Study of viral ecology and molecular profiling: Identification of Potexvirus TVX in "Thalassia testudinum" and characterization of "Sargassum fluitans" and "Sargassum polyceratium" of the Puerto Rican coasts: A molecular approach for the conservation of marine ecosystems

Details

Supervisors

Hance, Thierry

Faculty

Faculté des sciences

Degree label

Master [120] en biologie des organismes et écologie, à finalité approfondie

Abstract

enSeagrasses and macroalgae are key foundation species in tropical coastal ecosystems, providing primary production, habitat structure, carbon storage, and shoreline protection. In the Caribbean, "Thalassia testudinum" forms extensive meadows, while brown algae of the genus "Sargassum" occur in benthic ("S. polyceratium") and pelagic ("S. fluitans") forms. Their virobiota remains largely unexplored. A potexvirus, Turtlegrass Virus X (TVX), was recently reported from T. testudinum in Florida, but its presence in Puerto Rico has not been investigated. This study aimed to detect TVX in Guánica Bay (Puerto Rico) using molecular tools, with complementary goals of preliminarily characterizing the "T. testudinum" bacterial microbiota via 16S rRNA metabarcoding and performing an elemental (ICP-AES/CHN) comparison of the three macrophytes. Leaves of "T. testudinum" showing different visible health states were analyzed by conventional PCR and SYBR-based qPCR. TVX detection remained inconclusive due to non-specific products, late signals in negative controls, complex melt curves, and lack of sequence confirmation. Metabarcoding preparations succeeded for "T. testudinum" but yielded poorly for "S. polyceratium". Elemental analysis showed "T. testudinum" enriched in Ca/Mg with a low C/N ratio, "S. fluitans" with higher Na/K and detectable arsenic, and "S. polyceratium" with elevated Fe/Zn and a high C/N ratio. These findings highlight the ecological importance of monitoring marine macrophyte health and the need to improve methodologies for marine plant virology and DNA extraction. Integrating virome–microbiome–chemistry approaches could guide conservation strategies and the safe, local valorization of Caribbean macroalgal biomass.