I am working as a CNRS researcher at the laboratory of Marine Microbiology Geochemistry and Ecology (LMGEM). LMGEM is a CNRS/University laboratory (UMR 6117) belonging to the Center of Oceanography of Marseille (COM), located in the campus of Luminy in Marseille France.

My research activities are related to the study of the dissolved and particulate organic matter composition and distribution in marine waters as well as its degradation by bacteria in the water column. I am currently working with Bruno Charriere (CNRS engineer at LMGEM) and several post-doctoral fellows and PhD students (Marc Tedetti and Maher Abboudi : see details below).  Briefly my research activities can be divided into three fields :

1- Dissolved and total organic carbon (DOC, TOC) distribution and bacterial cycling in marine waters.

 Our objectives were to determine DOC stocks, DOC turnover rates and bacterial growth efficiencies in the water column. Several researchers worked actively in this topic including Evgeny Dafner (post-doctoral researcher at LMM during 2 years 1997-1999) and Rumi Fukuda-Sohrin (Post-doctoral researcher at LMM, 2000-2001), Clement Yoro (PhD student, 1995-1998) and Christos Panagiotopoulos (PhD student, 1998-2002) and in collaboration with Bruno Charriere (Cefrem, Univeristy of Perpignan), France Van Wambeke, Micheline and Armand Bianchi and Dominique Lefevre.

DOC and TOC analyses were carried out by using a TOC 5000 Shimadzu analyzer. 

More specifically, I worked in different areas including

1-1 Mediterranean Sea: We tried to contribute to establish a carbon budget in Mediterranean Basin in relation with external inputs such as those carried by Atlantic Ocean, Black Sea, riverine and atmospheric waters.  These studies were undertaken in the framework of the European programs (EMPS, CANIGO, MATER , ADIOS) and the CNRS-PROOF national programs Almofront2 and Prosope

1-2  Antarctic waters (Indian Sector). (Antares Program)

1-3 North Atlantic Ocean. (Pomme program)

2-Bacterial degradation of sinking particles in the water column

Our objectives were to determine (1) degradation rates of particulate organic carbon, particulate sugars and amino-acids in sinking particles (2) bacterial growth efficiencies during the degradation of particles. These experiments were carried out by following  in vitro bacterial degradation of  freshly collected particles by using in situ pumps or sediment traps. Mainly, Clement Yoro and Christos Panagiotopoulos worked in this field in collaboration with France Van Wambeke, Madeleine Goutx. These experimental work has been done in the framework of different European programs including EMPS, MATER, CANIGO, ADIOS and CNRS-PROOF national programs Dyfamed-Eimeto, Antares, Prosope and Pomme. Current objectives are related to bacterial degradation of particulate sugars (programme Medflux) in collaboration with others LMGEM scientists (M. Goutx, F. Van Wambeke) and also with US scientists (C. Lee; R. Amstrong, S. Wakeham). We will start to study in 2004, the bacterial degradation of sinking particles in meso-and bathy-pelagic waters through a collaboration with Christian Tamburini and Armand Bianchi (LMGEM) in the framework of the French CNRS-PROOF Programme (SINPA).

3-Sugar distribution and cycling in marine waters.

Our objectives were

1- to study monosaccharides in sinking particles. Monosaccharides were detected by using  HCl hydrolysis followed by chromatographic separation and pulsed amperomtric detection (HPEAC-PAD). We studied change in sugar content of particles (in comparizon with amino-acids and lipids) as well as molecular distribution during bacterial degradation of sinking particles. On study was also undertaken in order to compare molecular distributiuon of sugars amonf sinking particles collected by sediment traps in differents oceanic provinces including Mediterranezan Sea, Atlantic Ocean and Mediterranean Sea.

The last 5 years, most of these studies have been done within the PhD thesis of Christos Panagiotopoulos in collaboration with Philippe Kerherve

Research programs: CNRS-PROOF programs i.e. Antares, Prosope and Pomme.

4-Ultra-violet radiations (UV-R) of effects of dissolved organic matter (DOM) cycling in seawater.

Our objectives are to determine the effects of  UV-R on the molecular distribution of organic compounds including sugars, amino-acids and dicarboxylic acids in surface seawater. We are aiming to study direct effects of bacteria as well as secondary effects on the DOM bacterial cycling. These studies are undertaken in the framework of the CNRS-PROOF program UVECO (Pis : R. Sempere (LMGEM) and F. Joux (OOB-Banyuls/Mer).

Marc Tedetti (PhD student, supervisors : K. Kawamura and R. Sempere) is actively working on the UV effects on sugars, amino-acids and carbonyls compounds.

Maher Abboudi (PhD student, supervisors F. Joux and R. Sempere) is actively working on the UV effects on bacteria.