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Abstract  

Combination of radiochemistry with simultaneous determination of corresponding stable isotope concentration allows the study of the biogeochemical behavior of manganese in an estuarine system which is not at equilibrium. A bacterial uptake in the dark of 0.40 μM in 50 hours at 6 °C, corresponding to an uptake rate of 8 nM·h−1, was measured for the sample collected in winter. However, this biological uptake represents only 60% of the decrease in stable dissolved manganese concentration after 50 hours. Other abiotic processes inducing the precipitation of dissolved manganese are thus occurring in this low salinity region of the Scheldt estuary (Belgium).

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Abstract  

Transplants of the epiphytic lichen Parmelia sulcata were suspended in nylon bags within a rectangle of 15 km wide and 25 km long on a grid 2.5 km'2.5 km in the Sado estuary region. The transplants were oriented towards the wind (F) and opposing the wind (T) and were collected after 3, 6 and 9 months of exposure. Samples were analyzed by INAA and PIXE. Source identification was made by Monte Carlo Target Transformation Factor Analysis (MCTTFA) using three different combinations of data (all data, F data and T data). Five factors were identified for all the combinations performed. For two factors, F and T differentiation was observed.

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Abstract  

Depth profiles and inventories of237Np in sediment cores from the Ribble Estuary in the Irish Sea have been studied along with those of Pu isotopes,241Am and137Cs, to allow a more detailed look of anomalously high237Np content observed in this estuary previously. The comprehensive data obtained showed that the depth profiles of both237Np contents and237Np/239,240Pu activity ratios were clearly different from those of239,240Pu,241Am, and137Cs and their activity ratios. As much as 80–90% of237Np inventories (0.32–1.06 kBq/m2), found in three cores, were estimated to be derived from a source other than Sellafield, on the basis of comparison of the237Np/239,240Pu inventory ratio (0.65–1.74%) found in the Ribble Estuary cores with those (0.10–0.16%) in the Ravenglass Estuary cores.

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Abstract  

Two sediment cores (~30 m long) were retrieved at the mouth of the Minho Estuary to assess its palaeoenvironmental evolution for the last millennia. Samples were characterized by Energy-Dispersive X-Ray Fluorescence Spectrometry and Instrumental Neutron Activation Analysis, complemented by sedimentological analyses. Provenance of major and trace element contents (lithogenic or biogenic, continental or marine) is assessed. The influence of grain size effect on total element concentration is discussed. Most of the samples present a negative Eu anomaly. Sedimentological and geochemical parameters allow differentiating four geological units––fluvial, marine, estuarine and sand barrier––which reflects the temporal evolution of the Minho Estuary.

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Community Ecology
Authors: A.F.S. Garcia, A.M. Garcia, S.R. Vollrath, F. Schneck, C.F.M. Silva, Í.J. Marchetti, and J.P. Vieira

Food partitioning among coexisting species in different habitats remains an important research topic in trophic ecology. In this work, we combined carbon and nitrogen stable isotope ratios and stomach content analyses to investigate differences in diet and niche overlap of two congeneric juvenile mullet species (Mugil curema and Mugil liza) coexisting in a marine surf-zone and an estuarine zone in southern Brazil (29oS). These habitats have contrasting levels of food availability, especially in terms of prey diversity, with higher microalgae diversity in the estuary than in the marine surf-zone. In these contrasting conditions, we predicted that both mullet species will have (a) higher niche overlap and smaller niche breadth at the marine surf-zone due to the common exploration of highly abundant surf-zone diatoms and (b) lower niche overlap and higher niche breadth inside the estuary due to selective feeding on more diverse food resources. Isotope niche areas (measured as standard ellipse areas) were higher in the estuary (6.10 and 6.18) than in the marine surf-zone (3.68 and 3.37) for both M. curema and M. liza, respectively. We observed an overlap of 52% in isotopic niches of both species in the marine surf-zone and none in the estuary. We also found contrasting patterns in the diet composition between species according to the habitat. At the marine surfzone, diatoms of the classes Bacillariophyceae and Coscinodiscophyceae dominated (> 99%) the food content of both mullet species. In contrast, green algae, cyanobacteria, dinoflagellates and flagellates comprised the diet of both species in the estuary. These results could be explained by spatial differences in food availability (especially regarding diversity of microalgae) between both habitats. At the marine site, both species explored the most abundant microalgae available (mostly the surf-zone diatom Asterionellopsis cf. guyunusae and fragments of Coscinodiscus), whereas in the estuary both species shifted their diets to explore the greater diversity of microalgae resources. Overall, our findings revealed that niche partitioning theory could not fully predict changes in breadth and overlap of food niches of estuarine dependent fish species with complex life cycles encompassing marine to estuarine systems with contrasting food availabilities.

Open access

Abstract  

The Odiel and Tinto rivers, southwest Spain, form a fully mixed estuary. An industrial area that includes a complex dedicated to the production of phosphate fertilizers is located by the Odiel River. This complex released phosphogypsum wastes directly to the Odiel River and also disposed them on open air piles located by the Tinto River. Due to new EU regulations, wastes are not directly released to the Odiel from 1998 on, although they are still disposed on the open air piles. The behavior of 226Ra in a system like this estuary is complex, since radionuclides are affected by tidal actions and interactions with sediments through adsorption/desorption reactions and erosion/deposition processes. A numerical 2D depth-averaged model of the estuary has been developed, including processes mentioned above. It has been applied to reproduce experimental data measured after a release from the industrial complex in the Odiel River and after an accidental release in the Tinto River from the gypsum piles. The model has also been applied to simulate the self-cleaning process observed in the estuary after the direct releases from the fertilizer complex were stopped.

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Abstract  

Sediment cores were collected at the Cananeia-Iguape Estuary and thelevels of 210Pb, 226Ra and 137Cs were measuredby gamma-ray spectrometry. The total 210Pb levels in sedimentsvaried from 13.5 to 122.5 Bq . kg —1 , for 226Raranged from 2.4 to 28 Bq . kg —1 and for 137Csfrom 0.28 to 6.1 Bq . kg —1 . Sedimentation rates were calculatedfrom the slope of the excess 210Pb profile in the core. The valuesobtained varied from 5 to 10 mm . y—1 , depending on thesediment deposition inputs in the local of sampling.

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Abstract  

Gent air samplers were used for air particulate matter sampling in Sado estuary area, separating fine and coarse fractions. Three sampling sites were chosen (Palmela, Faralhão and Tróia), inside a 15 km × 25 km area at Setúba region, 50 km south of Lisbon, Portugal. Transplants of Parmelia sulcata Taylor were suspended in nylon bags within the same area following a 2.5 km × 2.5 km grid, during the same period as the aerosol collection. Both lichen transplants and filters were analysed by k 0-INAA. This work compares MCTTFA results given by the two air pollution monitoring procedures. The main differences concern a physiological factor in biomonitors and a better definition of traffic and re-suspension by aerosols.

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Abstract  

Instrumental analysis methods for 210Pb, 226Raand 137Cs by gamma-spectrometry in sediments, as well as the sedimentationrates in cores collected from Brazilian coastal region are presented. Samplinglocations have covered the Cananeia-Iguape estuary and the continental shelfof southern Sao Paulo State. Values for 210Pb ranged from 122.5to 14.3 Bq . kg —1 for estuarine sediments and from 195.5to 23.6 Bq . kg –1 at the continental shelf. For 226Ra thevalues obtained in sediments varied from 15.2 to 2.3 Bq . kg —1 in the estuary and from 30.1 to 16.1 Bq . kg —1 atthe continental shelf. Sedimentation rates are variable, ranging from 0.53to 0.98 cm . y —1 in estuary sediments and from 0.18 to 0.40cm . y —1 at the continental shelf.

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Abstract  

Twenty six bottom sediment samples were collected from the Cananéia estuary in summer and winter of 2005. Multielemental analysis was carried out by instrumental neutron activation analysis. Total mercury was determined by cold vapor atomic absorption. As, Cr, Hg and Zn concentrations were compared to the Canadian oriented values (TEL and PEL). Sample points 4 and 9 presented higher concentration for most elements and As and Cr exceeded the TEL values. Organic matter (>10%) associated with siltic and clay sediments was observed. Climatic conditions, hydrodynamic and biogeochemical processes promote differences in seasonal concentrations of elements at some points, which contribute to special distributions.

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