Living and dead benthic foraminiferal assemblages as proxies for the environmental characterization in the mesotidal tropical estuary: Cachoeira River (Bahia, Brazil)

: This study aimed to characterise the Cachoeira River Estuary (CRE) in Bahia, Brazil, using living (L) and dead (D) foraminiferal as bioindicators, focusing on the identification of environmental quality and anthropogenic impacts. Seventy-six species of foraminifera were identified, with the highest species richness and density found in the lower and middle estuary. Twenty species occurred only in the L assemblage and 26 species only in the D assemblage. The most abundant species in both assemblages were Paratrochammina clossi, Ammonia tepida morphospecies, and Elphidium excavatum. Four distinct regions were recognised based on the distribution of L and D foraminifera and sedimentological parameters. Region I represents the estuary mouth with the most active hydrodynamic conditions, represented mainly by Bolivina striatula (L and D); region II represents the confluence of the tributary rivers and is characterised by A. tepida and P. clossi (L and D); region III in the middle estuary area is represented by Quinqueloculina seminulum (L) and P. clossi (L and D); region IV represents the beginning of the upper estuary and is mainly represented by Trochammina inflata (L and D). Region IV receives more freshwater but is still influenced by the tides, which allow the significant presence of Q. seminulum (D) and P. clossi (D). The present study was efficient in the environmental characterisation and can be used as a baseline to understand natural or anthropogenic impacts in this ecosystem, as well as to improve sea level models in tropical mesotidal estuaries.