Auteur / Autrice : | Pauline Bazin |
Direction : | Benoît Véron |
Type : | Thèse de doctorat |
Discipline(s) : | Physiologie, biologie des organismes, populations, interactions |
Date : | Soutenance en 2013 |
Etablissement(s) : | Caen |
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Résumé
Located at the interface between inland aquatic systems and the coastal oceans, estuaries form complex and variable habitats for planktonic microorganisms. As a transition zone linking terrestrial and marine biomes, the structure like a “continuum” is an essential characteristic of the estuaries. However, these ecosystems are rarely considered in their full extent, in terms of biological composition and assemblages. The objective of this work was to provide more detailed insights into the diversity of phytoplankton communities and the other protists that can develop along a whole estuarine continuum. This study also aimed to characterize the changes in biodiversity and the distribution patterns of the taxa along the gradient. In order to have an overview of the different types of structures and biodiversity that can exist in estuaries, two contrasting ecosystems, under different climatic, environmental and human pressures, were analyzed. Phytoplankton community composition was estimated along the continuum using the traditional microscopical approach, and the protistan genetic diversity was explored through the construction of 18S rRNA gene clone libraries in three contrasting zones of the estuarine gradient. The complementarity of both morphological and molecular approaches is highlighted here; thus, neither should be put aside in the overall study of communities in their natural environment. A significant part of the microbial eukaryotic diversity has not yet been discovered in such complex ecosystems.