The Fundão dam failure, the worst environmental disaster in Brazilian history, launched 50 million m ³ of iron ore tailings mud through the Doce River, reaching the Atlantic Ocean. Generally, mine tailings increase the sediment inflow, leading to mud burial of epibenthic macrofauna, and the raise of metal(oid)s concentration causing macrofauna long-term changes. After almost four years, tailings mud was still spreading on the Doce River Shelf, while impacts on marine macrofauna were still unknown. Herein, the IMS index (a tracer of Fundão dam tailings mud), sediment variables, organic pollutants, and metal(oid)s were integrated to uncover the drives of macrofauna structure from Costas da Algas to Abrolhos bank MPAs. Tailings mud was present only in Doce River Mouth and Degredo, organic pollutants and metal(oid)s above safety levels were concentrated in those same areas. Tailings mud (IMS index) drastically reduced species richness and diversity, favoring the abundance of opportunistic species. Mud, IMS index and Al, Ba, and V, metal(oid)s linked to dam failure, structured macrofauna composition in this impacted area, dominated by resistant groups as Nuculidae, Spionidae, and Magelonidae. Conversely, an opposite pattern was found for further and deeper sites with high CaCO3 content and total nitrogen that also showed large grain size, in areas known to harbour biogenic structures, sustaining a macrofauna composition distinct from the impacted areas, dominated by Syllidae and Crassatellidae, sensitives to impacts. Macrofauna composition was most structured by sediment variables, followed by the intersection between metal(oid)s-IMS and Mud, both gradients acting almost entirely on a broad spatial scale. Benthic macrofauna at the Doce River Shelf is still impacted by Fundão dam tailings mud, even after almost four years of the disaster, and may continue to, since the influx of tailings does not stop, and sediment resuspension is a recurrent source for those impacts.

Since November of 2015, when ore tailings from a dam rupture reached the Atlantic Ocean, researchers are trying to assess the degree of impact across the Doce River and adjacent coastal area. This study aims to use the zooplankton dynamics as a tool to evaluate the environmental impact in the coastal region, five years after the rupture, during periods of low and high river flow. Doce River flow varied from 49 to 5179 m ³/s and structured the zooplankton community between periods of low and high river flow, but salinity and chlorophyll-a had stronger correlation with depth (r = 0.40 and − 0.40 respectively) than with the Doce River discharge variation along the sampling period (r < 0.2). On the other hand, inorganic particles in the water and total metal concentration (dissolved + particulate), used as tracers of the iron enriched tailing (Al, Cd, Cr, Cu, Fe, V), were correlated with fluvial discharge and showed to be the main factor driving the zooplankton community dynamics. For assessing the degree of environmental impact, we tested the ecological indexes for the zooplankton community. Margalef Richness, Pielou Evenness and Shannon-Wiener Diversity varied from 2.52, 0.40 and 1.39 (all registered during high river flow period) to 9.02, 0.85 and 3.44 (all registered during low river flow period), respectively. Along with those community indicators, we evaluated the response of representative taxonomical genera such as Paracalanus, Oikopleura and Temora, regarding the Doce River flow, and found population patterns that established a baseline for future monitoring in the region. Our results showed that the zooplankton community is more fragile when the river discharge is stronger, and this pattern is confirmed by all indicators tested.

Zooplankton were sampled five days after the tailings from the Samarco dam rupture reached the ocean in the coastal region at the mouth of the Doce River. This was one of the largest environmental disasters in Brazilian history, and the impacts on the marine biota are not yet fully understood. This study aimed to evaluate the zooplankton community short term responses to the metal enrichment after the tailings reached the coastal region in different scenarios. Our results showed an acute impact on the zooplankton community, which peaked in abundance (222,958.60 ind/m ³) and decreased in diversity (H′ = 1.23) near the river mouth. Two copepod species, Parvocalanus sp. and Oithona nana, composed up to 61% of the total abundance and they were correlated with concentrations of Fe, Pb, Cu and Zn in particulate fraction. These species feed opportunistically on nanophytoplankton, which dominated the autotroph community, possibly in response to the iron enrichment caused by the mud flow. A shift on zooplankton species composition was also observed. During the first three days, we found the presence of oceanic species in the 20 and 30 m isobaths during an incomplete upwelling event, which directly correlated with the presence of Calanoides carinatus. However, only three days later, following a cold front passage and consequent increase of water turbidity, those species were already absent, and the zooplankton community was significantly altered (PERMANOVA, df = 1, pseudo-F = 9.2247, p = .001). Zooplankton responded quickly to the environmental changes detected during our sampling period and proved to be key factors in costal monitoring, especially in dynamic oceanographic areas such as the Doce River coastal region.

Paq proxy was applied on mid and long-chain n-alkanes in order to develop an index to assist in the long-term assessment of changes and exchanges between aquatic communities in estuarine environments as a result of increased saline incursion. New boundaries are proposed according to n-alkanes abundance in the leaves of local mangrove tree species for better definition of emergent aquatic plant end-member. Molecular distribution and δ13C isotopic signatures of n-alkanes were also used to support the parameter. A predominance of odd carbon-numbered long chain (> C27 n-alkanes) indicated a main terrestrial input, although mid-chain n-alkanes (23 and 25 carbons) were also identified. Short-chain n-alkanes (< 19) were absent or found in a very small concentration. Carbon Preference Index and C/N ratio reinforced a terrestrial origin for the sedimentary organic matter. δ13C signatures of n-alkanes for C23, C25, C29 and C31 were characteristic of mangrove input, ranging from -27.57 ‰ (C23) to -34.40 ‰ (C29) for Piraquê-Mirim River (PM) and from -27.36 ‰ (C23) to -32.84 ‰ (C31) for Piraquê-Açu River (PA) without any particular trend. Paq proxy was successfully used to identify rises in marine macrophytes (mid-chain n-alkanes) input mainly in the confluence and PM probably as consequence of drought periods. The confluence presented a mixing sources of OM. PA was identified as a stable mangrove environment while PM was characterized by pulses of marine macrophytes input and should be managed with care in respect to its catchment for water use and dam constructions as a shortage of fresh water can alter the estuarine ecology.

The Piraquê-Açú and Piraquê-Mirim estuarine system (PAPMES) is considered to be a hydrologically unaltered estuary; however, several human activities including introduction of pollutants may have contributed to changes in this system. We have studied hydrocarbons, major elements (Al, Mg, Fe and Mn), trace elements (As, Ba, Cd, Co, Cr, Cu, Li, Ni, Pb, V and Zn), Corg./Ntotal ratio, and δ13C and δ15N stable isotopic composition of organic matter to assess the natural and anthropogenic depositional record in three sediment cores dated by 210Pb geochronology. The sediments showed a strong terrestrial C3 plant contribution to organic matter input in the rivers (−29.2 ≤ δ13C ≤ −25.1h; 2.1 ≤ δ15N ≤ 5.3h; 23.3 ≤ Corg./Ntotal ≤ 53.9), with a higher phytoplankton influence downstream (−29.3 ≤ δ13C ≤ −20.7h; 0.4 ≤ δ15N ≤ 6.6h, and 15.4 ≤ Corg./Ntotal ≤ 34.4). Greater n-alkane concentrations typical of higher plants (nC27, nC29, nC31) confirmed the terrestrial inputs. There was no indication of contamination by petrogenic sources, but relatively high amounts of 17β(H), 21β(H) and 17β(H), 21α(H) terpanes, indicate a possible association with biogenic activities (bacteria). The distributions of major and trace elements were associated with a high lithogenic input and iron and manganese oxides/hydroxides. Although there is little evidence of enrichment by direct human activity, the downstream sediments may be influenced by deforestation for charcoal production which occurred between the 1950s and 70s, exposing soils to weathering and erosion.

Although the Passagem Channel estuary, Espírito Santo State, Brazil, is located in an urbanized and industrialized region, it has a large mangrove system. Here we examined natural and anthropogenic inputs that may influence trace metal (Cd, Cr, Cu, Ni, Sc, Pb and Zn) and hydrocarbon (n-alkane and terpane) deposition in three sediment cores collected in the tidal flat zone of the estuary. The cores were also analyzed for carbonate, grain size and stable isotopic composition (δ13Corg. and δ15Ntotal). Metal enrichment and its association to petroleum hydrocarbons in the surficial sediments of one of the cores, indicate crude oil and derivative inputs, possibly from small vessels and road run-off from local heavy automobile traffic. At the landward sites, the major contributions for metals and hydrocarbons are from natural sources, but in one case, Cu may have been enriched by domestic effluent inputs.

Three sediment cores (50 cm depth) were collected at three different sites from a tidal flat estuary at Passagem Channel (Vitória, Espírito Santo State-Brazil) to evaluate the influence of recent urbanization processes on the deposition of organic matter (OM) in a complex polluted tropical estuary. In addition to geochronology (by excess 210Pb), the sources of natural and anthropogenic OM to the sediments were evaluated by total organic C (TOC – 14.29 ± 8.73, 30.43 ± 14.71 and 48.70 mg g−1 ± 25.46, respectively, for P1, P2 and P3), C/N molar ratio and lipid biomarkers (sterols and terpenoids). Taraxerol (3.10 ± 4.85, 9.71 ± 3.85 and 16.10 mg gTOC−1 ± 32.48 for P1, P2 and P3, respectively) and sitosterol (1.71 ± 2.72, 2.94 ± 6.41 and 4.07 mg gTOC−1 ± 4.41 for P1, P2 and P3, respectively) were the most abundant compounds in all cores, suggesting a major contribution of terrestrially-derived OM to the study region. Coprostanol levels and selected sterol index indicated significant contamination by fecal material. The organic geochemical indicators suggest that changes of OM reflect occupation and urbanization alteration processes around the Passagem Channel over the last 70 a, mainly the conversion of mangrove forest into urban areas, bridge building and Treatment Plant Station installation.

Estuaries are coastal environments that normally accumulate many contaminants in their sediments, where the estuary of the Canal da Passagem (Vitória-ES) falls in this type of coastal environment, because it is a region that has been suffering with urbanization and industrialization around. In order to evaluate the quality of the sediment of the estuary, were analyzed trace metals cadmium (Cd), Chromium (Cr), Copper (Cu), Nickel (Ni), Lead (Pb), Scandium (Sc) and Zinc (Zn), hydrocarbons (n-alkanes and hopanes), organic carbon and total nitrogen ratio (Corg/Ntotal) and stable isotopes (δ13C) in 3 sediment cores (P1, P2 and P3). The metal concentrations ranged from 0.06 to 0.93 μg/g (Cd) 4.03 to 63.45 μg/g (Cr) 1.27 to 32.72 μg/g (Cu), 1.12 - 10, 05 μg / g (Ni), 1.69 to 22.85 μg/g (Pb), 0.62 to 4.29 μg/g (Sc) and 19.62 to 166.17 μg/g (Zn).The concentrations hydrocarbon were 0.29 to 32.50 μg/g for the n-alkanes and from 0.06 to 14.44 μg/g for the hopanes. While the values of Corg/Ntotal and δ13C varied from 12.96 to 60.96, -36.20 to -25.01‰, respectively. The results show that the estuary of the Canal da Passagem has suffered an accumulation of pollutants over time, especially in the region of core P1, which showed characteristics of anthropogenic contribution to the contamination with oil and derivatives being the main source of metals and hopanes.