","DOIUrl":"10.1016/j.csr.2025.105620","url":null,"abstract":"<div><div>Seamounts and bathymetric highs are prominent features of the southwestern continental margin of India, yet their influence on sediment transport and deposition remains poorly understood. This study investigates the Alleppey Terrace (AT) and adjacent shelf using sediment texture, clay mineralogy, microfossil assemblages, suspended particulate matter fluxes, and regional circulation data to elucidate depositional dynamics and environmental controls. Grain-size analysis reveals a clear contrast between the sand-dominated outer shelf and the clay-rich AT sediments, indicating distinct depositional settings. Clay mineralogy signatures suggest that shelf sediments are primarily riverine in origin, whereas AT sediments derive largely from in situ weathering of local basaltic basement rocks. Microfossil assemblages indicate low surface productivity and minimal sediment reworking over the AT. Seasonal suspended particulate matter flux measurements using a submersible particle-size analyzer (LISST) confirm that land-derived material does not reach the AT regions. Overall, the interplay between limited sediment sources, bathymetric controls, and hydrodynamic processes has created a unique low-energy depositional environment in the AT, contrasting with the more dynamic adjacent shelf. These findings highlight the critical role of bathymetric highs in modulating sediment flux, preserving relic deposits, and influencing paleoenvironmental conditions along the continental margin.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105620"},"PeriodicalIF":2.2,"publicationDate":"2025-11-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145685335","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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