Volatile and semi-volatile gas-phase organic carbon (GOC) is a largely neglected component of the global carbon cycle, with poorly resolved pools and fluxes of natural and anthropogenic GOC in the biosphere. Substantial amounts of atmospheric GOC are exchanged with the surface ocean, and subsequent utilization of specific GOC compounds by surface ocean microbial communities has been demonstrated. Yet, the final fate of the bulk of the atmospheric GOC entering the surface ocean is unknown. Our data show experimental evidence of efficient use of atmospheric GOC by marine prokaryotes at different locations in the NE Subtropical Atlantic, the Arctic Ocean and the Mediterranean Sea. We estimate that between 2 and 27% of the prokaryotic carbon demand was supported by GOC with a major fraction of GOC inputs being consumed within the mixed layer. The role of the atmosphere as a key vector of organic carbon subsidizing marine microbial metabolism is a novel link yet to be incorporated into the microbial ecology of the surface ocean as well as into the global carbon budget. ; This is a contribution to projects RODA (CTM2004-06842-CO3-02), and ATOS (POL2006-00550/CTM) projects, funded by the Spanish Ministry of Science and Innovation and project THRESHOLDS funded by the 6th Framework Programme of the European Union. JA was supported by a "Ramón y Cajal" research fellowship from the Spanish Government. ; Peer reviewed
17 pages, 9 figures, 2 tables, supplementary material https://www.frontiersin.org/articles/10.3389/fmars.2021.683354/full#supplementary-material.-- Data Availability Statement: The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation ; Particulate organic matter (POM) lability is one of the key factors determining the residence time of organic carbon (OC) in the marine system. Phytoplankton community composition can influence the rate at which heterotrophic microorganisms decompose phytoplankton detrital particles and thus, it controls the fraction of OC that reaches the ocean depths, where it can be sequestered for climate-relevant spans of time. Here, we compared the degradation dynamics of POM from phytoplankton assemblages of contrasting diatom dominance in the presence of mesopelagic prokaryotic communities during a 19-day degradation experiment. We found that diatom-derived POM exhibited an exponential decay rate approximately three times lower than that derived from a community dominated by flagellated phytoplankton (mainly coccolithophores and nanoflagellates). Additionally, dissolved organic matter (DOM) released during the degradation of diatom particles accumulated over the experiment, whereas only residual increases in DOM were detected during the degradation of non-diatom materials. These results suggest that diatom-dominance enhances the efficiencies of the biological carbon pump and microbial carbon pump through the relatively reduced labilities of diatom particles and of the dissolved materials that arise from their microbial processing ; This research was funded by projects SUAVE (CTM2014-54926-R), ANIMA (CTM2015-65720-R), and BIOGAPS (CTM2016-81008-R) and the institutional support of the "Severo Ochoa Centre of Excellence" accreditation (CEX2019-000928-S) from the Spanish government. MC-B was supported by a FPU pre-doctoral contract (FPU16/01925) from the Spanish government. We acknowledge support for the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI) ; Peer reviewed
Special issue Polar Microbes.-- 22 pages, 4 figures, 5 tables, supplementary material https://doi.org/10.3390/microorganisms9020317.-- Data Availability Statement: All data is reported in the present article.-- This research is part of POLARCSIC activities ; The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column ; This research was part of the ATOS project, funded as part of the Spanish contribution to the International Polar Year (IPY) by the Spanish Ministry of Science and Innovation (POL200600550/CTM). J.A.B.'s work was supported by a PhD fellowship from the Spanish Ministerio de Ciencia e Innovación (FPU grant) ; With funding from the Spanish government through the 'Severo Ochoa Centre of Excellence' accreditation (CEX2019-000928-S) ; Peer reviewed
3 pages ; Microbes drive the Earth's biogeochemical cycles, exerting profound control over the global cycling of carbon and other elements (Falkowski et al., 2008). In aquatic systems, the importance of microbial extracellular enzymes to the mobilization, transformation, and turnover of organic and inorganic compounds in aquatic environments has been proved since the 80's (Hoppe, 1983; Chróst, 1989) and was summarized in the book "Microbial enzymes in aquatic environments" (Chróst, 1991). Since then, the field has advanced considerably, with new observations, assay methods, and molecular-level studies (Arnosti et al., 2014) and the measurement of extracellular enzyme activities has become standard in many labs. We now have rates of enzymatic activities in a wide variety of freshwater and marine environments, from polar to tropical and from surface to deep ocean, and from isolates obtained even from extreme environments. Additionally, in recent years measurement of enzyme activities has become an important tool to assess the impact of anthropogenic changes on microbial communities and biogeochemical cycles, such as in the events of oil spills, acidification, or global warming (e.g., Piontek et al., 2010; Sala et al., 2016; Ziervogel et al., 2016; Freixa et al., 2017) ; This study was supported by grant ANIMA (CTM2015-65720-R) funded by the Spanish Government to MS and by the NSF grant OCE-1464392 to AS ; Peer Reviewed
8 pages, 3 figures, 2 tables, supplementary material http://dx.doi.org/10.3389/fmicb.2015.01566 ; Volatile and semi-volatile gas-phase organic carbon (GOC) is a largely neglected component of the global carbon cycle, with poorly resolved pools and fluxes of natural and anthropogenic GOC in the biosphere. Substantial amounts of atmospheric GOC are exchanged with the surface ocean, and subsequent utilization of specific GOC compounds by surface ocean microbial communities has been demonstrated. Yet, the final fate of the bulk of the atmospheric GOC entering the surface ocean is unknown. Our data show experimental evidence of efficient use of atmospheric GOC by marine prokaryotes at different locations in the NE Subtropical Atlantic, the Arctic Ocean and the Mediterranean Sea. We estimate that between 2 and 27% of the prokaryotic carbon demand was supported by GOC with a major fraction of GOC inputs being consumed within the mixed layer. The role of the atmosphere as a key vector of organic carbon subsidizing marine microbial metabolism is a novel link yet to be incorporated into the microbial ecology of the surface ocean as well as into the global carbon budget ; This is a contribution to projects RODA (CTM2004-06842-CO3-02), and ATOS (POL2006-00550/CTM) projects, funded by the Spanish Ministry of Science and Innovation and project THRESHOLDS funded by the 6 Framework Programme of the European Union. JA was supported by a "Ramón y Cajal" research fellowship from the Spanish Government. ; Peer Reviewed
12 pages, 6 figures, supplemental material https://www.frontiersin.org/articles/10.3389/fmicb.2019.00760/full#supplementary-material ; Experiments with bacteria in culture have shown that they often display "feast and famine" strategies that allow them to respond with fast growth upon pulses in resource availability, and enter a growth-arrest state when resources are limiting. Although feast responses have been observed in natural communities upon enrichment, it is unknown whether this blooming ability is maintained after long periods of starvation, particularly in systems that are energy limited like the bathypelagic ocean. Here we combined bulk and single-cell activity measurements with 16S rRNA gene amplicon sequencing to explore the response of a bathypelagic community, that had been starved for 1.6 years, to a sudden organic carbon supply. We observed a dramatic change in activity within 30 h, with leucine incorporation rates increasing over two orders of magnitude and the number of translationally active cells (mostly Gammaproteobacteria) increasing 4-fold. The feast response was driven by a single operational taxonomic unit (OTU) affiliated with the Marinobacter genus, which had remained rare during 7 months of starvation. Our work suggests that bathypelagic communities harbor a seed bank of highly persistent and resourceful "feast and famine" strategists that might disproportionally contribute to carbon fluxes through fast responses to occasional pulses of organic matter ; This work was supported by grants DIFUMIC (2017SGR/1568, Generalitat de Catalunya), DOREMI (CTM2012-34294), HOTMIX (CTM2011-30010/MAR), REMEI (CTM2015-70340-R), and ANIMA (CTM2015-65720-R) funded by the Spanish Government, and EcoRARE (CTM2014-60467-JIN), funded by the Spanish Government and the European Regional Development Fund (ERDF). CRG was supported by a Juan de la Cierva contract (IJCI-2015-23505) and MS by a Viera y Clavijo contract funded by the ACIISI and the ULPGC ; Peer Reviewed
13 páginas, 4 figuras, 4 tablas ; Despite representing only a small fraction of the ocean's dissolved organic matter pool, dissolved free amino acids (DFAA) have high turnover rates and are major nitrogen and carbon sources for bacterioplankton. Both phytoplankton and bacterioplankton assimilate and release DFAA, but their consumption and production are difficult to quantify in nature due to their short residence times (min) as dissolved monomers. We segregated DFAA production by phytoplankton and bacterial consumption by measuring individual DFAA concentrations in four axenic phytoplankton cultures during the exponential growth phase, and also after 4 d incubations in the presence of a natural bacterioplankton community. The amounts and composition of the DFAA pool varied widely among phytoplankton species. The proportion of dissolved organic carbon attributed to DFAA varied among cultures. The picoeukaryotic prasinophyte, Micromonas pusilla, released higher amounts of DFAA than the other species tested (diatoms and dinoflagellate), especially alanine, which has been reported as the dominant individual DFAA in some oligotrophic environments. Community structure of heterotrophic prokaryotes responded to differences in the quality of organic matter released among microalgal species, with Roseobacter-related bacteria responding strongly to exudate composition. Our results demonstrate the specificity of DFAA extracellular release among several algal species and their preferential uptake by members of bacterial communities ; This work was supported by projects STORM (CTM2009-09352/MAR) and ICARO (PIE 200830I120) and DOREMI (CTM2012-34294) funded by Spanish Ministerio de Economia y Competitividad. H.S. benefited from fellowships from the Spanish 'Ministerio de Educación y Ciencia' (JCI-2008-2727) and Brazilian 'Ciências sem Fronteiras' Program from CAPES (BJT 013/2012); C.R.-C. was funded by a I3P-CSIC predoctoral fellowship within the project MODIVUS, CTM2005-04795/MAR; J.P. was funded by the Crafoord Foundation and the Swedish governmental strong research program Ecochange; G.T.T. was partially supported by a sabbatical fellowship from the Spanish 'Ministerio de Educación y Ciencia' ; Peer reviewed
Special issue The Interrelationships between Near-Surface Ecological Processes and Air–Sea Exchange of Gases and Particles.-- 19 figures, 5 figures, 2 tables, 2 appendices.-- Data of this work can be found at the Zenodo repository (https://doi.org/10.5281/zenodo.3773972).-- This research is part of POLARCSIC (https://polarcsic.es/) activities ; soprene is a biogenic trace gas produced by terrestrial vegetation and marine phytoplankton. In the remote oceans, where secondary aerosols are mostly biogenic, marine isoprene emissions affect atmospheric chemistry and influence cloud formation and brightness. Here, we present the first compilation of new and published measurements of isoprene concentrations in the Southern Ocean and explore their distribution patterns. Surface ocean isoprene concentrations in November through April span 1 to 94 pM. A band of higher concentrations is observed around a latitude of ≈40 ∘ S and a surface sea temperature of 15 ∘ C. High isoprene also occurs in high productivity waters near islands and continental coasts. We use concurrent measurements of physical, chemical, and biological variables to explore the main potential drivers of isoprene concentration by means of paired regressions and multivariate analysis. Isoprene is best explained by phytoplankton-related variables like the concentrations of chlorophyll-a, photoprotective pigments and particulate organic matter, photosynthetic efficiency (influenced by iron availability), and the chlorophyll-a shares of most phytoplankton groups, and not by macronutrients or bacterial abundance. A simple statistical model based on chlorophyll-a concentration and a sea surface temperature discontinuity accounts for half of the variance of isoprene concentrations in surface waters of the Southern Ocean ; This research was supported by the Spanish Ministry of Economy and Competitiveness through project PEGASO (CTM2012–37615) to RS, and by the Swiss Polar Institute and Ferring Pharmaceuticals through project SORPASSO–ACE#8 to RS and project ACE#1 to David Antoine (Remote Sensing and Satellite Research Group, Curtin University) and Sandy Thomalla (Southern Ocean Carbon and Climate Observatory, Council for Scientific and Industrial Research (CSIR) and Marine Research Institute, University of Cape Town). It was also partially funded by the Australian Government through the Australian Research Council's Discovery Projects funding scheme (project DP160103387) and South African CSIR Parliamentary Grant (SNA2011112600001). Project ACE#1 was also supported by CSIR Southern Ocean Carbon and Climate Observatory (SOCCO) programme. PRR was supported by a "la Caixa" Foundation PhD Fellowship (2015–2019)
Dall'Osto, Manuel . et al.-- 10 pages, 5 figures ; Climate warming affects the development and distribution of sea ice, but at present the evidence of polar ecosystem feedbacks on climate through changes in the atmosphere is sparse. By means of synergistic atmospheric and oceanic measurements in the Southern Ocean near Antarctica, we present evidence that the microbiota of sea ice and sea ice-influenced ocean are a previously unknown significant source of atmospheric organic nitrogen, including low molecular weight alkyl-amines. Given the keystone role of nitrogen compounds in aerosol formation, growth and neutralization, our findings call for greater chemical and source diversity in the modelling efforts linking the marine ecosystem to aerosol-mediated climate effects in the Southern Ocean ; The cruise was funded by the Spanish Ministry of Economy through projects PEGASO (CTM2012-37615) and Bio-Nuc (CGL2013-49020-R), and by the EU though the FP7-PEOPLE-2013-IOF programme (Project number 624680, MANU – Marine Aerosol NUcleations). [.] The NUI Galway and ISAC-CNR Bologna groups acknowledge funding from the European Union's Seventh Framework Programme (FP7/2007-2013) project BACCHUS under grant agreement n° 603445. The work was further supported by the CNR (Italy) under AirSEaLab: Progetto Laboratori Congiunti. The National Centre for Atmospheric Science NCAS Birmingham group is funded by the UK Natural Environment Research Council. [.] CC, MFF and RA acknowledge funding from the Marine Institute, University of Plymouth to enable participation in PEGASO ; Peer Reviewed
pages, 7 figures, 1 table, supporting information.-- https://doi.org/10.1111/mec.15454.-- DNA sequences and associated metadata: European Nucleotide Database (ENA) under accession numbers ERP109198 and ERS2539749–ERS2539903. The environmental metadata, and the complete non-rarefied OTU and taxonomic tables used in this study are provided as Supporting Information (Tables S1, S2, S3 and S4).-- This is a contribution of Grup Consolidat de Recerca of the Catalan Government 2014SGR/1179 ; Deep ocean microbial communities rely on the organic carbon produced in the sunlit ocean, yet it remains unknown whether surface processes determine the assembly and function of bathypelagic prokaryotes to a larger extent than deep‐sea physico‐chemical conditions. Here, we explored whether variations in surface phytoplankton assemblages across Atlantic, Pacific and Indian ocean stations can explain structural changes in bathypelagic (ca. 4000 m) free‐living and particle‐attached prokaryotic communities (characterized through 16S rRNA gene sequencing), as well as in prokaryotic activity and dissolved organic matter (DOM) quality. We show that the spatial structuring of prokaryotic communities in the bathypelagic strongly followed variations in the abundances of surface dinoflagellates and ciliates, as well as gradients in surface primary productivity, but were less influenced by bathypelagic physico‐chemical conditions. Amino acid‐like DOM components in the bathypelagic reflected variations of those components in surface waters, and seemed to control bathypelagic prokaryotic activity. The imprint of surface conditions was more evident in bathypelagic than in shallower mesopelagic (200‐1000 m) communities, suggesting a direct connectivity through fast‐sinking particles that escapes mesopelagic transformations. Finally, we identified a pool of endemic deep‐sea prokaryotic taxa (including potential chemoautotrophic groups) that appear less connected to surface processes than those bathypelagic taxa with a widespread vertical distribution. Our results suggest that surface planktonic communities shape the spatial structure of the bathypelagic microbiome to a larger extent than the local physico‐chemical environment, likely through determining the nature of the sinking particles and the associated prokaryotes reaching bathypelagic waters ; This work was funded by the Spanish Ministry of Economy and Competitiveness (MINECO) through the Consolider-Ingenio program (Malaspina 2010 Expedition, ref. CSD2008-00077), with contributions from grant CTM2015-70340R, CTM2015-65720-R, CTM2015-69936-P, RTI2018-101025-B-I00, Modeling Nature Scientific Unit (UCE.PP2017.03), CTM2015-69392-C3-2-R (co-financed with FEDER funds) and King Abdullah University of Science and Technology (KAUST). [.] CRG was supported by a Juan de la Cierva fellowship and the GRAMMI project (IJCI-2015-23505 and RTI2018717 099740-J-I00, MICINN, Spain). MSE was supported by a Viera y Clavijo contract funded by the ACIISI and the ULPGC. MM was supported by CONICYT (FONDAP IDEAL15150003 and FONDECYT-POSTDOCTORADO 3190369).
