Rocky-shore communities as indicators of water quality: a case study in the Northwestern Mediterranean.

The collection of 152 samples from the upper sublittoral zone along the rocky coasts of Catalonia (Northwestern Mediterranean) was carried out in 1999 in order to test the suitability of littoral communities to be used as indicators of water quality in the frame of the European Water Framework Directive. Detrended correspondence analysis were performed to distinguish between different communities and to relate communities composition to water quality. Samples collected in reference sites were included in the analysis. Mediterranean rocky shore communities situated in the upper sublittoral zone can be used as indicators of the water quality: there is a gradient from high to bad status that comprises from dense Cystoseira mediterranea forests to green algae dominated communities. The geographical patterns in the distribution of these communities show that the best areas are situated in the Northern coast, where tourism is the main economic resource of the area, and the worst area is situated close to the metropolitan zone of Barcelona with high population and industrial development. Thus, Mediterranean sublittoral rocky shore communities are useful indicators of water quality and multivariate analysis are a suitable statistical tool for the assessment of the ecological status.

A new methodology based on littoral community cartography dominated by macroalgae for the implementation of the European Water Framework Directive.

Macroalgae is a biological key element for the assessment of the ecological status in coastal waters in the frame of the European Water Framework Directive (WFD, 2000/60/EC). Here we propose a methodology for monitoring water quality based on the cartography of littoral and upper-sublittoral rocky-shore communities (CARLIT, in short). With the use of spatial databases, GIS, and available information about the value of rocky-shore communities as indicators of water quality, it is possible to obtain an environmental quality index representative of the ecological status of rocky coasts. This index, which completely fulfils the requirements of the WFD, is expressed as a ratio between the observed values in the sector of shore that is being assessed and the expected value in a reference condition zone with the same substrate and coastal morphology (Ecological Quality Ratio, EQR). The application of this index to the coast of Catalonia (North-Western Mediterranean) is presented.