Living and dead foraminifera assemblages as environmental indicators in the Almada River Estuary, Ilheus, northeastern Brazil

Analyses of living (L) and dead (D) foraminifera assemblages associated to environmental parameters were applied at the Almada River Estuary, aiming for assessments concerning local biodiversity, hydrodynamic sector and environmental quality. A total of 27 species were identified in the living assemblage and 35 in the dead, with the predominance of Ammonia tepida and Cribroelphium excavatum. A DCA for the living fauna demonstrated that C. excavatum Adelosina milletti, Elphidium discoidade, Rosalina bradyi and Triloculina oblonga were associated to shallow areas with muddy sediment and under marine influence in the estuary. Laryngosigma lactea and Pyrgo oblonga were associated to deep areas with sandy sediment under marine influence. All agglutinated species and the calcareous D. nitida and Miliolinella subrotunda were associated with organic matter and high chlorophyll levels from mangrove areas. A cluster analysis performed for L and D revealed five estuary regions: I - composed predominantly by D transported from the inner shelf; II - composed by L marine species; III - composed by D transported from region II and the inner shelf; IV - composed by living agglutinated species that delimit the beginning of the upper estuary area; and V - composed by transported agglutinated foraminifera and some calcareous species transported during storm episodes The present study was efficient in the environmental characterization of the Almada River Estuary and can be used as a baseline to understand natural or anthropic impacts in this ecosystem.

Automated summary

Analyses of living and dead foraminifera assemblages revealed the distribution patterns of different species in relation to environmental parameters and classified the estuary into five regions. This study efficiently characterized the environmental conditions of the Almada River Estuary and provided a basis for understanding natural or anthropic impacts on this ecosystem.