Rocky shore macroalgae communities of the Azores (Portugal) and the British isles : a comparison for the development of ecological quality assessment tools

Abstract

This thesis focuses on intertidal seaweed communities on rocky shores and was planned to provide solid scientific background for the application of the EU Water Framework Directive (WFD) to the Azores based on the tool developed for British shores. The main structuring factors for rocky shore intertidal communities are briefly described and characterized for each of the two regions. Rocky shore intertidal seaweed communities of the British Isles and the Azores are compared based on presence/absence data recorded in single occasion visits to individual stretches of shore. The existing numerical indices used for the assessment of ecological quality for the WFD in the British Isles and in northern Spain have been tested for Azorean shores and adaptations proposed in order to incorporate differences between regions. A new alternative index is proposed for the Azores and possibly for remaining Macaronesian archipelagos that combines features used in the British Isles and in northern Spain. A first account is given of seaweed communities and their ecological quality classification at two rocky shores affected by shallow water hydrothermal activity. In the Azores, this is the closest to polluted shores, with which to test quality assessment tools. The accumulation of heavy metals in different seaweeds has been quantified and compared between the vicinity of shallow water hydrothermal activity and of urban development in the Azores. The concentration of heavy metals in Fucus spiralis has been compared between samples affected by hydrothermal seeps in the Azores and by acid mine drainage in the British Isles. Preliminary culture experiments provide an insight on the influence of temperature and acidity on the growth and photosynthesis of F. spiralis, as measures of metal accumulation capacity of this species.