Lagunas litorales intermitentes en Andalucía, un modelo para la gestión

The main goal of this thesis is to contribute to a better understanding of the behavior and evolution of small intermittent coastal lagoons. These systems can be considered as a critical transition zone that link land, freshwater habitats, and the sea. They have been selected due to their important role in the maintenance of the biogeochemical fluxes at a planetary scale, allowing interchanges of mass, momentum and energy between oceans, continents and the atmosphere. The combination of agents at these areas encourages the appearance of gradients; natural systems tend to reply with lots of processes. These turn coastal lagoons into highly dynamic systems, being their productivity typically 10-15 times higher than continental shelves (Valiela, 1995). However, extreme fluctuations often occur in salinity, temperature, water level and dissolved oxygen within any single site, restricting the number of species in these environments. Consequently, essential ecosystem functions performed by species in critical transition zones are associated with a relatively low biodiversity (Levin et al., 2001). These authors and Danovaro and Pusceddu (2007) enumerate the main functions of the transition zones and the coastal lagoons, respectively, focusing on biological functions. Coastal lagoons usually make outstanding contributions to the socio-economic environment of their surroundings. They are attractive for tourist and recreational purposes, educational for children and are of economic interest to the people because they provide fishing, navigation, natural shelter, etc. If all these functions are being accomplished, the system is said to have a regular behavior; if not, the system moves into a failure mode. This failure mode entails some environmental or socio-economic risks, which depends on the probability of failure and its consequences. The limit between these two modes is usually a legal, social or scientific threshold. Failures can be induced not only by natural processes but also by human activities. Thus, when fixed the tasks of a system, management should be only considered to achieve a better performance of the system, to avoid failures, to minimize risks or to take the system out of a failure mode. The high amount of different interests converging in coastal lagoons makes their management fairly complex. The analysis of the theoretical behavior of these systems and the development of some tools to simulate the response of the system to different agents is a necessary requirement for integrated coastal managing purposes. This reasoning constitutes the main justification of this thesis.Tesis Univ. Granada. Departamento de Mecánica de Estructuras e Ingeniería Hidráulic