Prokaryote communities along a source-to-estuary river continuum in the Brazilian Atlantic Forest.

The activities of microbiomes in river sediments play an important role in sustaining ecosystem functions by driving many biogeochemical cycles. However, river ecosystems are frequently affected by anthropogenic activities, which may lead to microbial biodiversity loss and/or changes in ecosystem functions and related services. While parts of the Atlantic Forest biome stretching along much of the eastern coast of South America are protected by governmental conservation efforts, an estimated 89% of these areas in Brazil are under threat. This adds urgency to the characterization of prokaryotic communities in this vast and highly diverse biome. Here, we present prokaryotic sediment communities in the tropical Juliana River system at three sites, an upstream site near the river source in the mountains (Source) to a site in the middle reaches (Valley) and an estuarine site near the urban center of Ituberá (Mangrove). The diversity and composition of the communities were compared at these sites, along with environmental conditions, the former by using qualitative and quantitative analyses of 16S rRNA gene amplicons. While the communities included distinct populations at each site, a suite of core taxa accounted for the majority of the populations at all sites. Prokaryote diversity was highest in the sediments of the Mangrove site and lowest at the Valley site. The highest number of genera exclusive to a given site was found at the Source site, followed by the Mangrove site, which contained some archaeal genera not present at the freshwater sites. Copper (Cu) concentrations were related to differences in communities among sites, but none of the other environmental factors we determined was found to have a significant influence. This may be partly due to an urban imprint on the Mangrove site by providing organic carbon and nutrients via domestic effluents.

Bioaccumulation of chemical elements in fish from areas affected by oil on the coast of Bahia, Brazil.

In 2019, the Brazilian coast was affected by the largest oil spill in its history. We assessed the levels of chemical elements in Lutjanus synagris and Haemulon aurolienatum fish from Itacaré (least affected area), Tinharé-Boipeba (most affected area) and Madre de Deus (chronically affected area). The level of metals differed between species, tissues, life cycle phases, maturation stages and between sampled locations, indicating the influence of biological and environmental aspects on bioaccumulation. Only fish in Madre de Deus showed lead contamination, while arsenic concentrations in the three areas exceeded the maximum value acceptable by Anvisa (National Health Surveillance Agency). It is suggested that the oil spill may have impacted species differently, also having an impact in fish from less affected areas. However, metal concentrations in fish in Madre de Deus stood out when compared to populations in other studied areas.

Understanding seasonal variations in As and Pb river fluxes and their regulatory mechanisms through monitoring data.

The Doce River Basin (DRB) suffers with the adverse impacts of mining activities, due to its high level of urbanization and numerous industrial operations. In this study, we present novel insights into contaminant flow dynamics, seasonal variations, and the primary factors driving concentration levels within the region. We conducted an extensive analysis using a database sourced from the literature, which contained data on the contamination of arsenic (As) and lead (Pb) in the Doce River. Our primary aim was to investigate the patterns of As and Pb flow throughout the entire basin, their response to seasonal fluctuations, and the key parameters influencing their concentration levels. The results showed significant seasonal fluctuations in As and Pb fluxes, peaking during the rainy season. The 2015 Fundão dam breach in the DRB led to notable changes, elevating elemental concentrations, particularly As and Pb, which were subsequently transported to the Atlantic Ocean. These increased concentrations were primarily associated with iron and manganese oxides, hydroxides, and sulfates, rather than precipitation, as evidenced by regressions with low R2 values for both As (R2 = 0.07) and Pb (R2 < 0.001), concerning precipitation. The PCA analysis further supports the connection between these elements and the oxides and hydroxides of Fe and Mn. The approach employed in this study has proven to be highly effective in comprehending biogeochemical phenomena by leveraging data from the literature and could be a model for optimizing resources by capitalizing on existing information to provide valuable insights for drainage basin management, particularly during crises.

Distribution, toxicity and bioaccumulation of trace metals in environmental matrices of an estuary in a protected area.

Mangroves are productive ecosystems that are highly threatened by anthropogenic activities. We investigated the environmental quality of the Serinhaém river estuary located in a legally protected area. Through chemical analysis of sediments and tissues of Cardisoma guanhumi, in addition to bioassays with elutriate involving Nitokra sp. and Thalassiosira pseudonana, we determined the contamination status and risk factors related to trace metals in the estuary. For the sediment, the concentrations of Cr and Ni were above the limit established by CONAMA n° 454/2012 in the "City" site, and Cr above the TEL in all sampling sites. Ecotoxicological tests showed high toxicity in samples from "City" and "Tributary". The elements Cr, Mn, Ni and Zn were also higher in crabs from these sites. Cr levels exceeded the Brazilian limit for food consumption. The bioaccumulation factor was not significant. However, the overall analysis proved that this estuary is increasingly impacted by anthropogenic pressure.

Seasonal variation, contribution and dynamics of trace elements in the drainage basin and estuary of the Serinhaém river, BA.

In the present study a mass balance calculation was used to quantify trace elements (Al, Ba, Cd, Cr, Cu, Fe, Mn, Pb, Ti, V and Zn) fluxes exported from the Serinhaém River estuary to the Atlantic Ocean. The studied elements exportation in the particulate fraction showed higher fluxes in the first sampling campaign and a high export rate to the Atlantic Ocean during this period. The physical-chemical parameters showed the highest values in sampling campaign 1. These variations are probably the cause of the different trace elements behavior in fluvial and estuarine areas, where removal and addition processes between particulate and dissolved phases took place, affecting distribution coefficient and fluxes to the Atlantic Ocean. EPA ecosystems present values in accordance with Brazilian legislation for pristine areas, however, monitoring programs must be carried out in the region, to avoid future environmental problems.

Large-scale differences in diversity and functional adaptations of prokaryotic communities from conserved and anthropogenically impacted mangrove sediments in a tropical estuary.

Mangroves are tropical ecosystems with strategic importance for climate change mitigation on local and global scales. They are also under considerable threat due to fragmentation degradation and urbanization. However, a complete understanding of how anthropogenic actions can affect microbial biodiversity and functional adaptations is still lacking. In this study, we carried out 16S rRNA gene sequencing analysis using sediment samples from two distinct mangrove areas located within the Serinhaém Estuary, Brazil. The first sampling area was located around the urban area of Ituberá, impacted by domestic sewage and urban runoff, while the second was an environmentally conserved site. Our results show significant changes in the structure of the communities between impacted and conserved sites. Biodiversity, along with functional potentials for the cycling of carbon, nitrogen, phosphorus and sulfur, were significantly increased in the urban area. We found that the environmental factors of organic matter, temperature and copper were significantly correlated with the observed shifts in the communities. Contributions of specific taxa to the functional potentials were negatively correlated with biodiversity, such that fewer numbers of taxa in the conserved area contributed to the majority of the metabolic potential. The results suggest that the contamination by urban runoff may have generated a different environment that led to the extinction of some taxa observed at the conserved site. In their place we found that the impacted site is enriched in prokaryotic families that are known human and animal pathogens, a clear negative effect of the urbanization process.

δ13C, δ15N and TOC/TN as indicators of the origin of organic matter in sediment samples from the estuary of a tropical river.

The present study aimed to determine the total organic carbon (TOC), total nitrogen (TN), the carbon­nitrogen ratio (TOC/TN), carbon isotope (δ13C), and nitrogen isotope (δ15N) in five sediment cores collected from upstream to downstream of the Rio Serinhaem estuary, State of Bahia, Northeast Brazil, in order to investigate the origin of the deposited organic matter (OM).Significant positive correlation was found between TOC and NT (rs = 0.75); TOC/TN and TOC (rs = 0.64); δ15N and TOC (rs = 0.72); and δ15N and TOC/TN (rs = 0.63). The values of δ13C and δ15N found are characteristic of terrestrial sources. The TOC/TN ratio confirmed the data found for δ13C and δ15N, which recorded the origin of organic matter from terrestrial C3 type plants. Upstream of the estuary, the highest means of TOC/TN were found (T1 = 36.9 and T2 = 24.4), as reflected by the increase in TOC content or reduction in TN. The OM along the estuary is predominantly from plants with a C3 photosynthetic pattern, indicating that the Serinhaem River estuary is considered a relatively well-preserved environment.

Evaluation of the concentrations of elements at trace level in the Serinhaem River estuary, Bahia, Brazil, using chemometric tools.

The Serinhaém River estuary is located in the Environmental Protection Area (EPA) of Pratigi, in the State of Bahia, Brazil, which is recognized for being a relatively well-preserved environment. In this work, the levels of aluminum (Al), arsenic (As), barium (Ba), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), manganese (Mn), nickel (Ni), lead (Pb), vanadium (V), and zinc (Zn) were determined to evaluate the behavior of these chemical elements through geochemical parameters. Eighty-one sediment samples were collected in five sediment cores along the estuarine region. The results of the composition of the Serinhaém river basin showed high levels of Fe, Al, and Mn in the sediment samples. By using Principal Component Analysis, it was observed that 55.8% of the elements have a significant correlation with Fe, Al, and Mn, which may have the same origin or be associated with Fe and Mn oxy-hydroxides, and aluminosilicates. Although Cr, As, and V are correlated with Fe, Mn, and Al, their concentrations are above those established by NOAA, suggesting adverse effects on biota. Barium concentrations increased toward the outfall, where it meets the Camamu Bay, which is naturally enriched with this element. It was also possible to observe that along with the vertical profile, there were no variations in the concentrations of the elements, while along the estuary, it was possible to verify that the cores differ from each other. The estuary of the Serinhaém River can be considered to be influenced relatively little by human activities, and its concentrations can be considered as a base level for this coastal region.

Geochemical evaluation of potentially toxic elements determined in surface sediment collected in an area under the influence of gold mining.

In this present paper, the distribution of toxic metals and sediment quality were evaluated in five sampling points of the Itapicuru-Mirim River located in the city of Jacobina, Bahia, Brazil. The concentration of the elements arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), nickel (Ni), lead (Pb), and zinc (Zn) were determined from sediment samples collected from the superficial layer (0-10 cm) in November 2013. After the samples' total decomposition, the total concentration of metals was determined by inductively coupled plasma optical emission spectrometry (ICP OES), except for Hg, which was measured by inductively coupled plasma atomic emission spectrometry (ICP AES). A geochemical evaluation of sediment quality was performed using enrichment factor (EF), geoaccumulation index (Igeo), and pollution load index (PLIThe results of the total concentrations in the analyzed sediment samples were compared with the threshold effect levels (TELs) and probable (PELs) effect levels (PELs) in sediment quality guidelines (SQGs). For the fraction <75 µm, the decreasing order for the metal concentrations was (ppm): Fe (10.86%) > Mn (120.8) > Cr (122) > Zn (76.5) > Pb (49.6) > Cu (32.6) > Ni (28.6) > Hg (0.31) > Cd (0.13). Igeo suggested a moderate to seriously polluted category for Hg and moderately polluted for Cu. Generally, the results indicated probable risks to the biota caused by Cr, Ni, Pb, and Hg metals. However, only Hg, Cd, and Cu were of anthropogenic origin. Although the sediments are relatively preserved from pollution by these metals, there is a progressive deterioration of this compartment downstream of the Itapicuru-Mirim River in the city of Jacobina.

Assessment of health risk related to the ingestion of trace metals through fish consumption in Todos os Santos Bay.

This study was carried out to evaluate the concentration of trace elements (As, Cd, Cu, Pb, and Zn) in the muscle of carnivorous fish species from three different areas of Todos os Santos Bay (BTS), Bahia State, Brazil. Trace elements were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES), and consumption rates advisory for minimizing chronic systemic effects in children and adults were estimated. As concentrations in fish samples from Jiribatuba were higher than legal limits set by FAO, and Cd concentrations in fish from Iguape Bay were high in comparison with FAO and EC. This study provides information about the fish consumption limits, considering the elements concentrations observed in the analyses, in particular As and Cd, necessary for minimizing potential health risks.

Trace elements in muscle of three fish species from Todos os Santos Bay, Bahia State, Brazil.

In this study, an analysis was performed on the concentrations of the trace elements Al, As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn in muscle of two carnivorous and one planktivorous fish species collected at Todos os Santos Bay (BTS). The accumulation order of the trace elements in Lutjanus analis was Al >Zn >Fe >Cr >Ba >Ni. In Cetengraulis edentulus, the order was Al >Fe >Zn >Cr >Ni >Mn >As. In the species Diapterus rhombeus, the order was Al >Fe >Zn >Cr >Ni >Mn >Cd. To determine the risk related to the consumption of fish, toxicity guidelines were used as standard references. It was observed that the species C. edentulus contained concentrations of As exceeding WHO limits, but these concentrations were acceptable according to the Agência Nacional de Vigilância Sanitária (ANVISA) guidelines. Cd levels were found only in D. rhombeus and in low concentrations according to the determinations of WHO and ANVISA. Pb levels were not detected in any of the three fish species. The analyzed elements did not differ statistically according to the species and feeding habits. The results point to possible risks of human contamination by As related to the consumption of the fish species C. edentulus from the BTS.