Response of different biotic indices to gradients of organic enrichment in Mediterranean coastal waters: Implications of non-monotonic responses of diversity measures

► Seven biotic indices were calculated for a benthic dataset of Mediterranean infauna. ► The coastal areas studied were naturally poor in sediment organic matter content. ► Diversity indices did not show a monotonic response to gradients of organic content. ► Indicator taxa indices gave a more reliable picture of the benthic ecological status. ► M-AMBI was always less correlated with the gradient of organic content than AMBI.