Variações temporais das assembleias de foraminíferos bentônicos recentes produtores de carbonato sedimentar em área sob influência de emissário submarino, Litoral Norte da Bahia.

Abstract

The primary objective of this study was to characterize and assess the ecological status of the sedimentary environment on the continental shelf in an area adjacent to a submarine outfall along the Northern Coast of Bahia, Brazil, through the microfaunal analysis of benthic foraminifera (qualitative and quantitative composition of foraminiferal assemblages). This study aims to provide insights into the health of the ecosystem and the potential effects of pollution and local sediment dynamics in a paleoecological context, also addressing the taphonomy of the foraminiferal tests. For this purpose, grain size and foraminiferal fauna analyses were carried out at ten sites during the seasonal cycles (dry and rainy) of 2010 and 2018. In the first approach (Article 1), the results indicated homogeneity in the sedimentary environment, with sediments being predominantly biogenic and nutrient-poor, reflecting moderate to high hydrodynamic activity and the stability of the physicochemical parameters of seawater. The microfaunal analysis identified 96 species of foraminifera, revealing the dominance of symbiont-bearing species such as Amphistegina gibbosa, Peneroplis carinatus, and Archaias angulatus, which are bioindicators of good environmental quality, particularly in coral reef ecosystems. The spatiotemporal distribution of foraminiferal assemblages was consistent in both qualitative and quantitative composition, as well as in diversity estimates (H') and the FORAM Index (FI), suggesting a satisfactory ecological status for the studied portion of the continental shelf. A high rate of test anomalies was observed in symbiontbearing species, especially in areas closer to the outfall. These findings suggest the influence of anthropogenic pollution, as the study recorded the highest deformity rates near the diffuser structures. Nonetheless, the possibility that these alterations result from species regeneration in response to local hydrodynamic stress cannot be ruled out. The study confirmed that, despite the region's moderate to high hydrodynamic energy, the composition of foraminiferal assemblages and the temporal continuity of ecological patterns demonstrate the stability and resilience of the environment, even in the face of industrial activity. The second approach (Article 2) focused on the spatial-temporal distribution of the foraminiferal assemblages, their ecological characteristics, and the taphonomy (wear and coloration) of foraminiferal tests, relating these to the sedimentary environmental processes in the area. The persistent spatialtemporal patterns in the species composition and taphonomic characteristics suggest that, despite the moderate to high hydrodynamic energy typical of shallow tropical shelf environments, it does not significantly affect the distribution of foraminiferal assemblages, reflecting the uniformity in faunal composition and the clear temporal continuity observed.