Refinar búsqueda
Resultados 681-690 de 1,506
Macrobenthic community for assessment of estuarine health in tropical areas (Northeast, Brazil): Review of macrofauna classification in ecological groups and application of AZTI Marine Biotic Index
2012
Valença, Ana Paula M.C. | Santos, Paulo J.P.
The aim of the present study was to investigate the ecological quality of tropical estuaries on the northeastern coast of Brazil using the AMBI. Macrofauna classification based on ecological groups was reviewed using the Indicator Value (IndVal) coefficient. The results indicate that the ecosystems exhibit some level of disturbance. Most sites are situated between slightly-moderately disturbed boundaries due to the higher proportion of Nematoda (assigned here as Ecological Group I) and of Oligochaeta and Tubificidae (both classified as Ecological Group V). The AMBI proved efficient in evaluating environmental status, although the applicability of this index requires adjustments regarding some species in ecological groups. The present study also highlights the merits of the IndVal method for examining the assignments of species/taxa to an ecological group and demonstrates the validity of this coefficient is an assessment tool. Moreover, the complementary use of different methods is recommended for the assessment of ecosystem quality.
Mostrar más [+] Menos [-]The eutrophication commandments
2012
Fulweiler, R.W. | Rabalais, N.N. | Heiskanen, A.S.
Typically, rising atmospheric carbon dioxide concentrations are used to illustrate how humans have impacted the earth. However, we have also dramatically altered the amount of nitrogen (N) and phosphorus (P) cycling through the biosphere. Eventually these nutrients are carried to coastal receiving waters where they cause severe, often negative consequences including increased phytoplankton and macroalgae blooms, loss of submerged aquatic vegetation, low oxygen events, and decreased biodiversity. In many systems mitigation efforts are now underway to return these ecosystems to a less impacted state. While many uncertainties about the best way to manage eutrophic systems remain it is clear that we must take action to lessen our human nutrient footprint. Based on our current understanding of eutrophic systems we present ten eutrophication commandments or guidelines as a tool for scientists, policy makers, managers, and the public.
Mostrar más [+] Menos [-]The effect of mangrove reforestation on the accumulation of PCBs in sediment from different habitats in Guangdong, China
2012
Zhao, Bo | Zhou, Yan-wu | Chen, Gui-zhu
To investigate the influence of mangrove reforestation on the accumulation of PCBs, the concentrations and homologue patterns of polychlorinated biphenyls in surface sediments from different mangrove forests and their adjacent mud flats in Guangdong Province were determined. The total PCB concentrations in the sediments ranged from 3.03 to 46.62ngg⁻¹ (dry weight). Differences in the accumulation and distribution of PCBs were found between the mangrove sites and the mud flats. Furthermore, the natural forests and restored mangrove forests of native species showed slight PCB contamination, whereas the exotic species Sonneratia apetala exacerbated the PCB pollution at certain sites. It was suggested that the native mangrove species Kandelia candel and Aegiceras corniculatum could represent good choices for the phytoremediation of PCB contamination.
Mostrar más [+] Menos [-]Tracking contaminants in seabirds of Arctic Canada: Temporal and spatial insights
2012
Mallory, Mark L. | Braune, Birgit M.
Levels and trends of persistent organic pollutants and trace elements in seabirds breeding in the vast Canadian Arctic have been monitored since 1975. Data from this monitoring have indicated both spatial and temporal variation across the region, attributable in part to differences in species’ diets, differences in regional deposition patterns, and unidirectional trends in contaminants reaching this area from emissions in temperate and tropical areas to the south. Seabird tissues have served as effective biomonitors to examine this variation, and national and international collaboration in this monitoring effort has promoted valuable synthetic assessments of spatial and temporal patterns in Arctic contaminants. Here we review the history of the monitoring program, the critical role played by Environment Canada’s National Wildlife Specimen Bank, and we summarize important spatial and temporal trends in various contaminants in Canadian Arctic seabirds.
Mostrar más [+] Menos [-]The occurrence and distribution of pharmaceutical compounds in the effluents of a major sewage treatment plant in Northern Taiwan and the receiving coastal waters
2012
Fang, Tien-Hsi | Nan, Fan-Hua | Chin, Tzong-Shean | Feng, Huimin
The pharmaceutical residues in waste water from the largest sewage treatment plant (STP) in Northern Taiwan and in seawater around the effluent discharged area were determined. An environmental risk assessment for the marine environment was conducted based on the environment risk quotient (ERQ). The concentrations of the analyzed compounds in STP influent and effluent were generally higher than those found in coastal seawater. Relatively higher values were found at the estuarine mouth and the discharged area, suggesting that the STP effluent is a point source. The removal efficiency and half life of the analyzed compounds were 6.3–46.8% and 3–18days, respectively. The ERQ value theoretical calculation was generally greater than 1. However, when the measured concentrations replaced the predicated concentrations, the ERQ values were considerably lower than 1. Therefore, our results call for a re-evaluation of the risks posed by pharmaceuticals to coastal marine ecosystems in Northern Taiwan.
Mostrar más [+] Menos [-]GhostNet marine debris survey in the Gulf of Alaska – Satellite guidance and aircraft observations
2012
Pichel, William G. | Veenstra, Timothy S. | Churnside, James H. | Arabini, Elena | Friedman, Karen S. | Foley, David G. | Brainard, Russell E. | Kiefer, Dale | Ogle, Simeon | Clemente-Colon, Pablo | Li, Xiaofeng
Marine debris, particularly debris that is composed of lost or abandoned fishing gear, is recognized as a serious threat to marine life, vessels, and coral reefs. The goal of the GhostNet project is the detection of derelict nets at sea through the use of weather and ocean models, drifting buoys and satellite imagery to locate convergent areas where nets are likely to collect, followed by airborne surveys with trained observers and remote sensing instruments to spot individual derelict nets. These components of GhostNet were first tested together in the field during a 14-day marine debris survey of the Gulf of Alaska in July and August 2003. Model, buoy, and satellite data were used in flight planning. A manned aircraft survey with visible and IR cameras and a LIDAR instrument located debris in the targeted locations, including 102 individual pieces of debris of anthropogenic or terrestrial origin.
Mostrar más [+] Menos [-]Adaptive thresholding algorithm based on SAR images and wind data to segment oil spills along the northwest coast of the Iberian Peninsula
2012
Mera, David | Cotos, José M. | Varela-Pet, José | Garcia-Pineda, Oscar
Satellite Synthetic Aperture Radar (SAR) has been established as a useful tool for detecting hydrocarbon spillage on the ocean’s surface. Several surveillance applications have been developed based on this technology. Environmental variables such as wind speed should be taken into account for better SAR image segmentation. This paper presents an adaptive thresholding algorithm for detecting oil spills based on SAR data and a wind field estimation as well as its implementation as a part of a functional prototype. The algorithm was adapted to an important shipping route off the Galician coast (northwest Iberian Peninsula) and was developed on the basis of confirmed oil spills. Image testing revealed 99.93% pixel labelling accuracy. By taking advantage of multi-core processor architecture, the prototype was optimized to get a nearly 30% improvement in processing time.
Mostrar más [+] Menos [-]Analysis of Pacific oyster larval proteome and its response to high-CO₂
2012
Dineshram, R. | Wong, Kelvin K.W. | Xiao, Shu | Yu, Ziniu | Qian, Pei Yuan | Thiyagarajan, Vengatesen
Most calcifying organisms show depressed metabolic, growth and calcification rates as symptoms to high-CO₂ due to ocean acidification (OA) process. Analysis of the global expression pattern of proteins (proteome analysis) represents a powerful tool to examine these physiological symptoms at molecular level, but its applications are inadequate. To address this knowledge gap, 2-DE coupled with mass spectrophotometer was used to compare the global protein expression pattern of oyster larvae exposed to ambient and to high-CO₂. Exposure to OA resulted in marked reduction of global protein expression with a decrease or loss of 71 proteins (18% of the expressed proteins in control), indicating a wide-spread depression of metabolic genes expression in larvae reared under OA. This is, to our knowledge, the first proteome analysis that provides insights into the link between physiological suppression and protein down-regulation under OA in oyster larvae.
Mostrar más [+] Menos [-]Effects of chlorpyrifos on cholinesterase activity and stress markers in the tropical reef fish Acanthochromis polyacanthus
2012
Botté, E.S. | Jerry, D.R. | Codi King, S. | Smith-Keune, C. | Negri, A.P.
Tropical coastal ecosystems, including the Great Barrier Reef (GBR) of Australia are increasingly threatened by pollution; yet few studies have investigated the sensitivity of GBR species to these pollutants. Here we exposed juveniles of the tropical reef fish Acanthochromis polyacanthus (spiny damselfish) to three concentrations of the insecticide chlorpyrifos (CPF) and measured (i) muscle cholinesterase (ChE) activity; (ii) hepatic glutathione-S-transferase (GST) activity; and (iii) coenzyme Q (CoQ) redox balance, after 6h and 96h of exposure. After 96h, muscle ChE activity was significantly inhibited by 26%, 49% and 53% when fish were exposed to 1, 10 or 100μg/L CPF, respectively. Muscle ChE characterization revealed three types of ChEs, including two atypical forms. Hepatic CoQ antioxidant form significantly increased at 10μg/L after 6h of exposure, potentially demonstrating an early response to CPF-induced oxidative stress in liver. Hepatic GST was not affected by CPF exposure.
Mostrar más [+] Menos [-]Quantifying the sources of pollutants in the Great Barrier Reef catchments and the relative risk to reef ecosystems
2012
Waterhouse, J. | Brodie, J. | Lewis, S. | Mitchell, A.
Development of the Great Barrier Reef (GBR) catchments in the last 150years has increased the loads of suspended sediment, nutrients and pesticides (‘pollutants’) delivered to the GBR. The scale and type of development, the pollutants generated and the ecosystems offshore vary regionally. We analysed the relative risk of pollutants from agricultural land uses and identified the sources of these pollutants from different land uses for each region to develop priorities for management. The assessment showed the Wet Tropics and Mackay Whitsunday regions to be of relatively high risk dominated by sugarcane cultivation, contributing pesticide and dissolved inorganic nitrogen (DIN). The Burdekin and Fitzroy ranked medium–high risk dominated by grazing suspended sediment inputs for both, and additionally sugarcane DIN and pesticide inputs for the Burdekin. The Burnett Mary ranked medium risk, dominated by grazing and sugarcane. Cape York was not formally ranked but is considered to be low risk.
Mostrar más [+] Menos [-]