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Resultados 1121-1130 de 3,243
JNCC guidelines for minimising the risk of injury and disturbance to marine mammals from seismic surveys: We can do better
2015
Wright, Andrew J. | Cosentino, A Mel
The U.K.’s Joint Nature Conservation Committee 1998 guidelines for minimising acoustic impacts from seismic surveys on marine mammals were the first of their kind. Covering both planning and operations, they included various measures for reducing the potential for damaging hearing – an appropriate focus at the time. Since introduction, the guidelines have been criticised for, among other things: the arbitrarily-sized safety zones; the lack of shut-down provisions; the use of mitigation measures that introduce more noise into the environment (e.g., soft-starts); inadequate observer training; and the lack of standardised data collection protocols. Despite the concerns, the guidelines have remained largely unchanged. Moreover, increasing scientific recognition of the scope and magnitude of non-injurious impacts of sound on marine life has become much more widespread since the last revisions in 2010. Accordingly, here we present feasible and realistic recommendations for such improvements, in light of the current state of knowledge.
Mostrar más [+] Menos [-]Mass culture strategy for bacterial yeast co-culture for degradation of petroleum hydrocarbons in marine environment
2015
Priya, Anchal | Mandal, Ajoy K. | Ball, A. S. | Manefield, Mike | Lal, Banwari | Sarma, Priyangshu M.
In the present study a metabolically versatile co-culture with two Bacilli and one yeast strain was developed using enrichment culture techniques. The developed co-culture had affinity to degrade both aliphatic and aromatic fractions of petroleum crude oil. Degradation kinetics was established for designing the fermentation protocol of the co-culture. The developed mass culture strategy led to achieve the reduction in surface tension (26dynescm−1 from 69 dynescm−1) and degradation of 67% in bench scale experiments. The total crude oil degradation of 96% was achieved in 4000l of natural seawater after 28days without adding any nutrients. The survival of the augmented co-culture was maintained (109cellsml−1) in contaminated marine environment. The mass culture protocol devised for the bioaugmentation was a key breakthrough that was subsequently used for pilot scale studies with 100l and 4000l of natural seawater for potential application in marine oil spills.
Mostrar más [+] Menos [-]How Does Contamination of Rice Soils with Cd and Zn Cause High Incidence of Human Cd Disease in Subsistence Rice Farmers
2015
Chaney, Rufus L.
Rice (Oryza sativa L.) grown on Zn mine waste contaminated soils has caused unequivocal Cd effects on kidney and occasional bone disease (itai-itai) in subsistence rice farmers, but high intake of Cd from other foods has not caused similar effects. Research has clarified two important topics about how Cd from mine waste contaminated rice soils has caused Cd disease: (1) bioaccumulation of soil Cd into rice grain without corresponding increase in Zn, and (2) subsistence rice diets potentiate Cd absorption/bioavailability and risk to farm families. Absorption of Cd by rice roots occurs on the NRAMP5 Mn²⁺ transporter. Although other transporters can influence Cd uptake-transport to shoots and grain, making NRAMP5 null greatly reduces grain Cd. Zn²⁺ has little ability to inhibit Cd²⁺ transfer in rice but clearly inhibits Cd uptake in other plant species. The bioavailability of dietary Cd is increased for subsistence rice diets. Research has identified that low levels and bioavailability of Zn and Fe in polished rice grain cause upregulation of Cd absorption on the Fe²⁺ transporter of duodenum cells (DMT1). Added dietary Zn can also inhibit intestinal Cd absorption somewhat. Nutritional stress (Fe, Zn deficiency) in humans consuming subsistence rice diets thus promotes Cd accumulation and adverse effects. No other dietary (crop) Cd exposure has caused unequivocal Cd-induced renal proximal tubular dysfunction (the first adverse Cd effect) in humans. Recognition of the very unusual nature of Cd risk from rice compared to other crops should be taken into account in setting international limits of Cd in rice and other foods.
Mostrar más [+] Menos [-]Variations in the abundance and structural diversity of microbes forming biofilms in a thermally stressed coral reef system
2015
Mahmoud, Huda
Little information is known about biofilm formation in the thermally stressed coral reef systems north of the Arabian Gulf. The current study investigates the abundance and diversity of marine microbes involved in biofilm formation and their succession over a period of 14weeks (May–August 2007) at temperatures exceeding 32°C. The results showed variations in microbial numbers and the development of more stable biofilm communities as the biofilms aged. The culture-dependent technique and microscopic examination of the developed biofilms showed the dominance of key species known for their role in precipitating CaCO3 such as Vibrio and in facilitating coral larvae settlement and metamorphosis such as Pseudoalteromonas, Bacillariophyceae and Rhodophyceae. The results revealed biofilm formations with microbial diversities that have the potential to support the larval settlement and metamorphism of marine organisms and to consolidate and stabilize biofilms via the process of calcification in the thermally stressed coral reef system considered herein.
Mostrar más [+] Menos [-]Bacterial diversity patterns of the intertidal biofilm in urban beaches of Río de la Plata
2015
Piccini, C. | García-Alonso, J.
Intertidal benthic ecosystems in estuaries are productive sites where microbial processes play critical roles in nutrients mineralization, primary production and trophic web. In this groundwork study we analyzed the bacterial community of intertidal biofilms from Río de la Plata beaches with different anthropogenic impacts. Several environmental parameters were measured and bacterial assemblages were analyzed by 16S-rDNA pyrosequencing. The average OTU found per sample was 527.3±122.5, showing similar richness and diversity among them. However, sites having the highest and lowest salinity displayed higher bacterial diversity. Assemblages from a site nearby an oil refinery, showing the lowest salinity and oxygen concentration, were clearly distinct from the rest. The weight of this splitting relied on OTUs belonging to Thauera, known by its ability to metabolize aromatic compounds. Our results suggest that intertidal bacterial assemblages would be structured by major estuarine variables such as salinity, and that anthropogenic-induced environmental parameters might also be relevant.
Mostrar más [+] Menos [-]Micronucleus test in fishes as indicators of environmental quality in subestuaries of the Río de la Plata (Uruguay)
2015
Gutiérrez, Juan Manuel | Villar, Silvia | Acuña Plavan, Alicia
Genotoxic agents may exert damage that may be active through following generations. Micronuclei are cytoplasmic chromatin masses outside the main cell nucleus, indicators of chromosomal damage. This study applied micronuclei test to evaluate genetic damage of fish in three breeding and nursery areas of commercially important fishes exposed to differing degrees of anthropogenic impact: Pando, Solís Chico and Solís Grande sub-estuaries. The micronuclei test revealed differences in the presence and concentrations of genotoxic components in these sub-estuaries. Fish in the urban and industrialized Pando sub-estuary presented the highest percentages of micronuclei. The absence of seasonal changes in micronuclei in Pando fish could be explained by physical characteristics of the sub-estuary and by regional weather conditions. Odontesthes argentinensis (Valenciennes, 1835) was the species most susceptible to genotoxic components. It is recommended the use of a battery of biomarkers to better explain the health of organisms in that important nursery area.
Mostrar más [+] Menos [-]Passive samplers of hydrophobic organic chemicals reach equilibrium faster in the laboratory than in the field
2015
Booij, Kees | Tucca, Felipe
The use of passive sampling methods for monitoring hydrophobic organic chemicals frequently requires the determination of equilibration times and partition coefficients in the laboratory. These experiments are often carried out by exposing passive samplers in a finite water volume, and errors are easily made when the obtained results are applied to the field, where water volumes are essentially infinite. The effect of water volume on the equilibration rate constant is discussed, using a mechanistic model. Application of this model to two literature reports illustrates that aqueous concentrations in the field may be underestimated by a factor of 10 or more, when the water volume effect is neglected. Finally, it is shown that the concept of “sorption capacity” (sampler mass times partition coefficient) allows for a more intuitive understanding of the passive sampling process in small and large water volumes, which may reduce the risk of laboratory-field extrapolation errors.
Mostrar más [+] Menos [-]Environmental risk assessments and spatial variations of polycyclic aromatic hydrocarbons in surface sediments in Yangtze River Estuary, China
2015
Yu, Wenwen | Liu, Ruimin | Xu, Fei | Shen, Zhenyao
In this study, based on sampling data from 30 sites in August 2010, the environmental risks associated with 16 priority PAHs were estimated in surface sediments from the Yangtze River Estuary (YRE). The results indicated that the toxic equivalent quantities of the benzo[a]pyrene (TEQBap) from 30 sites were in the range of 1.93–75.88ngg−1, and the low-molecular-weight PAHs were the dominated species with higher potential toxicity. The results of the Incremental Lifetime Cancer Risk (ILCR) model indicated that the ILCR values of dermal contact were higher than 10−6 in the northeast region, suggesting that there were significant potential carcinogenic health risks for fishermen exposure to sedimentary PAHs via dermal contact in these areas. RQ values of PAHs indicated the various distributions of ecological risk levels in the study area. These variations might be caused by the natural and anthropogenic inputs and currents in the YRE.
Mostrar más [+] Menos [-]Evaluation for coastal reclamation feasibility using a comprehensive hydrodynamic framework: A case study in Haizhou Bay
2015
Feng, Lan | He, Jia | Ai, Junyong | Sun, Xiang | Bian, Fangyuan | Zhu, Xiaodong
Coastal reclamation (CR) is a prevailing approach to solve the contradiction between the land shortage and the growing demand of living space for human beings. In general, environmental impact assessment (EIA) focuses on evaluating the feasibility of individual coastal reclamation project (CRP). However, few studies have investigated the cumulative effect of multiple CRPs on surrounding environment. In this study, an integrated framework based on coastal hydrodynamics was established, and then applied to the feasibility evaluation of multiple CRPs for future coastal management in Haizhou Bay, China. The results indicated that three out of five reclamation projects were feasible and the remaining two were forbidden in the study area, whereas EIA approves of all the CRPs. It provides a scientific reference for effective management of coastal reclamation and future environmental impact researches when new CRPs are proposed.
Mostrar más [+] Menos [-]Trace elements and heavy metals in the Grand Bay National Estuarine Reserve in the northern Gulf of Mexico
2015
McComb, Jacqueline Q. | Han, Fengxiang X. | Rogers, Christian | Thomas, Catherine | Arslan, Zikri | Ardeshir, Adeli | Tchounwou, Paul B.
The objectives of this study are to investigate distribution of trace elements and heavy metals in the salt marsh and wetland soil and biogeochemical processes in the Grand Bay National Estuarine Research Reserve of the northern Gulf of Mexico. The results show that Hg, Cd and to some extent, As and Pb have been significantly accumulated in soils. The strongest correlations were found between concentrations of Ni and total organic matter contents. The correlations decreased in the order: Ni>Cr>Sr>Co>Zn, Cd>Cu>Cs. Strong correlations were also observed between total P and concentrations of Ni, Co, Cr, Sr, Zn, Cu, and Cd. This may be related to the P spilling accident in 2005 in the Bangs Lake site. Lead isotopic ratios in soils matched well those of North American coals, indicating the contribution of Pb through atmospheric fallout from coal power plants.
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