Purpose: Some marine organisms can be used as Biological Quality Elements to estimate the degree of environmental impact and to monitor the health of benthic habitats. Organisms with mineralized protections, such as benthic foraminifera, can provide helpful information on the evolution of the coastal system over a long period and determine the Paleo-Ecological Quality Status (Paleo-EcoQS). This work aims at reconstructing the Paleo-EcoQS in the heavily anthropized Sepetiba Bay (SB; Rio de Janeiro State, SE Brazil). Materials and methods: This work is based on a multiproxy approach, including textural, geochemical, and foraminiferal data along the core SP11 retrieved near the Pico da Marambaia (a mountain on the tip of the Marambaia Barrier Island). Geochemical analyses encompassing total organic carbon (TOC), total sulfur (S), total nitrogen (N), calcium carbonate (CaCO₃), stable isotopes in organic matter (_OMδ¹³C, and _OMδ¹⁵N) and elemental concentrations as well as ²⁰¹Pb, ¹³⁷Cs, and radiocarbon dating were performed to characterize the Paleo-EcoQS in the bay. Results: The values of the Paleo-EcoQS.st (standardized Paleo-EcoQS) index in core SP11 indicate that the paleoenvironmental quality varied from moderate to good between ≈50 AD and ≈1500 AD and from good to high between the ~ 1920s and ~ 1990s. Since the 1990s, the Paleo-EcoQS.st has deteriorated considerably, probably due to the deposition of contaminated dredging material in nearby areas. Ballast water discharge may have introduced alien species, such as Ammonia buzasi, into the SB. Conclusions: The results obtained in core SP11, compared to those of another core (i.e., SP8) from a nearby area, suggest that the reference level of maximum environmental quality is not always reached in a period before industrialization in coastal ecosystems with significant interaction with the ocean; natural factors, related, for example, to sedimentary dynamic processes or geomorphological changes, can lead to unexpected results.

A multiproxy approach involving grain size, geophysical (resistivity, magnetic susceptibility, and P-wave velocity), mineralogical (XRD), and geochemical (elemental, stable isotopes) data has been applied to core SP9 (128 cm long) to reconstruct natural and anthropogenic changes since ≈1850 AD (anno domine) (dating by ²¹⁰Pb and ¹²⁷Cs methods) in a distal region of Sepetiba Bay (SB), Rio de Janeiro State (SE Brazil). The analyzed core is a fine-grained sedimentary sequence (except its upper 20 cm). It comprises detrital particles derived from felsic and intermediate source rocks, as suggested by the fields defined by the biplot Zr vs TiO₂ and the Al₂O₃/TiO₂ ratios. Despite the increase in particle size at the top of the core, there was a progressive increase in the organic matter and potentially toxic elements (PTEs) contents and nutrients such as N and P. The geophysical data allowed us to identify the presence of subsurface (biogenic) gas, which suggests the occurrence of eutrophication processes in the study area despite its location in the outer region of the bay. Core SP9 records cyclical changes over the last ≈170 years in the mineralogical and elemental composition of the sediments and type of organic matter supplied to the bottom. These changes are associated with phases of more significant oceanic influence, salinity variations in the study area, and greater or lesser oxygen depletion in the sediment. These changes may have resulted from climatic oscillations or variations in the configuration and extension of the Ponta da Pombeba spit. The extent of this structure and the anthropic activities have contributed to the contamination of this area since 1975 AD. However, statistical analyses (Pearson correlations and principal components analysis) suggest that the transport and accumulation of PTEs (mainly Cd and Zn) did not strictly follow the general pattern of sedimentary dynamics prevailing in the studied area. Results indicate that this area became strongly polluted by Cd and Zn and with high ecological risk due to dredging and spoil disposal activities at sites close to the study area. It is noted that the environmental degradation reached higher levels here than in areas close to the primary source of the metals, the disabled Ingá Mercantil Company, in Madeira Island. This work demonstrates the temporal effect of dredge disposal activities in a distal region of Sepetiba Bay for the first time. It is a strong indicator that dredged spoil areas must be selected carefully, since healthy areas can become degraded due to the dumping of polluted waste.

Protected coastal areas, such as bays, estuaries, and coastal lagoons, are generally highly populated and impacted by anthropogenic activities. These regions are also vulnerable to the effects of climate change and sea level fluctuations. This work aims to study the records of temporal changes induced by shifts in rainfall and human factors in the western region of Ilha Grande Bay (BIG; Rio de Janeiro State, SE Brazil). The study compares textural, mineralogical, and geochemical data in two cores, BIG01 and BIG02, collected in Paraty Harbor and Saco de Mamanguá, respectively. The two cores have recorded sedimentary changes since 1950, as indicated by ²¹⁰Pb and ¹³⁷Cs dating. The statistically integrated results indicate higher moisture levels before ~ 2000 in this region and a general trend toward reduced rainfall since then, accompanied by an increase in the sediment accumulation rate since the 1980s, likely due to the progressive expansion of urbanization, deforestation, agriculture, and dredging activities in BIG. The Paraty region (BIG01) was most affected by recurrent landslides during concentrated rainfall in SACZ events and by anthropic impact, especially since ~ 1970. This impact has resulted in silting, eutrophication, and moderate pollution by potentially toxic elements, especially Cu, Pb, Sn, Zn, and As. The records of cores BIG01 and BIG02 highlight the influence of climate change, namely SACZ and human activities, on sedimentation and sediment quality. The recurrence of mega-events, such as SACZ paleo-events, and their impact on landslides in slope zones require further study, particularly in densely populated areas.

The municipality of Mangaratiba, located in the Sepetiba Bay region (Rio de Janeiro State; Southeast Brazil), has been taken over for several years by large structures, including real estate, tourism, industrial and ore export activities. Transportation and port activities, especially iron ore logistics from the Iron Quadrangle region (MG), have changed the landscape, particularly the beaches in the municipality of Mangaratiba. Thus, this study applies a multiproxy approach (textural, mineralogical, elemental and lead isotopic data) to iron ore samples and ore particles found on beaches and a waterfall from the Mangaratiba region, aiming to identify the impact caused by ore transport and dispersion in the study area. The results show that the sands of Sahy, Ribeira, Santo Antônio, Muriqui, Mangatiba’s Centro, Junqueira, Saco and Itacuruçá beaches have relatively high contents of pyrite, hematite, magnetite/maghemite and goethite, which are part of the ore composition samples. The variation in the ²⁰⁶Pb/²⁰⁴Pb and ²⁰⁷Pb/²⁰⁴Pb values show similarity in the isotopic fingerprints in the Fe ore samples and ore particles found on beaches, suggesting common sources. Iron ore has the highest sum of toxic units (ΣTUs 17.9–21.8). The highest toxicity degree ratio (TDR) based on ΣTUs values was found in the ore samples and at Junqueira Beach, Saco Beach, near the train line, and Santo Antônio Beach, close to the Guaiba Island iron ore export terminal. This work shows that ore dispersion during transportation is causing environmental degradation on most Mangaratiba beaches. There is a risk of exposure to the ore particles by the people who visit the beaches and inhabit the region and the organisms that live there. People may inhale dust (enriched in Sb, Mn, Fe, Cd, Ag, and Ge), which is dispersed during the ore transportation by strong wind and displays irritation of the skin and eyes, among other diseases. This study indicates the need to adopt mitigating measures to avoid severe environmental damage and public health problems.

There is a gap in knowledge about the biodiversity of living foraminifera (protozoa) in Brazil, particularly in coastal environments. In Sepetiba Bay (SE Brazil), a coastal system highly impacted by anthropogenic activities, several previous studies have been carried out on foraminifera based on total (living + dead) assemblages and sub-fossil records. Thus, this study intends to analyze for the first time the species richness of living foraminifera (stained with Rose Bengal) in Sepetiba Bay. Based on the morphological characteristics, 214 living species were identified in 50 samples collected in Sepetiba Bay in May 2022. The number of living specimens was counted as 6548. Living foraminifera density was < 252 specimens per gram of sediment and the species richness (S) ranged from 15 to 61 (mean 16.9 ± 15.5) in the analyzed stations. The main taxonomic classes found were Globothalamea and Tubothalamea. The main Globothalamea taxa belonged to the genus Ammonia, with Ammonia tepida, Ammonia buzasi, and Ammonia rolshauseni standing out, as well as the Bolivina, Buliminella, and Elphidium, represented mainly by Bolivina striatula, Buliminella elegantissima, and Elphidium excavatum. A non-Metric Multidimensional Scaling (nMDS) and cluster analysis based on a presence-absence matrix and Bray–Curtis similarity index allowed the identification of two main groups of stations: 1. Located in the innermost areas of Sepetiba Bay and surrounding the mainland and Marambaia Barrier Island, at shallower depths, with lower diversity; 2. an outermost group of stations with higher diversity in areas with greater oceanic influence. Compared with previous studies, the results of this work suggest an enlargement of the “innermost” zone with less diversity towards the oceanic region of Sepetiba Bay. This work shows that even using a matrix of presence/absence of living foraminifera and species richness, it is possible to distinguish environments in coastal systems. Data based on the living foraminifera is needed to understand current biodiversity to better characterize coastal environments and carry out biomonitoring studies.