The application of two benthic indices to investigate the effects of land-based fish farms in coastal transitional ecosystems: two case studies in Tuscany region (Italy)

The effects on the benthic ecosystem deriving from the activities of two land-based fish farms located in Italian coastal transitional ecosystems (CTEs) were investigated. Together with chemical and physical analysis, some biological analysis was performed. For each fish farm, three stations were sampled: two stations located inside the farm (ponds exit and farm exit) and one station located outside the fish farm, considered as reference site. The AZTI's Marine Biotic Index (AMBI) and the BENTIX index were calculated, which are being used in assessing the ecological status of benthic communities within the European Water Framework Directive (WFD). Results were compared in order to evaluate the more suitable index for this study area. Both the indices gave similar results but AMBI resulted more sensitive than BENTIX, probably due to the small size of the collected samples. This study seems to suggest that AMBI, being not dependent from sample size, could be preferred as descriptor of benthic health status in CTEs.