Comparaison de deux méthodes pour l’étude et le suivi des communautés coralligènes de Méditerranée occidentale : utilisation de prises de vues en photogrammétrie versus photoquadrats
propuesta de investigación
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Over the last few decades, Mediterranean ecosystems have been affected by severe heat waves, leading to massive mortality in many benthic species. These species belong and participate to the formation of one of the most important bioconstructed type of habitat in the Mediterranean Sea: coralligenous habitats. In view of these deaths, coralligenous habitats need to be monitored, both in terms of the composition of their assemblages and their structure. Traditionally, studies of these assemblages have been limited to the use of quadrats placed on the substrate, which do not allow access to the structure of these habitats. In recent decades, the development of photogrammetry in the marine environment has opened up new possibilities for simply accessing this structuration. Often used as a complement to traditional methods to study communities, the aim of this study was to explore the potential of photogrammetry as a tool for characterising coralligenous benthic marine communities. It had 2 objectives. (i) To develop a method for extracting quadrats from photogrammetric images at depths of interest, and for characterising the communities they contain. (ii) To apply this method to assess its ability to estimate the spatial variations of different organisms on a coralligenous cliff in the western Mediterranean. After presenting this new methodology, the results obtained were compared with those obtained in parallel using a traditional method. A total of 40 different genera were identified using the new method, compared with 89 using the traditional method. In general, the new method underestimated the overlap of many organisms, or failed to identify them. These differences made it possible to identify a significant effect of the method in the characterisation of assemblages when compared between the two methods. The main cause of these differences seems to be the ground resolution of this method, which does not allow small organisms to be distinguished from others. Nevertheless, this new approach is promising for organisms that can be easily identified in photographs. However, future studies will aim to overcome this resolution problem.
Propuesta de TFG de maestría con doble titulación coordinada con la Maestría Académica en Gestión Integrada de Áreas Costeras Tropicales.
- Biología