خيارات البحث
النتائج 581 - 590 من 2,459
Conservation management options and actions: Putative decline of coral cover at Palmyra Atoll, Northern Line Islands, as a case study
2014
Gardner, Jonathan P.A. | John Bartz, R. | Brainard, Russell E. | Collen, John D. | Dunbar, Robert B. | Garton, David W. | Powell, Sam
Localised loss of live coral cover at Palmyra Atoll (central Pacific Ocean) has been attributed to increased temperature and/or sedimentation arising from alterations made to the lagoon system. It has been hypothesised that a causeway spanning the lagoon hinders water circulation, resulting in warmer and/or more turbid water flowing towards a site of high coral cover and diversity (Coral Gardens). Analyses of a multi-site and multi-year data set revealed no differences in mean temperature or turbidity values on either side of the causeway and provided no evidence of significantly warmer or more turbid water at Coral Gardens. We conclude that the putative decline in live coral cover cannot be attributed to the presence of the causeway and that proposed management actions involving modification to the causeway cannot achieve the conservation outcomes suggested of them.
اظهر المزيد [+] اقل [-]Mercury speciation in coastal sediments from the central east coast of India by modified BCR method
2014
Chakraborty, Parthasarathi | Raghunadh Babu, P.V. | Vudamala, Krushna | Ramteke, Darwin | Chennuri, Kartheek
This is the first study to describe distribution and speciation of Hg in coastal sediments from the central east coast of India. The concentrations of Hg in the studied sediments were found to be much lower than the Hg concentration recommended in coastal sediments by the United State Environmental Protection Agency and the Canadian Council of Ministers of the Environment for the protection of aquatic life. This study suggests that the interactions between Hg and coastal sediments are influenced by particle size (sand, silt and clay) of the sediments and the total organic carbon (TOC) content in the sediments. It was found that the coastal sediments from the central east coast of India could act as a sink for Hg. The availability of strong uncomplexed-Hg binding sites in the coastal sediments was observed.
اظهر المزيد [+] اقل [-]Dietary mercury exposure to endangered California Clapper Rails in San Francisco Bay
2014
Casazza, Michael L. | Ricca, Mark A. | Overton, Cory T. | Takekawa, John Y. | Merritt, Angela M. | Ackerman, Joshua T.
California Clapper Rails (Rallus longirostris obsoletus) are an endangered waterbird that forage in tidal-marsh habitats that pose risks from mercury exposure. We analyzed total mercury (Hg) in six macro-invertebrate and one fish species representing Clapper Rail diets from four tidal-marshes in San Francisco Bay, California. Mercury concentrations among individual taxa ranged from lowest at Colma Creek (mean range: 0.09–0.2μg/gdw) to highest at Cogswell (0.2–0.7), Laumeister (0.2–0.9) and Arrowhead Marshes (0.3–1.9). These spatial patterns for Hg matched patterns reported previously in Clapper Rail blood from the same four marshes. Over 25% of eastern mudsnails (Ilyanassa obsolete) and staghorn sculpin (Leptocottus armatus) exceeded dietary Hg concentrations (ww) often associated with avian reproductive impairment. Our results indicate that Hg concentrations vary considerably among tidal-marshes and diet taxa, and Hg concentrations of prey may provide an appropriate proxy for relative exposure risk for Clapper Rails.
اظهر المزيد [+] اقل [-]In situ detrimental impacts of Prorocentrum donghaiense blooms on zooplankton in the East China Sea
2014
Lin, Jia-Ning | Yan, Tian | Zhang, Qing-Chun | Wang, Yunfeng | Liu, Qing | Zhou, Ming-Jiang
Large-scale algal blooms of the dinoflagellate Prorocentrum donghaiense have occurred frequently in the East China Sea (ECS) in recent decades. However, its impacts on the zooplankton in situ are still under not well understood. During a spring P. donghaiense bloom (April–May 2013) along the northern coast of Fujian Province (120°–121°30″E, 26°30″–28°N), we found that the bloom decreased the abundance of copepods and had no significant effect on chaetognaths and small jellyfish. However, the abundance of small jellyfish increased over the course of the study. The zooplankton community changed from being copepod and small jellyfish- to small jellyfish-dominated during the bloom. In the bloom areas, the copepod Calanus sinicus showed higher mortality and lower egg production rates (EPR) than those in the non-bloom areas. The results suggested that P. donghaiense blooms had detrimental effects on the structure of zooplankton community and the recruitments of C. sinicus.
اظهر المزيد [+] اقل [-]Physicochemical characteristics of PM2.5: Low, middle, and high–income group homes in Agra, India–a case study
2014
Singh, Pradyumn | Saini, Renuka | Taneja, Ajay
The present study shows the current scenario of the aggregate relation between income and pollution at the household level. The indoor sampling of fine particulate matter was conducted in low– middle– and high–income group homes in Agra City, the North Central region of India. The mean indoor concentrations of PM2.5 were 46.7μg/m3, 39.2μg/m3 and 25.6μg/m3 in low– middle– and high–income group homes respectively. The full–day variation revealed that the concentrations of fine particles were higher during morning and evening hours in all the three income group homes. The indoor meteorological parameters were also monitored. Using scanning electron microscopy coupled with energy dispersive x–ray spectrometer (SEM–EDS) chemical and elemental analysis of fine particles and their probable sources has been conducted in low– middle– high–income group homes. EDS spectra indicates the elemental composition of PM2.5 which can be distributed into following groups of particles i.e. C–O rich (54%), F rich (42%) and other (4%) in low–income group homes. In middle– and high–income group homes F rich (59–65%), C–O rich (32–37%) and other (3–4%) were observed in PM2.5. The SEM images of fine particles indicates that the particles are clustered into following groups i.e. aluminosilicates/silica particles, spherical carbon rich particles, nearly spherical fluorine rich particles, Mg–Si or Mg–Si–Al particles.
اظهر المزيد [+] اقل [-]Ballast water: A threat to the Amazon Basin
2014
Pereira, Newton Narciso | Botter, Rui Carlos | Folena, Rafael Dompieri | Pereira, José Pinheiro Fragoso Neto | da Cunha, Alan Cavalcanti
Ballast water exchange (BWE) is the most efficient measure to control the invasion of exotic species from ships. This procedure is being used for merchant ships in national and international voyages. The ballast water (BW) salinity is the main parameter to evaluate the efficacy of the mid-ocean ballast water exchange. The vessels must report to the Port State Control (PSC), via ballast water report (BWR), where and how the mid-ocean BWE was performed. This measure allows the PSC to analyze this information before the ship arrives at the port, and to decide whether or not it should berth.Ship BW reporting forms were collected from the Captaincy of Santana and some ships were visited near the Port of Santana, located in Macapá (Amazon River), to evaluate the BW quality onboard. We evaluated data submitted in these BWR forms and concluded that the BWE efficacy might be compromised, because data contained in these BWR indicate that some ships did not change their BW. We found mistakes in filling the BWR forms and lack of information. Moreover, these ships had discharged BW with high level of salinity, Escherichia coli and total coliforms into the Amazon River. We concluded that the authorities of the Amazon Region need to develop more efficient proceedings to evaluate the ballast water reporting forms and BW quality, as there is potential risk of future invasion of exotic species in Brazilian ports.
اظهر المزيد [+] اقل [-]Fish biological effect monitoring of chemical stressors using a generalized linear model in South Sea, Korea
2014
Jung, Jee-Hyun | Choi, Seung Bae | Hong, Sang Hee | Chae, Young Sun | Kim, Hana | Yim, Un Hyuk | Ha, Sung Yong | Han, Gi Myung | Kim, Dae Jung | Shim, Won Joon
To evaluate the health status at six different study areas, we used the generalized linear model approach with selected biochemical markers in resident fish from uncontaminated and contaminated sites. We also confirmed the independence between the biochemical indices and the morphometric indices including the hepato-somatic index (HSI), gonado-somatic index (GSI), and condition factor (CF) in fish from the sampling areas. The effect of area on the presence of biotransformation markers (ethoxyresorufin-O-deethylase activity; EROD) was significantly high in Masan Bay. The area with the greatest effect on acetylcholinesterase (AChE) activity was Jindong Bay, while there was no significant effect of GSI, HSI, CF, and sex in the EROD model and HSI, CF and sex in the AChE model. These results clarify that fish from Masan, Gwangyang and Jindong Bay were affected by pollutant stress, and the analysis of sensitive biochemical responses allowed for an improved interpretation of the results.
اظهر المزيد [+] اقل [-]Sediment-preserved diatom assemblages can distinguish a petroleum activity signal separately from the nutrient signal of the Mississippi River in coastal Louisiana
2014
Parsons, M.L. | Turner, R.E. | Overton, E.B.
We analyzed the preserved diatom assemblages in dated sediment cores collected from five locations in the Louisiana Bight to test if there was a signature of petroleum extraction activities (hopanes and barium) distinct from the well-documented effects of nutrient loading. The results of a multi-dimensional scaling analysis indicate that the diatom assemblage changes documented throughout the 40year record could be explained by three variables: barium and hopanes concentrations, and Mississippi River nitrogen loading. The results of a canonical correspondence analysis demonstrated that these signals could be distinguished through correlations with specific diatom species. The abundance of Actinoptychus senarius, for example, was negatively correlated with barium and the Pseudo-nitzschia delicatissima complex was positively correlated with nitrogen loading. These results provide a “proof-of-concept” demonstration that diatom assemblages preserved in the sediments can be used to study the effects of petroleum extraction activities, and that these ‘petroleum signals’ may be distinguished from other significant influences such as nutrient loading.
اظهر المزيد [+] اقل [-]Multiple stressors threatening the future of the Baltic Sea–Kattegat marine ecosystem: Implications for policy and management actions
2014
Jutterström, S. | Andersson, H.C. | Omstedt, A. | Malmaeus, J.M.
The paper discusses the combined effects of ocean acidification, eutrophication and climate change on the Baltic Sea and the implications for current management strategies. The scientific basis is built on results gathered in the BONUS+ projects Baltic-C and ECOSUPPORT. Model results indicate that the Baltic Sea is likely to be warmer, more hypoxic and more acidic in the future. At present management strategies are not taking into account temporal trends and potential ecosystem change due to warming and/or acidification, and therefore fulfilling the obligations specified within the Marine Strategy Framework Directive, OSPAR and HELCOM conventions and national environmental objectives may become significantly more difficult. The paper aims to provide a basis for a discussion on the effectiveness of current policy instruments and possible strategies for setting practical environmental objectives in a changing climate and with multiple stressors.
اظهر المزيد [+] اقل [-]Transitional and freshwater bioassessments: One site, two perspectives?
2014
Neto, J.M. | Feio, M.J. | Teixeira, H. | Patrício, J. | Serra, S.R.Q. | Franco, J.N. | Calapez, A.R. | Constantino, E.
The freshwater–saltwater-transition-zone was analysed using two different sampling protocols and assessment methodologies, developed for freshwater and estuaries, to compare their agreement level in terms of community composition and quality assessments. The use of different protocols resulted in significant differences in macroinvertebrate communities, in index scores and initially in quality classes. After modifications in the sensitivity scores of the IBMWP and AMBI indices (average scores or the use of a score of the other index when both were present), the differences were largely reduced and quality classes became coincident for the assessments provided by IPtIs and BAT tools. Such harmonisation of quality assessments for adjacent water categories (e.g., large rivers vs. transitional waters), exemplified here as an harmonisation in one of the metrics comprised in the assessment tools, is essential as it has direct implications on the expansion and accomplishment of River Basin Management Plans committed by the Water Framework Directive.
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