MAREL Carnot. Bilan d’une surveillance à haute fréquence en zone côtière sous influence anthropique (Boulogne-sur-Mer). Bilan de l’année 2015 Rapport N°10

Installée dans la rade de Boulogne-sur-Mer et inaugurée le 25 novembre 2004, la station MAREL Carnot mesure toutes les 20 minutes la salinité, la température de l’eau et de l’air, la fluorescence, la turbidité, la concentration en oxygène dissous, le pourcentage de saturation en oxygène, le P.A.R., l’humidité relative, la direction et la vitesse du vent, la hauteur d’eau et toutes les 12 heures, la concentration en nitrate, en phosphate et en silicium. Ce rapport vise à présenter les principaux éléments utiles à l’utilisateur des données afin de pouvoir adapter son étude en fonction de la disponibilité des données, de leur qualité et bien entendu de son objectif. Les résultats des paramètres fluorescence, turbidité, concentration en oxygène, température de l’eau sont présentés de manière plus détaillée afin de mettre en évidence les cycles saisonniers caractéristiques, la variabilité inter-annuelle et les éventuelles tendances.

Silanisation de polysaccharides en milieu liquide ionique et réactivité d’un organoalkoxysilane vis-à-vis de nucléophiles simples : vers des hydrogels injectables pour l’ingénierie tissulaire du cartilage

Tissue engineering is a real challenge for the treatment of cartilage pathologies. In this field, biomimetic hydrogels based on natural polymers are among the most commonly used matrices. A hydrogel made of silanized hydroxypropylmethylcellulose (HPMC-Si) is especially promising because it can be injected in cartilaginous lesions by minimally invasive surgery. However, the current synthesis of HPMC-Si is limited by the insolubility of hydroxypropylmethylcellulose (HPMC). This thesis work was focused on finding new synthesis conditions for the design of HPMC-Si hydrogel. In order to obtain a complete solubilization of HPMC and to improve its functionalization by the (3-glycidyloxypropyl) trimethoxysilane (GPTMS), the use of ionic liquids (IL), which are excellent solvents for polysaccharides, was undertaken. The beginning of this study was first devoted to the selection of an IL and then to the development of new reaction conditions. With these new conditions, higher silicon rates were obtained for HPMC modified in ionic liquid medium, however no hydrogel could be formed. The second part was therefore devoted to the synthesis of GPTMS 13C. Indeed, thanks to this radiolabeling, a structural characterization by 13C NMR of the HPMC-Si could be achieved. Finally, the reactivity in organic solvents of three organosilanes, including the GPTMS, was investigated toward nucleophiles representing the common functions found in natural polymers (e.g. -NH2, -OH, -SH). The results of this thesis have provided insights into the GPTMS reactivity in organic medium and thus paves the way to new conditions for the silanization of polysaccharides.

Nutrients limiting the Algal Growth Potential (AGP) in the Gulf of Riga, eastern Baltic Sea, in spring and early summer 1996

In May, June and July 1996, samples wcre collected along one transect greatly influenced by river discharge (eastern side of the gulf), along one transect slightly influence by river discharge (western side), at one station Iocated in the mouth of the main river (River Daugava), at one station located in the center of the Gulf and at several nearshore locations of the western side. Ratios of rnolecular concentrations of in situ dissolved ioorganic nitrogen, phosphorus and silicon, as weIl as enrichment bioassays were llsed to dctcrrnine which nutrient (s) lirnited the potential biomass of phytoplankton. Both comparison of (NO.d-N02+NJ.L): P04 (DIN: DIP) values with Redfic1d's ratio and bioassay inspection led to the sarne conclusions. Phosphorus was clearly the nutrient most limiting for the potcntial biornass of test species in nitrogen- rich waters, which occurred in mid spring, in the upper layer of the southern-eastern part of the Gulf which is greatly influenced by river discharge. In late spring, with the decrease of the total DIN reserve, nitrogen and phosphorus showed an equallimiting role. In deeper layers of this area and out of the river plume (western side and central part of the gulf), nitrogen was the limiting nutrient. In summer, whcn river discharge was the lowest, a11 DIN concentrations but one ranged between 1.6 and 2.6 µM, and the whole area was nitrogen-limited for both the cyanobacterial and the algal test strains. In 74% of the samples for which nitrogen was the limiting nutrient, phosphorus was recorded to be the second potentially limiting nutrient. In contrast, silicon never appeared as limiting the growth potential of either Microcystis aeruginosa or Phaeodactylum tricornutum; phosphorus was the limiting nutrient when DIN: Si03 values were >1 (in May), but DIN: Si03 was <1 when nitrogen was limiting (June and July). The authors conclude that the recently reported decrease of silicon loading in coastal waters and its subsequent enhanced importance in pushing the outcome of species competition towards harmful species may not yet be the most important factor for the Gulf of Riga. Iron appeared for 12% of the tests in the list of nutrients limiting the potential biomass. Tentative results also indicated that a significant fraction of the nitrogen (~,4 µg-atom N 1(-1) taken up by Microcystis aeruginosa may have been in the form of dissolved organic nitrogen (DON). It is thus also suggested tentatively that more attention be paid to these nitrients during further research in the Gulf of Riga.