This manuscript presents an inventory of the carbonate system from the main water masses comprising the marine current system on Brazil’s northeast coast (South Atlantic Ocean). For this purpose, four transects were conducted with an approximate length of 357 km (each one) through the platform and continental slope of the Sergipe–Alagoas sedimentary basin. Water samples were then collected in vertical profiles measuring from 5 to 1,799 meters depth, totaling 34 stations. Total alkalinity, calcium, and total boron were obtained analytically from these samples and by relationships with salinity. Speciation and concentration of the carbonate system were obtained by means of thermodynamic modeling. The results revealed that the empirical models used to calculate the concentrations of TA, calcium and total boron showed relevant variation when compared to the analytical values (TA: 5.0–6.5%; Ca: 0.4–4.8%; BT: 7.0–18.9%). However, the speciation and concentration of the carbonate system (CA, DIC, CO32−, CO2(aq), ΩCalc, and ΩArag) obtained from the empirical values of TA, calcium and total boron did not differ significantly from those obtained analytically (0.0–6.1%). On the other hand, the parameters of pH, HCO3‐, CO3(aq)2‐, CO2(aq), ρCO2, ΩCalc, and ΩArag varied significantly within the different water masses (p < 0.05). This study supports and encourages acidification monitoring projects in the South Atlantic Ocean, based on modeling the carbonate system parameters generated in real-time.

This study aimed at the ecological-economic valuation of the Potengi estuary mangrove wetlands, based on the integration of spatial data (mangrove forest coverage map, Nautical Chart, Environmental Sensitivity Chart) with data from literature on the biogeochemistry of nitrogen (N), phosphorus (P), and heavy metals in the mangrove estuary wetland Potengi) and field verification data (topographic profile of mangrove forest, GPS routes obtained in the field in the touristy sightseeing areas and plots of mariculture). The ecological and economic valuation of the services performed by the Potengi estuary mangrove wetlands, mainly as biogeochemical barrier for the transport of P, N and heavy metals in tropical coastal areas, were obtained just as if the retention of those elements was necessary by Wastewater Treatment Plants (WTP) with Stabilization Ponds, typical in the estuary, and Zeolitic plant, respectively. Closer to real scenarios were observed for obtaining the values of these ecological services, such as the release of the P, N and heavy metals in domestic and industrial sewage in the estuary, the capability of dilution and the influence of the tides in the estuary. The tourism potential of the Potengi estuary mangrove wetlands were assessed according to the current forms of use, and potential of aquaculture through the main types of farming in mangrove areas. For these ecological services, considerable values were obtained of about USS15,500/ha, such as costs of implementation and construction of sewage treatment plants, as well as costs of sewage treatment plants. Nearly US$ 12.500 / ha amount each year from tourism and aquaculture income, demonstrating the economic viability of the Potengi estuary mangrove wetlands conservation.

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Estuarine sediments represent important pools of trace metals, released from both anthropogenic and natural sources. Fluctuations in the water column physicochemical conditions, on the other hand, may transfer metals from solid to liquid compartment and resulting in contamination of the surrounding environment. The present research was carried out to evaluate the weakly bounded heavy metal levels in tropical hypersaline and positive estuaries, in order to quantify its potentially availability. The monitoring includes five metals (Cd, Cr, Cu, Pb, Zn) and cover nine estuaries in Rio Grande do Norte state/Brazil, including four hypersaline and five true estuaries. 50 surface sediment samples were collected in each estuary. At the same time, organic matter concentrations were evaluated in order to help explaining possible local variations in heavy metal levels. Organic matter results (0.7% -7.3%) suggest the positive Potengi estuary as the most critical environmental quality situation. On the other hand, according to heavy metals levels, both Conchas and Potengi estuaries registered the higher concentrations of Cr. The highest concentrations were observed in the hyper-saline estuaries, with the exception of the Zn. The present study revealed that the watershed occupation has significantly influenced the heavy metal concentrations in the estuaries.