Comunidades de macrofauna asociadas a zonas de rompiente de playas arenosas en el golfo de cádiz (so península ibérica)

Abstract

Among the great diversity of coastal ecosystems throughout the world, sandy beaches are one of the most important due to their size, occupying a third of the world's coastline, and their dynamism as an interface between land and ocean. Within beaches, the surf zone is of great biological importance due to the availability of shelter and resources, as well as the wave action characteristic of these areas. For this reason, surf zones are crucial areas for the growth and recruitment of numerous species. This doctoral thesis focuses on five surf zones along the coast of Cádiz in the Gulf of Cádiz (SW Iberian Peninsula), where monthly sampling was carried out using a beach seine net. The objectives of this thesis were to analyze the biological community present in these surf zones, study the age and feeding habits of the most important species, and estimate the monetary value of the fishery resources in these areas. Throughout the different chapters, the results obtained have shown that the biological communities in the surf zones studied have a high diversity of species, dominated by seven species, showing variations in their abundance depending on different environmental variables and beaches. On the other hand, the most common ages of the five species studied were between 0 and 2 years, suggesting that these species use the surf zones as nursery areas during the first years of their lives. Their diets were generally focused on the most abundant resources in these areas (small fish and crustaceans), with no competition for these resources due to their great availability. A positive relationship was observed between water temperature and the abundance of the cnidarian Carybdea marsupialis, which may have greater future implications due to increasing global warming. Finally, a higher monetary value was observed for potential fishery resources (juvenile fraction of the community) compared to exploitable fishery resources (adult fraction), highlighting the potential of beach surf zones as nursery areas for future resources from an ecosystem service point of view. These results highlight the biological and economic importance of surf zones, expanding the knowledge of these areas in the south of the Iberian Peninsula and providing tools for future management plans in these areas. They emphasize the need to continue monitoring and researching surf zones for their proper management and the minimization of future impacts.