Towards a more integrative approach for environmental decision-making in Brazilian transitional waters: improving biomonitoring surveys with a benthic foraminiferal biotic index

Abstract

This study represents the first attempt to determine the indicator values of benthic foraminiferal species in Brazilian transitional waters. It also uses a regionally adapted species list to explore the potential application of Foram-AMBI, a biotic index for ecological quality. To test this, we assigned 95 living (rose-bengal-stained) benthic foraminiferal species into five ecological groups (EGs), based on the weighted-averaging (WA) optimum and tolerance to the total organic carbon (TOC) contents. Selected and published regional studies were used as the database, while independent Brazilian datasets from Sepetiba Bay and Guanabara Bay – the most polluted regions – were used to validate the ecological group assignments through Foram-AMBI. Furthermore, ecological quality status (EcoQS) criteria adapted to Brazil were developed for Foram-AMBI. The index accurately reflects the degraded environmental conditions in these two ecosystems, with moderate to poor ecological quality status in the most polluted areas. This was further confirmed by significant correlations between Foram-AMBI and TOC in both bays. This study highlights the importance of developing regional species lists and EcoQS criteria for Foram-AMBI, as the accuracy of the Brazilian list was better than that of the European list. While further research across broader pollution gradients is needed, our findings confirm the suitability and reliability of benthic foraminifera as biological indicators for assessing environmental quality in transitional waters.