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| Registros recuperados: 27 | |
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| Joiris, C.R.. |
| The summer at-sea distribution of seabirds and marine mammals was quantitatively established both in Antarctica (Weddell Sea) and in the European Arctic: Greenland, Norwegian and Barents seas. Data can directly be compared, since the same transect counts were applied by the same team from the same icebreaking ship in both regions. The main conclusion is that densities of seabirds and marine mammals are similar in open water and at the ice edge from both polar regions, while the presence of Adélie penguins, minke whales and crabeater seals in densities more than one order of magnitude higher in Antarctic pack-ice must reflect a major ecological difference between both polar systems. The ecological implications of these observations are discussed, especially... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Aves [Birds] Cetacea [whales; Dolphins and porpoises] Pinnipedia. |
| Ano: 2000 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6822 |
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| Antoine, N.; Jansegers, I.; Holsbeek, L.; Joiris, C.R.; Bouquegneau, J.-M.. |
| In the North Sea, the contamination level of Cd in porpoises, Zn and Cu in seabirds and Hg in both appear to be very high. The other studied metals (Cr, Ti, Fe, Pb) concentrations are comparable to literature. Seabirds and porpoises are located at top of the food chains, however their use as bioindicators of the contamination level of the ecosystem they are feeding on remains debatable. Actually many differences appear in both the contamination level and the storage and detoxification mechanisms from a species to another. |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Aves [Birds]; Phocoenidae [porpoises]. |
| Ano: 1992 |
URL: http://www.vliz.be/imisdocs/publications/237547.pdf |
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| Sanga, R.N.; Bartell, S.M.; Ponce, R.A.; Boischo, A.A.P.; Joiris, C.R.; Pierce, C.H.; Faustman, S.M.. |
| This article presents a general model for estimating population heterogeneity and “lack of knowledge” uncertainty in methylmercury (MeHg) exposure assessments using two-dimensional Monte Carlo analysis. Using data from fish-consuming populations in Bangladesh, Brazil, Sweden, and the United Kingdom, predictive model estimates of dietary MeHg exposures were compared against those derived from biomarkers (i.e., [Hg]hair and [Hg]blood). By disaggregating parameter uncertainty into components (i.e., population heterogeneity, measurement error, recall error, and sampling error) estimates were obtained of the contribution of each component to the overall uncertainty. Steady-state diet:hair and diet:blood MeHg exposure ratios were estimated for each population... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 2001 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6917 |
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| Delbeke, K.; Joiris, C.R.; Bossicart, M.. |
| PCB levels in sediments (bulk and fraction <63µm), suspended matter and zooplankton from the Belgian continental shelf of the North Sea and the Scheldt estuary were educated in relation to their organic carbon content, their lipid content and, for sediments, their particle size distribution. PCB accumulation mechanisms are discussed, considering the importance of direct contamination (absorption onto the cell surfaces, absorption through the cell walls and partitioning into the cell lipids) for suspended matter and sediments, and of indirect contamination through the food for zooplankton. Geographical and seasonal variations are described. |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1990 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=2820 |
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| Holsbeek, L.; Siebert, U.; Joiris, C.R.. |
| Heavy metal concentrations (total and organic Hg, Ti, Cr, Cu, Zn, Cd and Pb) were determined in the muscle, liver and kidney of 36 dolphins stranded on the French Atlantic coast between 1977 and 1990: 29 common dolphins Delphinus delphis, five bottlenose dolphins Tursiops truncatus and two striped dolphins Stenella coeruleoalba. Total Hg concentration in the liver increased with age, while relative methylmercury concentration decreased, reflecting the existence of a slow demethylation process. To a lower extent, a similar pattern was observed in the kidney and muscle. No age-related increase was found for other heavy metals, although the highest levels for Cd and Cr were always found in adults. No difference in contamination could be detected between the... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1998 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6844 |
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| Joiris, C.R.; Tapia, G.; Holsbeek, L.. |
| Beached seabirds, mainly common guillemots Uria aalge, were collected on the Belgian coast during winter from 1990 to 1995. Concentrations of total and organic mercury, and of organochlorines (PCBs and pesticides) were determined in muscle, liver and kidney. They were high compared to summer data (up to one order of magnitude), and increased during winter. This increase is not due to changes of total body weight nor polar lipid content, and thus reflects an actual increase of the seabirds' contamination while wintering in the southern North Sea. The observed annual cycle can be understood by assuming differences in prey contamination: higher during winter in the southern North Sea ecosystem than during summer in the Atlantic water ecosystem. |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1997 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6846 |
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| Joiris, C.R.; Holsbeek, L.; Laroussi, M.N.. |
| This paper reports concentrations of total mercury and methylmercury in muscle, liver and gonads of two sardines (Sardinella aurita, n=184 and Sardina pilchardus, n=87) from three coastal areas off Tunisia. Mercury concentration in muscle and liver showed significant positive correlation with fish length (i.e. with age). The relative methylmercury concentration was high and constant in muscle (>85% MeHg), and was decreasing with age in liver (from 50% to 20%), which might reflect the existence of a slow demethylation process. From the geographic point of view, Hg concentration was similar in the northern and eastern areas (0.32 µg g-1 dw in muscle for Sardinella aurita, 0.41 for Sardina pilchardus), but significantly lower in the southern zone (0.19 and... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Sardina pilchardus; Sardinella aurita [round sardinella]. |
| Ano: 1999 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6838 |
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| Joiris, C.R.; Holsbeek, L.; Bossicart, M.; Tapia, G.. |
| Four sperm whales (three subadult males stranded on the Belgian coast, a fourth older male found dead at sea) were analysed for total mercury, methylmercury and organochlorines. All four were part of a total of 24 sperm whales that stranded on the North Sea coasts over a period of six months, a highly unusual phenomenon. Total mercury levels ranged from 0.5 µg/g fw in kidney and 1 in muscle, up to 15 in liver. The finding of at least 90% of the mercury in its inorganic form confirms the existence of detoxification mechanisms in the liver of cetaceans. PCB concentrations in muscle, liver, kidney and blubber ranged from 10 to 25 µg/g lipids. These results are in the same order of magnitude as literature data, which however does not imply that there is no... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Detoxification Mercury Social behaviour Stranding ANE; Belgium ANE; North Sea; Southern Bight. |
| Ano: 1997 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=837 |
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| Joiris, C.R.; Bertels, A.. |
| Comparison of measured primary production, by radioactive carbonate incorporation or oxygen production, with diel variations of oxygen, inorganic carbon and particulate carbon, shows that the net in situ production often exceeds the measured activity, especially in deeper marine ecosystems. In vitro incubations under fluctuating light conditions provide higher values of primary production at low light intensities, both with cultures and with natural populations. The same results are obtained with in situ incubations, by varying the depth of incubation. This method allows reevaluation of primary productivity at low light intensities and provides results in agreement with the in situ variations of oxygen, inorganic carbon and particulate carbon. It can... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1985 |
URL: http://www.vliz.be/imisdocs/publications/303172.pdf |
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| Baeyens, W.F.J.; Leermakers, M.; Molina, R.; Holsbeek, L.; Joiris, C.R.. |
| Aqueous distillation is a common initial step in the determination of monomethyl mercury (MMHg) in a variety of matrices. However, recently it was observed that during distillation, MMHg may be generated from inorganic mercury and induce in some cases significant analytical errors. Therefore we investigated a number of alternative analytical techniques for the determination of MMHg in sediments and biological tissues: (1) headspace-GC-AFS and some variants; (2) acid extraction-solvent extraction-GC-AFS; (3) acid extraction-solvent extraction-GC-ECD. Methods (2) and (3) showed MMHg generation when an inorganic Hg spike was added to the sediment sample. The headspace method yielded MMHg results in agreement with the reference values for biological and... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1999 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6829 |
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| Joiris, C.R.; Kampp, K.; Tahon, J.; Møbjerg Kristensen, R.. |
| The distribution at sea of seabirds was studied in the North-East Water (NEW) polynya, Greenland, during transect counts in the summers of 1991, 1992 and 1993 on board the ice-breaking RVs Polarstern and Polar Sea. Data collected within the polynya ‘box’ (78–82°N; 5–18°W) concern observations of 8000 birds counted during 1350 half-hour counts. Distribution is presented as density (N/km2) and calculated daily food intake. Five bird species were selected for discussion, representing more than 95% of the total numbers encountered: Fulmar (Fulmarus glacialis), Ivory Gull (Pagophila eburnea), Kittiwake (Rissa tridactyla), Glaucous Gull (Larus hyperboreus) and Ross's Gull (Rhodostethia rosea). For these species, densities are comparable in the NE Greenland... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1997 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6859 |
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| Joiris, C.R.; Billen, G.; Lancelot, MH.; Daro, M.H.; Mommaerts, J.-P.; Bertels, A.; Bossicart, M.; Nijs, J.; Hecq, J.H.. |
| The various biological compartments of the Belgian coastal zone of the North Sea were studied since 1971. The synthesis of available data on carbon cycling includes phytoplankton biomass and activities (particulate and dissolved primary production, respiration) , zooplankton biomass and activities (grazing, respiration) and planktonic and benthic microbial heterotrophic activities. These various carbon flux estimates allow the development of an overall budget of carbon cycling. This budget shows the importance of microbial (planktonic and benthic) heterotrophs versus zooplankton in the utilization of primary production. Comparison with literature data suggests that this could be a general feature of coastal, as opposed to open sea ecosystems. |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1982 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6908 |
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| Joiris, C.R.. |
| During the ARK V/2 expedition of RV <i>Polarstern</i> in the Norwegian and Greenland seas in June 1988, 380 half hour counts for marine vertebrates (seabirds, pinnipeds and cetaceans) were carried out. Results are presented as total numbers encountered and then converted into density and food intake. Mean food intake was 2.2 kg fresh weight per km<sup>2</sup> per day for seabirds, with a higher value in Atlantic water (2.5) lower values in polar water and the pack ice (1.7 and 1.9), and an intermediate value at the ice edge. The main species were the alcids (1.5, primarily Little Auk, <i>Alle alle</i> and Brünnich's Guillemot, <i>Urea Iomvia</i>), the Fulmar, <i>Fulmarus glacialis</i> (0.5), and... |
| Tipo: Info:eu-repo/semantics/article |
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| Ano: 1992 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6886 |
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| Billen, G.; Joiris, C.R.; Wijnant, J.; Gillain, G.. |
| Concentrations and utilization rates of alanine, aspartate, lysine, glucose, glycollic, acetic and lactic acids have been determined on 6 occasions at least, during a full seasonal cycle in the water column of 3 stations (Scheldt estuary, coastal North Sea and English Channel) with greatly differing biological characteristics. No significant differences in substrate concentration could be detected between the 3 stations, although the rate of utilization of all substrates differed greatly, decreasing in the order estuarine > coastal > open sea environment. This apparent paradox is explained by aid of a simple model showing that the steady state concentration of a particular substrate is independent of its rate of production (and thus of consumption)... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Organic compounds ANE; Belgium; Belgian Coast ANE; English Channel Belgium; Zeeschelde. |
| Ano: 1980 |
URL: http://www.vliz.be/nl/open-marien-archief?module=ref&refid=6912 |
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| Registros recuperados: 27 | |
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