Integration of ESCA index through the use of sessile invertebrates

The ESCA (Ecological Status of Coralligenous Assemblages) index was developed to assess the ecological quality of coralligenous habitat using macroalgae as a biological indicator. The aim of this study was to evaluate the response to human-induced pressures of macroalgae and sessile macro-invertebrates shaping the coralligenous habitat and to integrate their sensitivity into the ESCA index. Coralligenous assemblages were sampled at 15 locations of the NW Mediterranean Sea classified into three groups: i) marine protected areas; ii) low urbanized locations; and iii) highly urbanized locations. A sensitivity level value was assigned to each taxon/group on the basis of its abundance in each environmental condition, the data available in the literature and the results of an expert judgement survey. The index that includes the totality of the assemblages (named ESCA-TA), calculated using both macroalgae and sessile macro-invertebrates, detected the levels of human pressure more precisely than the index calculated with only macroalgae or with only invertebrates. The potential for assessing the ecological quality of marine coastal areas was thus increased with the ESCA-TA index thanks to the use of a higher variety of descriptors.