خيارات البحث
النتائج 1161 - 1170 من 3,208
Impact of intertidal oyster trestle cultivation on the Ecological Status of benthic habitats النص الكامل
2015
Forde, James | O’Beirn, Francis X. | O’Carroll, Jack PJ. | Patterson, Adrian | Kennedy, Robert
A considerable number of Ireland’s shellfish production areas co-occur with or are adjacent to Natura 2000 sites which are protected under European legislation. To investigate the general interaction between trestle oyster cultivation and the surrounding intertidal environment, six sites were selected within designated Natura 2000 sites. At each trestle site three Treatment areas were sampled. One Treatment area corresponded to potential impacts associated with cultivation activities occurring at trestle structures (designated the Trestle Treatment) while one Treatment area corresponded to potential impacts due to cultivation activities occurring along access routes (the Access Treatment). An area not subject to any known anthropogenic activity was used as a control (the Control Treatment). Potential impacts associated with Trestle Treatment areas included changes in sediment total organic matter (TOM) levels underneath trestles due to the bio-deposition of faecal/pseudofaecal material while the predominant impact associated with Access Treatment areas was compaction of sediments due to heavy vehicle traffic. In this study, macrobenthic communities at the sites were highly variable and exhibited low levels of diversity which prevented the detection of general effects of cultivation activity on community structure, diversity and secondary production. To overcome this variability, the Infaunal Quality Index (IQI) was used to assess impacts on Ecological Status (ES) of benthic communities (sensu Water Framework Directive). Relative to Control and Trestle Treatment areas, activities occurring at Access Treatment areas had a significant negative impact on ES. This study highlights the potential of the IQI for the management of aquaculture activity and provides validation for the use of the IQI in Irish intertidal environments. This study also highlights the IQI as a potential tool for assessing the conservation status of designated habitats in Natura 2000 sites.
اظهر المزيد [+] اقل [-]Experimental and numerical investigations on reliability of air barrier on oil containment in flowing water النص الكامل
2015
Lu, Jinshu | Xu, Zhenfeng | Xu, Song | Xie, Sensen | Wu, Haoxiao | Yang, Zhenbo | Liu, Xueqiang
Air barriers have been recently developed and employed as a new type of oil containment boom. This paper presents systematic investigations on the reliability of air barriers on oil containments with the involvement of flowing water, which represents the commonly-seen shearing current in reality, by using both laboratory experiments and numerical simulations. Both the numerical and experimental investigations are carried out in a model scale. In the investigations, a submerged pipe with apertures is installed near the bottom of a tank to generate the air bubbles forming the air curtain; and, the shearing water flow is introduced by a narrow inlet near the mean free surface. The effects of the aperture configurations (including the size and the spacing of the aperture) and the location of the pipe on the effectiveness of the air barrier on preventing oil spreading are discussed in details with consideration of different air discharges and velocities of the flowing water. The research outcome provides a foundation for evaluating and/or improve the reliability of a air barrier on preventing spilled oil from further spreading.
اظهر المزيد [+] اقل [-]Towards adaptive management of the natural capital: Disentangling trade-offs among marine activities and seagrass meadows النص الكامل
2015
Bas Ventín, Leticia | de Souza Troncoso, Jesús | Villasante, Sebastián
This paper investigates the ecological, social and institutional dimensions of the synergies and trade-offs between seagrasses and human activities operating in the Natura 2000 protected site of San Simón Bay (Galicia, NW Spain). By means of a multidisciplinary approach that brings together the development of a biological inventory combined with participatory mapping processes we get key spatial and contextual understanding regarding how, where and why marine users interact with seagrasses and how seagrasses are considered in policy making. The results highlight the fisheries' reliance on seagrass meadows and the controversial links with shellfisheries. The study also reveals unresolved conflicts among those management plans that promote the protection of natural values and those responsible for the exploitation of marine resources. We conclude that the adoption of pre-planning bottom-up participatory processes is crucial for the design of realistic strategies where both seagrasses and human activities were considered as a couple system.
اظهر المزيد [+] اقل [-]Magnetic properties of sediments in cores from the Mandovi estuary, western India: Inferences on provenance and pollution النص الكامل
2015
Prajith, A. | Rao, V Purnachandra | Kessarkar, Pratima M.
Magnetic properties of sediments were investigated in 7 gravity cores recovered along a transect of the Mandovi estuary, western India to understand their provenance and pollution. The maximum magnetic susceptibility of sediments was at least 6 times higher in the upper/middle estuary than in lower estuary/bay. The χfd% and χARM/SIRM of sediments indicated coarse, multi-domain and pseudo-single domain magnetic grains, resembling ore material in the upper/middle estuary and coarse stable single domain (SSD) to fine SSD grains in the lower estuary/bay. Mineralogy parameters indicated hematite and goethite-dominated sediments in the upper/middle estuary and magnetite-dominated sediments in the lower estuary/bay. Two sediment types were discernible because of deposition of abundant ore material in the upper/middle estuary and detrital sediment in the lower estuary/bay. The enrichment factor and Index of geo-accumulation of metals indicated significant to strong pollution with respect to Fe and Mn in sediments from the upper/middle estuary.
اظهر المزيد [+] اقل [-]Assessment of organotin and tin-free antifouling paints contamination in the Korean coastal area النص الكامل
2015
Lee, Mi-Ri-Nae | Kim, Ŭn-jung | Lee, In-Seok | Choi, Minkyu | Oh, Jeong-Eun
Twelve organotins (methyl-, octyl-, butyl-, and phenyl-tin), and eight tin-free antifouling paints and their degradation products were measured in marine sediments from the Korean coastal area, and Busan and Ulsan bays, the largest harbor area in Korea. The total concentration of tin-free antifouling paints was two- to threefold higher than the total concentration of organotins. Principal component analysis was used to identify sites with relatively high levels of contamination in the inner bay area of Busan and Ulsan bays, which were separated from the coastal area. In Busan and Ulsan bays, chlorothalonil and DMSA were more dominant than in the coastal area. However, Sea-Nine 211 and total diurons, including their degradation products, were generally dominant in the Korean coastal area. The concentrations of tin and tin-free compounds were significantly different between the east and west coasts.
اظهر المزيد [+] اقل [-]Polycyclic aromatic hydrocarbons in surface sediment from Yangpu Bay, China: Distribution, sources and risk assessment النص الكامل
2015
Li, Ping | Diao, Xiaoping | Zhang, Yu | Xie, Yanli | Yang, Fei | Zhou, Hailong | Han, Qian | Wang, Fuqiang | Cheng, Huamin | Wang, Haihua
The study investigated the occurrence of polycyclic aromatic hydrocarbons (PAHs) in the surface sediment from eleven sites in Yangpu Bay, China in December 2013 (winter) and July 2014 (summer). The 16 US EPA priority PAHs were found in the range of 1583.2–5701.7ng/g dry weights with an average of 3134.7±1241.3ng/g in winter and ranged from 2161.8 to 4527.2ng/g with an average of 3016.6±748.0ng/g in summer, respectively. The concentrations of the PAHs tended to be relatively high in comparison with other areas from the literatures. The identification using molecular indices analysis indicated that the PAHs originated mainly from pyrogenic and petrogenic sources in most of the sites. According to principle component analysis–multiple linear regression (PCA/MLR) for their source apportionment, the main sources of PAHs were vehicle emissions, petroleum products and biomass combustion. The risk assessment using international sediments quality guidelines and sediments quality criteria indicated that several PAHs, such as Nap, Flu, Phe, Ace, Acy and BghiP in most of the sites would potentially affect organisms in Yangpu Bay.
اظهر المزيد [+] اقل [-]Polybrominated Diphenyl Ethers (PBDEs) in Concepción Bay, central Chile after the 2010 Tsunami النص الكامل
2015
Pozo, Karla | Kukučka, Petr | Vaňková, Lenka | Přibylová, Petra | Klánová, Jana | Rudolph, Anny | Banguera, Yulieth | Monsalves, Javier | Contreras, Sergio | Barra, Ricardo | Ahumada, Ramón
PBDEs (10 congeners) were analyzed using GC–MS in superficial sediments and organisms of the Concepción Bay after the 2010 Tsunami. From all congeners analyzed PBDE-47, -99, -100 and -209 were the most frequently detected. Concentrations (ngg−1 d.w.) in sediments for ΣPBDE-47, -99, -100 were low (0.02–0.09). However, PBDE-209 showed significantly higher values ∼20ngg−1 d.w. This result were ∼10 times lower than those reported in a previous study of the 2010 Tsunami. The high result might be influenced by the massive urban debris dragged by the 2010 Tsunami. In organisms, concentrations of PBDE-47, -99, -100 (∼0.4ngg−1 d.w.) were higher than those found in sediments (∼0.04ngg−1 d.w.). Differences in PBDE pattern were also observed between different levels of the trophic food chain (primary and secondary consumers). This is the first attempt to assess the current status of Concepción Bay after the 2010 Tsunami.
اظهر المزيد [+] اقل [-]Baseline hydrocarbon levels in New Zealand coastal and marine avifauna النص الكامل
2015
McConnell, H.M. | Gartrell, B.D. | Chilvers, B.L. | Finlayson, S.T. | Bridgen, P.C.E. | Morgan, K.J.
The external effects of oil on wildlife can be obvious and acute. Internal effects are more difficult to detect and can occur without any external signs. To quantify internal effects from oil ingestion by wildlife during an oil spill, baseline levels of ubiquitous hydrocarbon fractions, like polycyclic aromatic hydrocarbons (PAHs), need to be established. With these baseline values the extent of impact from exposure during a spill can be determined. This research represents the first investigation of baseline levels for 22 PAHs in New Zealand coastal and marine avian wildlife. Eighty-five liver samples were tested from 18 species. PAHs were identified in 98% of livers sampled with concentrations ranging from 0 to 1341.6ng/g lipid wt or on wet wt basis, 0 to 29.5ng/g. Overall, concentrations were low relative to other globally reported avian values. PAH concentration variability was linked with species foraging habitat and migratory patterns.
اظهر المزيد [+] اقل [-]Biodegradation of dispersed Macondo oil in seawater at low temperature and different oil droplet sizes النص الكامل
2015
Brakstad, Odd G. | Nordtug, Trond | Throne-Holst, Mimmi
During the Deepwater Horizon (DWH) accident in 2010 a dispersant (Corexit 9500) was applied at the wellhead to disperse the Macondo oil and reduce the formation of surface slicks. A subsurface plume of small oil droplets was generated near the leaking well at 900–1300m depth. A novel laboratory system was established to investigate biodegradation of small droplet oil dispersions (10μm or 30μm droplet sizes) of the Macondo oil premixed with Corexit 9500, using coastal Norwegian seawater at a temperature similar to the DWH plume (4–5°C). Biotransformation of volatile and semivolatile hydrocarbons and oil compound groups was generally faster in the 10μm than in the 30μm dispersions, showing the importance of oil droplet size for biodegradation. These data therefore indicated that dispersant treatment to reduce the oil droplet size may increase the biodegradation rates of oil compounds in the deepwater oil droplets.
اظهر المزيد [+] اقل [-]Modelling the fate and transport of faecal bacteria in estuarine and coastal waters النص الكامل
2015
Gao, Guanghai | Falconer, R. A. | Lin, Binliang
This paper details a numerical model developed to predict the fate and transport of faecal bacteria in receiving surface waters. The model was first validated by comparing model predicted faecal bacteria concentrations with available field measurements. The model simulations agreed well with the observation data. After calibration, the model was applied to investigate the effects of different parameters, including: tidal processes, river discharges from the upstream boundaries and bacteria inputs from the upstream boundaries, wastewater treatment works (WwTWs), rivers and combined sewer overflows (CSO), on the concentrations of faecal bacteria in the Ribble Estuary. The results revealed that the tide and upstream boundary bacteria inputs were the primary factors controlling the distribution of faecal bacteria. The bacteria inputs from the WwTWs in the model domain were generally found not to have a significant impact on distribution of faecal bacteria in the estuary.
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