The ANR POTES program (Pressure effects On marine prokaryoTES) project concerns the role of marine micro-organisms in the mineralization of particulate (POM) and dissolved (DOM) organic matter and on the regeneration of biogenic compounds (silicates, carbonates) in the meso- and bathypelagic zones of the Ocean. Nowadays, most of the information regarding these processes comes from the epi-pelagic ... zone and/or does not take into account the effect of increasing pressure with depth. Yet, it is essential integrate effects of hydrostatic pressure forcing (as well as the associated decrease in temperature) when studying oceanic organic matter (OM) mineralization.
POTES participants have not only a thorough knowledge but also the required equipment (hyperbaric bottles and samplers, sinking particles simulator) developed in collaboration with a private society (M√©tro-Mesures SA) that make it one of the international leader laboratories on hyperbaric topics.
The major aim of the POTES project is to determine the effect of pressure on prokaryote community structure, and on their activities related to the OM transformation and mineralization using a double and innovative approach based on both laboratory experiments and in situ studies (ANTARES and DYFAMED sites, North-Western Mediterranean Sea). Due to the high inputs of anthropic OM in the Ocean ... (through wind inputs, rain falls, maritime transport, used waters), we will focus on the fate of both biogenic and anthropic OM. In this context, petroleum hydrocarbons will be considered as a model, as their fate in the meso- and bathypelagic zones remains actually unknown. The proposed experiments specifically allow to characterize and quantify the effects of an increase in hydrostatic pressure and a decrease in temperature on :
(i)The processes of OM mineralization (transformation of POC into DOC, hydrocarbon biodegradation, respiration) and on the regeneration of biogenic compounds (silicates, carbonates) in intermediary and deep oceanic waters;
(ii)The structural ((phylo)genetic) and functional (activities) dynamics of prokaryotic communities;
(iii)The flux of POM in the water column and the kinetic of particle transformation in the mesopelagic zone ; these information will be incorporated into a model describing the transformation of particles by micro-organisms in the entire water column.