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Impact of interactions between microorganisms on iron and carbon recycling in the Southern Ocean : consequences for iron limitation

Titel Englisch Impact of interactions between microorganisms on iron and carbon recycling in the Southern Ocean : consequences for iron limitation
Gesuchsteller/in Hassler Christel
Nummer 166197
Förderungsinstrument SNF-Förderungsprofessuren
Forschungseinrichtung Institut F.-A. Forel Université de Genève
Hochschule Universität Genf - GE
Hauptdisziplin Ozeanographie
Beginn/Ende 01.01.2017 - 31.12.2018
Bewilligter Betrag 804'745.00
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Alle Disziplinen (3)

Disziplin
Ozeanographie
Umweltforschung
Biochemie

Keywords (8)

iron limitation; DOC; bacteria; Southern Ocean; phytoplankton; recycling; EPS; bioavailability

Lay Summary (Französisch)

Lead
La pompe à carbone dans l'océan austral
Lay summary
L’océan austral joue un rôle critique pour le cycle global du carbone et donc pour la régulation du climat. Néanmoins, dans cette région, le cycle du carbone est largement influencé par le fer – un élément nutritif limitant. Afin de mieux comprendre comment la matière organique contrôle la biogéochimie du fer, nous allons concentrer puis caractériser cette matière organique dans des zones contrastées. Ce projet propose également de revisiter le rôle des bactéries et des virus sur les transformations, le recyclage et l’export d’éléments clefs tels le carbone et le fer. Dans un premier temps, la biodiversité bactérienne et virale sera mesurée lors de deux campagnes océanographiques, constituant ainsi les premières données sur les virus autour du Pôle Sud. Nous isolerons et ramènerons des souches bactériennes et virales afin de les étudier plus avant en laboratoire et explorer les interactions entre bactéries, matière organique, fer et virus. Ces souches seront également partagées librement dans le but de stimuler la recherche Antarctique, générant ainsi des avancées en dehors du domaine de l’environnement.
Direktlink auf Lay Summary Letzte Aktualisierung: 23.03.2017

Lay Summary (Englisch)

Lead
The carbon pump in the Southern Ocean
Lay summary

Processes occurring in the Southern Ocean are paramount for Earth's climate. This projects aims to improve our understanding of the functioning of the Southern Ocean and its role in the regulation of our climate. Here we are centered on two pivotal regulators: iron chemistry and dissolved organic carbon, both of with are controlling how microorganisms affect our climate. Here we will simultaneously study the biochemistry of iron, organic carbon and its role for microorganisms’ (phytoplankton, bacteria and viruses) mediated carbon pumps. This will be achieved by combining experiments at sea and in the laboratory. Here, we will isolate and characterize organic carbon present in iron-limited and iron replete regions chosen to represent the biochemical variability encountered across the Southern Ocean. We will characterize these compounds in order to understand their nature and role in iron chemistry and microorganisms activity. An extensive and unique analytical matrix is proposed to resolve key properties and functional groups in organic compounds as well as its iron binding properties, likely identifying, for the first time, the “dark matter” constituting these compounds involved in Fe binding as well as binding mechanism. This project also explores a novel research area: the role of viruses in the degradation of marine organic carbon and its impact for both the biological and the microbial pumps. Major breakthrough in the field of marine biogeochemistry is thus expected as well as solid contributions to international research programs. Being related to climate, ecosystem functioning and biodiversity, this project benefits to the scientific community at large.

Direktlink auf Lay Summary Letzte Aktualisierung: 23.03.2017

Verantw. Gesuchsteller/in und weitere Gesuchstellende

Mitarbeitende

Verbundene Projekte

Nummer Titel Start Förderungsinstrument
138955 Novel technologies to reveal the impacts of nutrient limitation in aquatic systems: from biodiversity to biogeochemical cycles 01.01.2013 SNF-Förderungsprofessuren

Abstract

The Southern Ocean (SO) plays a critical role on atmospheric CO2 sink mediated by the physical, biological and microbial pumps and thus affects our climate. The SO is the largest oceanic iron-limited region, and unsurprisingly it has been extensively studied. However, how iron limitation takes places and its consequences for the efficiency of the biological carbon pump mediated by phytoplankton remain mostly unresolved. The lack of understanding of the link between iron chemistry and its bioavailability as well as the key drivers and processes at play, significantly prevents advances in this research area. Because iron is mostly associated with organic ligands and limits the growth of phytoplankton in most of the SO, the biogeochemistry of Fe and carbon are closely inter-related. Moreover, the labile dissolved organic compounds excreted by phytoplankton are rapidly consumed by heterotrophic bacteria to fuel carbon export mediated by the microbial carbon pump. It is thus evident that both carbon pumps are inter-related with the production and recycling of organic carbon and bioavailable Fe acting as critical connectors in the SO. However, the link between these pumps is mostly conceptual and controlling mechanisms remain unknown. As this connection is critical for the functioning of this ecosystem including its footprint on our climate, it is urgent to learn how these pumps are connected and controlled.This project addresses specific aspects related to this major gap of knowledge by investigating pathways involved in the production/recycling of carbon and iron in surface water. This will be achieved by combining experiments at sea and in the laboratory. For this purpose, marine dissolved organic compounds (DOC) from various origins will be isolated and characterized. Here, we will isolate and characterize DOC from iron-limited and iron replete regions chosen to represent the biochemical variability encountered across the SO. Moreover, DOC produced by key biological players from the SO will be isolated and studied; including DOC excreted by bacteria, phytoplankton and grazers. Moreover, DOC sensitivity to photo- and viral degradations - two important transformation pathways - will be quantified. An extensive and unique analytical matrix is proposed to resolve key properties and functional groups in DOC as well as its iron binding properties, likely identifying, for the first time, the “dark matter” constituting DOC compounds involved in Fe binding as well as binding mechanism. The comparison of the various DOC compositions will identify whether a unique chemical traceable signature is associated with specific origin or transformation pathways. The impact on the microbial pump will be inferred from DOC lability whereas the impact on the biological pump will be inferred from iron bioavailability (55Fe bioaccumulation), pigments, photo-physiology and POC analyses.Finally, this project explores a novel research area: the role of viruses in the degradation of marine DOC and its impact for both the biological and the microbial pumps. Marine viruses constitutively bear enzymes that are efficient in passively degrading their hosts carbohydrates in solution, whose impact has never been addressed. Given the high concentration and diversity of viruses in the ocean, and the facts that carbohydrate constitute up to 50 % of marine DOC and can affect iron chemistry, this study might totally revisit the role of viruses in marine biogeochemistry and result in seminal publications. Important collaborative efforts on highly specialised techniques are put at play to solve the complexity of marine DOC and Fe-binding ligands. Major breakthrough in the field of marine biogeochemistry is thus expected as well as solid contributions to international research programs, such as SCOR and GEOTRACES. Being related to climate, ecosystem functioning and biodiversity, this project benefits to the scientific community at large.
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