Deep-sea Research Part Ii-topical Studies in Oceanography最新文献

{"title":"Optimal maternal feeding isotopic niche: influence of breeder trophic behaviour on larval growth and survival in bluefin tuna species","authors":"José M. Quintanilla ,&nbsp;Ricardo Borrego-Santos ,&nbsp;Estrella Malca ,&nbsp;Isabel Riveiro ,&nbsp;Francisco J. Abascal ,&nbsp;Miquel Planas ,&nbsp;Rasmus Swalethorp ,&nbsp;Michael R. Landry ,&nbsp;Raúl Laiz-Carrión","doi":"10.1016/j.dsr2.2026.105610","DOIUrl":"10.1016/j.dsr2.2026.105610","url":null,"abstract":"<div><div>Maternal effects play a fundamental role in shaping early larval growth and survival in marine fishes. This study explores the relationship between maternal trophic ecology and larval growth in bluefin tunas, with a focus on Southern Bluefin Tuna (SBT) and an expanded dataset from multiple Atlantic Bluefin Tuna (ABT) populations incorporated into the General Bluefin Model (GBM). Daily growth and stable isotopes (δ¹⁵N and δ¹³C) were obtained from 80 pre-flexion SBT larvae and 355 pre-flexion larvae from the GBM dataset. Results revealed a significant negative linear trend between larval age and δ¹⁵N values, consistent with the gradual attenuation of maternally inherited isotopic signatures during development. Faster growing larvae showed significantly lower δ¹⁵N and δ¹³C values, indicating that maternal trophic behaviour and prey sources critically influence larval growth potential. Maternal isotopic niche breadth, inferred from larval isotope data, was markedly narrower in groups with optimal larval growth, suggesting that specialized (stenophagous) maternal feeding strategies promote enhanced offspring performance. These patterns were observed consistently in two bluefin species across seven different populations, despite geographic and temporal variability, highlighting a robust ecological link between maternal foraging behaviour and larval development. From these findings, we introduce the hypothesis of an Optimal Maternal Feeding Isotopic Niche, representing a constrained isotopic range associated with increased larval growth and survival. This framework advances our understanding of the influence of maternal trophic ecology on offspring fitness and offers valuable insights for the conservation and management of highly migratory pelagic species with complex reproductive strategies.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"226 ","pages":"Article 105610"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146170525","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":"Differences in bloom phenology and seasonal chlorophyll-a variability in the Fram Strait's hydrographic subregions resolved by a machine learning approach","authors":"Vanessa Lampe,&nbsp;Andreas Oschlies,&nbsp;Markus Schartau","doi":"10.1016/j.dsr2.2026.105603","DOIUrl":"10.1016/j.dsr2.2026.105603","url":null,"abstract":"<div><div>The Fram Strait (FS) exhibits pronounced variability in chlorophyll-<em>a</em> (Chl-<em>a</em>) concentration on intra- and inter-annual scales, which is linked to the complex hydrography of the region, marked by two opposing currents separated by a frontal system. Here, we propose a machine learning approach that partitions the FS into three hydrographical subdomains (sectors) based on remotely sensed sea surface temperature, the main property for water mass identification besides salinity. The sectors resolve the cold Arctic, warm Atlantic, and intermediate front-influenced regions. This sectorisation allows for a nuanced analysis of variability, accounting for the dynamic behaviour of the currents and frontal system. Differences revealed in bloom phenology are reflected in remote-sensing Chl-<em>a</em> concentrations within these hydrographical sectors. Blooms (Chl-<em>a</em> &gt; 1 mg m⁻³) tend to occur in May in the Arctic-influenced sector, which is subject to variable sea ice cover. They appear later, in July, in the Atlantic-influenced sector. The absolute magnitude of Chl-<em>a</em> variability increases with its average concentration. However, concentration-normalised, the variability is notably higher in the Arctic-influenced sector, emphasising the impact of environmental differences within the hydrographic regimes on phytoplankton dynamics. Between 2016 and 2021, we could not detect clear trends in the sectors’ average Chl-<em>a</em> concentration or major changes in bloom timing. This study contributes to a broader comprehension of the expected variability ranges of Chl-<em>a</em> in the Fram Strait. Furthermore, it provides a valuable tool for analysing large geospatial data sets, especially when <em>in-situ</em> measurements of the physical seawater properties are limited in spatial and temporal coverage.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"226 ","pages":"Article 105603"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074852","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":"eDNA as a cornerstone for holistic long-term observations of Arctic marine biodiversity across trophic levels, habitats, and spatio-temporal scales","authors":"Katja Metfies ,&nbsp;Christina Bienhold ,&nbsp;Astrid Cornils ,&nbsp;Charlotte Havermans ,&nbsp;Henk-Jan Hoving ,&nbsp;Alexandra Kraberg ,&nbsp;Silke Laakmann ,&nbsp;Véronique Merten ,&nbsp;Barbara Niehoff ,&nbsp;Marlis Reich ,&nbsp;Matthias Wietz ,&nbsp;Kasper Skytte Andersen ,&nbsp;Magda Guadalupe Cardozo-Mino ,&nbsp;Eduard Fadeev ,&nbsp;Kristin Hardge ,&nbsp;Lars Harms ,&nbsp;Ayla Murray ,&nbsp;Stefan Neuhaus ,&nbsp;Eva-Maria Nöthig ,&nbsp;Ellen Oldenburg ,&nbsp;Antje Boetius","doi":"10.1016/j.dsr2.2026.105604","DOIUrl":"10.1016/j.dsr2.2026.105604","url":null,"abstract":"<div><div>Embedded in the interdisciplinary design of pelagic and benthic long-term observations at the Arctic long-term ecological research site HAUSGARTEN in Fram Strait (78°36,46′N - 79°56,63′N 10°50,91′E − 5°22,24′W; 250–5500 m), environmental DNA (eDNA)-based biodiversity studies span multiple habitats and trophic levels. These studies provide valuable insights into marine ecosystem functionality and carbon fluxes, including seasonal and interannual dynamics. Since 2009, eDNA studies of pelagic eukaryotic microbial communities have regularly been conducted. Recently, these studies have been expanded to cover the biodiversity of bacteria, archaea and metazoa such as zooplankton (including gelatinous taxa) and nekton (cephalopods and fish) alongside with microbial eukaryotes. The eDNA surveys have been coupled with measurements of physical and chemical properties, such as sea-ice coverage and water masses. By applying these approaches across spatial and trophic scales in a nested approach, we characterize the dynamics in biodiversity, its role in ecological processes, with a focus on current climate change. This is achieved by considering the complexity and interconnectivity of organisms, integrating information from different disciplines across scales and habitats, and focusing on functional processes including species composition. The resulting data improve our predictive capabilities for conservation and sustainable marine management in a rapidly changing Arctic. Here, we review the design of the first interdisciplinary Arctic eDNA long-term observatory and the results of more than ten years of method development and observations.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"226 ","pages":"Article 105604"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146169965","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":"Sinking particle export within and beneath the euphotic zone in the eastern Indian Ocean","authors":"Michael R. Stukel ,&nbsp;Tristan Biard ,&nbsp;Moira Décima ,&nbsp;Christian K. Fender ,&nbsp;Opeyemi Kehinde ,&nbsp;Thomas B. Kelly ,&nbsp;Sven A. Kranz ,&nbsp;Manon Laget ,&nbsp;Michael R. Landry ,&nbsp;Natalia Yingling","doi":"10.1016/j.dsr2.2026.105590","DOIUrl":"10.1016/j.dsr2.2026.105590","url":null,"abstract":"<div><div>The eastern Indian Ocean is substantially under sampled with respect to the biological carbon pump – the suite of processes that transport the carbon fixed by phytoplankton into the deeper ocean. Using sediment traps and other ecosystem measurements, we quantified sinking organic matter flux and investigated the characteristics of sinking particles in waters overlying the Argo Abyssal Plain directly downstream of the Indonesian Throughflow off northwest Australia. Carbon export from the euphotic zone averaged 7.0 mmol C m⁻² d⁻¹, which equated to an average export efficiency (export/net primary production) of 0.19. Sinking particle flux within the euphotic zone (beneath the mixed layer, but above the deep chlorophyll maximum) averaged slightly higher than flux at the base of the euphotic zone, suggesting that the deep euphotic zone was a depth stratum of net particle remineralization. Carbon flux attenuation continued into the twilight zone with a transfer efficiency (export at euphotic depth + 100m/export at euphotic depth) of 0.62 and an average Martin's <em>b</em>-value of 1.1. Within the euphotic zone, fresh phytoplankton (chlorophyll associated with sinking particles, possibly contained within appendicularian houses) were an important component of sinking particles, but beneath the euphotic zone the fecal pellets of herbivorous zooplankton (phaeopigments) were more important. Changes in carbon and nitrogen isotopic composition with depth further reflected remineralization processes occurring as particles sank. We show similarities with biological carbon pump functioning in a similar semi-enclosed oligotrophic marginal sea, the Gulf of Mexico, including net remineralization across the deep chlorophyll maximum.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"226 ","pages":"Article 105590"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145976432","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":"Time series of dissolved organic carbon in the Fram Strait (2010–2021): Indications for increased river export of DOC to the East Greenland Current?","authors":"Anja Engel ,&nbsp;Anabel von Jackowski ,&nbsp;Vanessa Lampe ,&nbsp;Eva-Maria Nöthig","doi":"10.1016/j.dsr2.2025.105586","DOIUrl":"10.1016/j.dsr2.2025.105586","url":null,"abstract":"<div><div>Climate change impacts the Arctic Ocean more profoundly than other regions, with uncertain consequences for carbon cycling. Additionally, allochthonous and autochthonous sources of organic carbon undergo extreme seasonal variability. Distinguishing climate-induced changes from seasonal variability in carbon cycling thus remains a significant challenge. We investigated interannual changes in dissolved organic carbon (DOC) concentration and lability. i.e., the lifetime of DOC, which we inferred from amino acid composition, in surface waters of the Fram Strait using time series data collected between 2010 and 2021. Sampling was conducted during summer with the <em>RV POLARSTERN</em> at or around the Long-Term Ecological Research observatory HAUSGARTEN. Our results show that the two major water masses in Fram Strait, the Polar Water (PW; T &lt; 0 °C; S &lt; 34.0) predominant in the East Greenland Current and the Atlantic Water (AW; T &gt; 3 °C; S &gt; 34.9) predominant in the West Spitzbergen Current, differ greatly in their DOC concentration and composition. PW carries high amounts of semi-labile DOC (SL-DOC) from the Arctic Ocean southwards, whereas AW contains less but more labile DOC. No clear trend in DOC concentration over the 10-year time series was detected for AW. In contrast, samples collected in PW between 2016 and 2021 showed a 15 % increase in DOC, which was attributable to an increase in SL-DOC. Interannual variability in DOC lability was most pronounced in the eastern Fram Strait, likely driven by differences in the seasonal progression of the pelagic ecosystem. Our data suggest that DOC dynamics in the Fram Strait are influenced by an enhanced riverine input of DOC to the Arctic Ocean, leading to an increased DOC export to the North Atlantic.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"226 ","pages":"Article 105586"},"PeriodicalIF":3.0,"publicationDate":"2026-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145963092","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":"New Zealand deep-sea black coral (Antipatharia) age and growth rates: Insights into early life growth patterns","authors":"Ashley N. Davis ,&nbsp;Dianne M. Tracey ,&nbsp;Erik Behrens ,&nbsp;Stewart J. Fallon ,&nbsp;John Hellstrom ,&nbsp;Peter Marriott ,&nbsp;Daniel J. Sinclair","doi":"10.1016/j.dsr2.2025.105562","DOIUrl":"10.1016/j.dsr2.2025.105562","url":null,"abstract":"<div><div>Black corals (Order Antipatharia) are a diverse group found worldwide and in high abundance around Aotearoa New Zealand where their spatial distribution extends from coastal regions to the deep sea. They provide biologically important habitats and host various benthic invertebrate organisms. There is concern however, that black corals are under threat from anthropogenic activities such as mining and bottom fishing as well as from environmental changes in temperature and dissolved oxygen concentrations. Understanding the potential for black corals to recover after disturbance requires knowledge of their longevity and growth rates. Fortunately, the proteinaceous skeletons of black corals can be radiometrically dated to high precision providing age and growth data to help inform impacts. Ten black corals from two genera (<em>Antipathella</em> and <em>Leiopathes</em>) were selected from the invertebrate collection at the National Institute of Water and Atmospheric Research and radiometrically dated using radiocarbon and uranium-thorium disequilibrium (U-Th) techniques. Coral lifespans ranged from 71 years (<em>Antipathella fiordensis</em>) up to 2221 years (Antipatharia), and skeletons show radial growth rates ranging from 2.6 (<em>Leiopathes</em> sp.) – 126.7 μm/yr (<em>A. fiordensis)</em>. High-resolution age-depth models (1.7–42.7 years/sample) were generated from U-Th age measurements leading to observations of an early life radial growth rate pattern that could provide further insights for black coral physiology. This pattern is comprised of a large growth slump after colony birth followed by a triple peak pattern which contained the maximum growth rate. These data advance our knowledge of longevity for these corals, the variability in ages and growth rates between species and regions, and their vulnerability to physical disturbances due to slow recovery rates.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"225 ","pages":"Article 105562"},"PeriodicalIF":3.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145880250","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":"Spatiotemporal patterns and implications of suspended Alexandrium catenella cysts in the Pacific Arctic region","authors":"Evangeline Fachon ,&nbsp;Robert S. Pickart ,&nbsp;Jie Huang ,&nbsp;Catherine Lalande ,&nbsp;Donald M. Anderson","doi":"10.1016/j.dsr2.2025.105567","DOIUrl":"10.1016/j.dsr2.2025.105567","url":null,"abstract":"<div><div>The persistent presence of a massive accumulation of resting cysts of the toxic dinoflagellate <em>Alexandrium catenella</em> on the Chukchi shelf represents a significant risk to Pacific Arctic ecosystems, as warming conditions are likely to promote harmful algal blooms of this species. While the majority of cysts are found in the benthos, cysts can also be suspended through the water column, allowing them to be transported by currents or to experience elevated temperature and light conditions that may accelerate germination. Spatial patterns of cyst suspension were investigated during a Fall 2020 survey, revealing broad presence of suspended cysts in near-bottom waters overlying benthic cyst accumulations. Enhanced suspension was observed at shallow, well-mixed stations – in some places extending beyond the bottom boundary layer into surface waters. Sinking particles collected continuously from 2017 to 2019 showed seasonal patterns of cyst flux, with export pulses during the late summer and wind-driven resuspension peaking during the fall. To evaluate the potential contribution of resuspension to bloom initiation, a hydrographic climatology of the southern Chukchi Sea was used to estimate cyst germination rates through the water column during the summer (June–September). This analysis was paired with wind-driven 1-D mixing simulations, demonstrating that cyst access to surface waters is enhanced under stormy conditions. While storm events are not currently common during the summer bloom season, a trend towards increasingly windy conditions points towards future potential for resuspended cysts to contribute to blooms in the shallow and warming waters of the Pacific Arctic region.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"225 ","pages":"Article 105567"},"PeriodicalIF":3.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145600479","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":"First findings of metal-rich particles from the central Indian ocean basin: Evidence of hydrothermal mineralization","authors":"Ankeeta Amonkar ,&nbsp;Sridhar D. Iyer","doi":"10.1016/j.dsr2.2025.105569","DOIUrl":"10.1016/j.dsr2.2025.105569","url":null,"abstract":"<div><div>Metalliferous sediments are known to exist at mid-ocean ridges and near active intraplate seamounts. Here we report the occurrence of metal-rich particles of variable compositions occurring in the sediments of the Central Indian Ocean Basin (CIOB) which is an intraplate basin. These metal-rich particles have been recovered from an average water depth of 5,000m from 79°E fracture zone (pelagic clays zone) and from seamount dominated area (from siliceous sediment, and siliceous<em>-</em>red clay transition zone).</div><div>The metal-rich particles observed in the studied sediment samples exhibit irregular, tabular, sub-rounded shapes and have a distinct crystalline structures. They occur both as native metals and as compounds such as oxides, sulphides, and sulphates. In addition to the previously reported magnetite and aluminium spherules from the CIOB sediments, our analysis reveals a high concentration of metal-rich particles containing zinc-copper and native copper, barium sulphides, lead-barium sulphates, native lead, and silver.</div><div>The sub-surface occurrence of these metal-rich particles in the sediments indicates their derivation from recent hydrothermal activity in the basin. The fracture zone and seamounts in the vicinity could be potential sites for degassing of volatiles and formation of metalloid elements and may have co-precipitated in the sediments that bear testimony of their hydrothermal origin. To our knowledge this is the first finding of metal-rich particles from abyssal depth of nearly 5000 m in the Indian Ocean.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"225 ","pages":"Article 105569"},"PeriodicalIF":3.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692361","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":"Revisiting daily growth and survival insights of Southern Bluefin Tuna (Thunnus maccoyii) larvae in the eastern Indian Ocean","authors":"Ricardo Borrego-Santos ,&nbsp;José M. Quintanilla ,&nbsp;Raúl Laiz-Carrión ,&nbsp;Alberto García ,&nbsp;Estrella Malca ,&nbsp;Francisco J. Abascal ,&nbsp;David Die ,&nbsp;Isabel Riveiro ,&nbsp;Rasmus Swalethorp ,&nbsp;Michael R. Landry","doi":"10.1016/j.dsr2.2025.105572","DOIUrl":"10.1016/j.dsr2.2025.105572","url":null,"abstract":"<div><div>This study analyzed the growth patterns and survival of Southern bluefin tuna (SBT, <em>Thunnus maccoyii</em>) larvae collected during January–February 2022 in their only known spawning area in the eastern Indian Ocean (IO). Otolith microstructure was examined to characterize both population-level and intra-population growth (OPT-optimal and DEF-deficient group), with special emphasis on the flexion process, as well as to provide insights into larval survival. SBT larvae began flexion at sizes and ages comparable to those reported in other bluefin tuna species. At the intra-population level, OPT larvae reached flexion earlier in a better physical condition, with greater length, weight, and body depth, likely increasing their chances of survival at later stages. The observed larval growth rates (0.38 mm d⁻¹) exceeded that from a historical study in 1987 (0.33 mm d⁻¹), likely due to a ∼2 °C increase in sea surface temperature and shifts in prey availability. Larval survival appears to depend on a selective process based on growth, in which only a small proportion of individuals (&lt;2 %) exhibited width increment in otoliths similar to those of surviving larvae, allowing for faster development and earlier access to larger prey. These findings highlight the need for expanded research on the early life stages of SBT, particularly in the context of ongoing ocean warming and climate change.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"225 ","pages":"Article 105572"},"PeriodicalIF":3.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145692360","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":"Exploring the roles of trophic mode and microbial prey size in grazing pathways of tropical oligotrophic waters of the eastern Indian ocean","authors":"Claudia Traboni ,&nbsp;Grace F. Cawley ,&nbsp;Karen E. Selph ,&nbsp;Michael R. Landry ,&nbsp;Moira Décima","doi":"10.1016/j.dsr2.2025.105573","DOIUrl":"10.1016/j.dsr2.2025.105573","url":null,"abstract":"<div><div>Prey removal incubations were conducted in the Argo Basin (eastern Indian Ocean) to investigate the trophic ecology of the zooplankton community supporting Southern Bluefin Tuna larvae. Copepod grazing and selectivity were evaluated considering prey trophic mode and size as food quality descriptors and compared with microzooplankton grazing. Copepods ingested between 3.4 and 138 ng carbon (C) ind⁻¹ d⁻¹. Diet was dominated by mixotrophic (5–89 %) and heterotrophic (0–84 %) prey, with autotrophs contributing 2–17 %. Nanoplankton provided the highest C intake to copepods (62–99 %) <em>versus</em> picoplankton (0.8–38 %), despite more picoplankton cells ingested. No measurable reduction in chlorophyll <em>a</em> (Chl<em>a)</em> concentration occurred from copepod grazing through food removal, suggesting an indirect trophic pathway, although gut content revealed ingestion of 0.8 μg Chl<em>a</em> ind⁻¹ d⁻¹. Calculations from disappearance incubations imply copepod selection on picoplankton (E = 0.3) over nanoplankton, but picoplankton were likely ingested as aggregates or depressed due to a trophic cascade of copepods ingesting nano-microzooplankton. Copepods ingested protistan consumers and/or metazoans fed on ¹⁵N-cyanobacteria with ∼5-fold higher N uptake from 1 to 2 μm ¹⁵N-Synechococcus than from &lt;1 μm ¹⁵N-Prochlorococcus. Microzooplankton grazing on eukaryotes (0.07–2.5 d⁻¹) and prokaryotes (0.3–2.1 d⁻¹) greatly exceeded copepod grazing. Microzooplankton diet consisted mostly of heterotrophs (25–59 %) and mixotrophs (13–41 %) followed by autotrophs (12–33 %), with more nano- (95–98 %) than picophytoplankton (2–5 %). Overall, microzooplankton removed most daily production (111 %) in contrast to 7 % for copepods. Our findings indicate that mixotrophy, intraguild grazing and nutrient channeling support the food web in this oligotrophic region.</div></div>","PeriodicalId":11120,"journal":{"name":"Deep-sea Research Part Ii-topical Studies in Oceanography","volume":"225 ","pages":"Article 105573"},"PeriodicalIF":3.0,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145747823","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}