Assessment of trophic status in Amazonian estuaries: a reinterpretation of TRIX values in mangrove estuaries

Abstract

stal waters is a key issue in environmental management, and for this purpose, in addition to other methods, indices have been widely used to evaluate the trophic status of these waters (e.g., Bricker et al., 2003). Among the various existing indices to characterize the trophic status of an estuary (Zaldívar et al., 2008; Borja et al., 2012), the Trophic Status Index (TRIX) developed by Vollenweider et al. (1998) has been widely used because it aggregates the main cause-effect variables of eutrophi-cation, including pressure response, biological response, and environ-mental disturbance (e.g., Devlin et al., 2011; Jayachandran and Bijoy Nandan, 2011; Cabrita et al., 2015). The present study evaluates and compares the trophic state of two estuaries located on the Amazon coast.