Affiner votre recherche
Résultats 671-680 de 2,512
Informing policy to protect coastal coral reefs: Insight from a global review of reducing agricultural pollution to coastal ecosystems Texte intégral
2014
Kroon, F. J. (Frederieke J.) | Schaffelke, Britta | Bartley, Rebecca
The continuing degradation of coral reefs has serious consequences for the provision of ecosystem goods and services to local and regional communities. While climate change is considered the most serious risk to coral reefs, agricultural pollution threatens approximately 25% of the total global reef area with further increases in sediment and nutrient fluxes projected over the next 50years. Here, we aim to inform coral reef management using insights learned from management examples that were successful in reducing agricultural pollution to coastal ecosystems. We identify multiple examples reporting reduced fluxes of sediment and nutrients at end-of-river, and associated declines in nutrient concentrations and algal biomass in receiving coastal waters. Based on the insights obtained, we recommend that future protection of coral reef ecosystems demands policy focused on desired ecosystem outcomes, targeted regulatory approaches, up-scaling of watershed management, and long-term maintenance of scientifically robust monitoring programs linked with adaptive management.
Afficher plus [+] Moins [-]Seasonal variations of epipelic algal community in relation to environmental factors in the Istanbul Strait (the Bosphorus), Turkey Texte intégral
2014
Aktan, Y. | Balkıs, N. | Balkıs, N.
This study was implemented to investigate the species composition, abundance, seasonal variations and diversity of epipelic algae, to determine environmental variables affecting them and to reveal the accumulation of total organic carbon in the sediment in the coastal zone of the Istanbul Strait, Turkey. Epipelic algal community consisted of 44 taxa with a low diversity. The sediment structure which is highly unstable due to the high hydrodynamism of the zone played a dominant role as the main factor in the epipelic algal flora along the coasts of Istanbul Strait. Low TOC and high carbonate values also support this result. The dominance of cyanobacteria in some periods and, as a result of this, the record of the lowest diversity index values indicated the effect of nutrient enrichment and the risk of coastal eutrophication. High dominance of cyanobacteria may also be explicated by climate changes considering its effect in the other areas.
Afficher plus [+] Moins [-]Regulation of CYP11B1 and CYP11B2 steroidogenic genes by hypoxia-inducible miR-10b in H295R cells Texte intégral
2014
Nusrin, Suraia | Tong, Steve K.H. | Chaturvedi, G. | Wu, Rudolf S.S. | Giesy, John P. | Kong, Richard Y.C.
Although numerous studies have shown that hypoxia affects cortisol and aldosterone production in vivo, the underlying molecular mechanisms regulating the steroidogenic genes of these steroid hormones are still poorly known. MicroRNAs are post-transcriptional regulators that control diverse biological processes and this study describes the identification and validation of the hypoxia-inducible microRNA, miR-10b, as a negative regulator of the CYP11B1 and CYP11B2 steroidogenic genes in H295R human adrenocortical cells. Using the human TaqMan Low Density miRNA Arrays, we determined the miRNA expression patterns in H295R cells under normoxic and hypoxic conditions, and in cells overexpressing the human HIF-1α. Computer analysis using three in silico algorithms predicted that the hypoxia-inducible miR-10b molecule targets CYP11B1 and CYP11B2 mRNAs. Gene transfection studies of luciferase constructs containing the 3′-untranslated region of CYP11B1 or CYP11B2, combined with miRNA overexpression and knockdown experiments provide compelling evidence that CYP11B1 and CYP11B2 mRNAs are likely targets of miR-10b.
Afficher plus [+] Moins [-]The application of a carrier-based bioremediation strategy for marine oil spills Texte intégral
2014
Sheppard, Petra J. | Simons, Keryn L. | Adetutu, Eric M. | Kadali, Krishna K. | Juhasz, Albert L. | Manefield, Mike | Sarma, Priyangshu M. | Lal, Banwari | Ball, A. S.
The application of recycled marine materials to develop sustainable remediation technologies in marine environment was assessed. The remediation strategy consisted of a shell carrier mounted bacterial consortium composed of hydrocarbonoclastic strains enriched with nutrients (Bioaug SC). Pilot scale studies (5000l) were used to examine the ability of Bioaug-SC to degrade weathered crude oil (10gl−1; initially 315,000±44,000mgl−1) and assess the impacts of the introduction and biodegradation of oil. Total petroleum hydrocarbon mass was effectively reduced by 53.3 (±5.75)% to 147,000 (±21,000) mgl−1 within 27weeks. 16S rDNA bacterial community profiling using Denaturant Gradient Gel Electrophoresis revealed that cyanobacteria and Proteobacteria dominated the microbial community. Aquatic toxicity assessment was conducted by ecotoxicity assays using brine shrimp hatchability, Microtox and Phaeodactylum tricornutum. This study revealed the importance of combining ecotoxicity assays with oil chemistry analysis to ensure safe remediation methods are developed.
Afficher plus [+] Moins [-]Amount and type of derelict gear from the declining black pearl oyster aquaculture in Ahe atoll lagoon, French Polynesia Texte intégral
2014
Andréfouët, Serge | Thomas, Yoann | Lo, Cedrik
Pearl oyster aquaculture is a major activity in French Polynesia atoll lagoons. After the economic decline that characterized the last decade, concerns recently rose about discarded installations and materials that supported aquaculture practices and by facilities abandoned after they had to close their activities. In May 2013, a first inventory of the type and amount of pearl farms derelict gear (PFDG) was achieved on 47 sites in Ahe lagoon. Surveys were conducted within and outside the boundaries of aquaculture concessions. Twenty types of PFDG littered the lagoon floor and the water column. The most impacted areas were near abandoned grafting houses with up to nine types of PFDG. Forty-five percent of the sites were impacted, including outside concessions. While management authorities are fully aware of the problem, this first assessment is a wake-up call to stimulate the cleaning of lagoons, enhance awareness among farmers, and identify potential ecological consequences on lagoon ecosystems.
Afficher plus [+] Moins [-]A year-long comparison of particle formation events at paired urban and rural locations Texte intégral
2014
Jun, Yun-Seok | Jeong, Cheol-Heon | Sabaliauskas, Kelly | Richard Leaitch, W. | Evans, Greg J.
Ultrafine particle size distribution data were collected in downtown Toronto and rural Egbert from May 2007 to May 2008. Particle formation events were observed in both locations and contributed to increased concentrations of particles less than 25nm in diameter. These events were more frequent in spring and fall and rarely occurred in winter. Stronger solar radiation and drier air were correlated with the occurrence of formation events at both locations. Nucleation events occurred simultaneously at both sites on 10% of the days, and these events involved a shared air mass. Half of these simultaneous events were associated with northern air masses and only a quarter with southerly air masses. The higher loading of aged particles in southerly air masses transported from upwind industrial sectors appeared to limit the occurrence of nucleation events. Formation events occurred less frequently in downtown Toronto than at the rural site, and the frequency was lower on weekdays. It is hypothesized that vehicular emissions were responsible for the suppression of nucleation events in downtown Toronto.
Afficher plus [+] Moins [-]A review of oil, dispersed oil and sediment interactions in the aquatic environment: Influence on the fate, transport and remediation of oil spills Texte intégral
2014
Gong, Yanyan | Zhao, Xiao | Cai, Zhengqing | O’Reilly, S.E. | Hao, Xiaodi | Zhao, Dongye
The 2010 Deepwater Horizon oil spill has spurred significant amounts of researches on fate, transport, and environmental impacts of oil and oil dispersants. This review critically summarizes what is understood to date about the interactions between oil, oil dispersants and sediments, their roles in developing oil spill countermeasures, and how these interactions may change in deepwater environments. Effects of controlling parameters, such as sediment particle size and concentration, organic matter content, oil properties, and salinity on oil–sediment interactions are described in detail. Special attention is placed to the application and effects of oil dispersants on the rate and extent of the interactions between oil and sediment or suspended particulate materials. Various analytical methods are discussed for characterization of oil–sediment interactions. Current knowledge gaps are identified and further research needs are proposed to facilitate sounder assessment of fate and impacts of oil spills in the marine environment.
Afficher plus [+] Moins [-]Description of a Multimetric Phytoplankton Index (MPI) for the assessment of transitional waters Texte intégral
2014
Facca, Chiara | Bernardi Aubry, Fabrizio | Socal, Giorgio | Ponis, Emanuele | Acri, Francesco | Bianchi, Franco | Giovanardi, Franco | Sfriso, Adriano
A Multimetric Phytoplankton Index (MPI) is proposed to support management policies for the assessment of transitional ecosystems and the implementation of the European Water Framework Directive. The MPI incorporates Hulburt’s dominance index, bloom frequency and Menhinick’s diversity index, calculated on the basis of phytoplankton species composition.Chlorophyll a concentrations were also included, to provide biomass data and to guarantee continuity and comparison with past evaluations. The MPI was calculated by averaging the ratios of the resulting values of each metric to those of a reference site characterised by low anthropogenic impact.The MPI was set up using data from over a 10-year period in several stations in Venice Lagoon (North-western Adriatic region), a highly valuable and heterogeneous transitional environment, subject to significant anthropogenic pressures. The dataset included physico-chemical data, nutrient and contaminant concentrations. Statistical analyses allowed us to gauge the MPI’s responses to anthropogenic pressures and to verify its reliability.
Afficher plus [+] Moins [-]Spatial distribution and ecological risk of polychlorinated biphenyls in sediments from Qinzhou Bay, Beibu Gulf of South China Texte intégral
2014
Zhang, Jinlian | Li, Yuanyuan | Wang, Yinghui | Zhang, Yuanyuan | Zhang, Dan | Zhang, Ruijie | Li, Jun | Zhang, Gan
The residual level of polychlorinated biphenyls (PCBs) was determined in the surface sediments collected from the Qinzhou Bay, Beibu Gulf of Southern China. The results showed that the total concentration of PCBs ranged from 1.62 to 62.63ng/g dry wt, with a mean of 9.87ng/g dry wt. Generally, the average PCBs concentrations in three sample groups descended in this order: inner bay>outer bay>rivers. On a mean level, with respect to the PCBs homologue profiles, the analysis suggested that tetrachlorinated biphenyls was the most abundant PCB, followed by hexachlorinated biphenyls, pentachlorinated biphenyls. PCB profiles varied according to the nature of the site and its proximity to the sources. PCA with multiple linear regression analysis indicated that Aroclor products contributed to the PCBs in Qinzhou Bay. Risk assessments conducted on the levels indicated that PCBs in sediments of Qinzhou Bay posed no significant risk to human health.
Afficher plus [+] Moins [-]Spatial and temporal dynamics in macrobenthos during recovery from salmon farm induced organic enrichment: When is recovery complete? Texte intégral
2014
Keeley, Nigel B. | Macleod, Catriona K. | Hopkins, Grant A. | Forrest, Barrie M.
This study documents eight years of benthic recovery at a highly impacted salmon farm. Substantial recovery occurred in the first 2years, and was assessed to be complete after ∼5years. However, minor differences were still evident, along with some on-going benthic instability, attributable to medium-scale spatial movements and successional patterns of macrobenthos. Quantifying the endpoint of ‘recovery’ proved challenging due to: lack of a widely accepted definition, inherent variability in recovering sediments, differing trajectories of impact and reference sites, and statistical challenges. More complex biotic indices and metrics incorporating multiple variables were the most robust indicators. Statistical tests for ‘parallelism’ in the trajectories of Cage and Reference sites proved useful, but results were contingent upon how the method was applied, and should therefore be used in conjunction with data-visualisation methods. The study highlights the importance of a predetermined recovery endpoint, and using multiple indicators and a weight-of-evidence assessment approach.
Afficher plus [+] Moins [-]