Assessment of the Ecological Quality of the Santos Estuarine Complex (SE Brazil): Predictive Models and Benthic Foraminifera-Based Index

The Santos Estuarine System, one of the most anthropogenically impacted coastal regions in Brazil, was studied using benthic foraminiferal assemblages to determine four distinct stages of organic pollution. Predictive models combined with the Ecological Quality Status (EcoQs) index were applied to relate pollution stages to abiotic parameters (total organic carbon, mud content, and salinity variability) and organic contaminants, including aliphatic (AHs) and aromatic hydrocarbons (PAHs), linear alkylbenzenes (LABs), and coprostanol. The pollution gradient ranged from low (São Vicente Channel and Santos Bay, characterized by Ammonia tepida and medium coprostanol concentrations), to moderate (Santos Channel, with Bulimina elongata and Triloculina sp.1), high (Bertioga Channel, showing Cribroelphidium poeyanum, Paratrochammina sp.1, high levels of LABs, and TOC), and severe (Upper Estuary, marked by Ammonia sp.1 and high concentrations of PAHs and coprostanol). A linear discriminant analysis (LDA) demonstrated an overall accuracy of 70%, suggesting that the discriminant model performs reasonably well in predicting the predictive ability of foraminifera species to distinguish between areas with varying pollution status based on organic pollutants. Also, the potential use of the EcoQs index in assessing the environmental quality of a subtropical estuary subjected to organic pollution was demonstrated.