Progress in Oceanography最新文献

{"title":"Pre-molt dispersal and use of marine protected areas by Southern Rockhopper Penguins (Eudyptes chrysocome) at the southernmost oceanic regions of South America","authors":"Samanta Dodino ,&nbsp;Ulises Balza ,&nbsp;Luciana Riccialdelli ,&nbsp;Michael J. Polito ,&nbsp;Klemens Pütz ,&nbsp;Andrea Raya Rey","doi":"10.1016/j.pocean.2024.103369","DOIUrl":"10.1016/j.pocean.2024.103369","url":null,"abstract":"<div><div>Marine Protected Areas (MPAs) are crucial for conserving marine biodiversity, and assessing the effectiveness of boundaries in protecting marine species is essential. In the Southwest Atlantic Ocean, four MPAs have been created. In this study we evaluate the use of these MPAs by Southern Rockhopper Penguins (<em>Eudyptes chrysocome</em>) that nest at Isla de los Estados, Argentina during the pre-molt period in February and March 2020 by combining geolocation sensor data and spatial analysis together with stable isotopes analysis (<em>δ</em>¹³C and <em>δ</em>¹⁵N) to assess their spatial and trophic niches. We recaptured 16 of 25 adults to which loggers had been attached (64 % recapture rate, 6 females and 10 males). Penguins dispersed mainly southward and used the MPAs as corridors towards feeding area such as the Antarctic Polar Frontal Zone (APFZ). We found no evidence of sex-specific spatial and trophic niche partitioning. To develop robust conservation strategies, future studies should span multiple years and enhanced sampling effort to comprehensively explore the pre-molt trophic ecology and at-sea distribution of Southern Rockhopper Penguins.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103369"},"PeriodicalIF":3.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142655933","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modelling global mesozooplankton biomass using machine learning","authors":"Kailin Liu ,&nbsp;Zhimeng Xu ,&nbsp;Xin Liu ,&nbsp;Bangqin Huang ,&nbsp;Hongbin Liu ,&nbsp;Bingzhang Chen","doi":"10.1016/j.pocean.2024.103371","DOIUrl":"10.1016/j.pocean.2024.103371","url":null,"abstract":"<div><div>Mesozooplankton are a crucial link between primary producers and higher trophic levels and play a vital role in marine food webs, biological carbon pumps, and sustaining fishery resources. However, the global distribution of mesozooplankton biomass and the relevant controlling mechanisms remain elusive. We compared four machine learning algorithms (Boosted Regression Trees, Random Forest, Artificial Neural Network, and Support Vector Machine) to model the spatiotemporal distributions of global mesozooplankton biomass. These algorithms were trained on a compiled dataset of published mesozooplankton biomass observations with corresponding environmental predictors from contemporaneous satellite observations (temperature, chlorophyll, salinity, and mixed layer depth). We found that Random Forest achieved the best predictive accuracy with <em>R²</em> and <em>RMSE</em> (Root Mean Standard Error) of 0.57 and 0.39, respectively. Also, the global distribution of mesozooplankton biomass predicted by the Random Forest model was more consistent with the observational data than other models. We used the Random Forest model to create a global map of mesozooplankton biomass which serves as a reference for validating process-based ecosystem models. The model outputs confirm that environmental factors, especially surface Chl <em>a</em>, a proxy for prey availability, significantly correlate with the spatiotemporal distribution of mesozooplankton biomass. The scaling relationship between the mesozooplankton biomass and Chl <em>a</em> can be used as an emergent constraint for model validation and development. Moreover, our model predicts that the global total mesozooplankton biomass will decrease by 3% by the end of this century under the “business-as-usual” scenarios, potentially reducing fishery production and carbon sequestration. Our study contributes to predicting global mesozooplankton biomass and provides deep insights into the underlying environmental impacts on the distribution of mesozooplankton biomass.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103371"},"PeriodicalIF":3.8,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Changes in glacial meltwater system around Amundsen sea Polynya illustrated by radium and oxygen isotopes","authors":"Guanghui Chen ,&nbsp;You Jiang ,&nbsp;Yi Wang ,&nbsp;Jun Zhao ,&nbsp;Yusheng Qiu ,&nbsp;Minfang Zheng ,&nbsp;Mengya Chen ,&nbsp;Jianming Pan ,&nbsp;Min Chen","doi":"10.1016/j.pocean.2024.103367","DOIUrl":"10.1016/j.pocean.2024.103367","url":null,"abstract":"<div><div>The Amundsen Sea Polynya (ASP) is the most biologically productive area around Antarctica due to the input of iron-rich glacial meltwater (GMW). However, the source and path of GMW in the ASP, and how these have changed since the Dotson Ice Shelf (DIS), a primary GMW supplier, began experiencing a cooling period after 2011, remain unclear. This study presents the distribution of GMW in the ASP during the austral summer of 2020. Subsurface GMW proportions were estimated using a composite tracer derived from potential temperature, salinity, and dissolved oxygen, while surface GMW were using ²²⁶Ra and ²²⁸Ra. The results indicate that GMW in the ASP originates from DIS and Pine Island Bay. Surface GMW upwelled from the melting basal cavity of DIS is transported northwestward by katabatic winds, while subsurface GMW is transported northwestward beneath the mixed layer, with the upper portion upwelling to the surface in the ASP center along isopycnals (σ_θ) of 27.40 to 27.45 kg/m³. Depth variations of these isopycnals correlate well with brine inventories released by winter sea ice formation, suggesting that sea ice formation influences seawater σ_θ structures and consequently the transport path of subsurface GMW. Compared to 2011, the GMW content in the ASP in 2020 decreased by nearly half, and the transport routes have also changed. These changes align with the significantly reduced GMW discharge from the DIS after 2012. Our study confirms that the GMW system in the ASP has undergone significant changes following the onset of the cooling period experienced by the DIS.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103367"},"PeriodicalIF":3.8,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Drivers of growth and decay of Sargassum in the Tropical Atlantic: A Lagrangian approach","authors":"Witold Podlejski ,&nbsp;Léo Berline ,&nbsp;Julien Jouanno ,&nbsp;Nicolas Barrier ,&nbsp;Christophe Lett","doi":"10.1016/j.pocean.2024.103364","DOIUrl":"10.1016/j.pocean.2024.103364","url":null,"abstract":"<div><div>The proliferation of <em>Sargassum</em> in the Tropical Atlantic has occurred almost every year since 2011, but a strong variability of biomass is observed among years. Essential knowledge about the drivers of <em>Sargassum</em> growth and decay is still lacking to explain this interannual variability. Benefiting from accurate basin scale <em>Sargassum</em> detections provided by remote sensing, and from physical and biogeochemical ocean simulations, we developed a Lagrangian drift-growth model to simulate <em>Sargassum</em> distribution over the period 2016–2020. The resulting trajectories and biomass time series of <em>Sargassum</em> aggregates were analyzed to highlight the main limiting factors of growth and decay. The nitrogen and phosphorous concentrations are found to be weakly restrictive compared to physical limiting factors, especially the temperature. In particular, the warm waters found off northern Brazil appear to be instrumental in triggering the end of seasonal growth of <em>Sargassum</em>. The timing of the seasonal warming of this region strongly impacts the quantities of <em>Sargassum</em> simulated each year. This suggests that this region should be monitored to anticipate the development of <em>Sargassum</em> and resulting strandings.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103364"},"PeriodicalIF":3.8,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Long-term variation of the eddy kinetic energy in the Northeastern South China sea","authors":"Baolan Wu ,&nbsp;Jianping Gan","doi":"10.1016/j.pocean.2024.103366","DOIUrl":"10.1016/j.pocean.2024.103366","url":null,"abstract":"<div><div>The seasonal to interannual variability of eddy kinetic energy (EKE) in the Northeastern South China Sea (NE-SCS) has been widely studied and it is recognized that they are strongly related to the state of the Kuroshio pathway in the Luzon Strait. While, due to the lack of long-term observations and high-resolution simulations, the decadal change of EKE in NE-SCS remains unexplored. In this study, we show the EKE trend in the past ∼ 30 years in the NE-SCS by using satellite observation and global HYbrid Coordinate Ocean Model reanalysis with the Navy Coupled Ocean Data Assimilation. It is found that due to the weakening of the Kuroshio in the Luzon Strait since 1990 s, the Kuroshio shows an enhanced looping path in the NE-SCS, inducing stronger EKE in this region. Further analysis confirms that the energy transfer by baroclinic instability is dominant for the increasing of EKE, when the Kuroshio intrudes into the NE-SCS and brings more potential energy inside the circulation. The Kuroshio state along the Luzon Strait is the key for modulating the EKE in the NE-SCS. Furthermore, the long-term weakening of Kuroshio current along the Luzon strait during 1993–2020 is determined by the decreasing of subtropical mode water, corresponding to the positive phase of the Atlantic Multidecadal Oscillation. This study provides insight into the interaction between marginal sea (i.e., the SCS) and the open ocean (i.e., the western Pacific Ocean), finally linking to the global climate change.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103366"},"PeriodicalIF":3.8,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142552122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stable carbon isotopic composition of particulate organic matter in the Cosmonaut and Cooperation Seas in summer","authors":"Jiawen Kang ,&nbsp;Qiang Hao ,&nbsp;Shunan Cao ,&nbsp;Jun Zhao ,&nbsp;Zifei Yang ,&nbsp;Zhen Tang ,&nbsp;Minfang Zheng ,&nbsp;Yusheng Qiu ,&nbsp;Mengya Chen ,&nbsp;Jianming Pan ,&nbsp;Jianfeng He ,&nbsp;Min Chen","doi":"10.1016/j.pocean.2024.103363","DOIUrl":"10.1016/j.pocean.2024.103363","url":null,"abstract":"<div><div>This study examined particulate organic carbon (POC) and its isotopic composition (δ¹³C_POC) in the Cosmonaut and Cooperation Seas in the Antarctica during the summer of 2019. Our results show that the spatial variation of POC concentration in summer surface water generally mirrors that of δ¹³C_POC, with higher POC and δ¹³C_POC values in the Cosmonaut Sea compared to the Cooperation Sea. The δ¹³C_POC values in both seas were positively correlated with the proportion of Chl-a in smaller particles (&lt; 20 μm). However, the relationship with the proportion of biogenic POC in smaller particles (&lt; 20 μm) differed between the two seas. This discrepancy is attributed to differences in the dominant phytoplankton species. In the Cosmonaut Sea, smaller phytoplankton (nano- and pico-phytoplankton) were dominated by <em>Phaeocystis antarctica</em>, whereas in the Cooperation Sea, they were dominated by pennate diatoms. The δ¹³C_POC in deep waters of both seas increased with depth, reflecting the effects of organic remineralization. The carbon isotope fractionation factors during remineralization, estimated using Rayleigh model, were 1.5 ± 0.2‰ and 1.6 ± 0.2‰ in the Cosmonaut Sea and the Cooperation Sea, respectively. These small isotope effects indicate that the isotope signals of organic matter exported from the upper layer are well preserved in the deep ocean. Additionally, anomalously high δ¹³C_POC values were observed in the bottom water outside the Cape Darnley polynya in the Cooperation Sea, reflecting the input of ice algae-derived organic matter from the shelf during AABW formation. A simple isotopic mass balance estimate suggests that 6–19% of the POC in the AABW of the Cooperation Sea is contributed by ice algae. Our study highlights the complexity of factors affecting δ¹³C_POC in the Southern Ocean, emphasizing the importance of phytoplankton community composition.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103363"},"PeriodicalIF":3.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529426","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Eastern Tropical Pacific atmospheric and oceanic projected changes based on CMIP6 models","authors":"Rafael Ricardo Torres Parra ,&nbsp;David Francisco Bustos Usta ,&nbsp;Luis Jesús Otero Díaz ,&nbsp;María Paula Moreno-Ardila","doi":"10.1016/j.pocean.2024.103362","DOIUrl":"10.1016/j.pocean.2024.103362","url":null,"abstract":"<div><div>Atmosphere and ocean dynamics and their projections for the 21st century are assessed in the Eastern Tropical Pacific, using an ensemble of 17 models from the Coupled Model Intercomparison Project – CMIP6, under two radiative scenarios. Projections in the Panama Bight (PB) and Equatorial Pacific cold tongue (CT) are studied in more detail. In the 2071–2100 period and SSP5-8.5 scenario, referenced to the 1985–2014 period, air temperature (sea surface temperature) is expected to rise ∼3.5 °C (∼3 °C). Precipitation is projected to increase &gt; 3 mm day⁻¹ in the mean position of the Intertropical Convergence Zone, and decrease toward the north. A similar meridional pattern is projected in sea level atmospheric pressure and sea surface salinity (SSS) with negative anomalies toward the south. Large seasonal variations, which dominate the region, are projected to remain similar for the rest of the century. However, in January-April a weakening in the Panama wind jet and intensification of surface wind in the CT is expected, while in the June-November season, a weakening of the Choco wind jet will affect both sub-regions. Mean sea surface height (SSH) is expected to decrease, probably dominated by barotropic wind effects over SSS reduction effect on SSH. However, sterodynamic sea level (SDSL) is projected to rise (∼21 cm) driven by the global mean thermosteric contribution. For the end of the century, a mean sea level rise of ∼69 cm is estimated in the ETP, with SDSL being about half the barystatic contribution. These projections should be used with caution, as climate models have shown limitation reproducing atmospheric and ocean observations in the tropical Pacific Ocean during the last decades, due to large internal variability and systematic biases.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103362"},"PeriodicalIF":3.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529427","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A food-web assessment model for marine mammals, fish, and fisheries in the Norwegian and Barents Seas","authors":"Benjamin Planque ,&nbsp;Lucas Bas ,&nbsp;Martin Biuw ,&nbsp;Marie-Anne Blanchet ,&nbsp;Bjarte Bogstad ,&nbsp;Elena Eriksen ,&nbsp;Hilaire Drouineau ,&nbsp;Cecilie Hansen ,&nbsp;Bérengère Husson ,&nbsp;Erik Askov Mousing ,&nbsp;Christian Mullon ,&nbsp;Torstein Pedersen ,&nbsp;Morten D. Skogen ,&nbsp;Aril Slotte ,&nbsp;Arved Staby ,&nbsp;Ulf Lindstrøm","doi":"10.1016/j.pocean.2024.103361","DOIUrl":"10.1016/j.pocean.2024.103361","url":null,"abstract":"<div><div>The Norwegian and Barents Seas host large commercial fish populations that interact with each other, as well as marine mammal populations that feed on plankton and fish. Quantifying the past dynamics of these interacting species, and of the associated fisheries in the Norwegian and Barents Sea is of high relevance to support ecosystem-based management. The purpose of this work is to develop a food-web model of intermediate complexity and perform a quantitative assessment of the Norwegian and Barents Sea ecosystems in the period 1988–2021 in a manner that is consistent with existing data and expert knowledge, and that is internally coherent. For this purpose, we use the modelling framework of chance and necessity (CaN). The model construction follows an iterative process that allows to confront, discuss, and resolve multiple issues as well as to recognise uncertainties in expert knowledge, data, and input parameters. We show that it is possible to reconstruct the past dynamics of the food-web only if recognising that some data and assumptions are more uncertain than originally thought. According to this assessment, consumption by commercial fish and catch by fisheries jointly increased until the early 2010s, after which consumption by fish declined and catches by fisheries stabilised. On an annual basis, fish have consumed an average of 135.5 million tonnes of resources (including 9.5 million tonnes of fish), marine mammals have consumed an average of 22 million tonnes of which 50 % (11 million tonnes) were fish. Fisheries and hunting have captured an average of 4.4 million tonnes of fish and 7 thousand tonnes of marine mammals.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103361"},"PeriodicalIF":3.8,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142529429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extreme mismatch between phytoplankton and grazers during Arctic spring blooms and consequences for the pelagic food-web","authors":"Paul E. Renaud ,&nbsp;Malin Daase ,&nbsp;Eva Leu ,&nbsp;Maxime Geoffroy ,&nbsp;Sünnje Basedow ,&nbsp;Mark Inall ,&nbsp;Karley Campbell ,&nbsp;Emilia Trudnowska ,&nbsp;Einat Sandbank ,&nbsp;Frida Cnossen ,&nbsp;Muriel Dunn ,&nbsp;Lionel Camus ,&nbsp;Marie Porter ,&nbsp;Magnus Aune ,&nbsp;Rolf Gradinger","doi":"10.1016/j.pocean.2024.103365","DOIUrl":"10.1016/j.pocean.2024.103365","url":null,"abstract":"<div><div>Food-web structure determines the cycling pathways and fate of new production in marine ecosystems. Herbivorous zooplankton populations are usually seasonally coupled with pelagic primary producers. Synchrony of phytoplankton blooms with reproduction, recruitment and seasonal ascent of their main grazers ensures efficient transfer of organic carbon to higher trophic levels, including commercially harvested species, especially in high-latitude systems. Changes in light, nutrient, and sea-ice dynamics due to accelerating climate change in the Arctic, however, create large uncertainties in how these systems will function in the future. To address such knowledge gaps, we surveyed the pelagic ecosystem of the Barents Sea Polar Front in May of two consecutive years (2021 and 2022) to investigate the pelagic food-web from primary producers to planktivorous fish. In both years we observed unprecedentedly high phytoplankton chlorophyll <em>a</em> values in open as well as ice-covered waters, much of which was invisible to satellite remote sensing. We also measured very low densities of grazing zooplankton across a wide area and extending for at least one month. This extreme mismatch resulted in low feeding by capelin, and further suggests a high potential for vertical export of carbon to the benthos rather than efficient assimilation into the pelagic food web. As the Arctic continues to warm and is characterized by thinner and more mobile sea ice, we may expect higher variability in phytoplankton bloom phenology and more frequent mismatches with grazer life-histories. This could have significant impacts on ecosystem functioning by re-directing the flow of energy through the system towards seafloor rather than to the production of commercially valuable pelagic marine resources.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103365"},"PeriodicalIF":3.8,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Spatiotemporal changes in the community and demography of mesozooplankton in the eastern Indian sector of the Southern Ocean during austral summer 2018/2019","authors":"Kohei Matsuno ,&nbsp;Rikuto Sugioka ,&nbsp;Yurika Maeda ,&nbsp;Ryan Driscoll ,&nbsp;Fokje L. Schaafsma ,&nbsp;Sara Driscoll ,&nbsp;Atsushi Yamaguchi ,&nbsp;Ryuichi Matsukura ,&nbsp;Hiroko Sasaki ,&nbsp;Hiroto Murase","doi":"10.1016/j.pocean.2024.103360","DOIUrl":"10.1016/j.pocean.2024.103360","url":null,"abstract":"<div><div>The Southern Ocean is facing rapid environmental changes. However, few studies have been conducted on the spatiotemporal variability of mesozooplankton communities under recent climatic conditions, particularly in the eastern Indian sector. This study describes the spatiotemporal variability of the mesozooplankton community and the demographics of large copepods and krill in this sector, sampled through a Rectangular Mid-Water Trawl with 1 m² mouth area (RMT1) during the austral summer of 2018/2019 as part of the KY1804 survey. Cluster analysis indicated that the mesozooplankton community was divided into five groups that showed only small longitudinal differences, as they were affected by oceanic fronts. Part of the variability was explained by physical (local upwelling) and biological features (e.g., the occurrence of species showing a specific spatial distribution, such as <em>Euphausia crystallorophias</em>). Horizontal changes in the zooplankton community structure were not attributed to temporal changes during the 2-month sampling period. The demographics of the dominant species, <em>Calanoides acutus</em>, <em>Calanus propinquus</em>, <em>Metridia gerlacheri,</em> and <em>Thysanoessa macrura</em>, exhibited significant temporal differences in abundance or mean stage index (MSI) between the early and late seasons. These differences matched the growth rates estimated in previous studies, suggesting that their growth during the study period was constant without regional differences. There were no evident changes in the abundance or demographics of <em>Rhinalanus gigas</em>, suggesting that they were in their reproductive season. These species-specific demographics could be explained by the species life cycles: growth in <em>C. acutus</em> and <em>C. propinquus</em> and reproduction in <em>R. gigas</em> during the austral summer. Abundances and MSIs confirmed the growth of dominant copepods and krill during the sampling period; however, no evident seasonal changes were observed in the zooplankton community structure. The findings of this study contribute to the understanding of lower trophic levels in marine ecosystems and the present carbon cycle in the eastern Indian sector of the Southern Ocean.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103360"},"PeriodicalIF":3.8,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418749","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}