De la profondeursur 2 sites en Guadeloupe pendant la saison sèche et la saison humide (Chapitre 3). A u cours de cette étude,les genres Ostreopsis et Prorocentrum étaient les plus abondants. Aucune influence de la profondeur n'a é;étrouvée sur l'abondance totale des dinoflagellés benthiques ; cependant les genres Ostreopsis et GambiericLscusétaient principalement abondants en surface, alors que le genre Coolia était présent plus en profondeur.L'approche d'écologie trophique concernait le lien trophique entre dinoflagellés benthiques toxiqueset méiofaune (Chapitre 1). Les transferts au sein des réseaux trophiques de phycotoxines synthétisées par lesdinoflagellés benthiques toxiques sont généralement étudiés chez les organismes de grande taille, délaissantles organismes de μeLile Laille qui sulll pourtant en contact direct avec les microalgues. Au cours de cetteétude, une attention particulière a été portée aux copépodes harpacticoïdes qui composent ia méiofaune.Cette étude expérimentale, par marquage des microalgues aux isotopes stables, s'est focalisée sur lescopépodes harpacticoïdes et a permis de mesurer le taux d'ingestion d'Amphidinium sp. et d'Ostreopsis sp ..Cette étude démontre que les organismes de la méiofaune peuvent constituer une voie d'entrée des toxinessynthétisées par les dinoflagellés benthiques dans les réseaux trophiques. / The distribution of benthic toxiï rlinofüeefü1tes is 1111known in (Juadeloupe and Martinique even if at theCaribbean basin spatial scale, those microalgae are responsible for serious poisoning such as ciguatera.During this thesis, the ecology of benthic toxic dinoflagellates μreseul was sLudieJ using: spatio-temporalstudies (Chapters 1, 2, 3) and a trophic ecology approach (Chapter 4).First, 27 sites were explored to describe the spatial distribution of benthic dinoflagellatf's prPsf'nt inGuadeloupe and Martinique (Chapter 1). Only the most abundant macrophytes (biological substrates ofbenthic dinoflagellates) at the different sites were considered. ln this study, 161 samples were analyzed and 7times more taxie benthic dinoflagellates were found in Guadeloupe than in Martinique. The genus Ostreopsisdominated the benthic dinoflagellate community in both islands, although this trend has only rarely beenfound in the Caribbean basin.Then, 3 sites per department were chosen in order to set up a monthly monitoring of benthicdinoflagellates abundances duringl8 months (Chapter 2). The sites selected i) had a high abundance ofbenthic toxic dinoflagellates and ii) were identified as potentially dangerous by the Agence Régionale de laSanté. During this study, 927 samples of macrophytes were analyzed and 5 times more benthic toxicdinoflagellates were found in Guadeloupe than in Martinique. Ostreopsis and Prorocentrum genera dominatedrespectively in Guadeloupe and in Martinique. Two times more Gambierdiscus were found in Martinique thanin Guadeloupe even if Guadeloupe is located in the high prevalence area and this genus being responsible forciguatera. This result suggested that species with different toxicities structured the benthic toxicdinoflagellates community in this area. The abundances of benthic dinoflagellates were little influenced byabiotic parameters (temperature and salinity) but structured by biotic parameters (host macrophytes).Halophila stipulacea an invasive angiosperm in the Lesser Antilles has been identified as promoting thedevelopment of the genus Gambierdiscus.. The distribution of benthic toxic dinoflagellates was also studied according to the depth at 2 sites inGuadeloupe during the dry and the wet seasons (Chapter 3). ln order to avoid bias due to the presence ofdifferent macrophytes, this experiment was conducted only on H. stipulacea constituting mono-specificmeadows along a strong depth gradient. ln this study, the Ostreopsis and Prorocentrum genera were the mostabundant. No influence of the depth was found on total abundance of benthic dinoflagellates; however,Ostreopsis and Gambierdiscus genera were mainly abundant near the surface while the genus Coolia was presentdeeper.The trophic ecology approach focused on the trophic link between taxie benthic dinoflagellates andmeiofauna (Chapter 4). Transfers within the food webs of phycotoxins synthesized by benthic dinoflagellatesare mainly studied in large organisms neglecting smaller ones in direct contact with microalgae. Thisexperimental study, by labeling the microalgae with stable isotopes, focused on harpacticoides copepod andmeasured for the first time their ingestion rates of Amphidinium sp. and Ostreopsis sp.. This studydemonstrated that meiofauna organisms can constitute an input channel of phycotoxins from benthicdinoflagellates in food webs.

This diploma thesis deals with the study of the utilization of Raman spectroscopy and Raman tweezers for analysis and isolation of polyhydroxyalkanoates (PHA) producing bacteria. Using gas chromatography with FID detection, we determined the polyhydroxybutyrate (P(3HB)) content of the PHA biomass of bacterial strains Burkholderia cepacia, Halomonas halophila, Cupriavidus necator H16 and its mutant strain Cupriavidus necator H16/PHB-4 and Lactobacillus delbrueckii, which is not a producer of polyhydroxyalkanoates but this bactrea was selected as representative of Gram-positive bacteria. Subsequently, thanks to Raman microspectroscopy, Raman tweezers and FT-IR spectrometer in combination with Raman FT-module, we were able to confirm or disprove the presence of P(3HB) in bacteria. Furthermore, the thesis describes Cupriavidus necator H16, which is a model organism for the production of P(3HB), and his mutant strain Cupriavidus necator H16/PHB-4. The bacterial strain Cupriavidus necator H16 was cultivated in a production mineral medium of various nitrogen contents, while cultivation was also carried out in liquid Nutrient Broth. By this cultivation we were able to reach various P(3HB) content in bacterial biomass, the spectra were subsequently compared with the spectrum of the bacterial strain Cupriavidus necator H16/PHB-4. Raman spectroscopy is well used to characterize the composition of individual bacterial cells, is a fast, versatile, and virtually non-invasive tool for studying cells.

The hierarchical levels at which resource selection occurs can have important consequences for individual and population energy budgets and structure the impacts of a forager on its ecosystem. Assessing factors affecting resource selection of large marine herbivores across scales is important because of their potentially large impacts on seagrass community dynamics and historical and current changes in their population sizes and those of their potential predators. I explored the factors (predation risk, resource abundance, quality and identity) affecting resource use of large marine herbivores (green turtles, Chelonia mydas) from the scale of habitat patches to forage species within patches. I used a combination of in-water surveys, aerial drone video transects, baited camera surveys, and seagrass community and nutrient content analyses to provide insights into resource use by turtles in multiple ecological contexts. In Abaco, The Bahamas I found relatively intact shark populations, including apex predators, relative to other parts of the Caribbean. In the context of healthy predator populations in Abaco, I tested a priori predictions rooted in Ideal Free Distribution (IFD) theory. Green turtles off Abaco deviated from predictions of an IFD determined by the standing stocks of seagrass. Instead, distributions are consistent with predictions of the foraging arena hypothesis with turtles largely restricted to safe habitat patches and selecting locations within these where seagrass N content is relatively high. Marine invasive species can have detrimental effects on coastal ecosystems and economies. Therefore, understanding the effects of, and factors influencing the rate of spread of the invasive seagrass Halophila stipulacea in the Caribbean is important. In the French West Indies (Guadeloupe, Martinique and St. Martin), I investigated foraging preferences for native versus invasive seagrass species and whether green turtles might facilitate or attenuate the invasion through their choice of habitats and feeding patterns. Green turtle distributions were correlated with native seagrass distributions. Also, despite similar nutrient contents, turtles preferred feeding on native seagrasses irrespective of their relative abundance within a patch. These results suggest that, as predicted by the Enemy Release Hypothesis, green turtles likely facilitate the invasion and spread of the invasive seagrass that may reduce energy flow into turtle populations.

El trabajo realizado en la Tesis Doctoral llega a las siguientes conclusiones:1.- T. halophila muestra una relación en peso raíz/parte aérea mayor que A. thaliana, y esta diferencia se ve incrementada en condiciones de estrés salino, lo que podría suponer una ventaja para afrontarlo.2.- El estrés salino produce en A. thaliana mayores reducciones en la absorción y en las concentraciones internas de K+ que en T. halophila, a la vez que T. halophila presenta menor absorción de Na+ y transporte a la parte aérea que A. thaliana. Ambas circunstancias resultan en una mayor relación K+/Na+ en T. halophila, lo que puede suponer una mayor tolerancia a la salinidad.3.- El gen ThHAK5 codifica para un transportador que media un transporte de K+ de alta afinidad en levaduras similar al observado en las plantas de T. halophila lo que sugiere que este transportador juega un papel fundamental en la absorción de K+ en el rango de la alta afinidad en esta especie vegetal.4.- Aunque AtHAK5 y ThHAK5 presentan una gran homología de secuencia y unas características funcionales similares, la regulación de los genes que los codifican difieren en condiciones salinas. Así, la salinidad reduce en menor medida la inducción de ThHAK5 por ayuno de K+. En consecuencia, la absorción de K+ de alta afinidad está menos afectada por la presencia de NaCl en el medio externo en T. halophila.5.- La mutagénesis al azar permite encontrar aminoácidos importantes para la función de las proteínas y ésta ha permitido identificar dos versiones mutantes del transportador de K+ de alta afinidad AtHAK5 más eficientes, capaces de transportar K+ a concentraciones externas de Na+ muy elevadas (0.1 mM K+ y 800 mM Na+). / The work done in this Thesis provides some interesting conclusions:1.- Thellungiella halophila show a weight ratio root/shoot bigger than Arabidopsis thaliana, and this difference arise under salt stress, what might provide an effective mechanism of salt tolerance to T. halophila.2.- In A. thaliana, salt stress induces a bigger reduction of K+ uptake and tissue concentrations than in T. halophila, and at the same time T. halophila shows a reduced Na+ uptake and Na+ transport to the shoot. Both properties enable a higher ratio K+/Na+ in T. halophila which might be another mechanism of salt tolerance. 3.- The ThHAK5 gene isolated in this Thesis, encode a K+ transporter that mediates high affinity K+ transport in Saccharomyces cerevisiae similar to the observed in intact plants of T. halophila, which suggest a key role of this transporter in the high affinity range of concentrations.4.- Although AtHAK5 and ThHA5 shows high sequence homology and similar functional properties, gene regulation is different under salt stress. Thus, salinity reduces to a lesser extent the K+-starvation ThHAK5 induction. As a consequence, high affinity K+ uptake is less affected by NaCl in T. halophila. 5.- Random mutagenesis allows the identification of important aminoacids for protein function, and with this technique two more efficient mutant versions of AtHAK5 have been isolated. The evolved AtHAK5 mutant versions are able to transport K+ at high Na+ external concentrations (0.1 mM K+ and 800 mM Na+) in yeast.

This diploma thesis deals with application of evolutionary engineering on PHA producing bacterial strains. Two bacterial strains, Cupriavidus necator H16 and Halomonas halophila, were chosen for the evolutionary experiments. Copper cations (Cu2+) and sodium chloride (NaCl) were chosen as the selective pressure for C. necator H16; acetic acid (AA) and levulinic acid (LA) for Halomonas halophila. The adapted strains were during long-time evolutionary experiments characterized by GC-FID and SEC-MALS. The growth of the adapted strains was studied by the mean of optical density measurement. The amount of viable cells was determined by spectral FC after their expositon to selected stress factors. Specific enzyme activities of enzymes involved in citrate and glyoxalate cycle, enzymes generating NADPH, LA metabolism enzyme and PHA biosynthesis enzymes were determined. The adapted strains were compared with the wild-type of strains. The successfull adaptation of C. necator H16 adapted to Cu2+ was detected. Biomass and PHA production of both wild and adapted H. halophila strains cultivated in lignocellulosis waste were determined. It was found out that H. halophila adapted to the LA is capable of producing more PHA than the wild strain of this bacteria.