Deep-Sea Research Part I-Oceanographic Research Papers最新文献

{"title":"New insights on the deep alkaline phosphatase paradox from a site in the Northeastern Pacific Ocean","authors":"Kerry Dykens ,&nbsp;Robert Letscher ,&nbsp;Atsushi Matsuoka ,&nbsp;Kai Ziervogel","doi":"10.1016/j.dsr.2024.104419","DOIUrl":"10.1016/j.dsr.2024.104419","url":null,"abstract":"<div><div>Extracellular hydrolytic enzymes are the main tools for microorganisms to access and degrade organic matter in the ocean. We investigated potential activities of four hydrolytic enzymes (alkaline phosphatase, beta-glucosidase, leucine aminopeptidase, chitinase) in the water column and surficial sediments at a deepwater site in the Northeastern Pacific Ocean (water depth: 2658 m). Our goal was to investigate the potential role of (re-)suspended particles as a source for enzyme activities in subsurface waters. Alkaline phosphatase (AP) dominated hydrolytic activities in subsurface waters and in sediments, reaching up to two orders of magnitude higher rates compared with the other three enzymes. Peak AP activities in the center of the oxygen minimum zone and in bottom waters were decoupled from concentrations of inorganic phosphorous (P_i), a pattern known as the <em>deep AP paradox</em>. A weak correlation between AP and bacterial abundances indicated that a fraction of AP was physically detached from their source cells (i.e., cell-free enzymes) and associated with particles either from surface waters (marine snow) or resuspended from the seafloor. We estimated that cell-free AP activities, which are decoupled from nutritional needs and oxidative processes of their source cells, contribute about 2%–9% of regenerated P_i in the bathypelagic Northeastern Pacific Ocean. (Re-)suspended particles as a source of cell-free AP thus play an important yet understudied role in deep-ocean elemental cycles.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"215 ","pages":"Article 104419"},"PeriodicalIF":2.3,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142747940","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":"Vertical zonation and environmental drivers of North-West Pacific abyssal and hadal mobile faunal communities","authors":"Denise J.B. Swanborn ,&nbsp;Todd Bond ,&nbsp;Jessica L. Kolbusz ,&nbsp;Megan E. Cundy ,&nbsp;Melanie S. Stott ,&nbsp;Elin A. Thomas ,&nbsp;Hiroshi Kitazato ,&nbsp;Alan J. Jamieson","doi":"10.1016/j.dsr.2024.104418","DOIUrl":"10.1016/j.dsr.2024.104418","url":null,"abstract":"<div><div>This study examines the composition, vertical zonation and drivers of mobile abyssal and hadal faunal assemblages to understand the environmental patterns underlying biological organisation at lower abyssal and hadal depths. Biological data were analysed from 96 baited lander deployments across five North-West Pacific subduction trenches and one triple trench junction (the Mariana Trench, Philippine Trench, Ryukyu Trench, Japan Trench, Izu-Ogasawara Trench and Boso Triple Junction) and combined with environmental metrics of terrain geomorphology and oceanography at deployment locations. Hierarchical clustering revealed three depth-driven faunal zones, representing an abyssal-hadal transition community (∼5500–6500 m), an upper hadal community (∼7000–7500 m) and a lower hadal community (&gt;8500 m). Clustering results support an abyssal-hadal ecotone &gt;6500 m depth and a further hadal transition ∼8000 m. Environmental factors explained 40.4% of community structure, with depth and location as main contributors to the final model. These factors, through the latter's relationships with surface oceanography and productivity, were also key determinants of relative abundance, diversity, richness and the total relative abundance of dominant faunal groups and families among deployments. Results suggest limited ecological effects of intra-trench environmental variability, and highlight a need for further high-resolution studies sampling a range of environmental conditions and their associated biodiversity within individual hadal features.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"215 ","pages":"Article 104418"},"PeriodicalIF":2.3,"publicationDate":"2024-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142697153","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":"Nutrient fluxes, oxygen consumption and fatty acid composition from deep-water demo- and hexactinellid sponges from New Zealand","authors":"Tanja Stratmann ,&nbsp;Kathrin Busch ,&nbsp;Anna de Kluijver ,&nbsp;Michelle Kelly ,&nbsp;Sadie Mills ,&nbsp;Sven Rossel ,&nbsp;Peter J. Schupp","doi":"10.1016/j.dsr.2024.104416","DOIUrl":"10.1016/j.dsr.2024.104416","url":null,"abstract":"&lt;div&gt;&lt;div&gt;Sponges are an important component of deep-water ecosystems enhancing eukaryotic biodiversity by hosting diverse endo- and epibiota and providing three dimensional habitats for benthic invertebrates and fishes. As holobionts they are important hosts of microorganisms which are involved in carbon and nitrogen cycling. While increasing exploration of deep-water habitats results in new sponge species being discovered, little is known about their physiology and role in nutrient fluxes. Around New Zealand (Southwest Pacific), the sponge biodiversity is particularly high, and we selected six deep-sea sponge genera (&lt;em&gt;Saccocalyx&lt;/em&gt;, &lt;em&gt;Suberites&lt;/em&gt;, &lt;em&gt;Tedania&lt;/em&gt;, &lt;em&gt;Halichondria&lt;/em&gt;/&lt;em&gt;Dendoricella&lt;/em&gt;, &lt;em&gt;Lissodendoryx&lt;/em&gt;) and a member of the Sceptrulophora order for &lt;em&gt;in-situ&lt;/em&gt; and &lt;em&gt;ex-situ&lt;/em&gt; experiments.&lt;/div&gt;&lt;div&gt;We investigated the biochemical composition of the sponges, measured oxygen consumption and inorganic nutrient fluxes, as well as bacterial and phospholipid-derived fatty acid (PLFA) compositions. Our aim was to assess differences in fluxes and fatty acid composition among sponges and linking their bacterial communities to nitrogen cycling processes.&lt;/div&gt;&lt;div&gt;All sponges excreted nitrite and ammonia. Nitrate and phosphate excretion were independent of phylum affiliation (Demospongiae, Hexactinellida). Nitrate was excreted by &lt;em&gt;Halichondria&lt;/em&gt;/&lt;em&gt;Dendoricella&lt;/em&gt; and &lt;em&gt;Lissodendoryx&lt;/em&gt;, whereas &lt;em&gt;Suberites&lt;/em&gt;, &lt;em&gt;Tedania&lt;/em&gt;, and Sceptrulophora consumed it. Phosphate was excreted by Sceptrulophora and &lt;em&gt;Halichondria&lt;/em&gt;/&lt;em&gt;Dendoricella&lt;/em&gt; and consumed by all other sponges. Oxygen consumption rates ranged from 0.17 to 3.56 ± 0.60 mmol O&lt;sub&gt;2&lt;/sub&gt; g C&lt;sup&gt;-1&lt;/sup&gt; d&lt;sup&gt;−1&lt;/sup&gt;.&lt;/div&gt;&lt;div&gt;The PLFA composition was very sponge-genera dependent and consisted mostly of long-chain fatty acids. Most PLFAs were sponge-specific, followed by bacteria-specific PLFAs, and others.&lt;/div&gt;&lt;div&gt;All sponges, except for &lt;em&gt;Suberites&lt;/em&gt;, were low-microbial abundance (LMA) sponges whose bacterial community composition was dominated by Proteobacteria, Bacteroidota, Planctomycetota, and Nitrospinota. &lt;em&gt;Suberites&lt;/em&gt; consisted of high-microbial abundance (HMA) sponges with Proteobacteria, Chloroflexota, Acidobacteriota, and Actinobacteriota as dominant bacteria.&lt;/div&gt;&lt;div&gt;Based on the inorganic nitrogen flux measurements, we identified three types of nitrogen cycling in the sponges: In type 1, sponges (&lt;em&gt;Dendoricella&lt;/em&gt; spp. indet., &lt;em&gt;Lissodendoryx&lt;/em&gt;) respired aerobically and ammonificated organic matter (OM) to ammonium, fixed N&lt;sub&gt;2&lt;/sub&gt; to ammonium, and nitrified aerobically heterotrophically produced ammonium to nitrate and nitrite. In type 2, sponges (&lt;em&gt;Halichondria&lt;/em&gt; sp., Sceptrulophora, &lt;em&gt;Suberites&lt;/em&gt;, &lt;em&gt;Tedania&lt;/em&gt;) respired OM aerobically and ammonificated it to ammonium. They also reduced nitrate anaerobically to ammonium via dissimilatory nitrate reduction to amm","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104416"},"PeriodicalIF":2.3,"publicationDate":"2024-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658364","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A new species of Erinaceusyllis (Annelida: Syllidae) discovered at a wood-fall in the eastern Clarion-Clipperton zone, central Pacific ocean","authors":"Christian L. Nilsson ,&nbsp;Helena Wiklund ,&nbsp;Adrian G. Glover ,&nbsp;Guadalupe Bribiesca-Contreras ,&nbsp;Thomas G. Dahlgren","doi":"10.1016/j.dsr.2024.104415","DOIUrl":"10.1016/j.dsr.2024.104415","url":null,"abstract":"<div><div>In the deep sea, organic falls provide temporary localized enrichments of organic matter to the otherwise nutrient-poor abyssal seafloor. Areas where organic falls land become ephemeral patches of increased biodiversity. Often rich in opportunistic species which are tolerant to the sulfidic environment formed from anaerobic breakdown of organic matter. On a wood-fall at abyssal depths in the eastern Clarion-Clipperton Zone, the novel species <em>Erinaceusyllis simonlledoi</em> (Annelida: Syllidae) was discovered in high abundance. This study entails the first description of a novel syllid species found in high density on a naturally occurring organic fall. Phylogenetic position was investigated using three genetic markers (16S, 18S, COI) and morphology was studied through light- and scanning electron microscopy. Genetic data and morphological analysis supported placement in the syllid genus <em>Erinaceusyllis</em>. Distinguishing features were lack of eyes, dorsal brooding of one egg per egg-bearing segment, lack of visible papillae across the body, incomplete fusion of palps, bidentate chaetae, as well as pyriform antennae and tentacular cirri. <em>Erinaceusyllis simonlledoi</em> sp. nov. is highly similar to a species found on hydrothermal vents belonging to the closely related genus <em>Sphaerosyllis</em>. The similarity between the two species, as well as findings of unspecified <em>Sphaerosyllis</em> species in various types of sulfidic habitats evoke questions of a possible syllid lineage adapted to sulfidic environments.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104415"},"PeriodicalIF":2.3,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142705108","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":"The microbiome of the main deep-water scleractinian reef-framework engineers from the Southwestern Atlantic","authors":"Aline Aparecida Zanotti ,&nbsp;Kátia Cristina Cruz Capel ,&nbsp;Carla Zilberberg ,&nbsp;Marcelo Visentini Kitahara","doi":"10.1016/j.dsr.2024.104417","DOIUrl":"10.1016/j.dsr.2024.104417","url":null,"abstract":"<div><div>Deep waters (&gt;150 m) shelter half of the extant diversity of scleractinian corals, including framework reef-forming species. However, to date, the relationship between microorganisms and corals has focused mainly on their zooxanthellate shallow-water counterparts. Here, using 16S rRNA gene amplicon sequencing, we explore the microbiome of all major Atlantic deep-water scleractinian reef framework engineers (<em>Desmophyllum pertusum</em>, <em>Solenosmilia variabilis</em>, <em>Madrepora oculata</em>, and <em>Enallopsammia rostrata</em>), and correlated them with environmental characteristics. Colony fragments of each coral species used in the present study were sampled from three sedimentary basins off the Southeastern coast of Brazil, including two water masses (Antarctic Intermediate Water and South Atlantic Coastal Water). Although representing distant scleractinian evolutionarily lineages, some evolving apart for more than 300Ma, our results suggest a taxonomic homogeneity in their microbial profile. The species-specific microbial core, as well as the core common to all examined species, were identified. Such cores are composed of bacterial genera that have already been observed in other coral species, including those from zooxanthellate species. Such a pattern suggests an active selection of the microbial community by their hosts, a phenomenon that seems to be fundamental for holobiont fitness, especially in long-lived species, such as corals. Besides the microbial core, for all examined species, part of the determined microbiome was flexible and responded to environmental drivers. This flexibility is most probably related to the host's ability to adapt in ecological time scales. Taken together, these holobiont abilities may be crucial to its success in both ecological and geological timescales.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104417"},"PeriodicalIF":2.3,"publicationDate":"2024-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658363","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":"Morphospace of lanternfish larvae and their interplay with oceanographic conditions from the southeastern Pacific Ocean","authors":"Fernanda S. Orrego ,&nbsp;Hugo A. Benítez ,&nbsp;Manuel I. Castillo ,&nbsp;Nicolás Cumplido ,&nbsp;Alejandra Fabres ,&nbsp;Yanara Figueroa-González ,&nbsp;Claudia Morales ,&nbsp;Francisca Zavala-Muñoz ,&nbsp;Mauricio F. Landaeta","doi":"10.1016/j.dsr.2024.104413","DOIUrl":"10.1016/j.dsr.2024.104413","url":null,"abstract":"<div><div>Lanternfish larval morphology is highly variable probably due to their adaptations to highly variable environmental conditions throughout ontogeny. To study the morphological variability of the larval stage of lanternfishes, samples were collected from the southeast Pacific Ocean between 2014 and 2022. Of the 24 species, nine belonged to the subfamily Lampanyctinae, two to the subfamily Diaphinae, one to the subfamily Notolychinae, one to the subfamily Gymnoscopelinae and 11 to the subfamily Myctophinae. A principal component analysis indicated the presence of body shapes varying from a slender and curved body, and upper jaw oriented downwards, with relatively rounded eyes, to taxa with robust bodies, particularly both the head and trunk, and elongated eyes in a dorsal-ventral plane (PC1 33%). Also, specimens varied from having short jaw, short snout, and slender body, to specimens with larger jaw (reaching behind the eye) and taller snout and trunk (PC2, 23%). Allometric effects were related to variations in body curvature and thickness (<em>Diaphus theta</em>, 12.9%), the curvature of the body and position of the eyes (<em>Lampanyctodes hectoris</em>, 25.1%), lengthening of the jaw and increase in eye size (<em>Diogenichthys atlanticus</em>, 24.6%), and a narrower body and smaller eyes (<em>Hygophum bruuni</em>, 20.5%). Four of the five subfamilies showed covariation between morphometrics and environmental conditions. Diaphinae, Gymnoscopelinae and Lampanyctinae body shape covaried with mean sea temperature of the water column, while Myctophinae larval shape covaried with mean salinity. In conclusion, this study quantifies shape variations during early lanternfish ontogeny from the southeastern Pacific Ocean, identifying main differences and allometric changes between the subfamilies belonging to Myctophidae, with a covariation between the shape of most lanternfish larvae and the environmental conditions experienced by myctophid early stages.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104413"},"PeriodicalIF":2.3,"publicationDate":"2024-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142553251","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":"Influence of mini warm pool extent on phytoplankton productivity and export in the Arabian sea","authors":"Nicholas Bock ,&nbsp;Joaquim Goes ,&nbsp;Hervé Claustre ,&nbsp;Vincent Taillandier ,&nbsp;Helga do Rosario Gomes","doi":"10.1016/j.dsr.2024.104406","DOIUrl":"10.1016/j.dsr.2024.104406","url":null,"abstract":"<div><div>The Arabian Sea is a highly productive tropical ecosystem of the Indian Ocean that supports high fluxes of particulate organic carbon to the mesopelagic zone from two distinct periods of elevated biological productivity associated with the semiannual reversals of the monsoonal wind system. There are now strong indications that the Arabian Sea's monsoonal wind patterns and hydrographic conditions are being impacted by long-term temperature increases, but the consequences of these changes on primary production and carbon export to the mesopelagic zone are unknown. This is especially true for the summer monsoon period when cloud cover obscures much of the Arabian Sea basin and therefore precludes remotely sensed ocean color measurements for estimating phytoplankton biomass and productivity. Here we overcome this limitation by using a database of bio-optical profiles from Biogeochemical Argo floats collected over the last decade to evaluate the impact of interannual temperature increases on Arabian Sea primary production and carbon export. We classify individual years of float observations based on the spatial extent of the Arabian Sea Mini Warm Pool that appears in the southeast Arabian Sea before the onset of the summer monsoon. This Mini Warm Pool, which begins to build in winter and collapses with the onset of the summer monsoon in late spring, has gained considerable interest on account of its influence on the timing of the onset of the summer monsoon. We observed a 35 percent decrease in primary production during the summer monsoon phytoplankton bloom in strong warm pool years, and a 13 percent decrease in particle stocks in the upper mesopelagic zone following the peak of the bloom. Decreases in production and export were additionally accompanied by a decrease in average particle size, indicating a shift from larger cells like diatoms that appear from fertilization of the oligotrophic waters to smaller phytoplankton size classes in response to a deepening of the thermocline and increased stratification of the water column. These results suggest changes in phytoplankton community structure and further decreases in primary production and carbon export in the Arabian Sea in response to future warming.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104406"},"PeriodicalIF":2.3,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142578196","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":"Discovery and description of a remarkable bathypelagic nudibranch, Bathydevius caudactylus, gen. et. sp. nov.","authors":"Bruce H. Robison ,&nbsp;Steven H.D. Haddock","doi":"10.1016/j.dsr.2024.104414","DOIUrl":"10.1016/j.dsr.2024.104414","url":null,"abstract":"<div><div>We describe an exceptional nudibranch, new to science, from bathypelagic depths in the eastern North Pacific Ocean. More than 100 individuals of <em>Bathydevius caudactylus</em> gen. et. sp. nov. have been observed in the water column at depths between 1013 and 3272 m. Twenty spawning individuals were observed on the seafloor at depths between 2269 and 4009 m. Anatomy, diet, behavior, bioluminescence, and habitat distinguish this surprising nudibranch from all previously described species, and genetic evidence supports its placement in a new family.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"214 ","pages":"Article 104414"},"PeriodicalIF":2.3,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142593200","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":"Wintertime productivity and carbon export potential across the Agulhas Current system","authors":"Kolisa Yola Sinyanya ,&nbsp;Tanya A. Marshall ,&nbsp;Raquel F. Flynn ,&nbsp;Eesaa Harris ,&nbsp;Mhlangabezi Mdutyana ,&nbsp;Raymond Roman ,&nbsp;David R. Walker ,&nbsp;Sina Wallschuss ,&nbsp;Sarah E. Fawcett","doi":"10.1016/j.dsr.2024.104405","DOIUrl":"10.1016/j.dsr.2024.104405","url":null,"abstract":"<div><div>The Agulhas Current plays a major role in heat and salt exchange between the Indian and Atlantic Oceans, yet little is known of its influence on ocean fertility. To investigate carbon production and export potential in the Agulhas Current system, we measured net primary production (NPP), nitrate and ammonium uptake, N₂ fixation, and nitrification along a transect of the current and adjacent subtropical subgyre (33.4°S–35.7°S) in winter when nutrient supply, and thus productivity, should be highest. Phytoplankton biomass was lowest in the current core, increasing into the subgyre as surface nitrate declined, and was dominated by nanoplankton (2.7–10 μm; 62 ± 5.1% of total biomass). NPP and nitrate uptake were generally high across the transect and increased from the current core into the subgyre; the rates were dominated by picoplankton (&lt;2.7 μm; 53–93%) in the current core and nanoplankton elsewhere (63–69%). On average, euphotic zone nitrification supplied 7.6 ± 6.4% of the nitrate consumed by phytoplankton and N₂ fixation was also low (2.1 ± 1.3% of new production); we thus consider nitrate uptake a reasonable proxy for new production, at least in winter. Nitrate uptake was highest at the southern edge of the current core, consistent with current-associated (sub)mesoscale mixing enhancing the upward nutrient supply. The fraction of NPP available for export (i.e., the <em>f</em>-ratio) was high across the transect, ranging from 0.44 to 0.69. Our data thus indicate that both total and new production are elevated across the Agulhas Current system in winter and suggest that the (sub)mesoscale dynamics associated with the current system may enhance carbon production and export in the otherwise oligotrophic southwest Indian Ocean.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"213 ","pages":"Article 104405"},"PeriodicalIF":2.3,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446034","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":"Interannual changes in nutrient and phytoplankton dynamics in the Eastern Mediterranean Sea (EMS) predict the consequences of climate change; results from the Sdot-Yam Time-series station 2018–2022","authors":"Tal Ben Ezra ,&nbsp;Alon Blachinsky ,&nbsp;Shiran Gozali ,&nbsp;Anat Tsemel ,&nbsp;Yotam Fadida ,&nbsp;Dan Tchernov ,&nbsp;Yoav Lehahn ,&nbsp;Tatiana Margo Tsagaraki ,&nbsp;Ilana Berman-Frank ,&nbsp;Michael Krom","doi":"10.1016/j.dsr.2024.104403","DOIUrl":"10.1016/j.dsr.2024.104403","url":null,"abstract":"<div><div>Global climate change is predicted to reduce nutrient fluxes into the photic zone, particularly in tropical and subtropical ocean gyres, while the occasional major storms will result in increased nutrient pulses. In this study the nutrient and phytoplankton dynamics have been determined at a new time-series station in the southeastern Levantine basin of the Eastern Mediterranean Sea (EMS) over 4.5 years (2017–2022). In 2018 and 2019, there was a moderate concentration of residual nitrate and nitrite (N + N) in the photic zone (280–410 nM) in winter, resulting in phytoplankton dynamics dominated by cyanobacteria with relatively few picoeukaryotes (280 ± 90 μgC m⁻²). Winter storm driven mixing was much reduced in 2020 and particularly in 2021, resulting in a lower concentration of N + N in the photic zone, which decreased during summer stratification, such that by August 2021, the N + N was highly depleted (&lt;60 nM) resulting in an integrated phytoplankton biomass of 23 μgC m⁻². A major storm in December 2021 (Storm Carmel) injected high N + N (750 nM; max = 1090 nM) in the upper 100 m, which stimulated pico and nanophytoplankton biomass (∼2400 μgC m⁻²) and according to our inference increased eukaryotes (diatoms). The pattern of measured silica reinforced our conclusion that we sampled 3 different nutrient and ecosystem states. Phosphate was always at or close to limit of detection (LoD) because of rapid uptake by cyanobacteria into their periplasm. These results predict that climate change in the EMS will result in periods of nutrient and phytoplankton depletion (Famine) interrupted by short periods of Mesotrophy (Feast) caused by major storms.</div></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"213 ","pages":"Article 104403"},"PeriodicalIF":2.3,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432477","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}