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The Ocean microbiome has a crucial role in Earth’s biogeochemical cycles. During the last decade, global cruises such as Tara Oceans and the Malaspina Expedition have expanded our understanding of the diversity and genetic repertoire of marine microbes. Nevertheless, there are still knowledge gaps regarding their diversity patterns throughout depth gradients ranging from the surface to the deep ocean. Here we present a dataset of 76 microbial metagenomes (MProfile) of the picoplankton size fraction (0.2–3.0 µm) collected in 11 vertical profiles covering contrasting ocean regions sampled during the Malaspina Expedition circumnavigation (7 depths, from surface to 4,000 m deep). The MProfile dataset produced 1.66 Tbp of raw DNA sequences from which we derived: 17.4 million genes clustered at 95% sequence similarity (M-GeneDB-VP), 2,672 metagenome-assembled genomes (MAGs) of Archaea and Bacteria (Malaspina-VP-MAGs), and over 100,000 viral genomic sequences. This dataset will be a valuable resource for exploring the functional and taxonomic connectivity between the photic and bathypelagic tropical and sub-tropical ocean, while increasing our general knowledge of the Ocean microbiome

Pocas áreas geográficas de nuestro planeta son tan fascinantes y, a su vez, tan desconocidas como las regiones polares. Su gran interés científico reside en el importante y decisivo papel que juegan en la dinámica y el futuro de nuestro planeta, especialmente en el actual contexto de cambio global, ya que las regiones polares son los grandes y principales motores reguladores del clima de la Tierra. Los drásticos cambios que están sufriendo en respuesta al aumento de temperatura, ocasionado por el incremento en la emisión de gases de efecto invernadero como consecuencia de las actividades humanas, están afectando directamente a la dinámica climática, oceanográfica y ambiental, tanto de los propios polos como de latitudes extrapolares. La Plataforma Temática Interdisciplinar (PTI) Polar CSIC presenta el videodocumental y teaser 360º ‘Campaña Antártica Española: Ciencia en el Polo Sur’, una iniciativa que ha contado con la participación del Comité Polar Español (CPE), el Instituto Geociencias Barcelona (GEO3BCN-CSIC) y el Instituto de Ciencias del Mar (ICM-CSIC). La presentación se celebra en el Instituto de Ciencias del Mar del CSIC, en Barcelona, y cuenta con la participación de Sonia Ramos (Comité Polar Español), Fernando Bohoyo (gestor del programa polar en la Agencia Estatal de Investigación (AEI), Dolors Vaqué (Scientific Committee on Antarctic Research, SCAR), Joan Riba (Unidad de Tecnología Marina, UTM) y Pepe Molina (fotógrafo y videoartista)

Background: Marine heterotrophic flagellates (HF) are dominant bacterivores in the ocean, where they represent the trophic link between bacteria and higher trophic levels and participate in the recycling of inorganic nutrients for regenerated primary production. Studying their activity and function in the ecosystem is challenging since most of the HFs in the ocean are still uncultured. In the present work, we investigated gene expression of natural HF communities during bacterivory in four unamended seawater incubations. Results: The most abundant species growing in our incubations belonged to the taxonomic groups MAST-4, MAST-7, Chrysophyceae, and Telonemia. Gene expression dynamics were similar between incubations and could be divided into three states based on microbial counts, each state displaying distinct expression patterns. The analysis of samples where HF growth was highest revealed some highly expressed genes that could be related to bacterivory. Using available genomic and transcriptomic references, we identified 25 species growing in our incubations and used those to compare the expression levels of these specific genes. Conclusions: Our results indicate that several peptidases, together with some glycoside hydrolases and glycosyltransferases, are more expressed in phagotrophic than in phototrophic species, and thus could be used to infer the process of bacterivory in natural assemblages

Viruses play a key role in controlling microbial abundance and composition, nutrient cycling and productivity in marine systems. However, although the viral dynamics and the spatial distribution are being studied, little is known about the temporal fluctuations of the viral community. Furthermore, climate change and its impacts on the environment may have consequences on the temporal dynamics of viruses and their potential hosts. One of the best approaches to study this occurrence is to have continuous time series with large datasets. During the last 20 years we have been collecting samples for viral abundances and other biological and environmental variables at the Blanes Microbial Observatory (BBMO, Catalan Coast). In this study we use time series analysis and Machine Learning approaches to assess and understand whether the environmental factors have changed along these 20 years, and if they have an effect on viral communities and their hosts. Our results showed that in the BBMO during this period, temperature, salinity and water transparency increased, while phosphate, chlorophyll concentration, bacterial and viral abundance decreased. This suggests an ongoing ecosystem transition towards oligotrophy. In particular, the last decade has been decisive for these changes and their influence on the (decreasing) viral abundance. Long-term studies like ours will allow for a better understanding of variations in virus dynamics in the oceans. Incorporating the viral component into future ocean and climate models will increase the accuracy of climate change predictions

There is a gap in knowledge on broad-scale diversity and functional patterns along the continuum between the photic and the dark ocean microbes, including trends in genome size (GS) and functional diversity. To address this gap, we present the Malaspina Microbial Vertical Profiles Metagenomes dataset, comprising 76 microbial metagenomes (0.2-3um) collected in 11 stations in the tropical and subtropical open oceans from 3 to 4,000 m deep, a 46.3 million gene catalog and 1,228 Metagenome-Assembled Genomes (MAGs). Our results show increased functional richness in the bathypelagic and a strong positive association between GS and depth for the most abundant phyla in samples up to 1,000 m, while this association is absent in the bathypelagic. Conversely, lower abundance taxa displayed a bimodal distribution of GS, with a smaller peak in the mesopelagic and a larger peak in the bathypelagic. Opposing trends were observed for protein-encoding gene density and functional diversity across epipelagic and deep ocean MAGs. Specifically, protein-encoding gene density was higher at the epipelagic and decreased towards the bathypelagic for most of the taxa, pointing out that genome streamlining generally holds true, but it is not universal for all microbes. Larger prokaryotic GS in the bathypelagic was associated with a higher prevalence of prophages and defense systems. We suggest that a combination of factors, including genome streamlining, metabolic diversification, viral infection, and molecular defense systems, drive the genomic diversity of marine prokaryotes across ocean layers

La Dolors i la Conxita participen en expedicions de recerca a l’Antàrtida i ens expliquen la seva experiència: Per què hi van, quin és el objectiu de les expedicions, com i quan hi van, com fan la recerca, quin és el seu dia a dia a l’Antàrtida, etc

Phytoplankton-derived organic matter sustains heterotrophic marine life in regions away from terrestrial inputs such as the Southern Ocean. Fluorescence spectroscopy has long been used to characterize the fluorescent organic matter (FOM) pool. However, most studies focus only in the dissolved FOM fraction (FDOM) disregarding the contribution of particles. In order to assess the dynamics and drivers of the dissolved and particulate fractions of FOM, we used a Lagrangian approach to follow the time evolution of phytoplankton proliferations at four different sites in the Southern Ocean and compared the FOM in filtered and unfiltered seawater aliquots. We found that filtration had little effects on FOM visible spectrum fluorescence intensities, implying that most of this signal was due to dissolved fluorophores. On the other hand, protein-like fluorescence was strongly supressed by filtration, with fluorescence of particles accounting for up to 90 % of the total protein-like FOM. Photobleaching was identified as the main driver of visible FDOM composition, which was better described by indices of phytoplankton photoacclimation than by measurements of the incident solar radiation dose. In contrast, protein-like FOM intensity and fractionation were primarily related to abundance, composition and physiological state of phytoplankton proliferations. The chlorophyll a concentration from non-diatom phytoplankton explained 91 % of the particulate protein-like FOM variability. The proportion of protein-like fluorescence found in the dissolved phase was predicted by the combination of potential viral and grazing pressures, which accounted for 51 and 29 % of its variability, respectively. Our results show that comparing FOM measurements from filtered and unfiltered seawater provides relevant information on the taxonomic composition and cell integrity of phytoplankton communities. A better understanding of the commonly overlooked FOM fractionation process is essential for the impl

The Western Antarctic Peninsula (WAP) has experienced significant changes in seawater temperature over the past 50 years. This warming affects seawater and sea ice microbial cycling of organic matter, where viral features could play a crucial role in sympagic sea ice melting environments. However, there is a lack of information about the sea ice viral abundances and processes (e.g. lysis rates and carbon release from microorganisms). To gain knowledge of sea ice viral, microbial, and chemical characteristics, we collected four different sea ice samples and their surrounding surface seawater during the Austral summer of 2019 north of the WAP. In each sample, we assessed viral and microbial abundances and environmental parameters. In the sea ice, we also measured viral-driven mortality rates on prokaryotes and protists and the consequent release of organic carbon. The viral and microorganism abundances in the sea ice were higher (4.5 ± 1.9 × 106 viruses mL−1; 1.5 ± 0.7 × 106 prokaryotes mL−1, 9.4 ± 5.0 × 102 protists mL−1) than in the surrounding surface seawater (1.7 × 106 viruses mL−1, 0.4 × 106 prokaryotes mL−1, 7.1 × 102 protists mL−1). Furthermore, viral lytic production on prokaryotes (4.5 ± 0.8 × 105 mL−1day−1) and protists (1.9 ± 1.0 × 104 mL−1 day−1) in sympagic environments had a higher viral impact on carbon release by protist (1.5 ± 1.1 µg C L−1 day−1) than by prokaryotes (0.3 ± 0.1 µg C L−1 day−1). Our results suggest that, after sea ice melting, viral abundances and activities may influence the functioning of the microbial food web by increasing the release of dissolved organic matter, affecting biogeochemical cycles and microbial communities in the underlying surface waters

Grazing controls bacterial abundances and composition in many ecosystems. In marine systems, heterotrophic flagellates (HFs) are important predators. Assemblages of HFs are primarily formed by species still uncultured; therefore, many aspects of their trophic behaviour are poorly known. Here, we assessed the functional response of the whole assemblage and of four taxa grown in an unamended seawater incubation. We used fluorescently labelled bacteria to create a prey gradient of two orders of magnitude in abundance and estimated ingestion rates. Natural HFs had a half-saturation constant of 6.7 × 105 prey ml−1, a value lower than that of cultured flagellates and within the range of marine planktonic bacterial abundances. Minorisa minuta was well adapted to low prey abundances and very efficient in ingesting bacteria. MAST-4 and MAST-7 were also well adapted to the typical marine abundances but less voracious. In contrast, Paraphysomonas imperforata, a typical cultured species, did not achieve ingestion rate saturation even at the highest prey concentration assayed. Our study, beside to set the basis for the fundamental differences between cultured and uncultured bacterial grazers, indicate that the examined predator taxa have different functional responses, suggesting that they occupy distinct ecological niches according to their grazing strategies and prey preferences

Within the Southern Ocean, the greatest warming is occurring on the Antarctic Peninsula (AP) where clear cryospheric and biological consequences are being observed. Antarctic coastal systems harbour a high diversity of marine and terrestrial ecosystems heavily influenced by Antarctic seaweeds (benthonic macroalgae) and bird colonies (mainly penguins). Primary sea spray aerosols (SSA) formed by the outburst of bubbles via the sea-surface microlayer depend on the organic composition of the sea water surface. In order to gain insight into the influence of ocean biology and bio-geochemistry on atmospheric aerosol, we performed in situ laboratory aerosol bubble chamber experiments to study the effect of different leachates of biogenic material - obtained from common Antarctic seaweeds as well as penguin guano - on primary SSA. The addition of different leachate materials on a seawater sample showed a dichotomous effect depending on the leachate material added - either suppressing (up to 52%) or enhancing (22–88%) aerosol particle production. We found high ice nucleating particle number concentrations resulting from addition of guano leachate material. Given the evolution of upper marine polar coastal ecosystems in the AP, further studies on ocean-atmosphere coupling are needed in order to represent the currently poorly understood climate feedback processes.

Una visió integral del coneixement de les zones polars i sobre les alteracions que estan patint com a conseqüència del canvi global. Les zones polars, principals responsables del clima del nostre planeta, estan patint canvis dràstics com a conseqüència de la seva alta sensibilitat al canvi global, que afecten directament a la dinàmica climàtica, oceanogràfica i ambiental de latituds extra polars. Aquest llibre pretén donar un punt de vista integral i multidisciplinari de l’estat del coneixement de les zones àrtiques i antàrtiques: la seva evolució geològica, els apressants problemes de contaminació d’aquests territoris, la caracterització dels diversos ecosistemes terrestres i marins, així com l’evolució passada i futura del clima polar. L’objectiu final es explicar, de forma clara i amena, les similituds i diferències entre els dos pols i conscienciar sobre les alteracions que estan patint degut al canvi global. Així mateix, es donen a conèixer les investigacions, de gran rellevància científica i social, realitzades pel personal científic i tècnic del Consell Superior d’Investigacions Científiques (CSIC), apropant-nos a la història i situació actual de la investigació polar a Espanya

Programa 11.00-11.10 Introducció a l’Ecologia Microbiana Marina. Dolors Vaqué. Departament de Biologia Marina i Oceanografia Institut de Ciències del Mar, CSIC 11.10-11.30 Estudi de l’estat fisiològic de la comunitat bacteriana del biofilm en llacunes hipersalines mitjançant anàlisis de biomarcadors lipídics. Ariadna Vidal. Facultat de Biologia Universitat de Barcelona 11.30-11.50 Diversity and Ecology of Aquatic Viruses. Felipe H. Coutinho. Departament de Biologia Marina i Oceanografia. Institut de Ciències del Mar, CSIC 11.50-12.10 On és el meu sopar? el paper de la comunicació química en les relacions de depredació del microplàncton marí. Queralt Güell. Departament de Biologia Marina i Oceanografia. Institut de Ciències del Mar, CSIC 12.10-12.30 Què tenen a veure els microbis marins amb les emissions de sofre i el canvi climàtic a l'Àrtic? Martí Galí. Departament de Biologia Marina i Oceanografia. Institut de Ciències del Mar, CSIC 12.30-12.50 Els bloomers, estudiant els canvis en l’estructura de les comunitats microbianes marines a escales temporals curtes. Ona Deulofeu. Departament de Biologia Marina i Oceanografia. Institut de Ciències del Mar, CSIC 12.50-13.10 Iluminando el océano oscuro: ecología microbiana y estrategias de supervivencia. Marta Sebastian. Departament de Biologia Marina i Oceanografia. Institut de Ciències del Mar, CSIC 13.10 -13:15 Conclusions i perspectives. Dolors Vaqué (ICM) i Jordi Urmeneta (UB)

[EN] The freshwater and marine water column are inhabited by planktonic microorganisms and viruses. Though they account for 90% of the living biomass of the oceans, there is a lack of knowledge about how many there are and what they do. In this article we will describe some aspects of their biology and the role they play in the biogeochemical cycles of the ocean and in maintaining life on the Planet, [CAT] A la columna d’aigües dolces i marines hi habiten microorganismes i virus planctònics. Malgrat contribuir amb el 90% de la biomassa viva dels oceans, hi ha un gran desconeixement sobre qui són, quants n’hi ha i què fan. En aquest article descriurem alguns aspectes de la seva biologia i del paper que juguen en els cicles biogeoquímics de l’oceà, així com en el manteniment de la vida del Planeta