Data/hora: 06/06/2024 01:32:26

Provedor de dados: | Institutional Archive of Ifreme (ArchiMer)
País: | France
Título: | Intégrité des habitats benthiques du plateau continental face aux perturbations physiques naturelles et aux arts trainants : quelles méthodes d'observations ? Comment suivre le retour vers un bon état écologique ?
Autores: | Jac, Cyrielle.
Data: | 2020-12-10
Ano: | 2020
Palavras-chave: | Mégafaune benthique; Méthode d'échantillonnage; Impact de la pêche; Sensibilité; Facteurs environnementaux; Bon état écologique; Benthic megafauna; Sampling methods; Fishing impact; Sensitivity; Natural drivers; Good environmental status.
Resumo: | In 2008, the European Union drew up the Marine Strategy Framework Directive (MSFD) with the aim of achieving Good Environmental Status of marine waters. By linking the changes observed to the pressures experienced, this directive is defined as a tool designed to better control environmental degradation factors and to assess their implications. Several descriptors are defined within the framework of MSFD, in particular descriptors 1 relating to the biological diversity of the seabed and 6 relating to the integrity of the seabed (i.e. the quality of its structures and functions). As dragging (trawling and dredging) is the main source of disturbance of continental shelf seabed, it is essential to study its impact. However, its effects depend on several criteria such as the type of gear used, the spatial and temporal distribution of fishing effort, the targeted habitats and the degree of natural disturbance existing in the area. The general objective of this thesis is to evaluate the impact of trawling activities in various hydrodynamic and sedimentary contexts and design a generalized assessment framework. Four zones were considered: the southern North Sea, the English Channel, the Gulf of Lion and the eastern part of Corsica. To monitor the impact of anthropogenic pressure on an ecosystem, it is necessary to determine which indicators and which sampling methods are the most appropriate. The comparison of fifteen indices and three sampling methods showed that sampling of the benthic megafauna with scientific trawls was particularly effective for monitoring the trawling impact on benthic communities and that video imaging could be a relatively interesting non-destructive alternative method for coarse bottoms. Indices based on species sensitivity to trawling, appeared to be the most relevant for monitoring the effect of trawling on benthic communities. A conceptual approach to detect effect thresholds and impacts was developed and, as a result, the ecological status of the four study areas could be determined and mapped. The evaluation of the effect of abrasion and various environmental parameters on these indices highlighted that the main factors structuring the benthic communities are not the same in all study areas. It is mainly physical processes (tide, swell...) which structure the benthic communities in the English Channel whereas it is mainly parameters linked to species growth (availability of food, temperature...) which influence the distribution and composition of Mediterranean benthic communities. Abrasion has also emerged as a structuring factor of these benthic communities. One of the previously selected indices was able, in areas where abrasion significantly influences the indices, to differentiate environmental effects from the effects of trawling.
Tipo: | Text
Idioma: | Francês

Identificador:

https://archimer.ifremer.fr/doc/00679/79149/81655.pdf

https://archimer.ifremer.fr/doc/00679/79149/

Editor: | Université de Montpellier
Formato: | application/pdf

Fonte:

info:eu-repo/semantics/openAccess

restricted use