Author /Editor: Mikel Zubikarai, Ángel Borja and Iñigo Muxika
The need to find efficient indices and indicators to assess the status of the marine enviroment and prevent further deterioration of coastal areas is one of the hot topics in today’s marine research. However, a detailed knowledge of benthic communities’ responses to anthropogenic impacts is essential to develop those indices. The studies on the response of benthic communities to sewage pollution and the management measures to remove that pollution on rocky shores are generally based on semiquantitative data and do not take into account both intertidal and subtidal levels. In order to fulfil this gap, the objetives of this study were: (i) to analyse the responses of benthic communities (both fauna and flora) to different phases in the management of wastewater discharges; and (ii) to determine wether if trophic guilds could be an adequate indicator of the changes shown after different management decisions. Hence, fauna and flora data from a quantitative (biomass) monitoring from three areas of the Basque coast were used, with organisms identified to the lowest taxonomic level, with information at intertidal (midlittoral and infralittoral fringes) and subtidal (5, 15 and 25 m) levels. After the different phases on the water treatment management (with or without treatment), investigation results show that the improvement in water quality significantly changed the structure and diversity of intertidal and subtidal assemblages. In fact, those differences were detected by the improvement in some univariate variables mean values, like richness. In turn, significant (p <0.05) differences were also found in fauna and flora biomass between tidal levels, transects, trophic guilds and evolution of the management phases. Moreover it has been found that, changes in trophic guilds and multivariate analyses seem to be an adequate way to monitor benthic hard substratum communities responses to changes in the management of anthropogenic pressures in the Basque coast. Hence, the evaluation of these changes in benthic communities may be useful to inform managers and the society in general about the effectiveness of these indices and indicators.