خيارات البحث
النتائج 431 - 440 من 1,546
Antibiotic resistant pathogens versus human impacts: A study from three eco-regions of the Chennai coast, southern India النص الكامل
2012
Vignesh, Sivanandham | Muthukumar, Krishnan | Arthur James, Rathinam
We assessed the occurrence of pollution indicators and antibiotic resistant bacterial isolates from water and sediment samples of three different eco-regions of the Chennai coast between March – May of 2010. Total of 960 bacterial strains belonging to four genera were isolated which show the highest frequencies of resistance to vancomycin (53.6%) and penicillin (52.6%) (except Enterococcus sp., which is highly resistant to erythromycin) and lowest frequencies of resistance to chloramphenicol (3.43%), ciprofloxacin (3.95%), gentamicin (4.68%), and tetracycline (6.97%). The E. coli, Vibrio sp., Salmonella sp. and Enterococcus sp. show high frequency of resistance to 2–5 antibacterials of 60.4%, 45.83%, 69.16% and 46.6%, respectively. High pollution indices (PI – 6.66–14.06) and antibiotic resistance indices (ARI – 0.29–0.343) indicate that the coastal environment is highly exposed to antibiotic sources that suggesting to avoid direct contact.
اظهر المزيد [+] اقل [-]Recent status of total mercury and methyl mercury in the coastal waters of the northern Gulf of Mexico using oysters and sediments from NOAA’s mussel watch program النص الكامل
2012
The current status of mercury concentrations in the Gulf of Mexico (GOM) were assessed using the Mussel Watch Program (MWP) contaminant monitoring data, which is based on the analysis of oyster tissue and sediment samples. In both matrices, tHg and MeHg concentrations varied broadly. Significant concentration differences (p<0.05) between the sub-regions of the eastern, central and western Gulf were observed with maximum concentrations (hotspots) found at specific sites all across the Gulf. Compared to the Food and Drug Administration’s action level in seafood, maximum mercury values were low. Based on the long-term MWP data, tHg in tissues show fairly static temporal trends along the central and western Gulf coast, while strong decreasing trends were observed in the eastern Gulf. However, the presence of mercury hotspots indicates that mercury is still a concern in the GOM. The results complement existing information to further the understanding of mercury distributions in the GOM.
اظهر المزيد [+] اقل [-]Photosynthetic response of two seaweed species along an urban pollution gradient: Evidence of selection of pollution-tolerant species النص الكامل
2012
Scherner, F. | Bonomi Barufi, J. | Horta, P.A.
Urbanization leads to the expansion of ephemeral seaweed species and the decline of important perennial, canopy-forming seaweed species. Understanding the mechanisms that lead to these changes is a current challenge. In the present study, laboratory assays and field transplantations were performed with two seaweed species: the perennial, canopy-forming seaweed Sargassum stenophyllum and the ephemeral seaweed Ulva lactuca. Photosynthetic efficiency was assessed using modulated chlorophyll fluorometry. Brief exposure to urban waters does not appear to be a major stressor to the photosynthetic efficiency of either species. However, after 26days of transplantation in urban waters, S. stenophyllum declined, whereas U. lactuca had enhanced photosynthetic efficiency. This difference reflects their divergent abilities to regulate the energy distribution at the PSII and shows that urban stressors alter these mechanisms. Our results provide evidence of the physiological causes for the decline of Sargassum species and the expansion of Ulva species in impacted urban areas.
اظهر المزيد [+] اقل [-]Remediation of muddy tidal flat sediments using hot air-dried crushed oyster shells النص الكامل
2012
Yamamoto, Tamiji | Kondo, Shunsuke | Kim, Kyung-Hoi | Asaoka, Satoshi | Yamamoto, Hironori | Tokuoka, Makoto | Hibino, Tadashi
In order to prove that hot air-dried crushed oyster shells (HACOS) are effective in reducing hydrogen sulfide in muddy tidal flat sediments and increasing the biomass, field experiments were carried out. The concentration of hydrogen sulfide in the interstitial water, which was 16mgSL⁻¹ before the application of HACOS, decreased sharply and maintained almost zero in the experimental sites (HACOS application sites) for one year, whereas it was remained at ca. 5mgSL⁻¹ in the control sites. The number of macrobenthos individuals increased to 2–4.5 times higher than that in the control site. Using a simple numerical model, the effective periods for suppression of hydrogen sulfide were estimated to be 3.2–7.6 and 6.4–15.2years for the experimental sites with 4 and 8tons per 10×10×0.2m area, respectively. From these results, it is concluded that HACOS is an effective material to remediate muddy tidal flats.
اظهر المزيد [+] اقل [-]UV filters, ethylhexyl methoxycinnamate, octocrylene and ethylhexyl dimethyl PABA from untreated wastewater in sediment from eastern Mediterranean river transition and coastal zones النص الكامل
2012
Amine, Helmieh | Gomez, Elena | Halwani, Jalal | Casellas, Claude | Fenet, Hélène
UVF may occur in the aquatic environment through two principal sources: direct inputs from recreational activities and indirect wastewater- and river-borne inputs. The aim of this study was to obtain a first overview of levels of three UVF (EHMC, OC and OD-PABA) in coastal areas subjected to river inputs, untreated wastewater discharges and dumpsite leachates. We selected three eastern Mediterranean rivers that have been impacted for decades by untreated wastewater release and collected sediment in the coastal zone during the hot and humid seasons. Western Mediterranean sites receiving treated wastewaters were analyzed for comparison. The results gave an overview of sediment contamination under these two contrasted situations representative of Mediterranean coastal areas without bathing activities. The analysis of the three UVF revealed the ubiquity and high point source contamination by EHMC and OC in transition and coastal zones, with levels as high as 128ngg⁻¹d.w. OD-PABA was also frequently detected, but at lower concentrations (<LOD-17ngg⁻¹d.w.). A temporal trend was observed, with a higher sediment concentration in the dry period (August and October). Based on these results, we conclude that there is background contamination from river input that could be exacerbated by the direct contribution in coastal bathing zones.
اظهر المزيد [+] اقل [-]Effects of intertidal seagrass habitat fragmentation on turbulent diffusion and retention time of solutes النص الكامل
2012
Lara, M. | Peralta, G. | Alonso, J.J. | Morris, E.P. | González-Ortiz, V. | Rueda-Márquez, J.J. | Pérez-Lloréns, J.L.
Effects of intertidal seagrass habitat fragmentation on turbulent diffusion and retention time of solutes النص الكامل
2012
Lara, M. | Peralta, G. | Alonso, J.J. | Morris, E.P. | González-Ortiz, V. | Rueda-Márquez, J.J. | Pérez-Lloréns, J.L.
An in-depth knowledge of solutes advection and turbulent diffusion is crucial to estimate dispersion area and retention time (tR) of pollutants within seagrass habitats. However, there is little knowledge on the influence of seagrass habitat fragmentation on such mechanisms. A set of dye tracer experiments and acoustic Doppler velocimeter measurements (ADV) were conducted. Solute transport conditions were compared in between fragmented (FM) vs homogeneous (HM) intertidal meadows, and in vertical gradients (canopy vs overlaying flow). Results showed the highest horizontal diffusion coefficient (Ky, c.a. 10⁻³m²s⁻¹) on FM and at the canopy-water column interface, whereas tR (2.6–5.6min) was not affected by fragmentation. It suggests that (1) FM are more vulnerable to pollution events in terms of dispersion area and (2) at low tide, advection rather than turbulent diffusion determines tR. Furthermore, Taylor’s theorem is revealed as a powerful tool to analyze vertical gradients on Ky within seagrass canopies.
اظهر المزيد [+] اقل [-]Effects of intertidal seagrass habitat fragmentation on turbulent diffusion and retention time of solutes النص الكامل
2012
Lara, M. | Peralta, G. | Alonso del Rosario, José Juan | Morris, Edward P. | González-Ortiz, V. | Rueda Márquez, J. J. | Pérez Lloréns, José Lucas
An in-depth knowledge of solutes advection and turbulent diffusion is crucial to estimate dispersion area and retention time (t R) of pollutants within seagrass habitats. However, there is little knowledge on the influence of seagrass habitat fragmentation on such mechanisms. A set of dye tracer experiments and acoustic Doppler velocimeter measurements (ADV) were conducted. Solute transport conditions were compared in between fragmented (FM) vs homogeneous (HM) intertidal meadows, and in vertical gradients (canopy vs overlaying flow). Results showed the highest horizontal diffusion coefficient (K y, c.a. 10 -3m 2s -1) on FM and at the canopy-water column interface, whereas t R (2.6-5.6min) was not affected by fragmentation. It suggests that (1) FM are more vulnerable to pollution events in terms of dispersion area and (2) at low tide, advection rather than turbulent diffusion determines t R. Furthermore, Taylor's theorem is revealed as a powerful tool to analyze vertical gradients on K y within seagrass canopies. © 2012 Elsevier Ltd. | This work was supported by the Spanish National Research Project IMACHYDRO (CTM2008-0012/MAR) and by the Andalusian Excellence Research Project FUNDIV P07-RNM-2516. First author is supported by a FPI grant of the Spanish Ministry of Science and Technology. | Peer Reviewed
اظهر المزيد [+] اقل [-]Geographical variability of environmental parameters versus GPS precision: Toward a better sampling strategy النص الكامل
2012
Beryouni, K. | Méar, Y. | Murat, A. | Poizot, E. | Chaibi, M.
To characterize a sedimentary environment, it is risky to take a single sample when the spatial variability is unknown. A reference station has to reflect the natural variations in order to allow the creation of long time series. However, it can remain unclear whether the temporal changes are real or due to a spatial variation. We highlight here the importance of spatial variability at the scale of precision of the GNSS. It appears that the number and arrangement of replicates depend on the environment and the studied parameters. InC, TOC and TS show a sufficiently low spatial variability to allow temporal tracking using GNSS without multiplying samples. The fine fraction percent shows a high spatial variability over small distances. The study of this parameter in the framework of temporal tracking requires a knowledge of its spatial variability during each period of sampling, and hence leads to the multiplication of samples.
اظهر المزيد [+] اقل [-]Centennial records of lead contamination in northern Atlantic bivalves (Arctica islandica) النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R.
Centennial records of lead contamination in northern Atlantic bivalves (Arctica islandica) النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R.
In the study, we establish centennial records of anthropogenic lead pollution at different locations in the North Atlantic (Iceland, USA, and Europe) by means of lead deposited in shells of the long-lived bivalve Arctica islandica. Due to local oceanographic and geological conditions we conclude that the lead concentrations in the Icelandic shell reflect natural influxes of lead into Icelandic waters. In comparison, the lead profile of the US shell is clearly driven by anthropogenic lead emissions transported from the continent to the ocean by westerly surface winds. Lead concentrations in the European North Sea shell, in contrast, are dominantly driven by local lead sources resulting in a much less conspicuous 1970s gasoline lead peak. In conclusion, the lead profiles of the three shells are driven by different influxes of lead, and yet, all support the applicability of Pb/Ca analyses of A. islandica shells to reconstruct location specific anthropogenic lead pollution.
اظهر المزيد [+] اقل [-](Fig. 5.4) Profile of Lead/Calcium ratios of an Arctica islandica shell collected in the North Sea near Helgoland, Germany النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R
Lead/Calcium profiles in the common time window 1770-2010 of the three Arctica islandica shells النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R
In the study, we establish centennial records of anthropogenic lead pollution at different locations in the North Atlantic (Iceland, USA, and Europe) by means of lead deposited in shells of the long-lived bivalve Arctica islandica. Due to local oceanographic and geological conditions we conclude that the lead concentrations in the Icelandic shell reflect natural influxes of lead into Icelandic waters. In comparison, the lead profile of the US shell is clearly driven by anthropogenic lead emissions transported from the continent to the ocean by westerly surface winds. Lead concentrations in the European North Sea shell, in contrast, are dominantly driven by local lead sources resulting in a much less conspicuous 1970s gasoline lead peak. In conclusion, the lead profiles of the three shells are driven by different influxes of lead, and yet, all support the applicability of Pb/Ca analyses of A. islandica shells to reconstruct location specific anthropogenic lead pollution.
اظهر المزيد [+] اقل [-]Centennial records of lead contamination in northern Atlantic bivalves (Arctica islandica) النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R.
In the study, we establish centennial records of anthropogenic lead pollution at different locations in the North Atlantic (Iceland, USA, and Europe) by means of lead deposited in shells of the long-lived bivalve Arctica islandica. Due to local oceanographic and geological conditions we conclude that the lead concentrations in the Icelandic shell reflect natural influxes of lead into Icelandic waters. In comparison, the lead profile of the US shell is clearly driven by anthropogenic lead emissions transported from the continent to the ocean by westerly surface winds. Lead concentrations in the European North Sea shell, in contrast, are dominantly driven by local lead sources resulting in a much less conspicuous 1970s gasoline lead peak. In conclusion, the lead profiles of the three shells are driven by different influxes of lead, and yet, all support the applicability of Pb/Ca analyses of A. islandica shells to reconstruct location specific anthropogenic lead pollution.
اظهر المزيد [+] اقل [-](Fig. 5.2) Profile of Lead/Calcium ratios of an Arctica islandica shell collected off the coast of Northeast Iceland النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R
(Fig. 5.3) Profile of Lead/Calcium ratios of an Arctica islandica shell collected off the coast of Virginia, USA النص الكامل
2012
Krause-Nehring, Jacqueline | Brey, Thomas | Thorrold, Simon R
Rapid increase in copper concentrations in a new marina, San Diego Bay النص الكامل
2012
Biggs, Trent W. | D’Anna, Heather
Concentrations of copper in water rose rapidly following the introduction of boats to a new marina in San Diego Bay. Two months after the marina reached half its capacity, a majority of water samples exceeded chronic and acute criteria for dissolved copper, and copper concentrations in several samples exceeded the highest concentrations observed in another marina that has been listed as an impaired water body. A box model suggested that a small fraction of the leached copper was sequestered in sediment. Copper concentrations in water entering the marina from the bay was more than half the chronic concentration limit, so only 50% of marina boat capacity could be accommodated without exceeding the chronic criterion more than 50% of the time. Copper concentrations in water may increase rapidly following boat introduction in small marinas, but could return to pre-introduction levels by controlling boat numbers or reducing use of copper-based paints.
اظهر المزيد [+] اقل [-]Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas) النص الكامل
2012
Mai Hương, | Cachot, Jérôme | Brune, Justine | Geffard, Oliver | Belles, Angel | Budzinski, Hélène | Morin, Bénédicte
Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas) النص الكامل
2012
Mai Hương, | Cachot, Jérôme | Brune, Justine | Geffard, Oliver | Belles, Angel | Budzinski, Hélène | Morin, Bénédicte
This study evaluated embryotoxicity and genotoxicity of two dissolved metals copper and cadmium (Cu and Cd) and two pesticides (metolachlor and irgarol) occurring in Arcachon Bay (SW France) in Pacific oyster (Crassostrea gigas) larvae and investigated the relationship between those two endpoints. Embryotoxicity was measured by calculating the percentage of abnormal D-shaped larvae and genotoxicity was evaluated with DNA strand breaks using the comet assay. After 24h exposure, significant increases of the percentage of abnormal D-larvae and the DNA strand breaks were observed from 0.1μgL⁻¹ for Cu, 10μgL⁻¹ for Cd and 0.01μgL⁻¹ for both irgarol and metolachlor in comparison with the controls. A strong positive relationship between embryotoxicity and genotoxicity was recorded for Cu, Cd and metolachlor. The current study suggests that copper, irgarol and metolachlor can induce larval abnormalities and DNA damage in a population of exposed oysters at environmentally relevant concentrations.
اظهر المزيد [+] اقل [-]Embryotoxic and genotoxic effects of heavy metals and pesticides on early life stages of Pacific oyster (Crassostrea gigas) النص الكامل
2012
Mai, Hong Ngoc | Cachot, J. | Brune, J. | Geffard, Olivier | Belles, A. | Budzinski, H. | Morin, Brice | Environnements et Paléoenvironnements OCéaniques (EPOC) ; École Pratique des Hautes Études (EPHE) ; Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) | Milieux aquatiques, écologie et pollutions (UR MALY) ; Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)
[Departement_IRSTEA]Eaux [TR1_IRSTEA]BELCA | International audience | This study evaluated embryotoxicity and genotoxicity of two dissolved metals copper and cadmium (Cu and Cd) and two pesticides (metolachlor and irgarol) occurring in Arcachon Bay (SW France) in Pacific oyster (Crassostrea gigas) larvae and investigated the relationship between those two endpoints. Embryotoxicity was measured by calculating the percentage of abnormal D-shaped larvae and genotoxicity was evaluated with DNA strand breaks using the comet assay. After 24 h exposure, significant increases of the percentage of abnormal D-larvae and the DNA strand breaks were observed from 0.1µg/L for Cu, 10 µg/L for Cd and 0.01 µg/L for both irgarol and metolachlor in comparison with the controls. A strong positive relationship between embryotoxicity and genotoxicity was recorded for Cu, Cd and metolachlor. The current study suggests that copper, irgarol and metolachlor can induce larval abnormalities and DNA damage in a population of exposed oysters at environmentally relevant concentrations.
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