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Результаты 1381-1390 из 4,241
Spatial variation of microbial communities in sediments along the environmental gradients from Xiaoqing River to Laizhou Bay
2017
Yu, Shu-Xian | Pang, Yun-Long | Wang, Yinju | Li, Jia-Lin | Qin, Song
The Laizhou Bay is famous for aquaculture, but has been subject to eutrophication and contamination for years. High concentrations of nutrients from the Xiaoqing River are considered as the main cause for significant eutrophication in the west of Laizhou Bay. Here we present results of the research on sedimentary microbial assemblages along this spatial gradient between riverine and marine environments by high-throughput sequencing. The predominant phyla/classes of bacteria and fungi clustered the samples into two distinct provinces, while discriminant taxa of each province were strongly associated with spatial factors and inorganic nitrogen. Spatial variation of bacterial communities was mainly related with the distribution of phosphates, suggesting a phosphate-limitation pattern for the bacterial communities. Alpha- and beta-diversity of fungal communities exhibited a significant correlation with water depth. We consider the distinct distributional gradients of bacterial and fungal communities partly explain the different roles in the biogeochemical processes of coastal sediment.
Показать больше [+] Меньше [-]Abundance and composition of juvenile corals reveals divergent trajectories for coral assemblages across the United Arab Emirates
2017
Pratchett, Morgan S. | Baird, Andrew H. | Bauman, Andrew G. | Burt, John A.
Marked shifts in the composition of coral assemblages are occurring at many locations, but it is unknown whether these are permanent shifts reinforced by patterns of population replenishment. This study examined the composition of juvenile coral assemblages across the United Arab Emirates (UAE). Densities of juvenile corals varied significantly among locations, but were highest where coral cover was highest. Juvenile coral assemblages within the Persian Gulf were dominated by Porites, while no Acropora were recorded. We expect therefore, continued declines in Acropora abundance, while observed dominance of Porites is likely to persist. In the Oman Sea, Pocillopora was the dominant juvenile coral, with Acropora and Stylophora also recorded. This study shows that taxonomic differences in replenishment are reinforcing temporal shifts in coral composition within the southern Persian Gulf, but not in the Oman Sea. Differences in environmental conditions and disturbance regimes likely explain the divergent responses between regions.
Показать больше [+] Меньше [-]Fusion of multi-source near-surface CO2 concentration data based on high accuracy surface modeling
2017
Mingwei, Zhao | Tianxiang, Yue | Xingying, Zhang | Jinglu, Sun | Ling, Jiang | Chun, Wang
Under the background of growing greenhouse gas emissions and the resulting global warming, researches about the spatial-temporal variation analysis of the concentration of carbon dioxide in the regional and global scale has become one of the most important topics in the scientific community. Simulating and analyzing the spatial-temporal variation of the carbon dioxide concentration on a global scale under limited observation data has become one of the key problems to be solved in the research field of spatial analysis technology. A new research approach based on high accuracy surface modeling data fusion (HASM-DF) method was proposed in this paper, in which the output of the CO2 concentration of the GEOS-Chem model were taken as driving field, and the observation values of CO2 concentration at ground observation station were taken as accuracy control conditions. The new approach's objective is to fulfill the fusion of the two kinds of CO2 data, and obtain the distribution of CO2 on a global scale with a higher accuracy than the results of GEOS-Chem. Root mean square error (RMSE) was chosen as the basic accuracy index, and the experimental analysis shows that the RMSE of the result of the proposed approach is 1.886 ppm, which is significantly lower than that of the GEOS-Chem's 2.239 ppm. Furthermore, compared with the results created by the interpolation methods used the observation values at stations; the fusion results keep a good spatial heterogeneity similar to the results of GEOS-Chem. This research analyzed the spatial distribution and time series variation of the near-surface CO2 based on the fusion result on a global scale. And it can found that areas such as East Asia, Western North American, Central South America and Central Africa and other region show a relatively high value of the near-surface CO2 concentration. And we also found that the near-surface CO2 concentration changes with season, especially in North America and Eurasia, the near-surface CO2 in summer was significantly lower than winter in these areas.
Показать больше [+] Меньше [-]Temporal and spatial variability of ground level atmospheric methane concentrations in the Ebro River Delta
2017
Àgueda, A. (Alba) | Grossi, Claudia | Pastor, Elsa | Rioja, Eva | Sánchez-García, Laura | Batet, Òscar | Curcoll, Roger | Ealo, Marina | Nofuentes, Manel | Occhipinti, Paola | Rodó, Xavier | Morguí, Josep-Anton
Deltas provide many worthy ecosystem services. Yet, delta basins are quite vulnerable, especially in the face of climate change, which can affect the outcome of both agriculture and biodiversity. Moreover, rice paddy cultivation is well known to contribute with strong emissions of greenhouse gases (GHGs), such as methane (CH4). Thus, knowing the atmospheric variability of CH4 in relation to the different stages of the rice culture cycle could help to improve GHGs' mitigation strategies in deltas.The Ebro River Delta, in the northwestern Mediterranean basin, forms part of the largest Spanish river basin and is mainly covered by rice fields. In this study, for the first time, ground level (40 cm a.g.l.) atmospheric CH4 concentrations have been monitored in this area, through twenty-seven car mobile transects, over the course of one year. Seasonal, diurnal and spatial variability of CH4 concentrations were studied to identify its relationship with rice cultivation, meteorological conditions and land-use distribution.With regard to seasonal variability, autumn transects showed the highest mean values for atmospheric CH4 (2.466 ppm) when dead rice straw is mixed with the sediment, and weed growth is prevented. Spring and summer measurements gave the highest mean CH4 values at dawn (1.897–3.544 ppm), whereas autumn and winter produced the mean values after sunset (2.148–2.930 ppm). Spatial differences were accounted for by proximity to urban areas, presence of shallow water storage structures, and distance to seawater.
Показать больше [+] Меньше [-]Polybrominated diphenyl ethers (PBDEs) and alternative flame retardants (NFRs) in indoor and outdoor air and indoor dust from Istanbul-Turkey: Levels and an assessment of human exposure
2017
Kurt-Karakus, Perihan Binnur | Alegria, Henry | Jantunen, Liisa | Birgul, Askin | Topcu, Aslinur | Jones, K. C. (Kevin C.) | Turgut, Cafer
Levels of polybrominated diphenyl ethers (PBDEs) and novel brominated flame retardants (NFRs) were measured in ambient outdoor air, indoor air and indoor dust collected in homes and offices at urban, semi-urban and rural locations in Istanbul, Turkey. Indoor air levels of Σ12PBDEs in homes and offices ranged from 36 to 730 pg/m3 and 160 to 10 100 pg/m3, respectively, while levels of Σ12NFRs ranged from 180 to 7600 pg/m3 and 180 to 42 400 pg/m3, respectively. Outdoor air levels ranged from 110 to 620 pg/m3 for Σ12PBDEs and 750 to 2800 pg/m3 for Σ12NFRs. I/O ratios that are greater than 1 suggest that air concentrations detected in indoor environments are mainly from indoor sources. Indoor dust levels in homes and offices of Σ12PBDEs ranged from 400 to 12 500 ng/g and 330 to 32 200 ng/g respectively and levels of Σ12NFRs ranged from 320 to 31 400 ng/g and 910 to 97 900 ng/g, respectively. The I/O ratios >1 for PBDEs and NFRs may indicate that emissions of these chemicals detected in homes and offices are mainly from indoor sources. Due to childrens' frequent hand-to-mouth behaviour, lower body weight and increased dust ingestion rate compared to adults, exposure rates to target chemicals for children were greater than those of adults. Based on median concentrations of chemicals of interest in dust and air samples from Istanbul, we estimate that exposure rates of children to PBDEs and NFRs are up to 160 times higher compared to adults but none of the estimated exposure rates results for children or adults were than the recommended daily oral reference dose values of certain analytes.
Показать больше [+] Меньше [-]Long-term variation of the macrobenthic community and its relationship with environmental factors in the Yangtze River estuary and its adjacent area
2017
Yan, Jia | Xu, Yong | Sui, Jixing | Li, Xinzheng | Wang, Hongfa | Zhang, Baolin
Using data from four periods from 1959 to 2015, we report the long-term variation of the macrobenthic community in the Yangtze River estuary and its adjacent area. In total, 624 species were collected, and Polychaeta was the dominant group. Significant differences between the four periods were found. The CCA (canonical correspondence analysis) and RDA (redundancy analysis) results revealed that temperature, salinity, and depth significantly influenced the macrobenthic communities (89.6% of the species-environment relationship variance was explained by the first two axes of CCA and 94.3% was explained by RDA). The results of K-dominance curves (the elevation increased over time), ABC (abundance/biomass comparison) curves (the W value changed from 0.311 to 0.167 during 1959 to 2014–2015) and the Shannon-Wiener index (log base=2; 2.29–5.03 in 1959, 2.86–4.55 in 2000–2001, 2.28–4.56 in 2011–2012, and 1.79–4.43 in 2014–2015) showed that the ecological status of the benthic study area was deteriorating.
Показать больше [+] Меньше [-]Analysis and occurrence of some phenol endocrine disruptors in two marine sites of the northern coast of Sicily (Italy)
2017
Errico, Sonia | Nicolucci, Carla | Migliaccio, Marina | Micale, Valeria | Mita, Damiano G. | Diano, Nadia
This study reports the occurrence of some endocrine disrupting chemicals in red mullet samples and sediments collected in two representative sites of the northern Sicilian coast (Italy). For this purpose, an improved method, using solid extraction and high-performance liquid chromatography analyses for the simultaneous determination of bisphenol A (BPA), 4-nonylphenol (4-NP) and 4-t-octylphenol (4-t-OP) in fish tissues and sediments, has been developed and validated. Method performance was demonstrated over the concentration range 0.1–200ng/mL, with detection limits from 0.06 to 0.1ng/mL. Recoveries ranged from 83.4% to 102.6%, with relative standard deviations of 7.7–14.0% for the entire procedure.Results showed that BPA, 4-t-OP and 4-NP were detected in all fish samples and sediments from two sampling sites, indicating that these chemicals have contaminated Mediterranean aquatic ecosystem and have accumulated in fish. The study provided more comprehensive fundamental data for risk assessment and contamination control of phenolic EDCs in aquatic environment.
Показать больше [+] Меньше [-]Molecular phylogeny and toxicity of harmful benthic dinoflagellates Coolia (Ostreopsidaceae, Dinophyceae) in a sub-tropical marine ecosystem: The first record from Hong Kong
2017
Leung, Priscilla T.Y. | Yan, Meng | Yiu, Sam K.F. | Lam, Veronica T.T. | Ip, Jack C.H. | Au, Maggie W.Y. | Chen, Chia-Yun | Wai, Tak-Cheung | Lam, Paul K.S.
Coolia are marine benthic dinoflagellates which are globally distributed and potentially toxic. This study provides the first investigation of species diversity and toxicity assessment of Coolia in Hong Kong waters. Fifty-one strains of four Coolia species, including C. malayensis, C. canariensis, C. tropicalis, and C. palmyrensis, were isolated from twelve sub-tidal habitats, and identified phylogenetically using 28S rDNA sequences. Exposure experiments (48-hour) demonstrated that the algal lysates extracted from the four Coolia species exhibited different toxic effects on the lethality and abnormality of two invertebrate larvae, i.e., brine shrimp Artemia franciscana and sea urchin Heliocidaris crassispina. Heliocidaris crassispina was more sensitive to the toxic effects of Coolia species than A. franciscana. Toxicity tests from both larvae revealed that C. malayensis was generally more toxic, and caused higher mortality rates when compared with the other three species. The emerging threat of harmful benthic dinoflagellates to marine environments and sensitive biota is discussed.
Показать больше [+] Меньше [-]Geochemical speciation, bioavailability and source identification of selected metals in surface sediments of the Southern Caspian Sea
2017
Bastami, Kazem Darvish | Neyestani, Mahmoud Reza | Esmaeilzadeh, Marjan | Haghparast, Sarah | Alavi, Camelia | Fathi, Sanaz | Nourbakhsh, Shahram | Shirzadi, Emam Ali | Parhizgar, Reyhane
Geochemical speciation of As, Cd, Co, Cr, Cu, Ni, Pb, V and Zn were determined in the surface sediments of the southern Caspian Sea. A five-step sequential extraction technique was used to determine the chemical forms of metals. Mean concentrations (ppm) of heavy metals were (mean±S.D.) As: 9.94±1.71, Cd: 0.87±0.23, Co: 14.85±2.80, Cr: 72.29±19.48, Cu: 18.91±4.48, Ni: 32.87±5.25, Pb: 12.48±3.22, V: 86.07±20.71 and Zn: 66.85±10.11. Among the metals, Cu, As, Pb and Zn exhibited relatively higher mobility, while Cd, Co, Cr, Ni and V were found mainly in the residual fractions. Cu and As showed the highest percentages in the exchangeable phase while Co and Cr had the lowest percentages in the phase. The Risk Assessment Code (RAC) values indicated that As, Cu and V had medium risk at some sampling sites. According to pollution load index (PLI), sediments from some sampling sites were polluted.
Показать больше [+] Меньше [-]GIS-based health assessment of the marine ecosystem in Laizhou Bay, China
2017
Song, Debin | Gao, Zhiqiang | Zhang, Hua | Xu, Fuxiang | Zheng, Xiangyu | Ai, Jinquan | Hu, Xiaoke | Huang, Guopei | Zhang, Haibo
According to 2014–2016 monitoring data, an assessment index system including water quality, depositional environment and ecosystem was built to evaluate the health statue of marine ecosystem in the Laizhou Bay using analytic hierarchy process (AHP) method. The results, spatialized in ArcGIS software, show: while the comprehensive ecological health index is 0.62, the ecological environmental quality in the Laizhou Bay is in a sub-healthy state; the unhealthy area is mainly concentrated in southwestern inshore region, and impacted by serious environmental problems, such as water eutrophication and heavy metal pollution; the northwestern and southeastern inshore regions are in a sub-healthy state, while the eastern inshore and northern areas are in the healthiest state. The land-based pollutants that discharge into the sea may be the leading factors that are causing ecological environment deterioration in the Laizhou Bay, and the reclamation work ongoing around the port has exacerbated the ecological risk.
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