خيارات البحث
النتائج 1551 - 1560 من 4,241
Capability of Paraguaçu estuary (Todos os Santos Bay, Brazil) to form oil–SPM aggregates (OSA) and their ecotoxicological effects on pelagic and benthic organisms
2017
For experiments concerning the formation of oil–suspended particulate matter (SPM) aggregates (OSA), oil and sediment samples were collected from Campos Basin and six stations of Paraguaçu estuary, Todos os Santos Bay, Brazil, respectively. The sediments samples were analyzed for organic matter determined by the EMBRAPA method, nitrogen determined by the Kjeldahl method, and phosphorus determined by the method described by Aspila. The oil trapped in OSA was extracted following the method described by Moreira. The experiment showed a relationship between the amount of organic matter and OSA formation and consequently the dispersion of the studied oil. On the basis of the buoyancy of OSA and the ecotoxicological effects on pelagic and benthic community, the priority areas for application of remediation techniques are Cachoeira, Maragogipe, and Salinas da Margarida because of the large amount of oil that accumulated at the bottom of the experiment flask (5.85%, 27.95%, and 38,98%; 4.2%, 17.66%, and 32.64%; and 11.82%, 8.07%, and 10.91% respectively).
اظهر المزيد [+] اقل [-]The value of remote sensing techniques in supporting effective extrapolation across multiple marine spatial scales
2017
Strong, J. (James Asa) | Elliott, Michael
The reporting of ecological phenomena and environmental status routinely required point observations, collected with traditional sampling approaches to be extrapolated to larger reporting scales. This process encompasses difficulties that can quickly entrain significant errors. Remote sensing techniques offer insights and exceptional spatial coverage for observing the marine environment. This review provides guidance on (i) the structures and discontinuities inherent within the extrapolative process, (ii) how to extrapolate effectively across multiple spatial scales, and (iii) remote sensing techniques and data sets that can facilitate this process. This evaluation illustrates that remote sensing techniques are a critical component in extrapolation and likely to underpin the production of high-quality assessments of ecological phenomena and the regional reporting of environmental status. Ultimately, is it hoped that this guidance will aid the production of robust and consistent extrapolations that also make full use of the techniques and data sets that expedite this process.
اظهر المزيد [+] اقل [-]Spatial and temporal distribution of pesticides and PCBs in the atmosphere using XAD-resin based passive samplers: A case study in the Quequén Grande River watershed, Argentina
2017
Silva-Barni, M.F. | Gonzalez, M. | Wania, F. | Lei, Y.D. | Miglioranza, K.S.B.
XAD-resin based passive air samplers were deployed at 10 sites in the Quequén Grande River watershed in Argentina during three periods to evaluate the spatial and temporal variations of pesticides and PCBs in the atmosphere. Endosulfan and chlorpyrifos were the most prevalent pesticide because of their continued usage in Argentina, while DDTs, HCHs, chlordanes, dieldrin and heptachlors registered lower levels, reflecting their use in the past. Atmospheric endosulfan levels were 1–2 orders of magnitude higher during the application period (application: 800–12,000 pg/m3, pre- and post-application: <2–350 pg/m3), suggesting that its use in the area continued even after a ban came into effect. The remaining organochlorine pesticides also reached higher concentrations during this period, which is more likely attributable to temperature controlled air-surface exchange than current applications. The highest concentrations of chlorpyrifos were recorded during the application period, in particular at agricultural sites, where its use is wide-spread on soybean fields. The fungicide chlorothalonil was found predominantly at urban sites and in proximity to Quequén harbor, suggesting that its use might be domestic and as a biocide in antifouling paints. A different temporal pattern was observed for the herbicide trifluralin, suggesting its use in the early stages of the wheat-growing season during winter. Limited spatial variations in PCBs levels indicate a diffuse contamination source in the study area, while their relatively high correlation with temperature suggests re-volatilization from local sources. Relative enrichment of lighter PCBs congeners could be attributed to re-evaporation from secondary sources as well as atmospheric transport from urban sites.
اظهر المزيد [+] اقل [-]Impingement of marine organisms in a tropical atomic power plant cooling water system
2017
A one-year impingement monitoring was conducted at Madras Atomic Power Station (MAPS), Kalpakkam, southeastern coast of India and identified a total of 67 species of marine organisms in the cooling water system. Estimates of total annual impingement contributed about 1.47×106 individuals and 142.5t of biomass. Jellyfish contributed about 6.8×105 individuals and 135.6t of biomass. Crabs, shrimps and fish were the most vulnerable organisms contributing about 4.29×105 individuals, 1.39×105 individuals and 2.16×105 individuals respectively. Commercially important species namely Trichiurus lepturus, Sardinella longiceps and Portunus pelagicus were found to be impinged 1.88% and 0.29% by number and weight of the total biomass respectively. Out of ~327 fish species recorded at Kalpakkam, only about 9.4% of species were impinged at MAPS. Multispecies impingement at MAPS poses the problem of finding the best mitigation options for tropical conditions.
اظهر المزيد [+] اقل [-]Marine debris in five national parks in Alaska
2017
Polasek, L. | Bering, J. | Kim, H. | Neitlich, P. | Pister, B. | Terwilliger, M. | Nicolato, K. | Turner, C. | Jones, T.
Marine debris is a management issue with ecological and recreational impacts for agencies, especially on remote beaches not accessible by road. This project was implemented to remove and document marine debris from five coastal National Park Service units in Alaska. Approximately 80km of coastline were cleaned with over 10,000kg of debris collected. Marine debris was found at all 28 beaches surveyed. Hard plastics were found on every beach and foam was found at every beach except one. Rope/netting was the next most commonly found category, present at 23 beaches. Overall, plastic contributed to 60% of the total weight of debris. Rope/netting (14.6%) was a greater proportion of the weight from all beaches than foam (13.3%). Non-ferrous metal contributed the smallest amount of debris by weight (1.7%). The work forms a reference condition dataset of debris surveyed in the Western Arctic and the Gulf of Alaska within one season.
اظهر المزيد [+] اقل [-]Metal concentration in the tourist beaches of South Durban: An industrial hub of South Africa
2017
Vetrimurugan, E. | Shruti, V.C. | Jonathan, M.P. | Roy, Priyadarsi D | Kunene, N.W. | Villegas, Lorena Elizabeth Campos
South Durban basin of South Africa has witnessed tremendous urban, industrial expansion and mass tourism impacts exerting significant pressure over marine environments. 43 sediment samples from 7 different beaches (Bluff beach; Ansteys beach; Brighton beach; Cutting beach; Isipingo beach; Tiger Rocks beach; Amanzimtoti beach) were analyzed for acid leachable metals (ALMs) Fe, Mg, Mn, Cr, Cu, Mo, Ni, Co, Pb, Cd, Zn and Hg. The metal concentrations found in all the beaches were higher than the background reference values (avg. in μgg−1) for Cr (223–352), Cu (27.67–42.10), Mo (3.11–4.70), Ni (93–118), Co (45.52–52.44), Zn (31.26–57.01) and Hg (1.13–2.36) suggesting the influence of industrial effluents and harbor activities in this region. Calculated geochemical indexes revealed that extreme contamination of Cr and Hg in all the beach sediments and high Cr and Ni levels poses adverse biological effects.
اظهر المزيد [+] اقل [-]Phosphate deficiency promotes coral bleaching and is reflected by the ultrastructure of symbiotic dinoflagellates
2017
Rosset, Sabrina | Wiedenmann, Jörg | Reed, Adam J. | D'Angelo, Cecilia
Enrichment of reef environments with dissolved inorganic nutrients is considered a major threat to the survival of corals living in symbiosis with dinoflagellates (Symbiodinium sp.). We argue, however, that the direct negative effects on the symbiosis are not necessarily caused by the nutrient enrichment itself but by the phosphorus starvation of the algal symbionts that can be caused by skewed nitrogen (N) to phosphorus (P) ratios. We exposed corals to imbalanced N:P ratios in long-term experiments and found that the undersupply of phosphate severely disturbed the symbiosis, indicated by the loss of coral biomass, malfunctioning of algal photosynthesis and bleaching of the corals. In contrast, the corals tolerated an undersupply with nitrogen at high phosphate concentrations without negative effects on symbiont photosynthesis, suggesting a better adaptation to nitrogen limitation. Transmission electron microscopy analysis revealed that the signatures of ultrastructural biomarkers represent versatile tools for the classification of nutrient stress in symbiotic algae. Notably, high N:P ratios in the water were clearly identified by the accumulation of uric acid crystals.
اظهر المزيد [+] اقل [-]The Atlantic blue crab Callinectes sapidus in southern European coastal waters: Distribution, impact and prospective invasion management strategies
2017
Mancinelli, Giorgio | Chainho, Paula | Cilenti, Lucrezia | Falco, Silvia | Kapiris, Kostas | Katselis, George | Ribeiro, Filipe
The native distribution of the blue crab Callinectes sapidus in the western Atlantic extends from Nova Scotia to Argentina. Introduced to Europe at the beginning of the 20th century, it is currently recorded almost ubiquitously in the Mediterranean and in the Black Sea. An overview of the occurrence, abundance, and ecological impact of the species in southern European waters is provided; additionally, we present a pragmatic assessment of its management scenarios, explicitly considering the dual nature of C. sapidus as both an invasive species and a fishery resource. We emphasise that the ongoing expansion of C. sapidus in the region may represent a stimulating challenge for the identification and implementation of future strategies in the management of invasive crustaceans. The impact of the invader could be converted into an enhancement of the services delivered by southern European coastal ecosystems, while mitigation costs could be transformed into profits for local populations.
اظهر المزيد [+] اقل [-]Plastic litter in aquatic environments of Maremma Regional Park (Tyrrhenian Sea, Italy): Contribution by the Ombrone river and levels in marine sediments
2017
Guerranti, Cristiana | Cannas, Susanna | Scopetani, Costanza | Fastelli, Paolo | Cincinelli, Alessandra | Renzi, Monia
During two surveys in 2015 and 2016, sediments samples were collected along the Ombrone river (Maremma Regional Park, province of Grosseto, Italy), in particular at its mouth and in the marine area in front of it, in order to quantify, identify and categorize plastic items (macro, meso and micro-plastics and colour, material etc.) and evaluate their potential sources. The Albegna and Osa rivers were identified as external areas of comparison. The results of the analysis showed different situations, especially as regards fluvial inputs, in addition to evidencing local provisions of plastic material derived from agricultural activities. The microplastics values per kg of sediment and the prevailing type of items found largely varied between the investigated sites (45–1069items/kg dry sample).
اظهر المزيد [+] اقل [-]Trace element concentrations in the apex predator swordfish (Xiphias gladius) from a Mediterranean fishery and risk assessment for consumers
2017
Gobert, S. | Pasqualini, V. | Dijoux, J. | Lejeune, P. | Durieux, E.D.H. | Marengo, M.
Swordfish (Xiphias gladius L., 1758) is an apex predator, highly migratory meso-pelagic fish widely distributed in the Atlantic Ocean and Mediterranean. As top predators, this fish may be the end reservoir of the bioaccumulation of trace elements in a food chain because they occupy higher trophic levels and are an important food source, causing them to be potentially hazardous to consume. This study aims to investigate the concentration of 18 trace elements of Swordfish, caught in the Mediterranean Sea and to discuss human exposure risks. The mean element levels in the fish muscles were clearly below the maximum allowable concentrations established by International food safety regulations. The data suggested that the risk is minor and acceptable for human health. The findings of this study amplify the scarce database on contaminants available, especially new data on “emerging elements”, for this species from the Mediterranean Sea.
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