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النتائج 781 - 790 من 2,459
Comparison of the efficacy of MODIS and MERIS data for detecting cyanobacterial blooms in the southern Caspian Sea
2014
Moradi, Masoud
Medium Resolution Imaging Spectrometer (MERIS) data, Moderate Resolution Imaging Spectroradiometer (MODIS) data, and hydro-biological measurements were used to detect two very severe blooms in the southern Caspian Sea in 2005 and 2010. The MERIS Cyanobacteria Index (CIMERIS) was more reliable for detecting cyanobacterial blooms. The CIMERIS and MODIS cyanobacteria indices (CIMODIS) were compared in an effort to find a reliable method for detecting future blooms, as MERIS data were not available after April 2012. The CIMODIS had a linear relationship with and similar spatial patterns to the CIMERIS. On the CIMODIS images, extremely high biomass cyanobacteria patches were masked. A comparison of classified in situ data with the CIMODIS and Floating Algal Index (FAI) from four images of a severe bloom event in 2005 showed that the FAI is a reliable index for bloom detection over extremely dense patches. The corrected CIMODIS, the MODIS FAI and in situ data are adequate tools for cyanobacterial bloom monitoring in the southern Caspian Sea.
اظهر المزيد [+] اقل [-]Triclosan causes toxic effects to algae in marine biofilms, but does not inhibit the metabolic activity of marine biofilm bacteria
2014
Johansson, C Henrik | Janmar, Lisa | Backhaus, Thomas
Effects of the antimicrobial agent triclosan to natural periphyton communities (biofilms, comprising primarily microalgae and bacteria) were assessed in two independent experiments during spring and summer. For that purpose a semi-static test system was used in which periphyton was exposed to a concentration range of 5–9054nmol/L triclosan. Effects on algae were analyzed as content and composition of photosynthetic pigments. The corresponding EC50 values were 39.25 and 302.45nmol/L for the spring and summer experiment, respectively. Effects on periphytic bacteria were assessed as effects on carbon utilization patterns, using Biolog Ecoplates. No inhibition of either total carbon utilization or functional diversity was observed, indicating a pronounced triclosan tolerance of the marine bacteria. In contrast, a small stimulation of the total carbon utilization was observed at triclosan concentrations exceeding 100nmol/L.
اظهر المزيد [+] اقل [-]Assessment of pollution in the Bizerte lagoon (Tunisia) by the combined use of chemical and biochemical markers in mussels, Mytilus galloprovincialis
2014
Barhoumi, Badreddine | Menach, Karyn Le | Clérandeau, Christelle | Ameur, Walid Ben | Budzinski, Hélène | Driss, Mohamed Ridha | Cachot, Jérôme
In order to assess the environmental quality of the Bizerte lagoon (Tunisia), biomarker and contaminant levels were measured in Mediterranean mussels (Mytilus galloprovincialis) from five selected sites. Persistent organic pollutants (POPs) were quantified in whole body and enzyme activities such as acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) in gills. Despite the relatively low levels of organic contaminants, the selected biomarkers responded differently according to the pollution level at the different sites. GST and AChE activities were correlated with the amount of DDTs in mussel tissues. These two enzymatic activities were also correlated to temperature and pH. No significant difference was observed for CAT activity. Principal component analysis showed a clear separation of sampling sites in three different assemblages which is consistent with POP body burden in mussels. Our results confirmed the usefulness of combining biomarker and chemical analyses in mussels to assess chemical pollution in the Bizerte lagoon.
اظهر المزيد [+] اقل [-]Use of GIS for the evaluation of heavy metal contamination in the Cunha Canal watershed and west of the Guanabara Bay, Rio de Janeiro, RJ
2014
Borges, Renata Coura | Caldas, Vanessa Godoy | Filho, Francisco Fernando Lamego Simões | Ferreira, Marcos Manoel | Lapa, Celso Marcelo Franklin
The Cunha Canal watershed, which is located in the municipality of Rio de Janeiro, suffered severe environmental degradation in recent decades due to rapid urban population growth. However, this substantial growth did not result in social development; instead, it exacerbated existing environmental and social problems. This study aimed to evaluate the pollution of the Canal do Cunha and Guanabara Bay, using GIS for mapping based on the result of the heavy metal concentrations obtained by spectrometry (ICP-OES). The analyzed data were monitored at five collection points. Five heavy metals (Cd, Pb, Cu, Ni and Zn) were evaluated. The results showed that the waters of the Cunha Canal watershed and the west side of Guanabara Bay have been altered and degraded. The concentration of heavy metals in the water was lower than the concentration in the sediments. The behaviors of the studied metals differed during the rainy and dry periods.
اظهر المزيد [+] اقل [-]Transcriptomic response to estrogen exposure in the male Zhikong scallop, Chlamys farreri
2014
An, Li-hui | Zheng, Bing-hui | Liu, Rui-zhi | Fan, Qiang | Wang, Qing-kui | Luo, Ying-feng
The transcriptomes of Zhikong scallop exposed to 17β-estradiol were determined using the Roche/454. A total of 51,997 unigenes, representing 45,030 contigs and 6967 singlets were obtained. And 14,028, 19,798 and 14,981 of these unigenes were annotated from the non-redundant nucleic acid database, non-redundant protein database and Swiss protein database, respectively. A total of 10,699 unigenes were further annotated to biological processes (9080), molecular functions (8692) and cellular components (7829) using the GO, and 8945 unigenes were mapped to biological pathways including the metabolism (2862) and genetic information processing (2263). Most importantly, 16,692 unigenes and 18,686 unigenes in testis, and 10,492 unigenes and 13,186 unigenes in digestive gland were up-regulated significantly after exposure to 50 and 500ngE2/L; while 10,212 unigenes and 9409 unigenes in testis and 10,629 unigenes and 9463 unigenes in digestive gland were down-regulated. These valuable information provides insights into the mechanisms in invertebrate exposure to EDCs.
اظهر المزيد [+] اقل [-]Effects of a coastal power plant thermal discharge on phytoplankton community structure in Zhanjiang Bay, China
2014
Li, Xue-Ying | Li, Bin | Sun, Xing-Li
The effects of a thermal discharge from a coastal power plant on phytoplankton were determined in Zhanjiang Bay. Monthly cruises were undertaken at four tide times during April–October 2011. There were significant differences for dominant species among seven sampling months and four sampling tides. Species diversity (H′) and Evenness showed a distinct increasing gradient from the heated water source to the control zone and fluctuated during four tides with no visible patterns. Species richness, cell count and Chl a at mixed and control zones were significantly higher than heated zones, and showed tidal changes with no obvious patterns. The threshold temperature of phytoplankton species can be regarded as that of phytoplankton community at ebb slack. The average threshold temperature over phytoplankton species, cell count and Chl a, and the threshold temperature of cell count can be regarded as that of phytoplankton community at flood slack during spring and neap respectively.
اظهر المزيد [+] اقل [-]The usefulness of transplantation studies in monitoring of metals in the marine environment: South African experience
2014
Greenfield, R. | Brink, K. | Degger, N. | Wepener, V.
Due to their close proximity to the point sources of pollution, estuaries and harbours are exposed to metals. Mussels are used worldwide to monitor marine pollution due to their ability to take up contaminants and the ease of transplantation. Mussels were collected from two reference sites and transplanted in Richards Bay Harbour (2006 and 2010) and in three harbours. Transplanted and resident mussels were removed after 6weeks exposure and metal concentrations were analysed using ICP-MS techniques. Transplanted mussels had higher metal concentrations than the resident mussels. This was attributed to regulation of metals by the resident mussels. Metal regulation was greater in mussels that are continuously submerged as opposed to those that undergo tidal influences. For monitoring it is essential that the reference population for transplantation is considered carefully as upwelling events in the pristine reference location results in significant increases in metal bioaccumulation.
اظهر المزيد [+] اقل [-]Molecular biomarkers in grey seals (Halichoerus grypus) to evaluate pollutant exposure, health and immune status
2014
Lehnert, K. | Muller, S. | Weirup, L. | Ronnenberg, K. | Pawliczka, I. | Rosenberger, T. | Siebert, U.
Grey seals as top-predators bioaccumulate contaminants and can be considered as sentinels of eco-system health. Pups are weaned after a short nursing period, characterised by an enormous lipid transfer and exposure to contaminants. This study established molecular biomarkers of the xenobiotic metabolism and immune system to help assess health and immune status. mRNA transcription of AHR, ARNT, PPARα and cytokine IL-2 and heat-shock-protein HSP70 was measured in blood of grey seal pups and adults in rehabilitation and permanent care using RT-qPCR and compared to rehabilitating harbour seal pups and haematology values. In pups highest levels at admission in xenobiotic biomarker, HSP70 and cytokine transcription may show contaminant exposure via lactation, stress during abandonment and dehydration. The significant decrease may be linked to diet, health improvement and adaptation. Adults showed higher levels and more variation in biomarker transcription and clear species-specific differences between harbour and grey seal pups were found.
اظهر المزيد [+] اقل [-]Distribution of mercury in coastal marine sediments of China: Sources and transport
2014
Meng, Mei | Shi, Jian-bo | Yun, Zhao-jun | Zhao, Zong-shan | Li, Hui-juan | Gu, Yu-xiao | Shao, Jun-juan | Chen, Bao-wei | Li, Xiang-Dong | Jiang, Gui-bin
A total of 220 surface sediments and eight sediment cores were analyzed to study the distribution and transport of Hg in Chinese marginal seas. Spatial distribution showed a general offshore decreasing trend towards the outer continental shelf. Vertical profiles of sediment cores displayed a general increasing trend from bottom to surface layers. Coastal land-based discharges and river-derived inputs are probably the main sources of Hg in coastal sediments of China seas, while TOC, pH, ocean currents and sediment characteristics could play important roles in the transport and spatial distribution of Hg in sediment. The influence of TOC on Hg concentration is more significant than that of pH. The mud deposits on the coastal shelves are main sinks of Hg in the region. The results showed that sedimentary Hg was affected by regional anthropogenic activities and riverine runoffs, and was also influenced by long-range atmospheric transport and ocean current circulations.
اظهر المزيد [+] اقل [-]Enzymatic methods for the determination of pollution in seawater using salt resistant alkaline phosphatase from eggs of the sea urchin Strongylocentrotus intermedius
2014
Menzorova, Natalie I. | Seitkalieva, Alexandra V. | Rasskazov, Valerу A.
A new salt resistant alkaline phosphatase from eggs of the sea urchin Strongylocentrotus intermedius (StAP) has been shown to have a unique property to hydrolyze substrate in seawater without loss of enzymatic activity. The enzyme has pH optimum at 8.0–8.5. Model experiments showed various concentrations of copper, zinc, cadmium and lead added to seawater or a standard buffer mixture to inhibit completely the enzyme activity at the concentrations of 15–150μg/l. StAP sensitivity to the presence in seawater of metals, pesticides, detergents and oil products appears to be considerably less. Samples of seawater taken from aquatic areas of the Troitsy Bay of the Peter the Great Bay, Japan Sea have been shown to inhibit the enzyme activity; the same was shown for the samples of fresh waters. The phosphatase inhibition assay developed proved to be highly sensitive, technically easy-to use allowing to test a great number of samples.
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