خيارات البحث
النتائج 1201 - 1210 من 4,044
Ecological quality assessment in the Eastern Mediterranean combining live and dead molluscan assemblages النص الكامل
2016
Leshno, Yael | Benjamini, Chaim | Edelman-Furstenberg, Yael
The EU directive to quantify ecological quality by deviation from pre-impacted conditions often fails to be implemented because past information is usually incomplete or missing. Molluscan death assemblages, representing long-term accumulation of shells on the sea floor, average out short-term variability and can serve as a baseline for quality assessment. AMBI, Bentix and Shannon–Wiener indices were calculated for live and dead assemblages from polluted and control stations on the highly oligotrophic Levantine shallow shelf of Israel. Bentix successfully tracked deterioration over time, from moderate EcoQS in the dead to poor in the live assemblage. Additional modification of the ecological classification of species by scoring the naturally abundant Corbula gibba as pollution-sensitive improved the utility of the Bentix index in monitoring in this part of the Mediterranean. This adjustment of Bentix, and use of death assemblages for an ecological baseline, should therefore be incorporated in monitoring for compliance with EU directives.
اظهر المزيد [+] اقل [-]Role of environmental particulate matters on corrosion of copper النص الكامل
2016
Saha, D. | Pandya, A. | Singh, J.K. | Paswan, S. | Singh, D.D.N.
Effect of environmental particulate materials on kinetics and mechanism of corrosion of industrial grade copper exposed in different parts of India is investigated. It is observed that the level of particulate materials in the atmosphere has more dominant role than the acidic gases on initiation of corrosion, formation of protective patina on the surface of the exposed samples leading to mitigation of corrosion. The identification of corrosion products formed on the surface of exposed samples by Raman spectroscopy provides very vital information to explain the observed corrosion rate of the metal computed in different environments. Electrochemical anodic polarization of the exposed samples supports the mechanism proposed for accelerating and protective effect on corrosion of the metals exposed in different environments.
اظهر المزيد [+] اقل [-]Assessment of factors enabling halite formation in a marsh in a humid temperate climate (Ajó Marsh, Argentina) النص الكامل
2016
Carol, Eleonora S. | Álvarez, María del Pilar | Borzi, Guido E.
The formation of evaporites associated with the final stages of the precipitation sequence, such as the case of halite, is frequent in marshes in arid areas, but it is not to be expected in those humid climates. This work, by means of the study of the hydrological, climatic and land use conditions, identifies the factors that allow the formation of saline precipitations in a marsh located in a humid climate area. The results obtained show that the exclusion of the marsh as a result of the embankment is the main reason for the presence of halite. It is to be expected that in the future the growth of the embanked marsh areas, together with the climatic and tidal condition tendencies recorded, will favour a higher rate of formation of evaporite salts. The identification of these factors makes it possible to set basic sustainable management guidelines to avoid soil salinisation.
اظهر المزيد [+] اقل [-]Seasonal changes in nutrient limitation and nitrate sources in the green macroalga Ulva lactuca at sites with and without green tides in a northeastern Pacific embayment النص الكامل
2016
Van Alstyne, Kathryn L.
In Penn Cove, ulvoid green algal mats occur annually. To examine seasonal variation in their causes, nitrogen and carbon were measured in Ulva lactuca in May, July, and September and stable nitrogen and oxygen isotope ratios were quantified in U. lactuca, Penn Cove seawater, upwelled water from Saratoga Passage, water near the Skagit River outflow, and effluents from wastewater treatment facilities. Ulvoid growth was nitrogen limited and the sources of nitrogen used by the algae changed during the growing season. Algal nitrogen concentrations were 0.85–4.55% and were highest in September and at sites where algae were abundant. Upwelled waters were the primary nitrogen source for the algae, but anthropogenic sources also contributed to algal growth towards the end of the growing season. This study suggests that small nitrogen inputs can result in crossing a “tipping point”, causing the release of nutrient limitation and localized increases in algal growth.
اظهر المزيد [+] اقل [-]Synoptic weather evolution and climate drivers associated with winter air pollution in New Zealand النص الكامل
2016
Fiddes, S.L. | Pezza, A.B. | Mitchell, T.A. | Kozyniak, K. | Mills, D.
Particulate matter pollution of less than 10 μm in diameter (PM10) is a problem for some regional and urban centres across New Zealand during the winter period when solid fuel (wood and coal) fires are used for home heating. Elevated levels of PM10 concentrations occur during stable atmospheric conditions, when cool air temperatures and low wind speeds allow for a surface inversion to occur and trap PM10. This study examined the relationships between PM10 and local and large-scale synoptic conditions at daily and seasonal scales. Minimum temperature and wind speed were both negatively correlated with PM10 during the winter season, whilst the combination of the two can explain 30–54% of variability in average PM10. Synoptic-scale daily composites of high PM10 days showed the evolution of an anticyclone in the Tasman Sea, with an injection of cool air over New Zealand and persistent south-westerly winds leading to cold and stable conditions on the day of exceedance. Both of these results indicate that there is some potential for predicting days in which atmospheric conditions could favour elevated PM10 concentrations. Furthermore, at the seasonal scale, weaker westerly winds were found to be associated with winters with higher exceedance days, although the relationship is not straightforward. These characteristics can be associated with other, predictable large-scale climate drivers such as the El Niño-Southern Oscillation, and may aid in identifying years in which a higher risk of PM10 pollution events exists.
اظهر المزيد [+] اقل [-]Microbial community structure shifts are associated with temperature, dispersants and nutrients in crude oil-contaminated seawaters النص الكامل
2016
Meng, Long | Liu, Han | Bao, Mutai | Sun, Peiyan
This study tracked structure shifts of bacterial compositions before, during and after invading by crude oil to determine the microbial response and explore how temperature, dispersants and nutrients affect the composition of microbial communities or their activities of biodegradation in artificial marine environment. During petroleum hydrocarbons exposed, the composition and functional dynamics of marine microbial communities were altered, favoring bacteria that could utilize this rich carbon source such as the Proteobacteria, Firmicutes, Actinobacteria and Bacteroidetes phyla. Low temperature as a dominant factor decreased bacterial richness and catabolic diversity due to abated enzymes activities in correlation with the process of biodegradation. Dispersants exerted no negative consequences on microbial composition, however, bacterial composition by the Chloroflexi, TM6, OP8, Cyanobacteria and Gemmatimonadetes phyla increased. It seemed that more frequent fertilizer application could be equally safe to bacteria and increased significantly the abundance of bacterial strains but Actinobacteria phyla decreased.
اظهر المزيد [+] اقل [-]Trophic transfer of toxic elements in the estuarine invertebrate and fish food web of Daliao River, Liaodong Bay, China النص الكامل
2016
Guo, Bobo | Jiao, Deqi | Wang, Jing | Lei, Kai | Lin, Chunye
In order to study element accumulation and trophic transfer in the food web, sixteen benthic invertebrate species and nine fish species were collected from the Daliao River estuary for analysis of toxic elements and nitrogen stable isotope in the muscle tissue. The concentrations ranged between 1.44–17.98, 0.01–9.30, 0.17–36.15, 0.7–145.4, 0.01–0.33, 0.14–14.88, 0.10–2.51, 0.02–0.14, and 19.3–221.1mgkg−1 for As, Cd, Cu, Hg, Ni, Pb, Sb, and Zn, respectively. As, Cd, Cu, and Zn were significantly higher in the benthic invertebrates than in fish, whereas Hg and Sb were significantly lower. In addition, the benthic invertebrates were characterized by the highest bioaccumulation factor (BAF) for Cd, whereas the fish were characterized by the highest BAF for Hg. A significant decrease in Cd, Cr, Cu, and Ni levels, and a significant increase in Hg and Sb levels were observed with increasing trophic levels.
اظهر المزيد [+] اقل [-]Assessment of the fitness of the mussel Mytilus galloprovincialis two years after the Hebei Spirit oil spill النص الكامل
2016
Donaghy, Ludovic | Hong, Hyun-Ki | Kim, Moonkoo | Park, Heung-Sik | Choi, Kwang-Sik
In December 2007, >150km of the West coast of Korea were heavily polluted by crude oil leaked from the oil tanker Hebei Spirit, leading to mass mortality of bivalve mollusks on the intertidal areas. Two years after, mussels Mytilus galloprovincialis were collected from two impacted sites to investigate sub-lethal effects of the oil spill. Tissue content in polycyclic aromatic hydrocarbons (PAHs), hemocyte parameters, reproductive status and energetic reserves were analyzed. PAHs in tissues of mussels as well as hemocyte parameters were not different between impacted and control sites. Energetic reserves were altered in mussels from the impacted sites. Glycogen content remained low at polluted sites, whatever the season. Two years after the Hebei Spirit oil spill, mussels then presented altered energetic metabolism. Further investigations are thus warranted to monitor the sustainability of mussel populations on the oil spilled West coast of Korea.
اظهر المزيد [+] اقل [-]A review of ghost gear entanglement amongst marine mammals, reptiles and elasmobranchs النص الكامل
2016
Stelfox, Martin | Hudgins, Jillian | Sweet, Michael
This review focuses on the effect that ghost gear entanglement has on marine megafauna, namely mammals, reptiles and elasmobranchs. A total of 76 publications and other sources of grey literature were assessed, and these highlighted that over 5400 individuals from 40 different species were recorded as entangled in, or associated with, ghost gear. Interestingly, there appeared to be a deficit of research in the Indian, Southern, and Arctic Oceans; and so, we recommend that future studies focus efforts on these areas. Furthermore, studies assessing the effects of ghost gear on elasmobranchs, manatees, and dugongs should also be prioritised, as these groups were underrepresented in the current literature. The development of regional databases, capable of recording entanglement incidences following a minimum global set of criteria, would be a logical next step in order to analyse the effect that ghost gear has on megafauna populations worldwide.
اظهر المزيد [+] اقل [-]Organotins in fish muscle and liver from the Polish coast of the Baltic Sea: Is the total ban successful? النص الكامل
2016
Filipkowska, Anna | Złoch, Ilona | Wawrzyniak-Wydrowska, Brygida | Kowalewska, Grażyna
Muscle and liver tissues of nine fish species were analyzed to assess butyltin and phenyltin contamination. The samples were collected from three basins located in the Southern Baltic Sea coastal zone that each represent different potential for organotin pollution. Maximum total concentrations of butyltin compounds (BTs) in the fish muscles and livers were 715 and 1132ng Sn g−1 d.w., respectively, whereas triphenyltin (TPhT) was not detected. In the muscle samples, the predominant compound in the sum of butyltins was tributyltin (TBT), while in the liver samples, tributyltin degradation products were found in the majority. The results demonstrate that 6–7years after the implementation of the total ban on harmful organotin use in antifouling paints, butyltins remain present in fishes from the Polish coast of the Baltic Sea. According to the HELCOM recommendation, eight samples exceeded the good environmental status boundary for tributyltin in seafood.
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