خيارات البحث
النتائج 951 - 960 من 3,243
Klebsiella sp. FIRD 2, a TBT-resistant bacterium isolated from contaminated surface sediment along Strait of Johor Malaysia
2015
Abubakar, Abdussamad | Mustafa, Muskhazli B. | Johari, Wan Lutfi Wan | Zulkifli, Syaizwan Zahmir | Ismail, Ahmad | Mohamat-Yusuff, Ferdaus Binti
A possible tributyltin (TBT)-degrading bacterium isolated from contaminated surface sediment was successfully identified as Klebsiella sp. FIRD 2. It was found to be the best isolate capable of resisting TBT at a concentration of 1000μgL−1. This was a concentration above the reported contaminated level at the sampling station, 790μgL−1. Further studies revealed that the isolate was Gram negative and resisted TBT concentrations of up to 1500μgL−1 in a Minimal Salt Broth without the addition of any carbon source within the first 48h of incubation. It is expected that additional work could be conducted to check the degradation activity of this new isolate and possibly improve the degradation capacity in order to contribute to finding a safe and sustainable remediation solution of TBT contamination.
اظهر المزيد [+] اقل [-]137Cs, 40K and 210Po in marine mammals from the southern Baltic Sea
2015
Ciesielski, Tomasz | Góral, Marta | Szefer, Piotr | Jenssen, Bjørn Munro | Bojanowski, Ryszard
This study provides information on baseline concentrations of the radionuclides Cesium-137, Potassium-40 and Polonium-210 in sea mammals from the Baltic Sea. The radionuclides were analyzed in the liver, kidney and muscle of harbor porpoises, striped dolphins, and gray and ringed seals from the Polish coast by γ- and α-spectrometry. Median 137Cs activities were 14.8, 13.2 and 23.2Bqkg−1 w.w. in the liver, kidney and muscles, respectively. Activities of 40K and 210Po in the respective tissues were found to be 79.1, 79.8 and 111Bqkg−1 for 40K and 58.1, 59.2 and 32.9Bqkg−1 for 210Po. The measured 137Cs concentrations were extraordinarily high in comparison to those reported in sea mammals from other locations. However, dose assessments did not imply health effects from 137Cs exposure in Baltic Sea mammals. Correlations between 137Cs tissue activities and reported sea water concentrations highlight the potential use of marine mammals for biomonitoring purposes.
اظهر المزيد [+] اقل [-]Latitudinal variation and residence time of 137Cs in Indian coastal environment
2015
Sartandel, S.J. | Jha, S.K. | Tripathi, R.M.
Anthropogenic 137Cs activity concentration, in surface sea water along the western and eastern coast of India has been estimated using the in-situ pre-concentration approach. Activity levels of 137Cs ranges from 0.09–1.30Bqm−3 with an overall mean of 0.69±0.29Bqm−3. Latitudinal variation and higher depletion in activity concentration of 137Cs at few locations were observed. Temporal change of 137Cs in sea water along Indian coast unveils a lower effective half-life of 13.8±0.7y in comparison to Asia Pacific regional sea water. The results prevailed that the spatial distribution confers no fresh input of 137Cs in Indian coastal region.
اظهر المزيد [+] اقل [-]A spatial assessment of baseline nutrient and water quality values in the Ashepoo–Combahee–Edisto (ACE) Basin, South Carolina, USA
2015
Keppler, C.J. | Bergquist, D.C. | Brock, L.M. | Felber, J. | Greenfield, D.I.
The Ashepoo–Combahee–Edisto (ACE) Basin (South Carolina, USA) National Estuarine Research Reserve System (NERRS) encompasses some of the least developed USA coastline. Yet, periodic sampling showed that certain regions have higher nutrient, fecal coliform, and chlorophyll a levels, often with lower dissolved oxygen, than other South Carolina estuaries. To evaluate the spatial extent of these issues, a summer (2008) baseline study was conducted. Physical water quality, total nitrogen and phosphorus, chlorophyll a, dissolved organic carbon, and suspended solids were measured from surface waters of 67 stations (30 tidal creek, 37 open water). Nutrient and chlorophyll a levels were significantly (p<0.01) and negatively correlated with the extent of open water (% land cover), and chlorophyll a and nitrogen levels were, at times, elevated relative to concentrations typical of other estuaries in the state, reinforcing previous findings. This survey also identified several creeks not previously monitored that exhibited elevated nutrients.
اظهر المزيد [+] اقل [-]Distributions, sources and ecological risk assessment of arsenic and mercury in the surface sediments of the southwestern coastal Laizhou Bay, Bohai Sea
2015
Zhuang, Wen | Gao, Xuelu
The spatial distributions of As and Hg in riverine and marine surface sediments of the coastal southwestern Laizhou Bay were obtained, and multiple indices and guidelines were applied to assess their contamination and ecological risks. The As concentrations in riverine sediments were close to those in marine sediments, and on the whole the dominant proportion of As was identified to be from natural sources. The Hg concentrations in riverine sediments were much higher than those in marine sediments, so river transportation was likely the main way of Hg into the southwestern Laizhou Bay. In respect of As, the sediment quality was fine according to the risk assessment methods used; in contrast, Hg presented an extremely contaminated status with a very high ecological risk in some riverine sediments, while most of the marine sediments were relatively much less polluted by Hg and under a lower ecological risk from it.
اظهر المزيد [+] اقل [-]Pollutant tracking for 3 Western North Atlantic sea grasses by remote sensing: Preliminary diminishing white light responses of Thalassia testudinum, Halodule wrightii, and Zostera marina
2015
Thorhaug, Anitra | Berlyn, Graeme P. | Poulos, Helen M. | Goodale, Uromi M.
Sea grasses are foundation species for estuarine ecosystems. The available light for sea grasses diminishes rapidly during pollutant spills, effluent releases, disturbances such as intense riverine input, and tidal changes. We studied how sea grasses’ remote-sensing signatures and light-capturing ability respond to short term light alterations. In vivo responses were measured over the entire visible-light spectra to diminishing white-light on whole-living-plants’ spectral reflectance, including 6h of full oceanic-light fluences from 10% to 100%. We analyzed differences by various reflectance indices. We compared the sea grasses species responses of tropical vs. temperate and intertidals (Halodule wrightii, and Zostera marina) vs. subtidal (Thalassia testudinum). Reflectance diminished with decreasing light intensity that coincided with greater accessory pigment stimulation (anthocyanin, carotenoids, xanthins). Chlorophyll a and Chlorophyll b differed significantly among species (Thalassia vs. Halodule). Photosynthetic efficiency diminished at high light intensities. The NDVI index was inadequate to perceive these differences. Our results demonstrate the leaf-level utility of data to remote sensing for mapping sea grass and sea grass stress.
اظهر المزيد [+] اقل [-]Distribution and pollution assessment of trace elements in marine sediments in the Quintero Bay (Chile)
2015
Parra, Sonnia | Bravo, Manuel A. | Quiroz, Waldo | Querol, X. (Xavier) | Paipa, Carolina
The aim of this study was to assess the levels of heavy metal pollution in the clay/silt fraction (<63μm fraction) of marine sediments from Quintero Bay, Chile. For this, sediment samples were collected from 14 sites from the bay and analyzed for major and minor element determination. The metal concentrations found suggest an anthropogenic origin related with Cu, Se, Mo, As, Sb and Pb. The mineralogical characteristics of the samples were determined by XRD and selected samples were examined by SEM to determine morphological differences. The results showed heavy metal-bearing particles such as Cu, Zn, As and Pb, which are most likely associated with by the copper smelter.
اظهر المزيد [+] اقل [-]Spatial–temporal variations and diversity of the bacterioplankton communities in the coastal waters of Kuwait
2015
Almutairi, Awatef
The dynamics and composition of the bacterial community in the coastal waters of Kuwait are poorly understood. In this study, the spatial–temporal variations in the bacterial composition in the surface water along the Kuwaiti coast was examined by 16S rRNA denaturing gradient gel electrophoresis (DGGE) fingerprinting and phylogeny analyses. The sampling sites were Kuwait Bay, Al-Sabbiya (north of the bay) and Al-Khairan (to the south). The bacterial composition was more variable in the summer for all sites. A cluster analysis of the DGGE fingerprint revealed two main clusters, indicating a temporal similarity between sites. Kuwait Bay and Al-Khairan were more similar to each other than to Al-Sabbiya. The bacterial community composition exhibited distinctive spatial variations, with more diversity at Al-Khairan and less diversity at Al-Sabbiya. At all sites, the dominant bacteria were Alphaproteobacteria, in particular Rhodobacteraceae, followed by Alteromonadaceae (Gammaproteobacteria) and Bacteroidetes.
اظهر المزيد [+] اقل [-]Environmental fate and ecological risks of nonylphenols and bisphenol A in the Cape D’Aguilar Marine Reserve, Hong Kong
2015
Xu, Elvis G.B. | Morton, Brian | Lee, Joseph H.W. | Leung, Kenneth M.Y.
Nonylphenols (NPs) and bisphenol A (BPA) are the most common endocrine disruptors detected in the coastal waters of Hong Kong. The Cape D’Aguilar Marine Reserve (CAMR), the only marine reserve in Hong Kong is close to urbanized areas, thus the resident marine organisms are inevitably influenced by partially treated wastewater from adjacent sewage treatment plants (STPs). Elevated levels of NPs and BPA were detected in all seawater, sediment and biota samples collected from the CAMR. Estrogenic activities of seawater from the CAMR, and sludge and sewage from a nearby STP were assessed using yeast estrogen screen assay. We found aromatase, estrogen receptor and vitellogenin genes in the marine medaka fish Oryzias melastigma were significantly up-regulated after exposure to the reserve’s seawater. According to a tissue-residue-based probabilistic risk assessment, the marine species living in the CAMR are having 35% and 21% of chance to be at risk due to exposure to NPs and BPA, respectively.
اظهر المزيد [+] اقل [-]Nutrient removal in a closed silvofishery system using three mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle)
2015
De-León-Herrera, R. | Flores-Verdugo, F. | Flores-de-Santiago, F. | González-Farías, F.
The removal of ammonium (NH4+), nitrite (NO2−), nitrate (NO3−), and phosphate (PO4−3) in a closed silvofishery system was examined using three mangrove species (i.e., Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle). Specifically, six closed tanks were installed for this experiment with a population of 60 Dormitator latifrons fishes per tank. We planted 40 seedlings in each of three experimental tanks separated by species, while the remaining tanks were used as control. During 15weeks, nutrient concentrations among the three mangrove systems presented no significant differences (P>0.05). However, nutrient removal variability was minimum during the last 2–5weeks. Mangroves presented an average efficiency of 63% for the removal of NH4+ and NO2−. Contrary, the average removal potential of NO3− and PO4−3 was 50%. Results from this study suggest that the three mangrove species could be used in a closed silvofishery systems for the biological removal of NH4+, NO2−, NO3−, and PO4−3.
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