“…It is known that meiofaunal communities provide a valuable tool for environmental assessments because of their fast response to environmental changes, and that they are more tolerant to oxygen depletion than benthic macrofauna (Alves, Caetano, Costa, Costa, & Marques, 2015; Austen & Wibdom, 1991; Della Patrona et al, 2016; Josefson & Widbom, 1988; Semprucci, Sbrocca, Baldelli, Tramontana, & Balsamo, 2017). Meiofauna are well studied in estuaries (Ansari & Parulekar, 1993; Bownes & Perissinotto, 2012; Capdeville et al, 2018; Costa, Valenca, & dos Santos, 2016; Fu, Cai, Cao, & Chen, 2017; Smol, Willems, Govaere, & Sandae, 1994; Soetaert, Vincx, Wittoeck, Tulkens, & Gansbeke, 1994; Yin, Tan, Yuan, Hu, & Liu, 2017). But there are only a few studies about meiofauna communities from upstream to the mouth of a river estuary, where those communities are exposed to steep environmental gradients (Quang et al, 2018; Semprucci et al, 2015).…”