Influence of Environmental Variations and Sedimentary Dynamics in the Distribution of Foraminifera in the Estuary of The Potengi River (RN, Brazil)

This work consists of the analysis of the spatial distribution of foraminifera as bioindicators of environmental stress and pollution in the surface sediments of the Potengi River estuary and adjacent shelf. Forty-two samples were collected in the years 2011 and 2012, and univariate and multivariate statistical analyzes (diversity, dominance, eveness, PCA, CLUSTER and BIOENV) were applied to a matrix of biotic (benthic foraminifera) and abiotic data (depth, salinity, temperature, grain size, organic matter, CaCO3). The estuary is dominated by hyaline foraminifera (Ammonia tepida, Hanzawaia boueana) associated with fine sandy fractions, while the inner shelf is dominated by porcelanaceous (Quinqueloculina lamarckiana, Q. miletti) and agglutinant species (Caronia exilis, Textularia earlandi), associated with coarser grains. The presence of these agglutinated mixohaline organisms (Caronia exilis and Trochammina spp.) is indicative of estuarine contribution in sediment composition of the shelf and also of sewage effluents deposition. Grain size, CaCO3, organic matter, river and marine contributions are interpreted as controlling the distribution of foraminifera. Opportunistic species (Ammonia tepida, Quinqueloculina patagonica) associated with fine grains and high levels of organic matter revealed critical acidity-like sites inside the estuary, which were maintained from 2011 to 2012.