Consulta: creatorFacets:"Obernosterer, Ingrid"
Registros recuperados: 14
Data/hora: 14/06/2024 16:17:02

Enhanced heterotrophic activity in the surface microlayer of the Mediterranean Sea
Provedor de dados: 5
Autores: Obernosterer, Ingrid; Catala, Philippe; Reinthaler, Thomas; Herndl, Gerhard J.; Lebaron, Philippe.
The abundance and activity of heterotrophic and autotrophic organisms were determined in the surface microlayer (SML) at marine and estuarine sites in the NW Mediterranean Sea from May to July 2003. At all study sites, community respiration in the SML exceeded that in the subsurface water (SSW) by factors between 1.7 and 28. The abundance of heterotrophic bacteria and the major groups of the autotrophic community displayed consistent, but low enrichment factors (EF) for the SML (mean 1.3). In contrast, EF for the abundance of heterotrophic nanoflagellates and the concentration of particulate organic carbon were, on average, 4 and 7, respectively. Community respiration rates in the SML were related to the concentration of total organic carbon; however, no...
Tipo: Text
Palavras-chave: Surface microlayer; Community respiration; Net community production; Neuston.
Ano: 2005
URL: https://archimer.ifremer.fr/doc/00243/35435/33960.pdf

Shifts in bacterial community composition associated with increased carbon cycling in a mosaic of phytoplankton blooms
Provedor de dados: 5
Autores: Landa, Marine; Blain, Stephane; Christaki, Urania; Monchy, Sebastien; Obernosterer, Ingrid.
Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify...
Tipo: Text
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00421/53293/54115.pdf

A two-component parameterization of marine ice-nucleating particles based on seawater biology and sea spray aerosol measurements in the Mediterranean Sea
Provedor de dados: 5
Autores: Trueblood, Jonathan, V; Nicosia, Alessia; Engel, Anja; Zancker, Birthe; Rinaldi, Matteo; Freney, Evelyn; Thyssen, Melilotus; Obernosterer, Ingrid; Dinasquet, Julie; Belosi, Franco; Tovar-sanchez, Antonio; Rodriguez-romero, Araceli; Santachiara, Gianni; Guieu, Cecile; Sellegri, Karine.
Ice-nucleating particles (INPs) have a large impact on the climate-relevant properties of clouds over the oceans. Studies have shown that sea spray aerosols (SSAs), produced upon bursting of bubbles at the ocean surface, can be an important source of marine INPs, particularly during periods of enhanced biological productivity. Recent mesocosm experiments using natural seawater spiked with nutrients have revealed that marine INPs are derived from two separate classes of organic matter in SSAs. Despite this finding, existing parameterizations for marine INP abundance are based solely on single variables such as SSA organic carbon (OC) or SSA surface area, which may mask specific trends in the separate classes of INP. The goal of this paper is to improve the...
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00688/79985/82974.pdf

Seasonal dynamics of active SAR11 ecotypes in the oligotrophic Northwest Mediterranean Sea
Provedor de dados: 5
Autores: Salter, Ian; Galand, Pierre E.; Fagervold, Sonja K.; Lebaron, Philippe; Obernosterer, Ingrid; Oliver, Matthew J.; Suzuki, Marcelino T.; Tricoire, Cyrielle.
A seven-year oceanographic time series in NW Mediterranean surface waters was combined with pyrosequencing of ribosomal RNA (16S rRNA) and ribosomal RNA gene copies (16S rDNA) to examine the environmental controls on SAR11 ecotype dynamics and potential activity. SAR11 diversity exhibited pronounced seasonal cycles remarkably similar to total bacterial diversity. The timing of diversity maxima was similar across narrow and broad phylogenetic clades and strongly associated with deep winter mixing. Diversity minima were associated with periods of stratification that were low in nutrients and phytoplankton biomass and characterised by intense phosphate limitation (turnover timeo5 h). We propose a conceptual framework in which physical mixing of the water...
Tipo: Text
Ano: 2015
URL: https://archimer.ifremer.fr/doc/00374/48560/48969.pdf

The Role of the Glyoxylate Shunt in the Acclimation to Iron Limitation in Marine Heterotrophic Bacteria
Provedor de dados: 5
Autores: Koedooder, Coco; Gueneugues, Audrey; Van Geersdaele, Remy; Verge, Valerie; Bouget, Francois-yves; Labreuche, Yannick; Obernosterer, Ingrid; Blain, Stephane.
Iron (Fe) is an essential element for marine microbial growth but is present in trace amounts (&lt;0.1 nM) in surface waters of the ocean. In heterotrophic bacteria, Fe-limitation particularly impacts ATP production as Fe is an essential co-factor of enzymes involved in the electron-transport chain as well as the tricarboxylic acid (TCA) cycle. Fe-limitation can therefore drastically reduce both bacterial growth and respiration, consequently affecting the efficiency of organic carbon remineralization. Heterotrophic bacteria possess various strategies to cope with Fe-limitation. In the present study we tested the hypothesis that the induction of the glyoxylate shunt can represent one such strategy. Genetic approaches were used to gain insight into the...
Tipo: Text
Palavras-chave: Iron; Fe-limitation; Photobacterium angustum S14; Glyoxylate shunt; Isocitrate lyase.
Ano: 2018
URL: https://archimer.ifremer.fr/doc/00468/58017/60413.pdf

Seasonal microbial food web dynamics in contrasting Southern Ocean productivity regimes
Provedor de dados: 5
Autores: Christaki, Urania; Gueneugues, Audrey; Liu, Yan; Blain, Stéphane; Catala, Philippe; Colombet, Jonathan; Debeljak, Pavla; Jardillier, Ludwig; Irion, Solène; Planchon, Frederic; Sassenhagen, Ingrid; Sime Ngando, Telesphore; Obernosterer, Ingrid.
Spatial and seasonal dynamics of microbial loop fluxes were investigated in contrasting productivity regimes in the Indian sector of the Southern Ocean. Observations carried out in late summer (February–March 2018; project MOBYDICK) revealed higher microbial biomasses and fluxes in the naturally iron‐fertilized surface waters of Kerguelen island in comparison to surrounding off‐plateau waters. Differences were most pronounced for bacterial heterotrophic production (2.3‐fold), the abundance of heterotrophic nanoflagellates (HNF; 2.7‐fold). Independent of site, grazing by HNF was the main loss process of bacterial production (80–100%), while virus‐induced mortality was low (&lt; 9%). Combining these results with observations from previous investigations...
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00649/76109/77064.pdf

Microbial iron and carbon metabolism as revealed by taxonomy-specific functional diversity in the Southern Ocean
Provedor de dados: 5
Autores: Sun, Ying; Debeljak, Pavla; Obernosterer, Ingrid.
Marine microbes are major drivers of all elemental cycles. The processing of organic carbon by heterotrophic prokaryotes is tightly coupled to the availability of the trace element iron in large regions of the Southern Ocean. However, the functional diversity in iron and carbon metabolism within diverse communities remains a major unresolved issue. Using novel Southern Ocean meta-omics resources including 133 metagenome-assembled genomes (MAGs), we show a mosaic of taxonomy-specific ecological strategies in naturally iron-fertilized and high nutrient low chlorophyll (HNLC) waters. Taxonomic profiling revealed apparent community shifts across contrasting nutrient regimes. Community-level and genome-resolved metatranscriptomics evidenced a moderate...
Tipo: Text
Palavras-chave: Metagenomics; Microbial biooceanography; Microbial ecology.
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00693/80483/83626.pdf

Composition of diatom communities and their contribution to plankton biomass in the naturally iron fertilized region of Kerguelen in the Southern Ocean
Provedor de dados: 5
Autores: Lasbleiz, Marine; Leblanc, Karine; Armand, Leanne K.; Christaki, Urania; Georges, Clement; Obernosterer, Ingrid; Queguiner, Bernard.
In the naturally iron-fertilized surface waters of the northern Kerguelen Plateau region, the early spring diatom community composition and contribution to plankton carbon biomass were investigated and compared with the High Nutrient Low Chlorophyll (HNLC) surrounding waters. The large iron-induced blooms were dominated by small diatom species belonging to the genera Chaetoceros (Hyalochaete) and Thalassiosira, which rapidly responded to the onset of favorable light-conditions in the meander of the Polar Front. In comparison, the iron-limited HNLC area was typically characterized by autotrophic nanoeukaryote-dominated communities and by larger and more heavily silicified diatom species (e.g. Fragilariopsis spp.). Our results support the hypothesis that...
Tipo: Text
Palavras-chave: Diatoms; Carbon biomass; Plankton community structure; Natural iron fertilization; Southern Ocean.
Ano: 2016
URL: https://archimer.ifremer.fr/doc/00347/45850/45512.pdf

A method for the use of the radiotracer 55Fe for microautoradiography and CARD-FISH of natural bacterial communities
Provedor de dados: 5
Autores: Fourquez, Marion; Obernosterer, Ingrid; Blain, Stephane.
Heterotrophic bacteria are key players in the biogeochemical cycle of iron (Fe) in the ocean, but the capability of different bacterial groups to access this micronutrient is ignored thus far. The aim of our study was to develop a protocol for the combined application of microautoradiography (MICRO) and catalyzed reporter depositionfluorescence in situ hybridization (CARD-FISH) using the radioisotope 55Fe. Among the different washing solutions tested, Ti-citrate-EDTA was the most efficient for the removal of extracellular 55Fe providing sufficiently low background values. We further demonstrate that the washing of cells with Ti-citrate-EDTA and the fixation with paraformaldehyde or formaldehyde do not induce leakage of intracellular 55Fe. Incubating...
Tipo: Text
Palavras-chave: Microautoradiography; 55Fe; CARD-FISH; Marine bacteria.
Ano: 2012
URL: https://archimer.ifremer.fr/doc/00143/25403/23555.pdf

Microbial iron metabolism as revealed by gene expression profiles in contrasted Southern Ocean regimes
Provedor de dados: 5
Autores: Debeljak, Pavla; Toulza, Eve; Beier, Sara; Blain, Stephane; Obernosterer, Ingrid.
Iron (Fe) is a limiting nutrient in large regions of the ocean, but the strategies of prokaryotes to cope with this micronutrient are poorly known. Using a gene‐specific approach from metatranscriptomics data, we investigated 7 Fe‐related metabolic pathways in microbial communities from High Nutrient Low Chlorophyll and naturally Fe‐fertilized waters in the Southern Ocean. We observed major differences in the contribution of prokaryotic groups at different taxonomic levels to transcripts encoding Fe uptake‐mechanisms, intracellular Fe storage and replacement, and Fe‐related pathways in the tricarboxylic acid (TCA) cycle. The composition of the prokaryotic communities contributing to the transcripts of a given Fe‐related pathway was overall independent of...
Tipo: Text
Ano: 2019
URL: https://archimer.ifremer.fr/doc/00488/59921/63113.eps

Impact of dust enrichment on Mediterranean plankton communities under present and future conditions of pH and temperature: an experimental overview
Provedor de dados: 5
Autores: Gazeau, Frédéric; Ridame, Céline; Van Wambeke, France; Alliouane, Samir; Stolpe, Christian; Irisson, Jean-olivier; Marro, Sophie; Grisoni, Jean-michel; De Liège, Guillaume; Nunige, Sandra; Djaoudi, Kahina; Pulido-villena, Elvira; Dinasquet, Julie; Obernosterer, Ingrid; Catala, Philippe; Guieu, Cécile.
In Low Nutrient Low Chlorophyll areas, such as the Mediterranean Sea, atmospheric fluxes represent a considerable external source of nutrients likely supporting primary production especially during stratification periods. These areas are expected to expand in the future due to lower nutrient supply from sub-surface waters caused by enhanced stratification, likely further increasing the role of atmospheric deposition as a source of new nutrients to surface waters. Yet, whether plankton communities will react differently to dust deposition in a warmer and acidified environment remains an open question. The impact of dust deposition both in present and future climate conditions was assessed through three perturbation experiments in the open Mediterranean Sea....
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00688/80015/82994.pdf

Distinct bacterial groups contribute to carbon cycling during a naturally iron fertilized phytoplankton bloom in the Southern Ocean
Provedor de dados: 5
Autores: Obernosterer, Ingrid; Catala, Philippe; Lebaron, Philippe; West, Nyree J.
We investigated the contribution of distinct bacterial groups to bulk abundance and leucine incorporation during a spring phytoplankton bloom induced by natural iron fertilization in the Southern Ocean (Kerguelen Ocean and Plateau Compared Study, January-February 2005). Oligonucleotide probes were designed to target five operational taxonomic units (OTUs) at a narrow phylogenetic level (&gt;= 99% identity of the 16S ribosomal ribonucleic acid [rRNA] gene). During the peak of the phytoplankton bloom, the Roseobacter groups NAC11-7 and RCA, the OTUs SAR92 belonging to Gammaproteobacteria, and the Bacteroidetes OTU Agg58 dominated bulk abundance and leucine incorporation. These four OTUs disappeared with the decline of the bloom, when the cosmopolitan groups...
Tipo: Text
Ano: 2011
URL: https://archimer.ifremer.fr/doc/00214/32503/30995.pdf

Mediterranean nascent sea spray organic aerosol and relationships with seawater biogeochemistry
Provedor de dados: 5
Autores: Freney, Evelyn; Sellegri, Karine; Nicosia, Alessia; Trueblood, Jonathan T; Rinaldi, Matteo; Williams, Leah R; Prévôt, André Sh; Thyssen, Melilotus; Gregori, Gerald; Haëntjens, Nils; Dinasquet, Julie; Obernosterer, Ingrid; Van Wambeke, France; Engel, Anja; Zancker, Birthe; Desboeufs, Karine; Asmi, Eija; Timmonen, Hilka; Guieu, Cécile.
The organic mass fraction from sea spray aerosol (SSA) is currently a subject of intense research. The majority of this research is dedicated to measurements in ambient air, although recently a small number of studies have additionally focused on nascent sea spray aerosol. This work presents measurements collected during a five-week cruise in May and June 2017 in the central and western Mediterranean Sea, an oligotrophic marine region with low phytoplankton biomass. Surface seawater was continuously pumped into a bubble bursting apparatus to generate nascent sea spray aerosol. Size distributions were measured with a differential mobility particle sizer (DMPS). Chemical characterization of the submicron aerosol was performed with a time of flight aerosol...
Tipo: Text
Ano: 2021
URL: https://archimer.ifremer.fr/doc/00688/80017/82995.pdf

Microbial community structure in the sea surface microlayer at two contrasting coastal sites in the northwestern Mediterranean Sea
Provedor de dados: 5
Autores: Joux, Fabien; Agogue, Helene; Obernosterer, Ingrid; Dupuy, Christine; Reinthaler, Thomas; Herndl, Gerhard J.; Lebaron, Philippe.
In an attempt to compare the microbial community structure between the sea surface microlayer (SML) and subsurface waters (SSW), we determined the enrichment factors (EF: the ratio of abundance or activity in the SML to abundance or activity in SSW) of 13 biological parameters. Samples were taken at 2 contrasting coastal sites in the Mediterranean Sea, corresponding to a high (Barcelona, Spain) and low (Banyuls-sur-Mer, France) urbanized area. Principal component analysis showed that temporal variability was much higher at Barcelona than at Banyuls, and that the characteristics of the SML and SSW samples were more closely related at Barcelona. At both sites, the SML was weakly enriched in heterotrophic bacteria (on average 1.1-fold), Synechococcus spp. (on...
Tipo: Text
Palavras-chave: Sea surface microlayer; Enrichment factor; Microbial structure; Virus-like particles; Bacteria; Microalgae; Nanoflagellates.
Ano: 2006
URL: https://archimer.ifremer.fr/doc/00243/35434/33961.pdf