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  • 1
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    Dissolved Organic Matter Fluorescence as a Tracer of Upwelling and Microbial Activities in Two Cyclonic Eddies in the Eastern Tropical North Atlantic (2023)
    Details
    Publication Date: 2024-01-24
    Description: 〈title xmlns:mml="http://www.w3.org/1998/Math/MathML"〉Abstract〈/title〉〈p xmlns:mml="http://www.w3.org/1998/Math/MathML" xml:lang="en"〉Mesoscale eddies are frequently observed in the Eastern Tropical North Atlantic (ETNA), yet their effects on the transport and distribution of biogeochemical solutes, and specifically on the production and remineralization of dissolved organic matter (DOM) remain difficult to elucidate. Here, we investigated the submesoscale variability of chromophoric DOM (CDOM) and fluorescent DOM (FDOM) together with microbial production and remineralization processes in two cyclonic eddies (CEs) in the ETNA during summer and winter 2019. One CE, formed near the coast off Mauritania during the post‐upwelling season, was sampled along a ∼900 km zonal corridor between Mauritania and the Cape Verde Islands. The other CE, formed nearby Brava Island, was out of coastal influence. Four fluorescent components were identified with parallel factor analysis, two humic‐like, and two protein‐like components. Humic‐like FDOM components correlated to optode‐based community respiration and were also good indicators of upwelling associated with the Brava Island CE as they correlated to physical parameters (e.g., temperature) and to dissolved inorganic nitrogen. The tryptophan‐like FDOM components correlated with the carbon and nitrogen content of semi‐labile DOM, phytoplankton biomass, community respiration, and bacterial production. Overall, our study revealed that DOM optical properties are suitable for tracing freshly produced organic matter and the transport of remineralized DOM within offshore eddies.〈/p〉
    Description: Plain Language Summary: Mesoscale eddies are ubiquitous circulation features in the ocean with horizontal scales on the order of 100 km and lifetimes of days to months. Their swirling motion can cause nutrients from deeper waters to be transported to the surface, stimulating phytoplankton biomass and resulting in the production of dissolved organic matter. However, these effects are difficult to quantify and proxies (biomarkers) are needed to monitor the impact of eddies at high resolution. In this work, we used the optical properties of the dissolved organic matter, especially the fraction capable of fluorescence (FDOM) as biomarker in two cyclonic eddies, one formed in an eastern boundary upwelling system and one formed offshore by winds/Island interaction. We identified four FDOM components, among which an indicator of cyclonic eddy productivity and two indicators of dissolved organic matter recycling, which also tracked nutrient transport in the offshore cyclonic eddy. Our study highlights that continuous FDOM data obtained with sensors could help to follow eddy development and influence on seawater biogeochemistry.〈/p〉
    Description: Key Points: 〈list list-type="bullet"〉 〈list-item〉 〈p xml:lang="en"〉Four fluorescent dissolved organic matter (FDOM) components were studied in two cyclonic eddies (CEs) in the Eastern Tropical North Atlantic〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Tryptophan‐like FDOM was an indicator of the CEs' productivity as it correlated with semi‐labile dissolved organic matter and microbial metabolic activities〈/p〉〈/list-item〉 〈list-item〉 〈p xml:lang="en"〉Humic‐like FDOM was a by‐product of microbial respiration; its distribution within an offshore CE covaried with nutrient upwelling〈/p〉〈/list-item〉 〈/list〉 〈/p〉
    Description: Bundesministerium für Bildung und Forschung http://dx.doi.org/10.13039/501100002347
    Keywords: ddc:https://doi.pangaea.de/10.1594/PANGAEA.959742 ; ddc:https://doi.org/10.1594/PANGAEA.950510 ; ddc:577.7 ; PARAFAC ; Atlantic Ocean ; Mauritanian upwelling system ; mesoscale eddies ; fluorescence dissolved organic matter (FDOM) ; DOC
    Language: English
    Type: doc-type:article
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    CITATION GEO-LEO
  • 2
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    Dissolved organic matter released by two marine heterotrophic bacterial strains and its bioavailability for natural prokaryotic communities (2021)
    Wiley | Society for Applied Microbiology
    Details
    Publication Date: 2024-02-07
    Description: Marine heterotrophic prokaryotes (HP) play a key role in organic matter processing in the ocean; however, the view of HP as dissolved organic matter (DOM) sources remains underexplored. In this study, we quantified and optically characterized the DOM produced by two single marine bacterial strains. We then tested the availability of these DOM sources to in situ Mediterranean Sea HP communities. Two bacterial strains were used: Photobacterium angustum (a copiotrophic gammaproteobacterium) and Sphingopyxis alaskensis (an oligotrophic alphaproteobacterium). When cultivated on glucose as the sole carbon source, the two strains released from 7% to 23% of initial glucose as bacterial derived DOM (B-DOM), the quality of which (as enrichment in humic or protein-like substances) differed between strains. B-DOM induced significant growth and carbon consumption of natural HP communities, suggesting that it was partly labile. However, B-DOM consistently promoted lower prokaryotic growth efficiencies than in situ DOM. In addition, B-DOM changed HP exoenzymatic activities, enhancing aminopeptidase activity when degrading P. angustum DOM, and alkaline phosphatase activity when using S. alaskensis DOM, and promoted differences in HP diversity and composition. DOM produced by HP affects in situ prokaryotic metabolism and diversity, thus changing the pathways for DOM cycling (e.g. respiration over biomass production) in the ocean.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Uncoupled seasonal variability of transparent exopolymer and Coomassie stainable particles in coastal Mediterranean waters (2021)
    University of California Press
    Details
    Publication Date: 2024-02-07
    Description: Transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP) are gel-like particles, ubiquitous in the ocean, that affect important biogeochemical processes including organic carbon cycling by planktonic food webs. Despite much research on both groups of particles (especially TEP) over many years, whether they exist as distinctly stainable fractions of the same particles or as independent particles, each with different driving factors, remains unclear. To address this question, we examined the temporal dynamics of TEP and CSP over 2 complete seasonal cycles at 2 coastal sites in the Northwestern Mediterranean Sea, the Blanes Bay Microbial Observatory (BBMO) and the L’Estartit Oceanographic Station (EOS), as well as their spatial distribution along a coast-to-offshore transect. Biological, chemical, and physical variables were measured in parallel. Surface concentrations (mean ± standard deviation [SD]) of TEP were 36.7 ± 21.5 µg Xanthan Gum (XG) eq L–1 at BBMO and 36.6 ± 28.3 µg XG eq L–1 at EOS; for CSP, they were 11.9 ± 6.1 µg BSA eq L–1 at BBMO and 13.0 ± 5.9 µg BSA eq L–1 at EOS. Seasonal variability was more evident at EOS, where surface TEP and CSP concentrations peaked in summer and spring, respectively, and less predictable at the shore-most station, BBMO. Vertical distributions between surface and 80 m, monitored at EOS, showed highest TEP concentrations within the surface mixed layer during the stratification period, whereas CSP concentrations were highest before the onset of summer stratification. Phytoplankton were the main drivers of TEP and CSP distributions, although nutrient limitation and saturating irradiance also appeared to play important roles. The dynamics and distribution of TEP and CSP were uncoupled both in the coastal sites and along the transect, suggesting that they are different types of particles produced and consumed differently in response to environmental variability.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Dissolved Organic Matter Fluorescence as a Tracer of Upwelling and Microbial Activities in Two Cyclonic Eddies in the Eastern Tropical North Atlantic (2023)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Mesoscale eddies are frequently observed in the Eastern Tropical North Atlantic (ETNA), yet their effects on the transport and distribution of biogeochemical solutes, and specifically on the production and remineralization of dissolved organic matter (DOM) remain difficult to elucidate. Here, we investigated the submesoscale variability of chromophoric DOM (CDOM) and fluorescent DOM (FDOM) together with microbial production and remineralization processes in two cyclonic eddies (CEs) in the ETNA during summer and winter 2019. One CE, formed near the coast off Mauritania during the post-upwelling season, was sampled along a ∼900 km zonal corridor between Mauritania and the Cape Verde Islands. The other CE, formed nearby Brava Island, was out of coastal influence. Four fluorescent components were identified with parallel factor analysis, two humic-like, and two protein-like components. Humic-like FDOM components correlated to optode-based community respiration and were also good indicators of upwelling associated with the Brava Island CE as they correlated to physical parameters (e.g., temperature) and to dissolved inorganic nitrogen. The tryptophan-like FDOM components correlated with the carbon and nitrogen content of semi-labile DOM, phytoplankton biomass, community respiration, and bacterial production. Overall, our study revealed that DOM optical properties are suitable for tracing freshly produced organic matter and the transport of remineralized DOM within offshore eddies. Key Points: - Four fluorescent dissolved organic matter (FDOM) components were studied in two cyclonic eddies (CEs) in the Eastern Tropical North Atlantic - Tryptophan-like FDOM was an indicator of the CEs' productivity as it correlated with semi-labile dissolved organic matter and microbial metabolic activities - Humic-like FDOM was a by-product of microbial respiration; its distribution within an offshore CE covaried with nutrient upwelling
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Corrigendum: Turnover time of fluorescent dissolved organic matter in the dark global ocean (2016)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2016-06-17
    Description: Corrigendum Nature Communications doi: 10.1038/ncomms12005 Authors: Teresa S. Catalá, Isabel Reche, Antonio Fuentes-Lema, Cristina Romera-Castillo, Mar Nieto-Cid, Eva Ortega-Retuerta, Eva Calvo, Marta Álvarez, Cèlia Marrasé, Colin A. Stedmon, X. Antón Álvarez-Salgado
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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    PAPER CURRENT
  • 6
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    Turnover time of fluorescent dissolved organic matter in the dark global ocean (2015)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2015-01-31
    Description: Article The microbial carbon pump may play an important role in carbon sequestration in the deep ocean, but quantifying organic matter in this dark realm is difficult. Here, the authors use fluorescence spectroscopy to investigate the turnover time of fluorescent dissolved organic matter. Nature Communications doi: 10.1038/ncomms6986 Authors: Teresa S. Catalá, Isabel Reche, Antonio Fuentes-Lema, Cristina Romera-Castillo, Mar Nieto-Cid, Eva Ortega-Retuerta, Eva Calvo, Marta Álvarez, Cèlia Marrasé, Colin A. Stedmon, X. Antón Álvarez-Salgado
    Electronic ISSN: 2041-1723
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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    PAPER CURRENT
  • 7
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    Nitrogen limitation of the summer phytoplankton and heterotrophic prokaryote communities in the Chukchi Sea (2018)
    Frontiers Media
    Details
    Publication Date: 2022-05-25
    Description: © The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Frontiers in Marine Science 5 (2018): 362, doi:10.3389/fmars.2018.00362.
    Description: Major changes to Arctic marine ecosystems have resulted in longer growing seasons with increased phytoplankton production over larger areas. In the Chukchi Sea, the high productivity fuels intense benthic denitrification creating a nitrogen (N) deficit that is transported through the Arctic to the Atlantic Ocean, where it likely fuels N fixation. Given the rapid pace of environmental change and the potentially globally significant N deficit, we conducted experiments aimed at understanding phytoplankton and microbial N utilization in the Chukchi Sea. Ship-board experiments tested the effect of nitrate (NO3-) additions on both phytoplankton and heterotrophic prokaryote abundance, community composition, photophysiology, carbon fixation and NO3- uptake rates. Results support the critical role of NO3- in limiting summer phytoplankton communities to small cells with low production rates. NO3- additions increased particulate concentrations, abundance of large diatoms, and rates of carbon fixation and NO3- uptake by cells 〉1 μm. Increases in the quantum yield and electron turnover rate of photosystem II in +NO3- treatments suggested that phytoplankton in the ambient dissolved N environment were N starved and unable to build new, or repair damaged, reaction centers. While some increases in heterotrophic prokaryote abundance and production were noted with NO3- amendments, phytoplankton competition or grazers likely dampened these responses. Trends toward a warmer more stratified Chukchi Sea will likely enhance summer oligotrophic conditions and further N starve Chukchi Sea phytoplankton communities.
    Description: Fieldwork and analysis for the ICESCAPE program was supported by Ocean Biology and Biogeochemistry Program of the National Aeronautic and Space Administration under Grant No. NNX10AF42G to KA.
    Keywords: Phytoplankton ; Nitrogen ; Chukchi Sea ; Nitrate ; Nutrient limitation
    Repository Name: Woods Hole Open Access Server
    Type: Article
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    PAPER (OA)
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