Pub Date : 2026-02-01Epub 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":"2026-02-01","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 : 2026-02-01Epub Date: 2025-11-20DOI: 10.1016/j.csr.2025.105615
Fernando A. Oreiro , Mónica M.E. Fiore , María F. de Azkue , María F. Canero , Luciano Banegas , Mariana C. Mora
This study presents a comprehensive analysis of relative mean sea level (MSL) variations along the Argentine coast, based on tide gauge data from 12 stations. Hourly water level records—collected by the Argentine Naval Hydrographic Service and other institutions—were quality-checked and processed to generate monthly MSL series. These series were corrected for seasonality by subtracting historical monthly means, and annual averages were used to estimate MSL trends. These trends were calculated over the full period of available data at each station, with values ranging from 0.79 mm yr−1 to 3.84 mm yr−1across time spans between 18 and 119 years. Trend analyses conducted over multiple time periods revealed consistent results among geographically close stations when the same periods were compared. For Buenos Aires and Puerto Quequén—both with over a century of observations—a marked acceleration in MSL rise since the 1960s was observed, with post-1965 trends nearly double those of the earlier period. At these stations, trends were estimated over 20-year windows, advanced in one-year increments throughout the entire series, yielding values ranging from −3 mm yr−1 to +9 mm yr−1. This highlights that such short intervals are insufficient for reliable long-term assessments for this stations. In contrast, variability decreased significantly when 40-year and 60-year periods were used. Overall, the findings confirm a consistent upward trend in sea level rise along the Argentine coast and provide critical baseline information for coastal risk management and climate change adaptation strategies.
本研究基于12个站点的潮汐计数据，对阿根廷海岸的相对平均海平面（MSL）变化进行了全面分析。每小时的水位记录——由阿根廷海军水文测绘局和其他机构收集——经过质量检查和处理，生成每月的MSL系列。这些序列通过减去历史月平均值来校正季节性，并使用年平均值来估计MSL趋势。这些趋势是在每个站点的整个可用数据期内计算的，在18至119年的时间跨度内，其值从0.79 mm yr - 1到3.84 mm yr - 1不等。在多个时期进行的趋势分析表明，在同一时期进行比较时，地理位置接近的站点的结果是一致的。对于布宜诺斯艾利斯和Puerto quequ - - -两者都有超过一个世纪的观测- - -自20世纪60年代以来，观测到MSL的显著加速上升，1965年后的趋势几乎是早期的两倍。在这些站点，估计了20年窗口的趋势，在整个系列中以一年为增量推进，得到的值从−3毫米/年−1到+9毫米/年−1。这突出表明，如此短的时间间隔不足以对这些台站进行可靠的长期评估。相比之下，当使用40年和60年的周期时，变异性显著降低。总体而言，这些发现证实了阿根廷沿海海平面上升的持续上升趋势，并为沿海风险管理和气候变化适应战略提供了关键的基线信息。
{"title":"Relative sea level trends along the Argentine coast: A multi-decadal analysis from tide gauge records","authors":"Fernando A. Oreiro , Mónica M.E. Fiore , María F. de Azkue , María F. Canero , Luciano Banegas , Mariana C. Mora","doi":"10.1016/j.csr.2025.105615","DOIUrl":"10.1016/j.csr.2025.105615","url":null,"abstract":"<div><div>This study presents a comprehensive analysis of relative mean sea level (MSL) variations along the Argentine coast, based on tide gauge data from 12 stations. Hourly water level records—collected by the Argentine Naval Hydrographic Service and other institutions—were quality-checked and processed to generate monthly MSL series. These series were corrected for seasonality by subtracting historical monthly means, and annual averages were used to estimate MSL trends. These trends were calculated over the full period of available data at each station, with values ranging from 0.79 mm yr<sup>−1</sup> to 3.84 mm yr<sup>−1</sup>across time spans between 18 and 119 years. Trend analyses conducted over multiple time periods revealed consistent results among geographically close stations when the same periods were compared. For Buenos Aires and Puerto Quequén—both with over a century of observations—a marked acceleration in MSL rise since the 1960s was observed, with post-1965 trends nearly double those of the earlier period. At these stations, trends were estimated over 20-year windows, advanced in one-year increments throughout the entire series, yielding values ranging from −3 mm yr<sup>−1</sup> to +9 mm yr<sup>−1</sup>. This highlights that such short intervals are insufficient for reliable long-term assessments for this stations. In contrast, variability decreased significantly when 40-year and 60-year periods were used. Overall, the findings confirm a consistent upward trend in sea level rise along the Argentine coast and provide critical baseline information for coastal risk management and climate change adaptation strategies.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105615"},"PeriodicalIF":2.2,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145555161","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 : 2026-02-01Epub Date: 2025-12-25DOI: 10.1016/j.csr.2025.105633
Canela Chaparro-Godoy , Clara M. Iachetti , Soledad L. Diodato , Sarah L. Friesen , Daniel O. Bruno
Understanding the dynamics of zooplankton communities is essential given their key role in aquatic food webs and their value as indicators of ecosystem health. This study examined the temporal variation of micro- and mesozooplankton communities in a flooded estuarine area influenced by glacial meltwater, during the spring-summer period, considering both temporal and diel scales. Physical, chemical, biological, and meteorological parameters were measured, and their relationships with zooplankton composition were analysed. Three microzooplankton and fourteen mesozooplankton taxa were identified. The dominant groups were copepod nauplii and adults and the cladoceran Podon leuckarti. Zooplankton composition varied among periods and between daytime and nighttime, with Podon leuckarti and Oithona similis contributing most to diel differences. Zooplankton composition was influenced by water temperature, salinity, microphytoplankton biomass, wind intensity, and time of day, with seasonal effects explaining the largest share of variability. Our results provide insights into zooplankton dynamics in a sub-Antarctic estuarine ecosystem across two temporal scales. We propose a possible mechanism in which zooplankton are transported into this shallow floodplain mainly by tidal advection and subsequently benefit from the favourable environmental conditions present during the season of highest diversity (spring-summer). This area may also function as an important feeding habitat for other aquatic organisms.
{"title":"Spring-summer temporal dynamics of the zooplankton community in a flooded inlet of a sub-Antarctic river (Tierra del Fuego National Park)","authors":"Canela Chaparro-Godoy , Clara M. Iachetti , Soledad L. Diodato , Sarah L. Friesen , Daniel O. Bruno","doi":"10.1016/j.csr.2025.105633","DOIUrl":"10.1016/j.csr.2025.105633","url":null,"abstract":"<div><div>Understanding the dynamics of zooplankton communities is essential given their key role in aquatic food webs and their value as indicators of ecosystem health. This study examined the temporal variation of micro- and mesozooplankton communities in a flooded estuarine area influenced by glacial meltwater, during the spring-summer period, considering both temporal and diel scales. Physical, chemical, biological, and meteorological parameters were measured, and their relationships with zooplankton composition were analysed. Three microzooplankton and fourteen mesozooplankton taxa were identified. The dominant groups were copepod nauplii and adults and the cladoceran <em>Podon leuckarti</em>. Zooplankton composition varied among periods and between daytime and nighttime, with <em>Podon leuckarti</em> and <em>Oithona similis</em> contributing most to diel differences. Zooplankton composition was influenced by water temperature, salinity, microphytoplankton biomass, wind intensity, and time of day, with seasonal effects explaining the largest share of variability. Our results provide insights into zooplankton dynamics in a sub-Antarctic estuarine ecosystem across two temporal scales. We propose a possible mechanism in which zooplankton are transported into this shallow floodplain mainly by tidal advection and subsequently benefit from the favourable environmental conditions present during the season of highest diversity (spring-summer). This area may also function as an important feeding habitat for other aquatic organisms.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"297 ","pages":"Article 105633"},"PeriodicalIF":2.2,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145840262","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 : 2026-02-01Epub 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":"2026-02-01","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":"2026-02-01","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 : 2026-02-01Epub 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":"2026-02-01","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}
Pub Date : 2026-02-01Epub 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":"2026-02-01","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}
Pub Date : 2026-02-01Epub 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":"2026-02-01","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 : 2026-01-01Epub Date: 2025-10-22DOI: 10.1016/j.csr.2025.105596
Ramsey R. Harcourt, John B. Mickett, K. Ravi Prakash
A widespread prevalence of subsurface acoustic ducts impacting mid-frequency sound propagation was observed over the outer shelf and the continental slope during a field experiment in July–August 2022 in the Pacific Northwest coastal ocean of North America. Simulations of the coastal shelf ocean using LiveOcean, a tidally driven operational model (MacCready et al., 2021), based upon a widely used variant of the Regional Ocean Modeling System (ROMS), were compared with observations of the thermohaline stratification layers responsible for the ducts, and found to have a nearly complete absence of these acoustic features due to excessive parametrized mixing. After implementing additional realistic constraints in the ‘k-ε’ second moment closure (SMC) to control instabilities in the turbulence mixing model with low background mixing, the source of instabilities was identified in a coding error for the default, third-order upstream advection of the turbulence parameters for TKE k and its dissipation ε, a longstanding and significant bug impacting mixing parametrization, and one also found in the older SMC ‘Mellor-Yamada 2.5’ mixing parametrization option in ROMS. With code improvements, LiveOcean was able to successfully simulate the production of observed subsurface acoustic ducts. The primary process for generating the ducts along the outer shelf involves the southward transport of low sound speed water during upwelling, combined with the cross-shelf displacement of higher sound speed water from offshore beneath this layer in bottom-driven Ekman transport.
{"title":"Taming turbulence closure in tidally driven simulations of coastal oceans and estuaries","authors":"Ramsey R. Harcourt, John B. Mickett, K. Ravi Prakash","doi":"10.1016/j.csr.2025.105596","DOIUrl":"10.1016/j.csr.2025.105596","url":null,"abstract":"<div><div>A widespread prevalence of subsurface acoustic ducts impacting mid-frequency sound propagation was observed over the outer shelf and the continental slope during a field experiment in July–August 2022 in the Pacific Northwest coastal ocean of North America. Simulations of the coastal shelf ocean using LiveOcean, a tidally driven operational model (MacCready et al., 2021), based upon a widely used variant of the Regional Ocean Modeling System (ROMS), were compared with observations of the thermohaline stratification layers responsible for the ducts, and found to have a nearly complete absence of these acoustic features due to excessive parametrized mixing. After implementing additional realistic constraints in the ‘k-ε’ second moment closure (SMC) to control instabilities in the turbulence mixing model with low background mixing, the source of instabilities was identified in a coding error for the default, third-order upstream advection of the turbulence parameters for TKE k and its dissipation ε, a longstanding and significant bug impacting mixing parametrization, and one also found in the older SMC ‘Mellor-Yamada 2.5’ mixing parametrization option in ROMS. With code improvements, LiveOcean was able to successfully simulate the production of observed subsurface acoustic ducts. The primary process for generating the ducts along the outer shelf involves the southward transport of low sound speed water during upwelling, combined with the cross-shelf displacement of higher sound speed water from offshore beneath this layer in bottom-driven Ekman transport.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"296 ","pages":"Article 105596"},"PeriodicalIF":2.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145418565","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}
Organoclastic sulfate reduction and anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SO42--AOM) are key processes regulating organic matter degradation and methane (CH4) consumption in marine sediments. We analyzed C-S-Fe, Mo, and U geochemistry in a sediment core collected from the shallow, seasonally hypoxic shelf off the West Coast of India (WCI; Eastern Arabian Sea) at 28.5 mbsl to study the past influence of benthic and AOM activity. Porewater profiles showed high hydrogen sulfide (ΣH2S) concentrations and a shallow sulfate-methane transition zone (SMTZ; 143–303 cmbsf). The molybdenum/Uranium enrichment factor ratio (MoEF/UEF) indicates persistently sulfidic porewaters during sediment deposition, attributed to SO42--AOM. The high-resolution pyrite sulfur isotope (δ34SCRS) record reveals two sulfidization trends (Trend I and II), characterized by isotopic fluctuations. Depleted δ34SCRS values may be attributed to early diagenetic Fe-sulfidization under open system conditions at the sediment-water interface involving benthic reworking during normoxia. In contrast, enriched δ34SCRS values reflect diminished benthic activity under hypoxic conditions and pyrite precipitation from 34S-enriched ΣH2S diffusing upward from the SMTZ. Furthermore, increasing δ34SCRS values (Trend II) below 336.5 cm suggest overprinting of early-stage sulfidization by deep burial sulfidization linked to SMTZ deepening. Therefore, the observed δ34SCRS variability reflects sulfidization resulting from mixing of isotopically distinct pyrite produced under variable benthic activity and vertical CH4 flux. Although focused on the seasonally hypoxic shelf off WCI, the findings of this study provide broader implications for understanding the coupled influences of bioturbation, CH4 flux, and redox variability on sulfur cycling and trace-metal enrichment in shelf sediments globally.
{"title":"Pyritization may archive the influence of Sulfate-AOM and bioturbation activities in marine sulfidic shelf sediments","authors":"Kalyani Sivan , Aninda Mazumdar , Aditya Peketi , A.K. Sudheer , S.P.K. Pillutla , Subhashree Mishra","doi":"10.1016/j.csr.2025.105591","DOIUrl":"10.1016/j.csr.2025.105591","url":null,"abstract":"<div><div>Organoclastic sulfate reduction and anaerobic oxidation of methane (AOM) coupled to sulfate reduction (SO<sub>4</sub><sup>2-</sup>-AOM) are key processes regulating organic matter degradation and methane (CH<sub>4</sub>) consumption in marine sediments. We analyzed C-S-Fe, Mo, and U geochemistry in a sediment core collected from the shallow, seasonally hypoxic shelf off the West Coast of India (WCI; Eastern Arabian Sea) at 28.5 mbsl to study the past influence of benthic and AOM activity. Porewater profiles showed high hydrogen sulfide (ΣH<sub>2</sub>S) concentrations and a shallow sulfate-methane transition zone (SMTZ; 143–303 cmbsf). The molybdenum/Uranium enrichment factor ratio (Mo<sub>EF</sub>/U<sub>EF</sub>) indicates persistently sulfidic porewaters during sediment deposition, attributed to SO<sub>4</sub><sup>2-</sup>-AOM. The high-resolution pyrite sulfur isotope (δ<sup>34</sup>S<sub>CRS</sub>) record reveals two sulfidization trends (Trend I and II), characterized by isotopic fluctuations. Depleted δ<sup>34</sup>S<sub>CRS</sub> values may be attributed to early diagenetic Fe-sulfidization under open system conditions at the sediment-water interface involving benthic reworking during normoxia. In contrast, enriched δ<sup>34</sup>S<sub>CRS</sub> values reflect diminished benthic activity under hypoxic conditions and pyrite precipitation from <sup>34</sup>S-enriched ΣH<sub>2</sub>S diffusing upward from the SMTZ. Furthermore, increasing δ<sup>34</sup>S<sub>CRS</sub> values (Trend II) below 336.5 cm suggest overprinting of early-stage sulfidization by deep burial sulfidization linked to SMTZ deepening. Therefore, the observed δ<sup>34</sup>S<sub>CRS</sub> variability reflects sulfidization resulting from mixing of isotopically distinct pyrite produced under variable benthic activity and vertical CH<sub>4</sub> flux. Although focused on the seasonally hypoxic shelf off WCI, the findings of this study provide broader implications for understanding the coupled influences of bioturbation, CH<sub>4</sub> flux, and redox variability on sulfur cycling and trace-metal enrichment in shelf sediments globally.</div></div>","PeriodicalId":50618,"journal":{"name":"Continental Shelf Research","volume":"296 ","pages":"Article 105591"},"PeriodicalIF":2.2,"publicationDate":"2026-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145364473","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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