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The diversity and composition of bacterial communities in mudflat and mangrove sediments were investigated under the stresses of endocrine-disrupting chemicals (EDCs) using high-throughput sequencing technique. Bacterial diversity in the original sediments was highest among all samples, followed by non-sterilized and sterilized sediments after 84-day incubation. Proteobacteria were the predominant phylum in both mangrove and mudflat sediments, which accounted for 40–60% of the total tags, followed by Cyanobacteria, Chloroflexi, Planctomycetes and Acidobacteria. Although the total population of bacteria was not significantly declined due to the addition of EDCs, bacterial community structures were considerably altered. The number of bacterial genera promoted or inhibited by EDCs was 288 and 324, respectively. Bacterial genera affected by EDCs varied greatly with the types of sediments and the initial status of bacterial communities. Overall, our results suggested that bacterial community structure in mangrove sediments were closely related to their re-development and responses to EDC contamination. [ABSTRACT FROM AUTHOR]

A study on vertical distribution of magnetic susceptibility, carcinogenic and endocrine disrupting PAHs was performed in the reclaimed mudflat sediments adjacent to the Thane Creek of Mumbai. The 5-rings PAHs and ΣC-PAHs were more dominant at 120 cm depth contributing 52.23% and 60.19% respectively to ∑ PAHs. The average ratio values of LMW/HMW PAHs (0.58); Fla/(Fla + Pyr) (0.50); Ant/(Ant + Phe) (0.50); BaA/(Chry + BaA) (0.48); BaP/BghiP (2.06), Phe/Ant (1.03) and BaA/Chr (0.93) indicate that the PAH contamination might have raised due to inefficient combustion and pyrogenic emissions during the open burning of solid waste in the vicinity. This was further supported by the anthropogenic ferri(o)magnetic loading over the last 100 years influencing the Creek sediments. The PAHs toxicity estimation was performed by calculating the toxic equivalent quantity (TEQ) value of 8.62 ng TEQ/g which was below the safe level (600 ng TEQ/g) suggested by the Canadian risk-based soil criterion for protection of human health. [ABSTRACT FROM AUTHOR]

To investigate the seasonal variation of denitrification rate (DR) and clarify the controlling factors of denitrification in the mudflat sediments of Ariake Bay, we conducted field surveys biweekly each month from April 2006 to January 2008. NH4+-N porewater concentration increased from summer to autumn due to the organic material mineralization under higher sediment temperatures. The seasonal pattern of NH4+-N flux between sediments and overlying water interface indicated that the mudflat sediments were a source of NH4+-N in summer. NO3-+NO2--N porewater concentrations were low, ranging from 0.53 to 11.46 μM, and mudflat sediments were sinks of NO3-+NO2--N throughout the year. The mean number of denitrifiers tended to increase in July-September (2188-75,057 MPN g-1) and to decrease in March-May (500-3740 MPN g-1). DR tended to increase in summer, ranging from 76.03 to 990.21 μmol m-2 day-1, and to decrease in winter, ranging from 25.01 to 206.07 μmol m-2 day-1. There was no significant correlation between DR and denitrifier number. Environmental factors influencing DR during the investigation period were determined by multiple regression analysis with the stepwise method. The results indicated that NO3-+NO2--N flux was an important factor in denitrification of mudflat sediments in Ariake Bay. Denitrification was depended on nitrate diffusing from overlying water into sediments under reduced sediment conditions during summer-mid-autumn. On the other hand, in late autumn-winter at Eh>+200 mV and sediment temperature >10 °C, nitrate produced by sediment nitrification was thought to be denitrified subsequently; that is, the coupled nitrification-denitrification may have taken place in the upper layer of mudflat sediments. [ABSTRACT FROM AUTHOR]

The present study aimed to examine whether the use of dispersant would be suitable for favoring the hydrocarbon degradation in coastal marine sediments without impacting negatively micro- and macrobenthic organisms. Mudflat sediments, maintained during 286 days in mesocosms designed to simulate natural conditions, were contaminated or not with Ural blend crude oil (REBCO) and treated or not with third-generation dispersant (Finasol OSR52). While the dispersant did not lead to an increase of hydrocarbon biodegradation, its use enables an attenuation of more than 55 % of the sediment concentration of total petroleum hydrocarbons (TPH). Canonical correspondence analysis (CCA) correlating T-RFLP patterns with the hydrocarbon content and bacterial abundance indicated weak differences between the different treatments except for the mesocosm treated with oil and dispersant for which a higher bacterial biomass was observed. The use of the dispersant did not significantly decrease the macrobenthic species richness or macroorganisms' densities in uncontaminated or contaminated conditions. However, even if the structure of the macrobenthic communities was not affected, when used in combination with oil, biological sediment reworking coefficient was negatively impacted. Although the use of the dispersant may be worth considering in order to accelerate the attenuation of hydrocarbon-contaminated mudflat sediments, long-term effects on functional aspects of the benthic system such as bioturbation and bacterial activity should be carefully studied before. [ABSTRACT FROM AUTHOR]

210Pb geochronologies of Cd, Cu, Hg, and Pb fluxes were obtained from the intertidal mudflat sediments of the coastal lagoons Chiricahueto, Estero de UrIas, and Ohuira in the Mexican Pacific. The Cu and Hg sediment concentrations at the three lagoons fell within the ranges of 6-76 μg g-1 and 0.1 to 592 ng g-1, respectively; Chiricahueto and Esterb de UrIas sediments had comparable Cd and Pb concentrations within the ranges of 0.2-2.1 μg g-1 and 10-67 μg g-1, respectively; whereas in Ohuira lagoon, Cd concentrations were lower (0.1-0.5 μg g-1) and Pb concentrations were higher (115- 180 μg g-1) than in the other lagoons. The metal fluxes (μg cm-2 y-1) for the three lagoons fell within the ranges of 0.02-0.15 for Cd, 0.7-6.0 for Cu, 0.001-0.045 for Hg, and 0.7-20 for Pb. The Hg pollution in Estero de Urlas was attributed to the exhausts of the thenrioelectric plant of Mazatlan and the metal enrichment in Chiricahueto and Ohuira was related to the agrochemical wastes from the croplands surrounding these lagoons. [ABSTRACT FROM AUTHOR]

Documenting the prevalence of microplastics in marine-coastal ecosystems serves as a first step towards understanding their impacts and risks presented to higher trophic levels. Estuaries exist at the interface between freshwater and marine systems, and provide habitats for a diverse suite of species, including shellfish, fish, and birds. We provide baseline values for estuarine mudflats using sediment samples collected at Cowichan-Koksilah Estuary in British Columbia, Canada, a biologically-rich estuary. The estuary also contains a marine shipping terminal, forestry log sort area, and input of contaminants from nearby residential and agricultural areas. Microplastics, both fragments and fibers, occurred in 93% (13/14) of sediment samples. A mean of 6.8 microfibers/kg dw (range: 0–12 microfibers/kg dw) and 7.9 microfragments/kg (range: 0–19 fragments/kg dw) occurred in individual samples, and counts of fibers and fragments were strongly correlated (r = 0.78, p = 0.008, n = 14). The abundance of microplastics tended to be higher on the north side of the estuary that receives greater inputs from upland sources relative to the south side. Size distributions of microplastic fragments and fibers were similar to sediment grain size distribution with size categories 0.063 to 0.25 mm and 0.25 to 0.6 mm being the most common for plastics and sediment, indicating the occurrence of microplastics likely followed existing depositional processes within the estuary. Microplastics in sediments were composed of a variety of polymers, including high density polyethylene (HDPE), Nylon 6/6 (polyhexamethylene adipamide), and polyethylene terephthalate-PETE (poly(1,4-cyclohexylene dimethylene terephthalate)). This study indicates that microplastics occur throughout most of the Cowichan-Koksilah Estuary, and future studies should focus on the exposure risk and potential for bioaccumulation for wildlife species that feed on the surface of intertidal mudflats. [Display omitted] • Microplastics occurred in 93% of samples from the Cowichan-Koksilah Estuary. • Microplastics abundances were correlated to sediment grain size distributions. • HDPE, PETE & Nylon 6/6 were the most common plastic polymers detected in sediments • Sediment deposition patterns likely influence sediments' microplastics distribution [ABSTRACT FROM AUTHOR]