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Resultados 1421-1430 de 5,098
Experimental and modeled thermoregulatory costs of repeated sublethal oil exposure in the Double-crested Cormorant, Phalacrocorax auritus
2018
Mathewson, Paul D. | Hanson-Dorr, Katie C. | Porter, Warren P. | Bursian, Steven J. | Dean, Karen M. | Healy, Kate | Horak, Katherine | Link, Jane E. | Harr, K.E. | Dorr, Brian S.
To fully understand the impact of oil exposure, it is important to understand sublethal effects like how increased thermoregulatory costs may affect survival and reproduction. However, it is difficult and time-consuming to measure these effects in wild animals. We present a novel use of a bioenergetics model, Niche Mapper™, to estimate thermoregulatory impacts of oiling, using data from captive Double-crested Cormorants (Phalacrocorax auritus) experimentally exposed to oil. Oiled cormorants had significant increases in surface body temperatures following exposure. Niche Mapper accurately predicted surface temperatures and metabolic rates for unoiled and oiled cormorants and predicted 13–18% increased daily energetic demands due to increased thermoregulatory costs of oiling, consistent with increased food consumption observed in experimentally oiled cormorants. We show that Niche Mapper can provide valuable insight into sublethal oiling effects by quantifying the extent to which thermoregulatory costs divert energy resources away from important life processes like maintenance, reproduction and migration.
Mostrar más [+] Menos [-]Levels of trace metals on microplastic particles in beach sediments of the island of Vis, Adriatic Sea, Croatia
2018
Maršić-Lučić, Jasna | Lušić, Jelena | Tutman, Pero | Bojanić Varezić, Dubravka | Šiljić, Jasna | Pribudić, Joško
The aim of this study was to determine the levels of trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) in plastic pellets collected from two sandy beaches on the island of Vis, Croatia. A total of 92 pellets in a sediment volume of 3965 mL were collected at the investigated sampling sites. Concentrations of pellets in sediment samples ranged from 6 to 36 particles dm−3 of wet sediment. Mean particle weight of the collected beached pellets ranged from 17 mg to 31 mg. Trace metal concentrations in plastic pellets were greater than the concentrations reported for seawater in the investigated area, which indicates that plastic pellets sorb metals from the marine environment. The adsorbed trace metals may enter the food chain due to incidental ingestion of microplastic particles by marine animals, which presents a potential human health risk due to consumption of seafood.
Mostrar más [+] Menos [-]Numerical modelling of mercury evasion in a two-layered Adriatic Sea using a coupled atmosphere-ocean model
2018
Tomažič, Špela | Ličer, Matjaž | Žagar, Dušan
A new mercury (Hg) evasion model for the Adriatic Sea was developed accounting for the ocean mixed layer depth in order to decrease Hg depletion at the surface. Previously modelled airborne Hg species and measured Hg in the ocean were used. Simulations were run using one- and two-way coupled atmosphere-ocean models. Discrepancies in evasion between the applied coupling schemes were shown to be insignificant. The model was evaluated by applying various wind parameterisations and diffusive coefficient formulae. Relatively high discrepancies among the applied methods were observed. The results of a shorter simulation were extrapolated over a one-year period by applying a measurement-based adaptation. We obtained good agreement with previously published data on Hg evasion in the entire Mediterranean area, thus confirming the suitability of the new model for Hg evasion simulations. Model computations performed for the Adriatic Sea resulted in levels of evasion approximately two times lower than previously estimated.
Mostrar más [+] Menos [-]The distribution and seasonal variations of sedimentary organic matter in the East China Sea shelf
2018
Zhou, Fengxia | Gao, Xuelu | Yuan, Huamao | Song, Jinming | Chen, Fajin
We sampled the surface sediments of the East China Sea shelf (ECSS) in spring and autumn, 2014, and analyzed the biogenic element concentrations and stable carbon (δ13C) and nitrogen (δ15N) isotopic compositions to study the distribution and seasonal variations of sedimentary organic matter (OM). The average concentrations of TOC, TN and OP in autumn decreased obviously compared with those in spring. The increase of δ15N values in autumn indicated the priority utilization of 14N by bacterial decomposition activity. The values of δ13C were used to trace organic matter sources. The estimated percentages for terrestrial OM were in the range of 0–34.6%. They generally decreased seaward in nearshore areas, indicating the decrease of terrigenous influence. There was an obvious tongue-shaped region with relatively low percentages of terrestrial OM (<12%) in the northern part of the ECSS, which may be a reflection of the intrusion pathway of the outer seawater.
Mostrar más [+] Menos [-]Anticyclonic eddies increase accumulation of microplastic in the North Atlantic subtropical gyre
2018
Brach, Laurent | Deixonne, Patrick | Bradern, Loraline | Durand, Edmée | Desjean, Marie-Christine | Perez, Emile | van Sebille, Erik | ter Halle, Alexandra
There are fundamental gaps in our understanding of the fates of microplastics in the ocean, which must be overcome if the severity of this pollution is to be fully assessed. The predominant pattern is high accumulation of microplastic in subtropical gyres. Using in situ measurements from the 7th Continent expedition in the North Atlantic subtropical gyre, data from satellite observations and models, we show how microplastic concentrations were up to 9.4 times higher in an anticyclonic eddy explored, compared to the cyclonic eddy. Although our sample size is small, this is the first suggestive evidence that mesoscale eddies might trap, concentrate and potentially transport microplastics. As eddies are known to congregate nutrients and organisms, this phenomenon should be considered with regards to the potential impact of plastic pollution on the ecosystem in the open ocean.
Mostrar más [+] Menos [-]Ammunition detection using high frequency multibeam snippet backscatter information
2018
Kunde, Tina | Held, Philipp | Sternberg, Harald | Schneider von Deimling, Jens
The present study reports the evaluation of snippet backscatter information gathered with a high-frequency multibeam echosounder system (200–400 kHz) due to their usability to detect ammunition of different sizes in shallow coastal waters. Besides the feasibility of the snippet backscatter data, it was focused on the attainable horizontal accuracy in comparison to side-scan sonar and autonomous underwater vehicle (AUV) surveys. The data was collected in shallow coastal waters of up to 18 m water depth (Baltic Sea) close to an ammunition dumping site characterized by an almost flat seafloor covered with sand and silt sediments. The analysis of the multibeam compared to sidescan data indicates the snippet backscatter to be a promising prospective method for ammunition detection and being able to improve horizontal position accuracy of up to 0.08 m.
Mostrar más [+] Menos [-]Now, you see me: High concentrations of floating plastic debris in the coastal waters of the Balearic Islands (Spain)
2018
Ruiz-Orejón, Luis F. | Sardá, Rafael | Ramis-Pujol, Juan
Coastal ecosystems are under significant human pressure, partly due to the proximity of pollution sources. In this study, a total of 20 samples were taken in summer around the coastal waters of the Balearic Islands (Spain) using a manta trawl net to examine the concentrations of floating plastic debris through the NIXE III project campaign. Although plastic concentrations showed high variability along the coast, the higher particle concentration (max: 4,576,115 items ⋅ km⁻²) and weight (max: 8,102.94 g(DW) ⋅ km⁻²) values were located at the north of the Balearic Promontory. The particle size analysis showed the high prevalence of microplastics (< 5 mm) in these waters, where particles of approximately 0.7 mm and 1 mm² were the most frequent in the range analyzed. The high plastic concentration values in the N-NW coast of Ibiza and Mallorca in sparsely populated locations suggest that the plastic particle distribution was mostly conditioned by the hydrodynamic surface conditions.
Mostrar más [+] Menos [-]Ozone Production Efficiency in Highly Polluted Environments
2018
Wang, Junhua | Ge, Baozhu | Wang, Zifa
When developing ozone control strategies, the empirical kinetic modeling approach curve cannot easily be applied to practical problems. On this basis, the ozone production efficiency (OPE) is proposed as an indicator to represent the effects of NOₓ on ozone. The research results of the OPE are reviewed and include the definition and calculation of OPE, observations and model simulations, several factors affecting the OPE, and the application of OPE. The measurements and applications of the OPE have improved and become widespread after decades of development. OPE is mostly used to measure regional atmospheric oxidation characteristics, which play an important role when developing ozone control strategies (especially in highly polluted areas). However, there have been few studies on the advancement of chemical mechanisms in the OPE in recent years. In addition, there is no detailed interpretation of the strong linear correlation between ozone and NOz. The results may be significant for improving simulation results and understanding the formation of ozone.
Mostrar más [+] Menos [-]A change in phytoplankton community index with water quality improvement in Tolo Harbour, Hong Kong
2018
Lei, Yue | Whyte, Callum | Davidson, Keith | Tett, Paul | Yin, Kedong
Water quality in Tolo Harbour and Channel (Tolo) has been improved since 1998 after the diversion of sewage effluent. However, it remains poorly understood how nutrient loading reduction has impacted the phytoplankton community. To evaluate this, we applied a Phytoplankton Community Index PI(mp) to the 23-year data (1991–2013) at inner (TM4) and outer (TM8) sites in Tolo, with the former being more eutrophic than the latter. The results show that 1) the phytoplankton community changed with time after sewage diversion; 2) “diatoms and dinoflagellates” were better indicators of nutrient impact than “autotrophic/mixotrophic and heterotrophic dinoflagellates”; 3) the rate of recovery differed between the two stations, but both reached a similar state at a similar time; 4) seasonality of the phytoplankton community showed greater disturbance in spring than in other seasons. Our findings indicate that the nutrient reduction in the Tolo resulted in a positive change in the phytoplankton community.
Mostrar más [+] Menos [-]Improving the monitoring of a dumping site in a dynamic environment. Example of the Octeville site (Bay of Seine, English Channel)
2018
Méar, Yann | Poizot, Emmanuel | Murat, Anne | Beryouni, Khadija | Baux, Noémie | Dauvin, Jean-Claude
Dredged sediments have different physical and chemical characteristics compared with the sediments in place, which generates multiple effects on the environment.In this study, we show that the sampling strategy used to monitor the effects of dredge spoil deposition on the surrounding environment can lead to different interpretations. It appears that sediment sample replicates may or may not be necessary, depending on the studied area, the prevailing environmental forcings before sediment sampling and the combination of these two factors. The proposed modus operandi allows us to optimize both the confidence on the obtained results and the cost of the sediment studies (sampling and laboratory analyses). The results are based on the sediment fine fraction, which is considered as a key environmental component due, for example, to its strong association with the structure of benthic faunal communities as well as its role in the build-up of pollutants.
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