Progress in Oceanography最新文献

{"title":"Habitat shifts of the vulnerable crinoid Leptometra phalangium under climate change scenarios","authors":"Jade Millot ,&nbsp;Vincent Georges ,&nbsp;Valentina Lauria ,&nbsp;Tarek Hattab ,&nbsp;Carlos Dominguez-Carrió ,&nbsp;Vasilis Gerovasileiou ,&nbsp;Christopher J. Smith ,&nbsp;Chryssi Mytilineou ,&nbsp;M. Teresa Farriols ,&nbsp;Marie-Claire Fabri ,&nbsp;Pierluigi Carbonara ,&nbsp;Daniela Massi ,&nbsp;Paola Rinelli ,&nbsp;Adriana Profeta ,&nbsp;Giovanni Chimienti ,&nbsp;Angélique Jadaud ,&nbsp;Ioannis Thasitis ,&nbsp;Kelly Camilleri ,&nbsp;Jurgen Mifsud ,&nbsp;Sandrine Vaz","doi":"10.1016/j.pocean.2024.103355","DOIUrl":"10.1016/j.pocean.2024.103355","url":null,"abstract":"<div><div>Crinoid beds of <em>Leptometra phalangium</em> (Müller, 1841) have been identified as sensitive habitats by the General Fisheries Commission for the Mediterranean (GFCM) due to their high vulnerability to bottom trawl fisheries. Poorly resilient to physical damage, <em>L. phalangium</em> has been listed as a potential indicator of Vulnerable Marine Ecosystems (VMEs) in the Mediterranean Sea. If fishing activities represent the main cause of habitat destruction for this species, the ongoing changes in climate conditions may rapidly exacerbate the process. In this study, we developed an ensemble Species Distribution Modeling framework to predict the potential habitat of <em>L. phalangium</em> for present-days in the Mediterranean Sea, and used the model to infer potential changes in its spatial distribution by 2050 under two different climate scenarios (IPCC Representative Concentration Pathways RCP2.6 and RCP8.5). True presence-absence records were used and correlated to a parsimonious set of environmental predictors considered as important drivers of benthic species distribution. In present conditions, <em>L. phalangium</em> seems to be widely distributed along the continental slopes of the western and central Mediterranean. This crinoid is often described as confined to the continental shelf-break (100–200 m), but our results show that it can be found over a wider depth range, between 100 and 500 m. Our predictions obtained for the mid-21st century indicate an important habitat loss for <em>L. phalangium</em> under future climate conditions, mainly in the central and southern basins. Declines of 50 to 70 % in its suitable habitat were predicted under RCP2.6 and RCP8.5 compared to present-day predictions. Climate refugia (i.e., areas where environmental conditions remain suitable for the species in the future) were restricted to the northwestern basin (e.g., Gulf of Lion, the Catalan Sea, the Balearic Sea, Ligurian Sea) and in the southern Adriatic Sea. Provided by a robust statistical framework, climate refugia predictions, along with uncertainty assessments, must support the identification of priority areas for the conservation of VME indicator species by governmental bodies and regional management organizations.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103355"},"PeriodicalIF":3.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142326512","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":"Altimeter-derived poleward Lagrangian pathways in the California Current System: Part 1","authors":"P. Ted Strub ,&nbsp;Corinne James ,&nbsp;Jennifer L. Fisher ,&nbsp;Melanie R. Fewings ,&nbsp;Samantha M. Zeman ,&nbsp;Vincent Combes ,&nbsp;Jessica C. Garwood ,&nbsp;Anna E. Bolm ,&nbsp;Andrew Scherer","doi":"10.1016/j.pocean.2024.103353","DOIUrl":"10.1016/j.pocean.2024.103353","url":null,"abstract":"<div><div>We use altimeter-derived geostrophic velocities, with and without the addition of surface Ekman transports, to create trajectories for virtual parcels in the California Current System (CCS). The goal is to investigate the poleward transport of passive water parcels in the surface 50–100 m of the nominally equatorward system. Motivation for the study is provided by observations of anomalous biomass of copepods with warm water affinities along the Newport Hydrographic Line off central Oregon (44.7°N) during El Niño years, as well as during and following the 2014–2016 marine heat wave. By backward tracking virtual parcels from 44.7°N, we find that the most distant source of passive water parcels in the upper ocean during a one-year period of travel is from within the Southern California Bight (SCB), north of 30°N. To make that journey, parcels use the Inshore Countercurrent off southern and central California during summer–winter and the Davidson Current off northern California and Oregon during autumn–winter. The inclusion of small-scale eddy diffusion usually increases the number of parcels that reach more northern latitudes, while the inclusion of Ekman velocities more often reduces those numbers. Even so, parcels can travel from the SCB to central Oregon in either the Ekman layer or beneath it in the geostrophic flow. Using backward tracking, we find that parcels arrive at 44.7°N most often in winter–spring, least often in autumn. They arrive from within the large-cape region off northern California (41°–42°N) during all years and all months, from just south of the large-cape region (38°–39°N) during most years but seldom in autumn, from south of Monterey Bay along central California (36°N) and within the SCB (34.5°N) during a third (or less) of the years and only in winter-spring. The shortest average transit times are found in winter: for parcels reaching 44.7°N in February, the average transit time is 2 months for parcels coming from 41°–42°N, 4 months for parcels coming from 38°–39°N, and 5–6 months or more for parcels coming from south of 36°N. Transit times increase as the arrival time progresses from winter to autumn. The longest average transit times are for parcels reaching central Oregon in autumn (9–12 months in October for parcels coming from south of 39°N). This makes the journey a multi-generational task for the copepods. Interannual variability in the observed southern copepod species biomass off central Oregon correlates highly with years when more virtual parcels from the south reach central and northern Oregon, providing increased confidence in the results found with the altimeter-derived parcel trajectories.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103353"},"PeriodicalIF":3.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442944","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":"Assessment of high-resolution regional ocean reanalysis K-ORA22 for the Northwest Pacific","authors":"Inseong Chang ,&nbsp;Young Ho Kim ,&nbsp;Young-Gyu Park ,&nbsp;Hyunkeun Jin ,&nbsp;Gyundo Pak ,&nbsp;Jae-Il Kwon ,&nbsp;You-Soon Chang","doi":"10.1016/j.pocean.2024.103359","DOIUrl":"10.1016/j.pocean.2024.103359","url":null,"abstract":"<div><div>The Korea Institute of Ocean Science and Technology developed the Korea Operational Oceanographic System-Ocean Predictability Experiment for Marine Environment (KOOS-OPEM), a high-resolution (1/24°, 51 vertical levels) ocean prediction model for the Northwest Pacific Ocean that incorporates ensemble optimal interpolation. In this study, we present KOOS-OPEM ReAnalysis version 2022 (K-ORA22), which covers the period from 2011 to 2022. We conducted a comparative analysis between K-ORA22 and other high-resolution (1/10°–1/12°) global reanalyses, including the Hybrid Coordinate Ocean Model, Global Ocean Reanalysis and Simulation (GLORYS), and Bluelink ReAnalysis (BRAN), to demonstrate the reproducibility and reliability of regional characteristics. Statistical comparisons revealed that while K-ORA22 exhibited some warm biases, its sea surface temperature (SST) anomaly correlation after removing the seasonal cycle was approximately 0.87, comparable to other reanalyses. Additionally, K-ORA22 effectively reproduced coastal upwelling, which is characterized by a sharp decrease in SST, as observed by marine meteorological buoys in the Southwest of the East/Japan Sea. K-ORA22 exhibits a warm bias of approximately 0.50 °C around 200 m, slightly higher than those of GLORYS and BRAN, while maintaining a low salinity bias in the subsurface. Notably, K-ORA22 outperformed the other reanalyses in accurately reproducing the unique characteristics of North Pacific and East Sea intermediate waters, characterized by a salinity minimum layer. In addition, K-ORA22 stands out in its ability to accurately reproduce the Yellow Sea Cold Water Mass with a low-temperature root-mean-square error (RMSE) of 0.76 °C in the Yellow Sea (YS) region. However, it exhibited the highest RMSE for salinity in the YS region and Korea/Tsushima Strait, indicating a potential overestimation of river discharge from Korea and China. While the sea surface height (SSH) anomaly correlation of K-ORA22 did not surpass 0.80 in the entire region because of limitations in the background error covariance used, its ability to reproduce the Kuroshio path was comparable to those of other reanalysis datasets. In conclusion, K-ORA22 excels in reproducing the unique characteristics of Korean marginal seas. Still, it exhibits weaknesses, such as the overestimation of river discharge and a somewhat limited ability to simulate SSH variability, compared with other global reanalyses. We plan to enhance K-ORA22 by updating background error covariance, addressing biases related to river discharge and assimilating the best available <em>in situ</em> observations and satellite data.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103359"},"PeriodicalIF":3.8,"publicationDate":"2024-09-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142418165","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":"Three-dimensional structure of temperature, salinity, and Velocity of the summertime Vietnamese upwelling system in the South China Sea on the interannual timescale","authors":"Mai-Han Ngo ,&nbsp;Yi-Chia Hsin","doi":"10.1016/j.pocean.2024.103354","DOIUrl":"10.1016/j.pocean.2024.103354","url":null,"abstract":"<div><div>Summertime upwelling system off the southern Vietnamese coast is one of the most essential oceanographic features in the South China Sea. This system is divided into two regions along the coast, the Southern Coastal Upwelling (SCU; south of 12.5°N) and Northern Coastal Upwelling (NCU; north of 12.5°N), and one in the offshore area, the Offshore Upwelling (OU; east of 110°E). Utilizing the HYCOM ocean reanalysis product in the period of 1994–2015, vertical characteristics of this upwelling system on the interannual timescale are investigated. Furthermore, the omega equation is applied to reconstruct vertical velocity to quantify its intensity and clarify the corresponding leading factors in the three regions. The analysis indicates that the kinematic deformation effect is the primary contributor to coastal upwelling formation while the momentum effect plays the leading role in offshore upwelling. The SCU variability is more sensitive to the momentum effect; however, in the NCU, the kinematic deformation effect is offset by the momentum effect and the upwelling is enhanced as the kinematic deformation (momentum) effect increases (decreases). The summertime mean vertical velocities in the central areas of SCU, NCU, and OU are estimated at 0.16 m/d, −0.08 m/d, and 0.003 m/d, respectively. The vertical velocity speeds up to 0.32 m/d, 0.07 m/d, and 0.08 m/d as the strong upwelling event occurs.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103354"},"PeriodicalIF":3.8,"publicationDate":"2024-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0079661124001605/pdfft?md5=387cb28233e0ebbefb94e39ed849470a&pid=1-s2.0-S0079661124001605-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142311451","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":"Effects of increased temperature and altered POC composition on a bathyal macrofaunal community in Cabo Verde, NE Atlantic","authors":"Daniela Y. Gaurisas ,&nbsp;Daniëlle S.W. de Jonge ,&nbsp;Andrew K. Sweetman ,&nbsp;Angelo F. Bernardino","doi":"10.1016/j.pocean.2024.103352","DOIUrl":"10.1016/j.pocean.2024.103352","url":null,"abstract":"<div><p>Deep-sea ecosystems are particularly important to the cycling of matter and energy in the oceans and therefore in regulating Earth’s climate. The Atlantic Ocean is already experiencing significant abiotic changes, with expected warmer temperatures coupled with decreased particulate organic carbon (POC) export flux. However, there is yet a large gap in our understanding of warming impacts on deep benthic ecosystems and in the organic matter processing by benthic organisms in the seafloor. This study employed an experimental approach to assess the single and cumulative effects of two climate change stressors, temperature and POC quality, on macrofaunal benthic assemblages in the Cabo Verde Basin (CVB, Equatorial Atlantic) bathyal continental slope. Incubation enrichment experiments with ¹³C and ¹⁵N labelled diatoms <em>Phaeodactylum tricornutum</em> simulated climate projections for the next century with a balanced design, studying the effect of either increased temperature (+2°C), reduced POC quality (dialysed labile fraction), or both, against a control treatment. We found that echinoderms and polychaetes rapidly ingested labelled algae at rates between 0.02 and 21.9 µg C m⁻² d^-1. Given a strong spatial variability in macrofaunal biomass, the carbon and nitrogen incorporation by macrofauna was not affected by a + 2 °C warming, by a decreased organic matter quality, or the combination of both factors. Our study provides valuable insights into the biodiversity, biomass, and ecosystem functioning (C and N uptake rates) of deep-sea benthic ecosystems in the N Atlantic, and stress that potential effects of warmer temperatures and POC quality on carbon and nitrogen incorporation by macrofauna remain uncertain. We highlight the value of these experiments to better understand the effects of climate change on deep-sea ecosystems.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103352"},"PeriodicalIF":3.8,"publicationDate":"2024-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142239575","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":"Jigsaw puzzle of the interwoven biologically-driven ocean carbon pumps","authors":"Louis Legendre","doi":"10.1016/j.pocean.2024.103338","DOIUrl":"10.1016/j.pocean.2024.103338","url":null,"abstract":"<div><div>The biological pumping of carbon in the ocean and its effects on ocean carbon sequestration are being studied by researchers from several disciplines. These studies address the biological carbon pump (also called organic, soft-tissue, or biogeochemical carbon pump), the carbonate pump (or counter-pump) and the microbial carbon pump, which are most often treated separately. In the present study, the three pumps are treated together for the first time, under the generic name of “biologically-driven ocean carbon pumps”, in short, “bio-pumps”. The interactions among the carbon fluxes of three interwoven bio-pumps are summarized in the bio-pump jigsaw puzzle.</div><div>The bio-pump literature presents a wide range of approaches to the nature and processes of carbon pumps and the ensuing carbon sequestration in the ocean, approaches that often differ significantly. It is shown that sequestration fluxes from all three bio-pumps can occur throughout the water column, albeit in different forms, and this “continuous vertical sequestration” concept is used to propose a target framework to simplify the research on bio-pumps, and unify the studies carried out by researchers from different disciplines. The review of the wide range of approaches to ocean biologically-driven carbon pumping and sequestration in the literature includes both a look back at the initial ocean carbon pump concept and an analysis of current approaches. It also includes estimates of century-scale (≥100 years) global sequestration fluxes in the water column by the three bio-pumps, which are about 1–3, 0.7 and 0.2 Pg C y^–1 for the biological, carbonate and microbial pumps, respectively. The value of 0.7 Pg C y^–1 appears to be the first ever published for the carbonate pump. The review is followed by detailed analysis of the functioning of the bio-pumps and their carbon sequestration processes, which is organized around four common components, i.e. downward fluxes of biogenic carbon from the upper ocean (i.e. export), transformation fluxes of the exported biogenic carbon in the lower ocean, carbon sequestration fluxes throughout the water column, and upward flux of dissolved inorganic carbon. It is recommended that future carbon-pump publications use representations that include these four components. This leads to a synthetic description of the processes involved in the three bio-pumps and their carbon sequestration, and a proposed unification of research on the interwoven bio-pumps.</div></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103338"},"PeriodicalIF":3.8,"publicationDate":"2024-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142359191","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":"Circulation and dispersal in California’s Borderland Basins","authors":"James C. McWilliams ,&nbsp;Pierre Damien ,&nbsp;Faycal Kessouri","doi":"10.1016/j.pocean.2024.103349","DOIUrl":"10.1016/j.pocean.2024.103349","url":null,"abstract":"<div><p>The Borderland Basins off Southern California are semi-isolated sea-floor depressions with connections to each other and to the open Pacific Ocean over narrow sills. A high-resolution, multi-year simulation is analyzed for its currents, stratification, and dissolved oxygen, with a focus on the mean conditions, intrinsic variability, and exchange rates with surrounding waters. The three shallowest, closest basins are given the most attention: Santa Barbara, Santa Monica, and San Pedro. Below the basin sill depths, the water masses in the basins are distinct from surrounding waters at the same density indicating a degree of dynamical isolation. The mean circulations are anti-clockwise around the topographic edges of the basins, consistent with eddy-driven flows (<em>i.e.,</em> topostrophy). The mesoscale eddy variability is stronger than the mean flow, and at least partially it is comprised of topographic Rossby waves circuiting the edge slopes. Its magnitude is similar to the high-frequency currents (mostly tidal). There are recurrent cross-sill flows driven by an unbalanced pressure-gradient force, and these intermittently cause water mass flushing of the basins. The oxygen levels in the basins are occasionally anoxic, and they are maintained by a balance of downward physical transport from above, local respiration, and flux into the sediments. From a combination of multiple means of estimation, the deep basin water mass renewal times are on the order of a year or more, and this time is somewhat shorter in the Santa Barbara Basin than the others. The renewal processes are by intermittent sill overflows and by vertical exchanges through eddies and tides.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103349"},"PeriodicalIF":3.8,"publicationDate":"2024-09-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142274362","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 microbial carbon biomass variability in two oceanic regions of the Gulf of Mexico","authors":"L. Linacre ,&nbsp;R. Durazo ,&nbsp;V. Camacho-Ibar ,&nbsp;U. Mirabal-Gómez ,&nbsp;J.A. Velásquez-Aristizábal ,&nbsp;C. Sánchez-Robles ,&nbsp;J.R. Lara-Lara ,&nbsp;C. Bazán-Guzmán","doi":"10.1016/j.pocean.2024.103348","DOIUrl":"10.1016/j.pocean.2024.103348","url":null,"abstract":"<div><p>The microbial plankton community is an integral part of the pelagic ecosystem. It hosts essential functional groups that play a vital role in organic carbon production, release, uptake, and degradation within open-ocean ecosystems. Given its significance, carbon biomass estimates are urgently needed, especially in oligotrophic regions, to provide and enhance our knowledge of biogenic carbon pools. They also aid in validating biogeochemical models that characterize the functioning of these extensive marine ecosystems within the global carbon cycle. This study addresses the temporal variability of microbial community biomass in two oceanic zones: the west-central (Perdido) and southern (Coatzacoalcos) areas of the Gulf of Mexico. During three seasonally contrasting periods (<em>nortes</em>, <em>rainy</em>, and <em>dry</em> seasons), seawater samples were collected from the euphotic zone in both regions to estimate the carbon biomass of different pico- (&lt;2–3 µm), nano-, and microplankton groups (&gt;3–200 µm). Carbon biomass assessments for the microbial groups were based on their abundance and carbon conversion factors. Overall, we found a significant contribution of pico-prokaryotic components (heterotrophic bacteria, <em>Prochloroccocus</em>, and <em>Synechoccocus</em>) to the total microbial carbon stock of the euphotic zone (84–89 % global estimates). The finding suggests these microorganisms are key functional groups that drive carbon production and fate in the Gulf of Mexico ecosystem. Pico-cyanobacteria, especially <em>Prochloroccocus</em>, were the dominant primary producers (68–82 % total autotrophic carbon), mainly in the upper layer of the oligotrophic euphotic zone. This vertical pattern implies that the deep chlorophyll-<em>a</em> maximum (DCM) depth level was unrelated to a net increase in phytoplankton biomass in the three study periods. The distribution of microbial carbon biomass exhibited striking differences associated with winter mixing (the <em>nortes</em> season), high river discharge accompanied by cross-shelf transport (the <em>rainy</em> season), and the dynamics of mesoscale structures. Ecological aspects, such as the habitat preference of the organisms and the seasonal complementary development of mixotrophic and heterotrophic grazers and their prey, were also essential drivers in regulating the microbial carbon pool of both oceanic regions. The microbial carbon assessments conducted in this study contribute to identifying and quantifying key planktonic functional groups involved in the biogeochemical carbon cycle in the Gulf of Mexico open-ocean ecosystem.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103348"},"PeriodicalIF":3.8,"publicationDate":"2024-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142274555","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":"Nutrient stoichiometry drives the phytoplankton populations during the progression of upwelling along the eastern Arabian Sea","authors":"B. Bikram Reddy ,&nbsp;Anil Kumar Vijayan ,&nbsp;V. Sudheesh ,&nbsp;C.K. Sherin ,&nbsp;Rajdeep Roy ,&nbsp;N.N. Vishnu ,&nbsp;G.V.M. Gupta","doi":"10.1016/j.pocean.2024.103347","DOIUrl":"10.1016/j.pocean.2024.103347","url":null,"abstract":"<div><p>The basin-wide phytoplankton succession and community behaviour in response to varying nutrient patterns during various upwelling phases are detailed, for the first time, in the eastern Arabian Sea (EAS, ∼6^◦ to 22^◦N) during the summer monsoon (SM) of 2018. Three consecutive observations were carried out during early SM (June-July), peak SM (August), and late SM (September-October), representing different phases of upwelling. During the early phase of upwelling, high phytoplankton biomass was observed in the south (column-integrated chlorophyll <em>a</em>: 74.09 ± 60.05 mg m⁻²) and moderate levels in the central (25.75 ± 6.51 mg m⁻²) and north (30.31 ± 12.32 mg m⁻²) EAS coastal waters. Diatoms were the dominant group (60–90 %) in the coastal stations throughout the upwelling period. Offshore regions characterised by deeper nutriclines (&gt;50 m) had pico-phytoplankton dominance, including cyanobacteria (14–30 %), chlorophytes (19–24 %) and prochlorophytes (12–15 %); however, due to low nitrogen to phosphorous ratio (N/P: 2.6 ± 1.31) during this period, the contribution of diatoms decreased to less than 20 % in the offshore waters compared to the coastal EAS. During peak SM, upwelling induced shoaling of nutriclines and high N/P conditions (8.4 ± 5.25) in the mixed layers of south EAS coastal waters substantially enhanced phytoplankton biomass (chlorophyll <em>a</em>: 129.06 ± 96.24 mg m⁻²). Additionally, the shallow nutriclines supported diatoms dominance in offshore waters, particularly in the central EAS (up to 65 %), relative to the south and north EAS (22 to 33 %), where the upwelling intensity was weaker. The withdrawal of upwelling led to a deepening of nutricline and low N/P conditions (3.33 ± 2.77 in coastal and 3.35 ± 2.26 in offshore waters) during late SM. This supported the occurrence of cyanobacteria and dinoflagellates, as the contribution of diatoms to the total phytoplankton community sharply decreased to 50 %. In other words, upwelling in the EAS brings nitrogen-deficient (denitrified) waters; the available nitrogen is immediately consumed by the diatom community, resulting in low N/P conditions that favour the dominance of the cyanobacterial population towards late SM. Overall, substantial intra-seasonal variability was observed in nutrient stoichiometry, strongly modulated by the intensity of physical processes affecting the phytoplankton populations. Continuous monitoring is required to understand the phytoplankton populations, their impact on higher trophic levels, and the overall health of aquatic food web structure in the EAS.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103347"},"PeriodicalIF":3.8,"publicationDate":"2024-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142173458","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":"Environmental variability shapes trophic and resource partitioning between epipelagic and mesopelagic biomes in oceanic provinces: Implications in a globally changing ocean","authors":"Pavanee Annasawmy ,&nbsp;Frédéric Ménard ,&nbsp;Francis Marsac ,&nbsp;Jean-François Ternon ,&nbsp;Yves Cherel ,&nbsp;Evgeny Romanov ,&nbsp;François Le Loc’h","doi":"10.1016/j.pocean.2024.103339","DOIUrl":"10.1016/j.pocean.2024.103339","url":null,"abstract":"<div><p>Trophic links between the epipelagic (&lt; 200 m) and mesopelagic layers of the Indian Ocean were investigated by carbon and nitrogen stable isotope ratios of 2405 samples collected from 2002 to 2016, and that encompass the base of trophic webs, and primary, secondary and tertiary consumers. The samples include particulate organic matter, gastropods, gelatinous organisms such as salps and pyrosomes, crustaceans, mesopelagic fishes, micronektonic and nektonic squids, tuna and swordfish. Stable δ¹³C and δ¹⁵N values were used to investigate trophic and resource partitioning between epipelagic <em>vs</em> mesopelagic (migrators and non-migrators), feeding patterns (zooplanktivorous <em>vs</em> micronektivorous), and at seamounts and off-seamount locations. We also investigated how contrasting environmental conditions within two biogeochemical provinces, the ISSG (Indian South Subtropical Gyre) and EAFR (East African Coastal Province), influenced stable isotope patterns. Our data suggest that broad-scale biogeochemical differences and local environmental conditions significantly shape trophic and resource partitioning. In oligotrophic systems, epipelagic migrating and non epipelagic-migrating organisms rely on food webs where suspended particles are ¹⁵N-enriched and organic matter recycled/re-processed. We show that seamounts form strong isotopic topographic barriers (which we define as “isobiome”) that impact the trophic linkages/connections between epipelagic migrants and non-epipelagic migrants, and those with zooplanktivorous feeding patterns. This study reveals that the trophic and resource partitioning in the ocean is more complex than initially thought, when environmental variability, bathymetric gradients, and a wider range of samples are taken into account compared to earlier studies. We also showed that a warmer ocean led to a reduction in productivity, lower values of δ¹³C and δ¹⁵N, and potential shifts in food web trophic structure that remain to be investigated further. Finally, we discuss how important it is to unravel this complexity on a global scale given the vulnerability of epipelagic and mesopelagic communities due to anthropogenic pressures in the Anthropocene.</p></div>","PeriodicalId":20620,"journal":{"name":"Progress in Oceanography","volume":"229 ","pages":"Article 103339"},"PeriodicalIF":3.8,"publicationDate":"2024-09-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142229234","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}