Using seaweed assemblages on intertidal rocky shores to assess the ecological status of Andalusian coasts. Biogeographical implications.

Abstract

According to the Water Framework Directive (WFD), the ecological status of European coastal waters must be assessed using different biological quality elements (BQE). One of the four proposed BQE is based on the composition and abundance of the marine macroalgae. Because of the biogegraphical differences along the European coasts, six ecoregions have been considered for biological indices development (Atlantic, Baltic, North Sea, Barents Sea, Norway Sea and Mediterranean Sea). The geographical position of Andalusia (Southern Spain), as a transition zone between the Atlantic and the Mediterranean Sea implies some technical and theoretical difficulties. Coastal waters of Andalusia belong to two different ecoregions, and their evaluation can be carried out with up to seven different macroalgal based indices. Moreover, the existence of a natural gradient along this coast interferes in the final value of the indices. The main objectives of this thesis were: i) the adaptation and comparison of indices based on macroalgae for the assessment of the ecological status in coastal waters of Andalusia; and ii) the provision of useful information for management about the ecology and the biogeography of littoral communities in southern Iberian Peninsula. The first objective is addressed in three chapters. In chapters 1 and 2, the Reduced Species List (RSL) and CARtography of LITtoral communities (CARLIT) indices were adapted to the particularities of Andalusian coasts. Afterwards, both indices were compared in the Strait of Gibraltar and the western Alboran Sea (chapter 3). The results showed that these indices were suitable to assess the ecological status in Andalusian coastal waters, and they yielded similar results. Overall, the ecological status of Andalusian water bodies (WBs) was good or high, excepting some highly modified WBs. The second block is focused on the ecology and biogeography of macroalgal communities in southern Iberian Peninsula. In chapter 4 the biogeographical patterns of the Alboran Sea were studied based on the landscape and the species composition of littoral and upper-sublitoral communities, and compared to regional oceanographic patterns. The results pointed out the influence of regional oceanographic patterns in the littoral communities, and the existence of three different subregions: western, central and eastern Alboran. In chapter 5, considering the ecological importance of Cystoseira mediterranea, C. amentacea and C. tamariscifolia, a genetic approach based on microsatellites was developed to assess the taxonomic identity and the genetic structure of these populations along the southern Iberian Peninsula. The preliminary results suggest that only a genetic entity, probably C. tamariscifolia, is present in the Alboran Sea. Furthermore, these populations showed a moderate differentiation among them, being the most genetically diverse populations those in western and central Alboran. The knowledge of these ecological and biogeographic patterns will be essential for a proper management (e.g. design a network of marine protected areas) and to interpret the results yielded by indices based on macroalgae.