Are the eulittoral invertebrate assemblages suitable in detecting the effects of sewage discharges in atlantic and mediterranean coastal areas?

Abstract

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Coastal areas are under high human pressure, being affected by several sources of impacts, such as sewage effluents. Eulittoral assemblages of intertidal rocky shores are often exposed to sewage discharges. Such assemblages are accessible to sample, and their dominant species are easy to identify and widely distributed. These features make eulittoral assemblages potentially cost-effective in discerning between disturbed and undisturbed environmental conditions. In this study, a first attempt has been made to understand whether such assemblages are a suitable indicator of human impacts related to sewage discharges, able to consistently respond over large spatial scales. Sampling occurred in different environmental (sewage outfall and reference areas) and geographical locations (Atlantic insular, Atlantic mainland and Mediterranean). Multivariate analyses showed that the structure of eulittoral assemblages differed significantly between reference and impacted areas only on the Mediterranean shores. In all shores, limpet populations (genus Patella) appear to be affected by sewage discharge. The response of limpet populations differed between Atlantic and Mediterranean shores, probably due to within-species heterogeneities of ecological traits. Our results suggest that the response of limpets might be strictly context-dependent, thus limiting their potential to serve as general targets in monitoring the effects of sewage impact over large spatial scales.

Keywords

• nutrient enrichment
• Ecological Indicators
• Rocky shores
• eulittoral assemblages
• sewage pollution