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Результаты 861-870 из 2,459
Study of landscape patterns of variation and optimization based on non-point source pollution control in an estuary
2014
Jiang, Mengzhen | Chen, Haiying | Chen, Qinghui | Wu, Haiyan
Appropriate increases in the “sink” of a landscape can reduce the risk of non-point source pollution (NPSP) to the sea at relatively lower costs and at a higher efficiency. Based on high-resolution remote sensing image data taken between 2003 and 2008, we analyzed the “source” and “sink” landscape pattern variations of nitrogen and phosphorus pollutants in the Jiulongjiang estuary region. The contribution to the sea and distribution of each pollutant in the region was calculated using the LCI and mGLCI models. The results indicated that an increased amount of pollutants was contributed to the sea, and the “source” area of the nitrogen NPSP in the study area increased by 32.75km2. We also propose a landscape pattern optimization to reduce pollution in the Jiulongjiang estuary in 2008 through the conversion of cultivated land with slopes greater than 15° and paddy fields near rivers, and an increase in mangrove areas.
Показать больше [+] Меньше [-]ALien Biotic IndEX (ALEX) – A new index for assessing impacts of alien species on benthic communities
2014
Çinar, Melih Ertan | Bakir, Kerem
Biotic indices are mainly aimed at assessing levels of deterioration caused by chemical or organic pollution. However, no biotic index to date has been developed to detect impacts of alien species on benthic communities. In this paper, a new biotic index, namely ALEX, is proposed to address the objectives of the Water Framework Directive and was tested in Mersin Bay (Levantine Sea, Turkey). Species were divided into four biogeographic groups, namely native species, casual species, established species and invasive species, and the metric considers the relative importance of these groups in samples. The index classified the ecological status of some stations which are shallow, and close to harbor and river mouths as bad or poor in February and October. The ALEX values were positively and significantly correlated with total nitrogen, silicate and silt percentage in sediment, and negatively correlated with depth and the distance from the harbor.
Показать больше [+] Меньше [-]A multivariate approach to the determination of an indicator species pool for community-based bioassessment of marine water quality
2014
Xu, Guangjian | Zhong, Xiaoxiao | Wang, Yangfan | Warren, Alan | Xu, Henglong
Previous studies in Chinese coastal waters of the Yellow Sea have shown that periphytic ciliates are reliable indicators of marine water quality. However, traditional community-based bioassessments are time-consuming because they rely on the identification and enumeration of all species within the community. In order to improve bioassessment efficiency, step-best-matching analysis was used to identify which are the most reliable indicator species among periphytic marine ciliate communities. Based on indices of species richness, diversity and evenness, a subset of 48 species (out of a total of 141) was found to retain sufficient information for accurately predicting water quality, and was more strongly related to changes of environmental variables than the full species set. These results demonstrate that the step-best-matching analysis is a powerful approach for identifying an indicator species pool from a full species dataset of a community, and allows the development of time-efficient sampling protocols for community-based marine bioassessment.
Показать больше [+] Меньше [-]A comparative study of marine litter on the seafloor of coastal areas in the Eastern Mediterranean and Black Seas
2014
Ioakeimidis, C. | Zeri, C. | Kaberi, H. | Galatchi, M. | Antoniadis, K. | Streftaris, N. | Galgani, F. | Papathanassiou, E. | Papatheodorou, G.
In the present work, abundance, spatial distribution and qualitative composition, of benthic marine litter, were investigated in five study areas from the Eastern Mediterranean and Black Seas (Saronikos, Patras and Echinades Gulfs; Limassol Gulf; Constanta Bay). Surveys were performed using the monitoring protocol proposed by the Technical Group for Marine Litter. Densities ranged from 24items/km2 to 1211items/km2, with the Saronikos Gulf being the most affected area. Plastics were predominant in all study areas ranging from 45.2% to 95%. Metals and Glass/Ceramics reached maximum values of 21.9% and of 22.4%. The size distribution of litter items showed that ⩾50% fall into medium size categories (10×10cm, 20×20cm) along with an elevated percentage of small-sized (<5×5cm) plastic litter items. The comparative analysis of the data highlighted the dependence of the marine litter problem on many local factors (human sources and oceanographic conditions) and the urgent need for specific actions.
Показать больше [+] Меньше [-]Cover versus recovery: Contrasting responses of two indicators in seagrass beds
2014
Soissons, Laura M. | Han, Qiuying | Li, Baoquan | van Katwijk, Marieke M. | Ysebaert, Tom | Herman, Peter M.J. | Bouma, Tjeerd J.
Despite being a highly valuable key-stone ecosystem, seagrass meadows are threatened and declining worldwide, creating urgent need for indicators of their health status. We compared two indicators for seagrass health: standing leaf area index versus relative recovery from local disturbance. Disturbance was created by removing aboveground biomass and recording the rate of regrowth for Zostera marina meadows exposed to contrasting wave regimes and nutrient stress levels.Within the experimental period, relative regrowth in gaps was around 50% in most plots, except for the ambient nutrient treatment at the sheltered site, where it exceeded 100%. The two indicators showed an opposite response to disturbance: the higher the standing leaf area index, the lower the relative recovery from disturbance. This conflicting response raises the question on the proper interpretation of such indicators to estimate seagrass health and resilience, and how to ideally monitor seagrass ecosystems in order to predict collapse.
Показать больше [+] Меньше [-]All aboard! A biological survey of ballast water onboard vessels spanning the North Atlantic Ocean
2014
Steichen, Jamie L. | Schulze, Anja | Brinkmeyer, Robin | Quigg, Antonietta
Global movement of nonindigenous species, within ballast water tanks across natural barriers, threatens coastal and estuarine ecosystem biodiversity. In 2012, the Port of Houston ranked 10th largest in the world and 2nd in the US (waterborne tonnage). Ballast water was collected from 13 vessels to genetically examine the eukaryotic microorganism diversity being discharged into the Port of Houston, Texas (USA). Vessels took ballast water onboard in North Atlantic Ocean between the Port of Malabo, Africa and Port of New Orleans, Louisiana, (USA). Twenty genera of Protists, Fungi and Animalia were identified from at least 10 phyla. Dinoflagellates were the most diverse and dominant identified (Alexandrium, Exuviaella, Gyrodinium, Heterocapsa, Karlodinium, Pfiesteria and Scrippsiella). We are reporting the first detection of Picobiliphytes, Apusozoa (Amastigomonas) and Sarcinomyces within ballast water. This study supports that global commerce by shipping contributes to long-distance transportation of eukaryotic microorganisms, increasing propagule pressure and invasion supply on ecosystems.
Показать больше [+] Меньше [-]Polycyclic aromatic hydrocarbons in pine needles (Pinus halepensis) along a spatial gradient between a traffic intensive urban area (Barcelona) and a nearby natural park
2014
van Drooge, Barend L. | Garriga, Guillem | Grimalt, Joan O.
Polycyclic aromatic hydrocarbons (PAHs) are emitted into the atmosphere from combustion of fuels, such as emissions from traffic in urban areas, which on their terms can be important sources for the translocation of these toxic compounds to the surrounding region. Pine needles can be used as time–integrated passive air–samplers for PAHs. Pine needles were collected between 2009 and 2011 along a spatial gradient (5km) from urban background sites towards sites situated in a natural park (Collserola) within the metropolitan area of Barcelona. City samples showed PAH levels that were two times higher than the levels in the natural park. A seasonal trend was reflected by the substantially higher PAH levels in pine needles collected in the colder sampling period than those collected in the warmer period. The observed trend can be explained in terms of source emission strength, dilution and photo–chemical degradation, while also gas–pine needles partitioning may have played an important role. The city is the major source area for the translocation of PAHs towards the nearby natural park.
Показать больше [+] Меньше [-]Temporal trends and spatial distribution of DDT in bivalves from the coastal marine environments of the continental United States, 1986–2009
2014
Sericano, José L. | Wade, Terry L. | Sweet, Stephen T. | Ramírez, Juan | Lauenstein, Gunnar G.
Analysis of DDT isomers and breakdown products, DDD and DDE, in over 3500 bivalve samples collected from more than 300 locations along the continental United States indicates that concentrations are decreasing. Overall average concentrations for the East (45.8±24.6ng/gdw), Gulf (42.4±21.1ng/gdw), and West (90.9±43.3ng/gdw) coasts are declining with an environmental half-life between 10 and 14years and are predicted to decrease below 10% of today’s concentrations by 2050. Geographically, areas with high and low levels are well identified. Bivalves yielding the highest concentrations were collected in areas linked to areas of DDT production or heavy usage. These areas are clustered in the southern California and San Francisco area, on the West coast; Delaware and Hudson/Raritan Estuary, on the East coast; and in Alabama and northwestern Florida, on the Gulf of Mexico. Statistically significant decreasing trends in ΣDDT concentrations are apparent at most of these locations.
Показать больше [+] Меньше [-]Microbial release from seeded beach sediments during wave conditions
2014
Phillips, Matthew C. | Feng, Zhixuan | Vogel, Laura J. | Reniers, Ad J.H.M. | Haus, Brian K. | Enns, Amber A. | Zhang, Yifan | Hernandez, David B. | Solo-Gabriele, Helena M.
Beach sands can sustain indigenous and introduced populations of enterococci. The objective of this study was to evaluate wave action in promoting the release of introduced bacteria. To accomplish this objective this study developed a method to assess attachment and identified conditions under which introduced bacteria are integrated into the sand. A new “shearing assay” showed that attachment of the introduced spike mimicked that of the natural sand when the spike was allowed to integrate into the sand for 24h at room temperature at a sand moisture content of 20%. Experiments in a wave flume showed that waves were capable of releasing about 60% of the total bacteria added. This suggests that for the range of wave conditions evaluated (height: 1.9–10.5cm, period:1–2.7s), waves were incapable of releasing all of the bacteria. Further study is needed to evaluate bacteria attachment mechanisms.
Показать больше [+] Меньше [-]Source speciation resolving hydrochemical complexity of coastal aquifers
2014
Sonkamble, Sahebrao | Chandra, Subash | Ahmed, Shakeel | Rangarajan, R.
There is a growing concern of seawater intrusion to freshwater aquifers due to groundwater overexploitation in the eastern coastal belt of Southern India. The problem becomes complex in the regions where industrial effluents are also contaminating the freshwater aquifers. In order to understand the hydrochemical complexity of the system, topographic elevation, static water level measurements, major ion chemistry, ionic cross plots, water type contours and factor analysis were applied for 144 groundwater samples of shallow and deep sources from Quaternary and Tertiary coastal aquifers, located within the industrial zone of 25 km2 area near Cuddalore, Southern India. The ionic cross plots indicates dissolution of halite minerals from marine sources and seawater mixing into inland aquifers up to the level of 9.3%. The factor analysis explains three significant factors totaling 86.3% of cumulative sample variance which includes varying contribution from marine, industrial effluent and freshwater sources.
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