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Reference : UMR9190-SANDEV-003
Workplace : MONTPELLIER
Date of publication : Monday, July 19, 2021
Type of Contract : FTC Technical / Administrative
Contract Period : 13 months
Expected date of employment : 1 October 2021
Proportion of work : Full time
Remuneration : between 2460 and 2650 gross monthly according to experience
Desired level of education : PhD
Experience required : 1 to 4 years
Presentation of the scientific theme
The objective of the post-doctoral project will be to study the responses of planktonic food web components to the phenomenon of marine brownification. This phenomenon is the consequence of leaching from watersheds during periods of heavy precipitation, which can lead to the transfer of a large quantity of terrigenous matter and terrigenous dissolved organic carbon (tDOC) into coastal waters. The first effect of the transport of tDOC is the increase in water turbidity and consequently the attenuation of light in the water column which can decrease the photosynthetic capacity of phytoplankton communities. The tDOC has a second important effect, this time favoring prokaryotic microorganisms, especially bacteria that assimilate DOC. Since tDOC have an impact on the two major components at the base of the food webs, they can cause a change in the structure and functioning of planktonic food webs and as a result, of the trophic and metabolic states of the pelagic system.
The change in the precipitation regime due to climate change can lead to an increase in flash floods and terrigenous inputs in the Mediterranean climate, and thus the brownification of the waters. In addition, the expected increase in marine water temperature in the coming years may also alter the structure and functioning of marine plankton food web. There are few studies on the effects of brownification in marine waters, let alone on the interactive effects of the simultaneous increase in brownification and water temperature.The objective of this post-doctoral project is therefore to study the separate and combined responses of the micro- and macroorganisms of the planktonic food web to brownification and water temperature increase. In order to study both all planktonic food web microorganisms and their interactions subjected to forcing as close as possible to natural forcing, this study was carried out under controlled experimental conditions with an approach that can encompass all pelagic micro- and macroorganisms. This approach is based on the use of in situ pelagic mesocosms. An experiment in in situ mesocosm (closed incense immersed in the water column of the Thau lagoon of 2200 liters) was carried out in spring 2021 as part of the ANR RESTORE 2020-2024 project entitled: Microbial responses to terrestrial dissolved organic matter input in freshwater and marine ecosystems in a changing environment. During this experiment, physical, chemical and biological variables were monitored with continuous and high frequency automated sensors. Other measurements to estimate the abundance or biomass of different planktonic organisms and key processes (i. e. growth and grazing rates) were performed. Other important processes such as community production and respiration have also been studied. Parallel experiments, this time in microcosms (2 liters), have already been carried out using different types of soil (forest versus vineyard) and with the addition of forest soil combined with the temperature increase of 3°C. Some samples have already been analysed and the data will be available to the post-doctoral candidate and further analysis will be required.
The brownification of coastal waters is a widespread phenomenon in different coastal areas of the globe. Therefore, in addition to the mesocosm and microcosm experiments carried out in spring 2021 in coastal waters in the south of France (Thau lagoon), there will be the possibility of carrying out further mesocosm or microcosm experiments in other coastal zones, including a project funded by the Institut polaire français Paul-Émile-Victor (https://www.institut-polaire.fr/language/fr/). This project which will be carried out in the summer of 2022 in Svalbard is entitled: Study of Ny-Ålesund plankton community responses to brownification (Ny-Ålesund-Plankton).
The research team where the post-doc will be integrated is also involved in the European project AQUACOSM-Plus 2020-2024 (https://www.aquacosm.eu/project-information/aquacosm-plus/) and the post-doc could also participate in an experiment planned in this project and he/she could work on some aspects related to brownification effect or other climate change forcing factor in another coastal area.
• Analysis of marine plankton-related samples, including samples of heterotrophic flagellates, ciliates including tintinnids, and metazooplankton (by microscopy).
• Data processing of environmental variables and plankton from mesocosm and microcosm experiments.
• Writing several articles from these analyses/data processing as the first author.
• Participating in the brownification experiment in Svalbard.
The position requires strong knowledge in marine ecology and/or biological oceanography. A thesis in marine plankton ecology, marine ecology or biological oceanography is therefore required. A very good knowledge of statistical tools and in the processing of large databases proved by the publication of scientific articles is indispensable. Strong knowledge and active participation in mesocosm experiments in previous studies is an asset. Very good knowledge and practice of R software is indispensable. Good oral and written communication skills are also required to present research results at conferences and written articles in scientific journals, notably as a first author. Good facility of oral and written English is therefore indispensable. The candidate will need to demonstrate a good ability to work in teams with French and foreign collaborators on multidisciplinary projects.
The proposers of this research topic have a long experience in the field of plankton food web under the influence of forcing factors related to climate change (increase of ultraviolet radiation, water temperature, etc.) and proposed and carried out several research programs to study the structure and functioning of the planktonic food web in response to natural or anthropogenic environmental forcing factors by realizing in situ observations or experimentations under controlled conditions in mesocosms. The successful candidate will carry out his or her research under the supervision of the proposers of this research topic at the MARBEC laboratory in Montpellier and will integrate into their «Project Team» composed of a Ph.D. student, several trainees and other colleagues involved in their research projects outside the MARBEC laboratory.
Constraints and risks
Participation to the field experiments. Travel in France and other countries is possible.
Anr Restore project number ANR N°19-CE32-0013-02 and others ressources.
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