Inferring the ecological quality status based on living benthic foraminiferal indices in transitional areas of the Guanabara bay (SE Brazil)*

Using benthic foraminifera, we evaluate the ecological quality status (EcoQS) of transitional waters of the Guanabara Bay (SE Brazil) by applying the diversity-based index exp (H ' bc) and the sensitivity-based ForamAMBI for the first time in South America. The Guanabara Bay was selected for this study as it is one of the largest transitional ecosystems in the State of Rio de Janeiro and has been severely impacted by anthropogenic activities. Concentrations of potentially toxic elements (PTEs) were assessed by sequential chemical extraction in three phases (i.e., dissolved in water, adsorbed on organic matter, and Mn oxy-hydroxides). Total organic carbon, total nitrogen, and stable isotope (delta C-13 and delta N-15) signatures of organic matter were analyzed to trace environmental stress. The Ammonia/Elphidium ratio suggests hypoxic conditions at most of the sampled sites. Principal component analysis identifies the first component as environmental stress underlying organic matter and PTE enrichment (in all three phases), which is positively related to Foram-AMBI and negatively to exp (H ' bc). The exp (H ' bc) and Foram-AMBI indices reveal that stations near the Governador Island and Niter ' oi margin have the worst EcoQS, showing medium to extreme pollution. Additionally, Foram-AMBI and exp (H ' bc) provide a congruent EcoQS classification for similar to 64% of the sites. Although these results are promising, they suggest that a significant effort should be made to obtain better knowledge of foraminiferal ecological requirements to employ benthic foraminifera as a biomonitoring and management method.

Automated summary

Using benthic foraminifera, this study assesses the ecological quality status of the Guanabara Bay transitional waters in South America for the first time. The results indicate that the Bay has been severely impacted by anthropogenic activities, leading to medium to extreme pollution levels. The indices used reveal that stations near the Governador Island and Niter 'oi margin have the worst ecological quality status.