Improvement of the Esca index for the evaluation of ecological quality of coralligenous habitats under the European framework directives

Abstract

The ESCA (Ecological Status of Coralligenous Assemblages) index was recently developed to evaluate the ecological quality of coralligenous habitats. The study aims to improve the first index proposal through testing responses to different sources of anthropogenic pressures and optimizing the sampling effort. ESCA was calculated for 14 sites and tested against a gradient of human pressures. Moreover, the main scales of spatial variability of assemblages were evaluated and values of index obtained with different sampling designs were compared. Results showed that study sites resulted in high, good or moderate ecological status, according to an increasing gradient of anthropization level. Values of ESCA index obtained with different methods have been compared, and photographic methods provide EQR values lower than destructive methods. Spatial variability of assemblages was higher at large and small scales than at intermediate ones. Two locations for each study site and 20 replicated samples for each location may be consider the best sampling combination providing reliable values of ESCA index for the evaluation of ecological quality of coralligenous assemblages.