10 results on '"Montserrat Aldunate"'
Search Results
2. Do phytoplankton require oxygen to survive? A hypothesis and model synthesis from oxygen minimum zones
- Author
-
Jane C. Y. Wong, John A. Raven, Montserrat Aldunate, Sebastián Silva, Juan Diego Gaitán‐Espitia, Cristian A. Vargas, Osvaldo Ulloa, and Peter von Dassow
- Subjects
Aquatic Science ,Oceanography - Abstract
It is commonly known that phytoplankton have a pivotal role in marine biogeochemistry and ecosystems as carbon fixers and oxygen producers, but their response to deoxygenation has scarcely been studied. Nonetheless, in the major oceanic oxygen minimum zones (OMZs), all surface phytoplankton groups, regardless of size, disappear and are replaced by unique cyanobacteria lineages below the oxycline. To develop reasonable hypotheses to explain this pattern, we conduct a review of available information on OMZ phytoplankton, and we re-analyze previously published data (flow cytometric and hydrographic) on vertical structure of phytoplankton communities in relation to light and O-2 levels. We also review the physical constraints on O-2 acquisition as well as O-2-dependent metabolisms in phototrophs. These considerations, along with estimates of the photosynthetic capacity of phytoplankton along OMZ depth profiles using published data, suggest that top-down grazing, respiratory demand, and irradiance are insufficient to fully explain the vertical structure observed in the upper, more sunlit portions of OMZs. Photorespiration and water-water cycles are O-2-dependent pathways with low O-2 affinities. Although their metabolic roles are still poorly understood, a hypothetical dependence on such pathways by the phytoplankton adapted to the oxic ocean might explain vertical patterns in OMZs and results of laboratory experiments. This can be represented in a simple model in which the requirement for photorespiration in surface phytoplankton and O-2-inhibition of OMZ lineages reproduces the observed vertical fluorescence profiles and the replacement of phytoplankton adapted to O-2 by lineages restricted to the most O-2-deficient waters. A high O-2 requirement by modern phytoplankton would suggest a positive feedback that intensifies trends in OMZ extent and ocean oxygenation or deoxygenation, both in Earth's past and in response to current climate change.
- Published
- 2023
3. Carbon Assimilation by the Picoplanktonic Community Inhabiting the Secondary Chlorophyll Maximum of the Anoxic Marine Zones of the Eastern Tropical North and South Pacific
- Author
-
Osvaldo Ulloa, Cristian A. Vargas, Peter Von Dassow, and Montserrat Aldunate
- Subjects
Global and Planetary Change ,Ocean Engineering ,Aquatic Science ,Oceanography ,Water Science and Technology - Abstract
Anoxic marine zones (AMZs) constitute pelagic systems distinguished from the oxygen minimum zones (OMZs) by the complete absence of detectable oxygen and the accumulation of nitrite in mid-waters. At the top of the oxygen-depleted layer and below the oxycline, nutrients are abundant; light intensity is very much reduced (13CPOC in the top of the oxygen-depleted layer. This data showed significant differences among stations with and without the development of a SCM, being 3.0‰ heavier when a SCM is developed, and indicating photosynthetic activity and/or remineralization in the top of the AMZ. More depleted δ13CPOC values were also found when no SCM was present indicating stronger chemoautotrophic activity, potentially driven by anammox and sulfur-oxidizing bacteria activity. Assimilation rate data show that when sufficient light and Prochlorococcus are present, photosynthesis exceeds chemoautotrophic carbon fixation, and can exceed heterotrophic assimilation of glucose or acetate. However, in the majority of the stations, assimilation rates of both glucose and acetate exceeded carbon fixation rates under light stimulation, suggesting that often the SCM is still a net heterotrophic system.
- Published
- 2022
- Full Text
- View/download PDF
4. High genetic diversity in the pelagic deep-sea fauna of the Atacama Trench revealed by environmental DNA
- Author
-
Salvador Ramírez-Flandes, Carolina E. González, Montserrat Aldunate, Julie Poulain, Patrick Wincker, Ronnie N. Glud, Rubén Escribano, Sophie Arnaud Haond, and Osvaldo Ulloa
- Abstract
A current paradigm in marine biodiversity states that faunal richness decreases with depth. However, the deep-ocean ecosystem has been significantly under-sampled, hindering a complete view of its biodiversity. This situation is accentuated in ultra-deep waters, where the remote and extreme conditions unfit the traditional sampling methods. Using environmental DNA, we assessed the pelagic metazoan diversity of the Atacama Trench from the high-productive near-surface level down to ~8000 m depth. Our results show that waters deeper than 4000 m contributed up to 50% of the overall genetic diversity. These findings contrast with similar observations in the less-productive Kermadec Trench, where the diversity in deep waters was lower than in shallower waters. Moreover, both deep pelagic ecosystems exhibited some unknown phylogenetic clades within the dominant taxonomic groups: hydrozoans and copepods. The deep-ocean biota may thus contribute to global biodiversity far more than hitherto suggested, especially in zones influenced by high primary production. Our results underline the need for increased effort to study these remote ecosystems and improve our understanding of their contribution to the ecology and biogeochemistry of the deep-sea pelagic and benthic realms.
- Published
- 2022
5. Physical-chemical factors influencing the vertical distribution of phototrophic pico-nanoplankton in the Oxygen Minimum Zone (OMZ) off Northern Chile: The relative influence of low pH/low O
- Author
-
Edson, Piscoya, Peter, von Dassow, Montserrat, Aldunate, and Cristian A, Vargas
- Subjects
Oxygen ,Seawater ,Chile ,Hydrogen-Ion Concentration ,Ecosystem - Abstract
The vertical distribution of phytoplankton is of fundamental importance in the structure, dynamic, and biogeochemical pathways in marine ecosystems. Nevertheless, what are the main factors determining this distribution remains as an open question. Here, we evaluated the relative influence of environmental factors that might control the coexistence and vertical distribution of pico-nanoplankton associated with the OMZ off northern Chile. Our results showed that in the upper layer Synechococcus-like cells were numerically important at all sampling stations. Pico-nano eukaryotes and phototrophic nanoflagellates (PNF) also showed high abundances in the upper layer decreasing in abundance down to the upper oxycline, while only Prochlorococcus showed high abundances under oxycline and within the oxygen-depleted layer. Statistical analyses evidenced that temperature, oxygen, and carbonate chemistry parameters (pH and dissolved inorganic carbon, DIC) influenced significantly the vertical distribution of phototrophic pico-nanoplankton. Additionally, we experimentally-evaluated the combined effect of low pH/low O
- Published
- 2022
6. Genome-resolved viral ecology in a marine oxygen minimum zone
- Author
-
Ahmed A. Zayed, Margaret R. Mulholland, Christine L. Sun, Montserrat Aldunate, Matthew B. Sullivan, Maria Consuelo Gazitúa, Dean R. Vik, and Osvaldo Ulloa
- Subjects
0303 health sciences ,Community ,030306 microbiology ,Ecology ,viruses ,Ecology (disciplines) ,Microbiota ,Community structure ,Biology ,Oxygen minimum zone ,Microbiology ,Genome ,Anoxic waters ,Oxygen ,03 medical and health sciences ,Viruses ,Metagenome ,Alpha diversity ,Seawater ,Nitrogen cycle ,Ecology, Evolution, Behavior and Systematics ,030304 developmental biology - Abstract
Oxygen minimum zones (OMZs) are critical to marine nitrogen cycling and global climate change. While OMZ microbial communities are relatively well-studied, little is known about their viruses. Here, we assess the viral community ecology of 22 deeply sequenced viral metagenomes along a gradient of oxygenated to anoxic waters (
- Published
- 2020
7. Oxygen modulates bacterial community composition in the coastal upwelling waters off central Chile
- Author
-
Rodrigo De la Iglesia, Montserrat Aldunate, Anthony D. Bertagnolli, and Osvaldo Ulloa
- Subjects
0301 basic medicine ,Desulfobacterales ,biology ,Bacterioplankton ,Oceanography ,Oxygen minimum zone ,biology.organism_classification ,Salinity ,03 medical and health sciences ,chemistry.chemical_compound ,Terminal restriction fragment length polymorphism ,030104 developmental biology ,Water column ,chemistry ,Dissimilatory sulfate reduction ,Environmental chemistry ,Sulfate - Abstract
Bacterial community composition and its relationship to oxygen were investigated in the non-sulfidic shelf waters exposed to seasonal upwelling and oxygen deficiency off central Chile. Using 16S rRNA gene clone libraries, terminal restriction fragment length polymorphism (T-RFLP) and iTAG sequencing analyses of nearly 4 years of monthly sampling through the water column (5–80 m depth), we found a clear partitioning of community composition that could be attributed to dissolved oxygen (Spearman correlation coefficient = 0.578) in comparison to other environmental variables, such as light, fluorescence, temperature, salinity, microbial abundance or nutrients. Bacteroidetes (orders Sphingobacteriales and Flavobacteriales), SAR11 (subclades Ia - Candidatus Pelagibacter ubique and II), an unclassified group of Alphaproteobacteria, and SAR86 dominated in waters containing dissolved oxygen concentrations ≥70 μM. In contrast, taxonomic groups associated with capabilities of either oxidative or reductive cycling of inorganic sulfur dominated in waters with dissolved oxygen from ~70 μM to undetectable levels. The dominant groups were Arctic96BD-19, SUP05 and SAR324 (sulfur oxidation) and Desulfobacterales (sulfate reduction). Desulfobacterales are known to come primarily from sulfidic, nitrate/nitrite-depleted waters and sediments. Their presence, therefore, provides taxonomic evidence for pelagic dissimilatory sulfate reduction within oxygen-depleted coastal environments.
- Published
- 2018
8. Nitrogen assimilation in picocyanobacteria inhabiting the oxygen‐deficient waters of the eastern tropical North and South Pacific
- Author
-
Margaret R. Mulholland, Qixing Ji, Bess B. Ward, Jessica A. Lueders-Dumont, Peter von Dassow, Carlos Henríquez-Castillo, Montserrat Aldunate, Osvaldo Ulloa, Universidad de Concepción [Chile], Princeton University, Old Dominion University [Norfolk] (ODU), Evolutionary Biology and Ecology of Algae (EBEA), Pontificia Universidad Católica de Chile (UC)-Sorbonne Université (SU)-Universidad Austral de Chile-Centre National de la Recherche Scientifique (CNRS)-Station biologique de Roscoff (SBR), and Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
0303 health sciences ,Oxygen deficient ,030306 microbiology ,Ecology ,Chemistry ,Nitrogen assimilation ,Aquatic Science ,Oceanography ,[SDV.MP.BAC]Life Sciences [q-bio]/Microbiology and Parasitology/Bacteriology ,03 medical and health sciences ,13. Climate action ,14. Life underwater ,[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography ,030304 developmental biology - Abstract
Prochlorococcus and Synechococcus are the most abundant free-living photosynthetic microorganisms in the ocean. Uncultivated lineages of these picocyanobacteria also thrive in the dimly illuminated upper part of oxygen-deficient zones (ODZs), where an important portion of ocean nitrogen (N) loss takes place via denitrification and anaerobic ammonium oxidation. Recent metagenomic studies revealed that ODZ Prochlorococcus have the genetic potential for using different N forms, including nitrate and nitrite, uncommon N sources for Prochlorococcus, but common for Synechococcus. To determine which N sources ODZ picocyanobacteria are actually using in nature, the cellular N-15 natural abundance (delta N-15) and assimilation rates of different N compounds were determined using cell sorting by flow cytometry and mass spectrometry. The natural delta N-15 of the ODZ Prochlorococcus varied from -4.0 parts per thousand to 13.0 parts per thousand (n = 9), with 50% of the values in the range of -2.1-2.6 parts per thousand. While the highest values suggest nitrate use, most observations indicate the use of nitrite, ammonium, or a mixture of N sources. Meanwhile, incubation experiments revealed potential assimilation rates of ammonium and urea in the same order of magnitude as that expected for total N in several environments including ODZs, whereas rates of nitrite and nitrate assimilation were very low. Our results thus indicate that reduced forms of N and nitrite are the dominant sources for ODZ picocyanobacteria, although nitrate might be important on some occasions. ODZ picocyanobacteria might thus represent potential competitors with anammox bacteria for ammonium and nitrite, with ammonia-oxidizing archaea for ammonium, and with nitrite-oxidizing bacteria for nitrite.
- Published
- 2019
9. Single cell genomic and transcriptomic evidence for the use of alternative nitrogen substrates by anammox bacteria
- Author
-
Cory C. Padilla, Rex R. Malmstrom, Konstantinos T. Konstantinidis, Annie Bourbonnais, Montserrat Aldunate, Tanja Woyke, Mark A. Altabet, Laura A. Bristow, Nigel Blackwood, Anthony D. Bertagnolli, Osvaldo Ulloa, Sangita Ganesh, Bo Thamdrup, and Frank J. Stewart
- Subjects
Carbon-Nitrogen Lyases/genetics ,0301 basic medicine ,Technology ,Nitrogen ,Oceans and Seas ,030106 microbiology ,Microbial metabolism ,Bacteria/genetics ,Urease/genetics ,Cyanase ,Microbiology ,Article ,03 medical and health sciences ,chemistry.chemical_compound ,Ammonium Compounds ,Carbon-Nitrogen Lyases ,Nitrogen/metabolism ,Seawater/microbiology ,Genetics ,Ammonium ,Seawater ,14. Life underwater ,Anaerobiosis ,Nitrogen cycle ,Life Below Water ,Ecology, Evolution, Behavior and Systematics ,biology ,Bacteria ,Gene Expression Profiling ,Human Genome ,Genomics ,Biological Sciences ,biology.organism_classification ,Anoxic waters ,Urease ,6. Clean water ,Ammonium Compounds/metabolism ,030104 developmental biology ,Biochemistry ,chemistry ,13. Climate action ,Anammox ,Scalindua ,Single-Cell Analysis ,Oxidation-Reduction ,Environmental Sciences - Abstract
© 2018, International Society for Microbial Ecology. Anaerobic ammonium oxidation (anammox) contributes substantially to ocean nitrogen loss, particularly in anoxic marine zones (AMZs). Ammonium is scarce in AMZs, raising the hypothesis that organic nitrogen compounds may be ammonium sources for anammox. Biochemical measurements suggest that the organic compounds urea and cyanate can support anammox in AMZs. However, it is unclear if anammox bacteria degrade these compounds to ammonium themselves, or rely on other organisms for this process. Genes for urea degradation have not been found in anammox bacteria, and genomic evidence for cyanate use for anammox is limited to a cyanase gene recovered from the sediment bacterium Candidatus Scalindua profunda. Here, analysis of Ca. Scalindua single amplified genomes from the Eastern Tropical North Pacific AMZ revealed genes for urea degradation and transport, as well as for cyanate degradation. Urease and cyanase genes were transcribed, along with anammox genes, in the AMZ core where anammox rates peaked. Homologs of these genes were also detected in meta-omic datasets from major AMZs in the Eastern Tropical South Pacific and Arabian Sea. These results suggest that anammox bacteria from different ocean regions can directly access organic nitrogen substrates. Future studies should assess if and under what environmental conditions these substrates contribute to the ammonium budget for anammox.
- Published
- 2018
10. Cryptic oxygen cycling in anoxic marine zones
- Author
-
Gérald Grégori, Emilio Garcia-Robledo, Osvaldo Ulloa, Aurélien Paulmier, Cory C. Padilla, Frank J. Stewart, Montserrat Aldunate, Niels Peter Revsbech, Aarhus University [Aarhus], Georgia Institute of Technology [Atlanta], Universidad de Concepción [Chile], Centro de Investigación Oceanográfica en el Pacífico Sur Oriental (COPAS), Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Institut méditerranéen d'océanologie (MIO), Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Université de Toulon (UTLN)-Centre National de la Recherche Scientifique (CNRS), Universidad de Concepción - University of Concepcion [Chile], Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), and Institut de Recherche pour le Développement (IRD)-Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Toulon (UTLN)
- Subjects
Chlorophyll ,0301 basic medicine ,Aquatic Organisms ,Biogeochemical cycle ,Denitrification ,Nitrogen ,Oceans and Seas ,Photosynthesis ,Global Warming ,Carbon Cycle ,03 medical and health sciences ,oxygen minimum zone ,Peru ,secondary chlorophyll maximum ,Anaerobiosis ,Mexico ,[SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography ,Prochlorococcus ,Multidisciplinary ,metatranscriptomics ,biology ,Ecology ,Microbiota ,Carbon fixation ,aerobic metabolism ,Biological Sciences ,biology.organism_classification ,Nitrification ,Anoxic waters ,Oxygen ,030104 developmental biology ,Anaerobic exercise - Abstract
Oxygen availability drives changes in microbial diversity and biogeochemical cycling between the aerobic surface layer and the anaerobic core in nitrite-rich anoxic marine zones (AMZs), which constitute huge oxygen-depleted regions in the tropical oceans. The current paradigm is that primary production and nitrification within the oxic surface layer fuel anaerobic processes in the anoxic core of AMZs, where 30–50% of global marine nitrogen loss takes place. Here we demonstrate that oxygenic photosynthesis in the secondary chlorophyll maximum (SCM) releases significant amounts of O2 to the otherwise anoxic environment. The SCM, commonly found within AMZs, was dominated by the picocyanobacteria Prochlorococcus spp. Free O2 levels in this layer were, however, undetectable by conventional techniques, reflecting a tight coupling between O2 production and consumption by aerobic processes under apparent anoxic conditions. Transcrip-tomic analysis of the microbial community in the seemingly anoxic SCM revealed the enhanced expression of genes for aerobic processes, such as nitrite oxidation. The rates of gross O2 production and carbon fixation in the SCM were found to be similar to those reported for nitrite oxidation, as well as for anaerobic dissimilatory nitrate reduction and sulfate reduction, suggesting a significant effect of local oxygenic photosynthesis on Pacific AMZ biogeochemical cycling.
- Published
- 2017
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.