Mesoscale hydrodynamics around the Balearic Islands: spatio-temporal variability and its relation with shing resources.
The Balearic Islands, located in the Western Mediterranean Sea, are the natural limit between the Balearic subbasin, at the noth and the Algerian subbasin, at the south. Previous studies based on hydrographic data have revealed that each of the basins have a di erent oceanographic climatology. One o...
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| Tipo de recurso: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2014 |
| País: | España |
| Institución: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/285626 |
| Acceso en línea: | http://hdl.handle.net/10803/285626 |
| Access Level: | acceso abierto |
| Palabra clave: | Mar Balear Mesoscala Eddies Aristeus antennatus Fishing Reosurces Oceanografía física 53 |
| Sumario: | The Balearic Islands, located in the Western Mediterranean Sea, are the natural limit between the Balearic subbasin, at the noth and the Algerian subbasin, at the south. Previous studies based on hydrographic data have revealed that each of the basins have a di erent oceanographic climatology. One one hand, the Balearic subbasin has colder and saltier waters as a result of the water modi - cation during the cyclonic circulation of the Mediterranean Sea. On the other, the Algerian subbasin waters are warmer and fresher, incoming directly from the Atlantic Ocean and entering into the Mediterranean through the Strait of Gibraltar. These two subbasins are connected via the topographic channels between the islands, whose hydrodynamic properties are governed by the mesoscale situation: non-permanent small scale phenomena (.100 km). Studying the mesoscale situation around the Balearic Islands can be useful for understanding how the water exchanges between the two subbasins are. Moreover, mesoscale structures, such as eddies, laments or fronts, can temporarily change the hydrodynamic conditions. When it occurs, mesoscale variability not only a ects the hydrodynamic conditions (water exchanges, alteration of the main currents, . . . ), but may also impact on the local ecosystems. Understanding how the shing resources from the Balearic Islands are a ected by the mesoscale hydrodynamic situation has been one of the objectives of the IDEADOS project (CMT2008-04489-C03-01), the framework in which this thesis has been developed. The project focused in two areas of shing interest: one located northwards of Mallorca Island, in the Balearic subbasin (Sóller), and another placed southwards, inside the Mallorca Channel (Cabrera). As part of the above mentioned research project, two mooring lines were deployed, one in the limit of each shing ground and were maintained during 15 months. Using recorded data from the moorings, together with satellite observations and landing data from different species, we addressed questions such as: How is the hydrodynamic activity in each zone and which are the similarities and/or di erences between both places from an oceanographic perspective? Which are the main features of the mesoscale phenomena detected? And, how does the hydrography a ect the sediment ux dynamics and the shing resources of each zone? The chapters of this thesis, which correspond to published articles in scienti c journals, are organized following the previous questions. In the rst chapter the data recorded by each mooring is analyzed with the aim of characterizing each zone and compare them. Derived from this study and in the second chapter, one of the mesoscale events detected in Sóller is deeply analyzed. This structure was an eddy which lasted about one month, reached down to the sea oor and completely changed the mean oceanographic properties in the complete water column. In the third chapter, the data collected by the sediment traps is analyzed and a relationship between the sediment uxes measured and the possible triggering mechanisms is addressed. Finally, a study about the relationship between the observed hydrodynamics and the red shrimp (Aristeus antennatus) dynamics is performed. It is observed that the adult individuals of red shrimp would be a ected by the bottom turbidity generated by the mesoscale phenomena. In turn, they would respond moving away from the shing grounds, probably towards greater depths. As the main mesoscale events take place in Sóller during winter time, this could provoke the reported reduction of the amount of large individuals of red shrimp caught during this part of the year in this shing ground. The results of this thesis reinforce the lately recognized theory that shing resources are not only a ected by their exploitation or the self oscillations of the ecosystem (biotic factors), but they are also in uenced by the changing oceanographic situation (abiotic factor). |
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