Pub Date : 2024-10-18DOI: 10.1016/j.pocean.2024.103364
Witold Podlejski , Léo Berline , Julien Jouanno , Nicolas Barrier , Christophe Lett
The proliferation of Sargassum 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 Sargassum growth and decay is still lacking to explain this interannual variability. Benefiting from accurate basin scale Sargassum detections provided by remote sensing, and from physical and biogeochemical ocean simulations, we developed a Lagrangian drift-growth model to simulate Sargassum distribution over the period 2016–2020. The resulting trajectories and biomass time series of Sargassum 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 Sargassum. The timing of the seasonal warming of this region strongly impacts the quantities of Sargassum simulated each year. This suggests that this region should be monitored to anticipate the development of Sargassum and resulting strandings.
{"title":"Drivers of growth and decay of Sargassum in the Tropical Atlantic: A Lagrangian approach","authors":"Witold Podlejski , Léo Berline , Julien Jouanno , Nicolas Barrier , 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}
Pub Date : 2024-10-16DOI: 10.1016/j.pocean.2024.103366
Baolan Wu , Jianping Gan
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.
{"title":"Long-term variation of the eddy kinetic energy in the Northeastern South China sea","authors":"Baolan Wu , 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}
Pub Date : 2024-10-15DOI: 10.1016/j.pocean.2024.103363
Jiawen Kang , Qiang Hao , Shunan Cao , Jun Zhao , Zifei Yang , Zhen Tang , Minfang Zheng , Yusheng Qiu , Mengya Chen , Jianming Pan , Jianfeng He , Min Chen
This study examined particulate organic carbon (POC) and its isotopic composition (δ13CPOC) 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 δ13CPOC, with higher POC and δ13CPOC values in the Cosmonaut Sea compared to the Cooperation Sea. The δ13CPOC values in both seas were positively correlated with the proportion of Chl-a in smaller particles (< 20 μm). However, the relationship with the proportion of biogenic POC in smaller particles (< 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 Phaeocystis antarctica, whereas in the Cooperation Sea, they were dominated by pennate diatoms. The δ13CPOC 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 δ13CPOC 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 δ13CPOC in the Southern Ocean, emphasizing the importance of phytoplankton community composition.
{"title":"Stable carbon isotopic composition of particulate organic matter in the Cosmonaut and Cooperation Seas in summer","authors":"Jiawen Kang , Qiang Hao , Shunan Cao , Jun Zhao , Zifei Yang , Zhen Tang , Minfang Zheng , Yusheng Qiu , Mengya Chen , Jianming Pan , Jianfeng He , 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 (δ<sup>13</sup>C<sub>POC</sub>) 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 δ<sup>13</sup>C<sub>POC</sub>, with higher POC and δ<sup>13</sup>C<sub>POC</sub> values in the Cosmonaut Sea compared to the Cooperation Sea. The δ<sup>13</sup>C<sub>POC</sub> values in both seas were positively correlated with the proportion of Chl-a in smaller particles (< 20 μm). However, the relationship with the proportion of biogenic POC in smaller particles (< 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 δ<sup>13</sup>C<sub>POC</sub> 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 δ<sup>13</sup>C<sub>POC</sub> 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 δ<sup>13</sup>C<sub>POC</sub> 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}
Pub Date : 2024-10-15DOI: 10.1016/j.pocean.2024.103362
Rafael Ricardo Torres Parra , David Francisco Bustos Usta , Luis Jesús Otero Díaz , María Paula Moreno-Ardila
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 > 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.
{"title":"Eastern Tropical Pacific atmospheric and oceanic projected changes based on CMIP6 models","authors":"Rafael Ricardo Torres Parra , David Francisco Bustos Usta , Luis Jesús Otero Díaz , 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 > 3 mm day<sup>−1</sup> 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}
Pub Date : 2024-10-15DOI: 10.1016/j.pocean.2024.103361
Benjamin Planque , Lucas Bas , Martin Biuw , Marie-Anne Blanchet , Bjarte Bogstad , Elena Eriksen , Hilaire Drouineau , Cecilie Hansen , Bérengère Husson , Erik Askov Mousing , Christian Mullon , Torstein Pedersen , Morten D. Skogen , Aril Slotte , Arved Staby , Ulf Lindstrøm
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.
{"title":"A food-web assessment model for marine mammals, fish, and fisheries in the Norwegian and Barents Seas","authors":"Benjamin Planque , Lucas Bas , Martin Biuw , Marie-Anne Blanchet , Bjarte Bogstad , Elena Eriksen , Hilaire Drouineau , Cecilie Hansen , Bérengère Husson , Erik Askov Mousing , Christian Mullon , Torstein Pedersen , Morten D. Skogen , Aril Slotte , Arved Staby , 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}
Pub Date : 2024-10-13DOI: 10.1016/j.pocean.2024.103365
Paul E. Renaud , Malin Daase , Eva Leu , Maxime Geoffroy , Sünnje Basedow , Mark Inall , Karley Campbell , Emilia Trudnowska , Einat Sandbank , Frida Cnossen , Muriel Dunn , Lionel Camus , Marie Porter , Magnus Aune , Rolf Gradinger
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 a 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.
食物网结构决定了海洋生态系统中新生物的循环途径和归宿。食草浮游动物种群通常与浮游初级生产者季节性结合。浮游植物的大量繁殖与主要食草动物的繁殖、招募和季节性上升同步进行，确保了有机碳向更高营养级（包括商业捕捞物种）的有效转移，尤其是在高纬度系统中。然而，由于北极地区气候变化加速，光照、营养物质和海冰动力学发生了变化，这给这些系统未来如何发挥作用带来了巨大的不确定性。为了填补这些知识空白，我们在连续两年（2021 年和 2022 年）的五月对巴伦支海极地前沿的浮游生态系统进行了调查，以研究从初级生产者到浮游鱼类的浮游食物网。在这两年里，我们在开阔水域和冰覆盖水域都观测到了前所未有的高浮游植物叶绿素 a 值，其中大部分是卫星遥感观测不到的。同时，我们还在大面积水域测量到了极低的浮游动物密度，并持续了至少一个月。这种极端的不匹配导致毛鳞鱼的摄食量很低，进一步表明碳很有可能被垂直输出到底栖生物中，而不是被有效地同化到浮游食物网中。随着北极地区持续变暖，海冰越来越薄，流动性越来越大，我们可能会预期浮游植物开花物候的变化会更大，与食草动物生命史的不匹配也会更频繁。这可能会对生态系统功能产生重大影响，使能量流经该系统重新流向海底，而不是用于生产具有商业价值的浮游海洋资源。
{"title":"Extreme mismatch between phytoplankton and grazers during Arctic spring blooms and consequences for the pelagic food-web","authors":"Paul E. Renaud , Malin Daase , Eva Leu , Maxime Geoffroy , Sünnje Basedow , Mark Inall , Karley Campbell , Emilia Trudnowska , Einat Sandbank , Frida Cnossen , Muriel Dunn , Lionel Camus , Marie Porter , Magnus Aune , 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}
Pub Date : 2024-10-09DOI: 10.1016/j.pocean.2024.103360
Kohei Matsuno , Rikuto Sugioka , Yurika Maeda , Ryan Driscoll , Fokje L. Schaafsma , Sara Driscoll , Atsushi Yamaguchi , Ryuichi Matsukura , Hiroko Sasaki , Hiroto Murase
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 Euphausia crystallorophias). 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, Calanoides acutus, Calanus propinquus, Metridia gerlacheri, and Thysanoessa macrura, 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 Rhinalanus gigas, suggesting that they were in their reproductive season. These species-specific demographics could be explained by the species life cycles: growth in C. acutus and C. propinquus and reproduction in R. gigas 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.
{"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 , Rikuto Sugioka , Yurika Maeda , Ryan Driscoll , Fokje L. Schaafsma , Sara Driscoll , Atsushi Yamaguchi , Ryuichi Matsukura , Hiroko Sasaki , 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 m<sup>2</sup> 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}
Commercially important fish spend their vulnerable early life stages in the Kuroshio Current, resulting in high fishery production even in the vicinity of poor prey availability under oligotrophic conditions. Nevertheless, little information is available on how ichthyoplankton are supported by trophodynamics in complicated food webs. Here, we have explored trophic sources and pathways toward ichthyoplankton in the Kuroshio and its neighboring waters based on metabarcoding analysis of gut DNA content for major taxonomic groups of mesozooplankton and ichthyoplankton. Calanoids were found to be the most predominant and frequently appearing prey, whereas non-crustaceans were the secondary prey for most mesozooplankton and ichthyoplankton groups. Trophic networks based on gut DNA content demonstrated that calanoids were the most important sector with multiple linkages among their prey and predators, and gelatinous and non-crustacean mesozooplankton were the secondary sectors. These findings suggest that calanoids are important hubs of trophic pathways toward ichthyoplankton, and that gelatinous and non-crustacean mesozooplankton groups strengthen trophic relationships with multiple components. Contrary to general thought, our metabarcoding analysis has revealed that trophodynamics toward ichthyoplankton are not strongly dependent on the grazing food chain, but are supported by multiple trophic pathways in the Kuroshio and its neighboring waters.
具有重要商业价值的鱼类在黑潮中度过其脆弱的早期生命阶段，因此，即使在低营养条件下猎物供应不足的附近，渔业产量也很高。然而，关于鱼类浮游生物如何在复杂的食物网中获得营养动力学支持的信息却很少。在此，我们根据对中生浮游生物和鱼类浮游生物主要分类群的肠道 DNA 含量的代谢编码分析，探索了黑潮及其邻近水域鱼类浮游生物的营养源和营养途径。结果发现，桡足类是最主要和最经常出现的猎物，而非甲壳类则是大多数中生浮游动物和鱼类的次要猎物。以肠道 DNA 含量为基础的营养网络表明，桡足类是最重要的部分，其猎物和捕食者之间存在多种联系，胶状和非甲壳类中浮游动物是次要部分。这些发现表明，钙类是鱼类浮游生物营养途径的重要枢纽，而胶状和非甲壳类中浮游生物群则加强了与多个组成部分的营养关系。与一般观点相反，我们的代谢编码分析表明，黑潮及其邻近水域中鱼类浮游生物的营养动力学并不强烈依赖于放牧食物链，而是得到了多种营养途径的支持。
{"title":"Comparison of the trophic sources and pathways of mesozooplankton and ichthyoplankton in the Kuroshio current and its neighboring waters","authors":"Toru Kobari , Ayane Taniguchi , Manami Hirata , Gen Kume , Mutsuo Ichinomiya , Tomohiro Komorita , Masafumi Kodama , Fumihiro Makino , Junya Hirai","doi":"10.1016/j.pocean.2024.103356","DOIUrl":"10.1016/j.pocean.2024.103356","url":null,"abstract":"<div><div>Commercially important fish spend their vulnerable early life stages in the Kuroshio Current, resulting in high fishery production even in the vicinity of poor prey availability under oligotrophic conditions. Nevertheless, little information is available on how ichthyoplankton are supported by trophodynamics in complicated food webs. Here, we have explored trophic sources and pathways toward ichthyoplankton in the Kuroshio and its neighboring waters based on metabarcoding analysis of gut DNA content for major taxonomic groups of mesozooplankton and ichthyoplankton. Calanoids were found to be the most predominant and frequently appearing prey, whereas non-crustaceans were the secondary prey for most mesozooplankton and ichthyoplankton groups. Trophic networks based on gut DNA content demonstrated that calanoids were the most important sector with multiple linkages among their prey and predators, and gelatinous and non-crustacean mesozooplankton were the secondary sectors. These findings suggest that calanoids are important hubs of trophic pathways toward ichthyoplankton, and that gelatinous and non-crustacean mesozooplankton groups strengthen trophic relationships with multiple components. Contrary to general thought, our metabarcoding analysis has revealed that trophodynamics toward ichthyoplankton are not strongly dependent on the grazing food chain, but are supported by multiple trophic pathways in the Kuroshio and its neighboring waters.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103356"},"PeriodicalIF":3.8,"publicationDate":"2024-09-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-26DOI: 10.1016/j.pocean.2024.103357
Joana Brito , Ambre Soszynski , Johanna J. Heymans , Simone Libralato , Eva Giacomello , Laurence Fauconnet , Gui M. Menezes , Telmo Morato
Marine ecosystems associated with mid-oceanic elevations harbour unique pelagic and benthic biodiversity and sustain food webs critical for Nature’s contributions to people (NCP). The United Nations Sustainable Development Goals and the Convention on the Law of the Sea recognize the need to implement ecosystem-based management approaches to conserve the structure and functioning of oceanic and deep-sea ecosystems within sustainable reference points. However, uncertainties regarding the interactions between multiple drivers of change, and their impacts on the state of these ecosystems and the NCP, present significant challenges to effective management. Trophic models offer a holistic approach to identify the main drivers affecting the dynamics of marine ecosystems. Here, we used a food web model of the open-ocean and deep-sea environments of the Azores for identifying the drivers that best explain historical biomass trends of demersal fish of high commercial value. Our hindcast simulations suggested that historical trends can be explained by the combined effects of deep-sea fisheries exploitation and variability in environmental conditions, likely dominated by primary productivity anomalies. In particular, deficits in primary production and high levels of fishing exploitation might have contributed to the pronounced decline in biomass observed between 2008 and 2012. These findings reinforce that failure to consider environmental factors in ecosystem-based management may result in shortfalls at achieving biodiversity conservation and sustainability objectives, particularly in the context of climate change.
{"title":"Drivers of trophodynamics of the open-ocean and deep-sea environments of the Azores, NE Atlantic","authors":"Joana Brito , Ambre Soszynski , Johanna J. Heymans , Simone Libralato , Eva Giacomello , Laurence Fauconnet , Gui M. Menezes , Telmo Morato","doi":"10.1016/j.pocean.2024.103357","DOIUrl":"10.1016/j.pocean.2024.103357","url":null,"abstract":"<div><div>Marine ecosystems associated with mid-oceanic elevations harbour unique pelagic and benthic biodiversity and sustain food webs critical for Nature’s contributions to people (NCP). The United Nations Sustainable Development Goals and the Convention on the Law of the Sea recognize the need to implement ecosystem-based management approaches to conserve the structure and functioning of oceanic and deep-sea ecosystems within sustainable reference points. However, uncertainties regarding the interactions between multiple drivers of change, and their impacts on the state of these ecosystems and the NCP, present significant challenges to effective management. Trophic models offer a holistic approach to identify the main drivers affecting the dynamics of marine ecosystems. Here, we used a food web model of the open-ocean and deep-sea environments of the Azores for identifying the drivers that best explain historical biomass trends of demersal fish of high commercial value. Our hindcast simulations suggested that historical trends can be explained by the combined effects of deep-sea fisheries exploitation and variability in environmental conditions, likely dominated by primary productivity anomalies. In particular, deficits in primary production and high levels of fishing exploitation might have contributed to the pronounced decline in biomass observed between 2008 and 2012. These findings reinforce that failure to consider environmental factors in ecosystem-based management may result in shortfalls at achieving biodiversity conservation and sustainability objectives, particularly in the context of climate change.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103357"},"PeriodicalIF":3.8,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142444686","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-24DOI: 10.1016/j.pocean.2024.103358
Xueqi Liu , Hui Zhou , Hengchang Liu , Wenlong Yang
The interannual variations of eddy kinetic energy (EKE) in the western equatorial Pacific Ocean are investigated based on satellite observations and model outputs in this study. Results reveal that the EKE exhibits vigorous interannual variations, especially in the region of North Equatorial Countercurrent (NECC) and north of New Guinea, and the variations differ between the two types of El Niño events. The energy budget diagnosis indicates that the EKE variations are mainly attributed to the barotropic instability associated with the background currents. Specifically, the energetic NECC behaves northward shift and a stronger meander path, which favors the enhancement of EKE variations due to the enhanced barotropic instability. The interannual fluctuations of the strength of the New Guinea Coastal Current/Undercurrent (NGCC/NGCUC) and the eastward current along the equator contribute to the significant EKE interannual variations north of New Guinea. Further, the distinct features of EKE variations in two types of El Niño events are as follows: EKE typically weakens in the western equatorial Pacific during Eastern Pacific El Niño (EP-El Niño) events, whereas it intensifies north of New Guinea during Central Pacific El Niño (CP-El Niño) events. The opposite features north of New Guinea are attributed to the wind work and a stronger eastward current along the equator in CP-El Niño events. These results can contribute to a better understanding of the low-frequency eddy-mean flow interactions.
{"title":"Characteristics and dynamics of the interannual eddy kinetic energy variation in the Western Equatorial Pacific Ocean","authors":"Xueqi Liu , Hui Zhou , Hengchang Liu , Wenlong Yang","doi":"10.1016/j.pocean.2024.103358","DOIUrl":"10.1016/j.pocean.2024.103358","url":null,"abstract":"<div><div>The interannual variations of eddy kinetic energy (EKE) in the western equatorial Pacific Ocean are investigated based on satellite observations and model outputs in this study. Results reveal that the EKE exhibits vigorous interannual variations, especially in the region of North Equatorial Countercurrent (NECC) and north of New Guinea, and the variations differ between the two types of El Niño events. The energy budget diagnosis indicates that the EKE variations are mainly attributed to the barotropic instability associated with the background currents. Specifically, the energetic NECC behaves northward shift and a stronger meander path, which favors the enhancement of EKE variations due to the enhanced barotropic instability. The interannual fluctuations of the strength of the New Guinea Coastal Current/Undercurrent (NGCC/NGCUC) and the eastward current along the equator contribute to the significant EKE interannual variations north of New Guinea. Further, the distinct features of EKE variations in two types of El Niño events are as follows: EKE typically weakens in the western equatorial Pacific during Eastern Pacific El Niño (EP-El Niño) events, whereas it intensifies north of New Guinea during Central Pacific El Niño (CP-El Niño) events. The opposite features north of New Guinea are attributed to the wind work and a stronger eastward current along the equator in CP-El Niño events. These results can contribute to a better understanding of the low-frequency eddy-mean flow interactions.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103358"},"PeriodicalIF":3.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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