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Abstract: The vertical distribution of Hg and Pb were determined in a sediment core collected from the Sagua estuary (North Cuba) that receives input from the Sagua river, one of the most polluted rivers discharging into the Cuban coastal environment. Depth profiles of metal concentrations were converted to time-based profiles using the 210Pb dating method and confirmed with the 137Cs fallout peak. The mean mass accumulation rate was estimated to be 0.17±0.04gcm−2 y−1 (mean sediment accumulation rate 0.52±0.13cmy−1) and the core bottom was estimated to date back about 130years. The historical sedimentary record showed a strong enrichment of mercury concentrations in the past decades, caused by the incomplete treatment of industrial wastes from a chlor-alkali plant with mercury-cell technology in the Sagua river basin. Lead fluxes to sediments showed a gradual increase from the 1920s to present, which agrees with a population increase in Sagua la Grande City. Fluxes of both metals have increased the past 25years, with values reaching a maximum of 0.5 and 3.9μgcm−2 y−1 for Hg and Pb, respectively. [Copyright &y& Elsevier]

Spatial and temporal variability of mercury concentrations in sediments was evaluated in 210Pb-dated sediment cores from offshore and intertidal areas in the southern Gulf of Mexico. In offshore cores, mercury concentrations were comparable (11.2–69.2 ng g−1), and intermediate between concentrations in intertidal cores from the eastern (6.0–34.4 ng g−1) and the western (34.9–137.7 ng g−1) inlets of Términos Lagoon. The enrichment factor (EF) indicated minimal contamination (EF < 2) in most offshore cores, whereas in some intertidal cores steadily increasing mercury enrichment and fluxes were observed along the past century. No evidence of oil industry related mercury contamination was found, as the minor but increasing enrichment in intertidal cores is most likely related to land-derived sources such as catchment eroded soils and waste water runoff. Results highlight the importance to control catchment erosion and untreated sewage releases to reduce mercury loadings to the coastal zone. Unlabelled Image • Hg contamination trends were studied in sediment cores of southern Gulf of Mexico. • Null to minor Hg enrichment was observed during the past 100 years in the area. • Recent Hg concentrations in most offshore cores were close to preindustrial levels. • Minor Hg contamination in intertidal areas is likely associated to surface runoff. • Hg concentrations are not a risk to benthic biota in the region. [ABSTRACT FROM AUTHOR]

Coastal lagoons provide important ecosystem services worldwide but are subject to high and multiple environmental stresses. Little information exists on the inner creeks of low-flow coastal lagoons, where the low-exchange rates may exacerbate anthropogenic impacts. In this work, we used a model with high spatio-temporal resolution to describe the hydrodynamics and to estimate the accumulation of conservative contaminants in the upper estuary of the Urias sub-tropical coastal lagoon, in northwestern Mexico. The lagoon shows a weak anti-estuarine behavior and its hydrodynamics is governed by astronomical tides and topography. The mean steady-state water age in the three lagoon areas was ∼15, ∼30 and ∼70 days in the Harbor, Intermediate and Upper Areas, respectively. Thus, the Upper Area, which shelters a mangrove forest, is the most vulnerable to pollution due to the high potential for accumulation. As a best case scenario, the simulation of the release of conservative substances in the Upper area indicated that, 50 days after the release started, conservative pollutants mostly remained in the Upper Area and were not significantly exported to the open ocean. This methodology can be used to model the impact of conservative substances in coastal lagoons worldwide, and can be complementary and useful for the optimization of long-term coastal zone management activities. [ABSTRACT FROM AUTHOR]

• Sediment accumulation in contrasting mangrove areas showed similar temporal trends. • Mass accumulation rates (MAR) increased exponentially over the last century. • MAR mainly accelerated since the 1950s and it was attributed to continental erosion. • Continental erosion was associated with land-use changes and population growth. • Mangroves accumulated sediments at pace with local sea-level rises. Mangrove sediments are valuable records to reconstruct the impacts of human-induced changes on the coastal zone. Seven lead-210 dated sediment cores were used to evaluate temporal trends of sedimentation rates over the past century in Mexican mangrove areas at Términos Lagoon (TL; southern Gulf of Mexico) and El Verde Camacho Lagoon (EV; northern Mexican Pacific coast). We hypothesized that the contrasting characteristics (e.g., meteorological, demographic, and land-use change) would lead to significant differences in sedimentation rates between the study sites. Sediment accumulation rates (SAR) in both sites (TL 0.03–2.1 cm yr−1; EV 0.04–4 cm yr−1) were comparable to the global SAR range for mangrove forests. Mass accumulation rates (MAR) in the TL cores (0.03–0.47 g cm−2 yr−1) were consistent with previous studies of the region. Excluding conspicuous MAR maxima, attributed to meteorological events, MAR values in the EV cores (0.04–0.9 g cm−2 yr−1) were higher than in other mangrove areas of the Mexican Pacific coast, but comparable to other sites in the world. Similar exponentially increasing MAR values towards present in both sites were attributed to general factors driving sediment accumulation in mangroves, mainly continental erosion promoted by land-use changes, which has accelerated since the 1950s, associated with (i) population growth and the consequent expansion of human activities and (ii) sea-level rise, similar in the studied regions and from which mangrove ecosystems seem to adapt. Intensifying population growth and land-use change are already reducing the extent of mangrove coverage in some parts of the study areas. Adaptation to an accelerating sea-level rise depends on maintaining conditions that allow mangroves to accrete vertically. However, both global change pressures may pose future threats to these ecosystems. Efforts to monitor sediment accretion and adapt the management of mangrove conservation areas are required to understand better mangrove response to global change impacts. [ABSTRACT FROM AUTHOR]