Tag Archive for: Global change biology

The TONGA mission

David Gonzalez Santana and Géraldine Sarthou from the Chibido team are on board the R/V Atalante in the South Pacific for the TONGA cruise (PIs Sophie Bonnet (MIO) and Cécile Guieu (LOV), + link on the CHIBIDO team website).

The objective of TONGA is to study the inputs of trace elements from shallow hydrothermal sources and their potential impact on biological productivity and the biological carbon pump.

Halfway through the cruise, they are on their way to the ultra-oligotrophic waters (their reference station) after having studied a shallow area (~ 200 m) particularly intense in terms of hydrothermal activity.

Then, the search of a second hydrothermal site is scheduled.

You can follow them on their Twitter account.

(C) Hubert Bataille/ IRD

Links between biogeochemical cycles of metals and living organisms

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Improving our knowledge of the metal cycle in contrasting environments of the world ocean is absolutely necessary for a better understanding of the oceanic biogeochemical cycles of major elements (C, Si, N, S) and the biological carbon pump. LEMAR is internationally recognised in this field, in particular through our strong involvement in the GEOTRACES programme. We combine observations, field or laboratory experiments and modelling. Our originality lies in the combined study of the dissolved and particulate phases, as well as their speciation (redox and organic), in order to better understand the interactions between these two reservoirs, which are fundamental in the metal cycle and yet are still little studied. Our expertise also includes the study of interactions between the metal cycle and plankton, by linking metal speciation to the bioavailability of micronutrients for marine plankton (phytoplankton and bacteria). The integration of omics tools (functional genomics, transcriptomics, etc.) into this theme is currently essential to further investigate the link between biogeochemical cycles of metals and interactions with living organisms. These explorations will continue to be carried out, both during oceanographic missions and in laboratory studies, notably thanks to our numerous international collaborations and our involvement in the future international programme BioGeoSCAPES (‘Ocean metabolism and nutrient cycles on a changing planet’). The strong international momentum of the GEOTRACES programme and the forthcoming BioGeoSCAPES programme now allows us to build and meet the challenge of integrated microbial biogeochemistry projects that require international coordination with a multidisciplinary approach.

Role of complex trophic interactions in biogeochemical cycles

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In the ocean, trophic interactions between individuals are still mainly represented in a predator-prey pattern. However, meta-analyses of taxonomic co-occurrences, made possible by advances in molecular biology, suggest that many planktonic organisms are involved in complex interactions ranging from facultative predation to symbiosis to mutualism. While these relationships appear to be the rule rather than the exception in the ocean, research efforts are focused on a few emblematic examples. In CHIBIDO, we are trying to identify new interactions and are particularly interested in mixotrophic organisms (both phototrophic and phagotrophic), the trophic mode of the majority of dinoflagellates, and in diazotrophs that often live in symbiosis with other organisms. To better understand the role of trophic interactions on biogeochemical cycles (especially nitrogen and carbon), it is necessary to couple tools.

The team is internationally recognised for its expertise in the use of 13 C and 15 N stable isotopes to quantify oceanic fluxes. In recent years, it has coupled this approach with new tools (e.g. nanoSIMS or flow cytometry sorting) that make it possible to visualise and quantify fluxes between the environment and organisms and/or between organisms.

Ecology and physiology of photosynthetic organisms

Context

As a “primary” biomass, phytoplankton and microphytobenthos are widely involved in the functioning of trophic chains, in the dynamics of biogeochemical cycles and ocean-atmosphere exchanges, which makes them an important and transverse subject of study for LEMAR teams. Quantitative and qualitative fluctuations in phytoplankton communities depend on physical, chemical and biological factors in the rapidly changing environment under the pressure of human activities. Knowledge in this field is now limited to the description of some of the “major” phenomena: seasonal fluctuation and succession of species, specific blooms… Studies highlight significant disturbances of these communities under the influence of anthropogenic forcings such as increased land inputs (e.g. trace metals, Fe, Cu, Co), increased atmospheric CO2 and temperature. The spatial and temporal evolution of the phytoplankton and microphytobenthic community resulting from this, such as the development of toxic micro-algae blooms, directly impacts ocean/atmosphere transfers (carbon, trace metals), but also on pelagic and benthic food resources (scallops, oysters, etc.). Phytoplankton composition has a direct impact on the entire ecosystem.

Objectives: In this context, we have identified several objectives common to the 3 LEMAR teams, including:

– study and better characterize the spatial and temporal distribution of phytoplankton and micro-phytobenthic populations

– assess the impact of biotic and abiotic factors on this spatial distribution

– study the biological and physiological responses of these phytoplanktonic and microphytobenthic populations to environmental forcings.

Around these themes, the objective of the transversal axis will therefore be:

(1) to share the knowledge and collaborations acquired individually by LEMAR researchers,

(2) to generate inter-team projects to better respond to the issues raised

(3) to better characterize our needs for advanced equipment and researchers specializing in the physiology and ecology of marine microbial communities.

Animation

Aude LEYNAERT (CNRS), Cécile KLEIN (UBO)

Organization

An effort of animation and training will be made within this transversal axis, in particular through the implementation of several actions.

1- bibliographic seminars: participants will meet regularly to present in a few minutes publications that are significant for the conceptual or technical progress they provide, or for the controversy they may generate.

2- Practical training on the laboratory’s instruments and culture facilities: a special effort will be made to train doctoral students in order to facilitate their autonomy on dedicated equipment.

3- Organisation of external training courses for the acquisition of new techniques and technologies concerning the problems developed.

4- Collective reflection on the needs for experimental and analytical structures (mesocosms, in situ measurements, community analysis, etc.).

5- Consultation and coordination on the purchase, installation and management of common equipment essential for experiments.

Tag Archive for: Global change biology

ADjUST

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Bars (PACIO)

Tag Archive for: Global change biology