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See detailSeasonal Variation in Abundance and Time-Budget of Bottlenose Dolphins (Tursiops truncatus) in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg; Cammareri, Alejandro; Holsbeek, Ludo et al

Poster (2012, March 26)

The abundance and time-budget of bottlenose dolphins (Tursiops truncatus) was assessed in Bahía San Antonio, Patagonia (Argentina) in the years 2009 and 2010. A total of 366.4 boat-based survey hours ... [more ▼]

The abundance and time-budget of bottlenose dolphins (Tursiops truncatus) was assessed in Bahía San Antonio, Patagonia (Argentina) in the years 2009 and 2010. A total of 366.4 boat-based survey hours resulted in 64 contact hours with a total of 88 dolphin groups. Mark-recapture abundance estimations, based on 63 identified dolphins, resulted in a corrected maximum estimate of 97 and 83 individuals during winter, and a minimum of 34 and 38 individuals during autumn of 2009 and 2010 respectively. Between 25% and 68% of the population consisted of unidentifiable individuals depending on the season, indicating the high presence of juveniles and calves. Behavioural data indicated that the dolphin¿s time-budget consisted mainly out of resting and feeding, variable over the seasons. Dolphins increased their time feeding and socializing during winter and spring, whereas feeding dropped to a minimum in autumn. During summer, the dolphins spent up to 46% of their time diving, a behaviour presumably associated with a tail out/peduncle-dive foraging strategy. Based on these data, we assume more prey availability during winter and spring (main food source being pelagic fish) and a notable decrease in prey availability during summer with benthic prey species being the main food source. In autumn, even less prey items might be available. Furthermore, the increase in social behaviour during winter and spring combined with a peak in the presence of calves during these seasons, suggests the existence of a mating and calving season. These estimates of abundance are in line with the sizes of other coastal populations of bottlenose dolphins elsewhere in the world, and fit the occupancy patterns described for other coastal areas with small resident communities. The study furthers suggests that dolphins specifically use the study area to rest and feed, and to give birth and raise their young, specifically during winter and spring. [less ▲]

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See detailAlteration of Southern Right Whale (Eubalaena australis) Behaviour by Human-Induced Disturbance in Bahía San Antonio, Patagonia, Argentina
Vermeulen, Els ULg; Cammareri, Alejandro; Holsbeek, Ludo

in Aquatic Mammals (2012), 38(1), 56-64

A study was conducted to assess the behavioural response of southern right whales (Eubalaena australis) to human-induced disturbance in Bahía San Antonio, Province of Río Negro, Argentina. Behavioural ... [more ▼]

A study was conducted to assess the behavioural response of southern right whales (Eubalaena australis) to human-induced disturbance in Bahía San Antonio, Province of Río Negro, Argentina. Behavioural observations were made from June to October in 2008, 2009, and 2010. Aerial observa-tions carried out in 2010 show that up to one third of the whale groups were mating groups, indicat-ing that the study area is an important reproduction area for the species. The study compares 65.8 h (on a total effort of 120.3 h and 24 groups of whales) of land-based “undisturbed” whale behaviour obser-vations to 43.6 h of boat-based whale behaviour in a “disturbed” state (total effort of 326.1 h and 34 groups of whales). Analysis of the behavioural data show that whales significantly altered their behaviour by cutting social interactions short (on average 13%) when confronted with human short-range presence. At the same time, travelling whales experienced a significant increasing tendency to continue travelling (+21%) instead of starting to rest (-21%). However, social behavioural patterns returned swiftly to normal levels after the approach had ended, with a relative increase in “resting” (+18%) as opposed to “travelling” (-30%) rates.These data show that whale behaviour is altered by human approaches, pointing out the need for effective conservation measures and mitigation of behavioural impacts in relation to whale-based tourism. [less ▲]

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See detailAN IDENTIFICATION STUDY ON BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) IN NORTHEAST PATAGONIA, ARGENTINA
Vermeulen, Els ULg; Cammareri, Alejandro; Failla, Mauricio et al

Poster (2008, October 13)

In Argentina, bottlenose dolphin (Tursiops truncatus) sightings decreased notably since the late 80s in regions where it used to be frequent to observe them. Nowadays, Northeast Patagonia is one of the ... [more ▼]

In Argentina, bottlenose dolphin (Tursiops truncatus) sightings decreased notably since the late 80s in regions where it used to be frequent to observe them. Nowadays, Northeast Patagonia is one of the few regions where they still can be seen frequently, although local increasing human activities result in increasing need for information. In general, photo-identification has been established as a helpful tool in cetacean research. However, only few studies have applied this method to bottlenose dolphins in Argentina. This study is therefore aimed to obtain basic information concerning bottlenose dolphins through their identification, this way contributing to their conservation. Land-based observations were made in the northern Gulf of San Matías, Patagonia, Argentina, from August 2006 up to June 2008. Over 15.000 digital pictures of dorsal fins were analysed using the computer assisted identification systems FinEx and FinMatch. Dolphins re-identified during all four seasons in one year were defined as residents. The degree of residency was further estimated by the re-identification frequency (RF); non-resident (RF=1-3) - occasional (RF=4-7) - frequent (RF=8-11) - common (RF¿12). In total, 221 surveys were conducted with an average observation effort of 3.2h per survey, resulting in a total observation effort of 915h of which 124h were spent with 182 dolphin groups. A total of 50 dolphins were identified of which the vast majority (82%) was photographed only in the Natural Protected Area Bahía San Antonio (NPABSA), due to the higher observation effort in this region. Nevertheless, 12% of the catalogued dolphins could be photographed in both NPABSA and the Río Negro estuary, indicating that their home-range might include at least the whole northern region of the Gulf San Matias. Dolphins could be re-identified up to 13 days with 54% showing a degree of residency for NPABSA. This study shows the first data concerning bottlenose dolphins in Northeast Patagonia, but further investigation is highly necessary to improve their conservation. Therefore, the obtained photo-identification catalogue from the presented study is meant to serve as a primary tool for progressing research concerning this species in Argentina. [less ▲]

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See detailSIGHTING FREQUENCY AND PHOTO-IDENTIFICATION OF BOTTLENOSE DOLPHINS (TURSIOPS TRUNCATUS) ALONG THE COAST OF BAHÍA SAN ANTONIO, PATAGONIA, ARGENTINA
Holsbeek, Ludo; Cammareri, Alejandro; Failla, Mauricio et al

Poster (2008, March 10)

The sighting frequency (SF), site fidelity, home-range and group composition of bottlenose dolphins (Tursiops truncatus) were assessed during a photo-identification study in 2006-2007. This study aims to ... [more ▼]

The sighting frequency (SF), site fidelity, home-range and group composition of bottlenose dolphins (Tursiops truncatus) were assessed during a photo-identification study in 2006-2007. This study aims to provide first data on this unknown austral bottlenose dolphin population to answer to their increasing conservation needs. Data and pictures were collected during 132 surveys with an average observation effort of 2.8h (SD=1.6) per survey. All clear pictures were analysed using the automatic identification systems FinEx and FinMatch (EuroPhlukes Initiative). The SF was obtained dividing the number of sightings by the amount of effort. Site-fidelity was estimated using the Capture Mark Recapture method and the degree of residency by the re-identification frequency following Culloch (2004). In total, 377.4h were spent searching for bottlenose dolphins of which 57.3h were spent in the presence of 126 dolphin groups divided in 105 sightings. The SF was 0.28/h with and average duration of 43.2min/sighting (SD=0.76). A total of 43 dolphins were classified into an identification catalogue. These recognizable dolphins were re-identified up to 10 days with 44% (n=43) showing a degree of residency (resighting frequency (RF)¿4). The average group size was 6.1 (SD=7.9) ranging from one to fifty animals. Group size increased significantly with the presence of calves and with the distance from the coast. Nevertheless, all dolphins were seen in inshore waters ¿20m deep. The most frequent group formation was loose (34.5%), variable (29.8%), disperse (20.2%) and tight (15.5%). At least 6 identified dolphins, including one mother with her calf, were photographed in the mouth of the Rio Negro 250km from the study area indicating that their home-range is far from limited to Bahia de San Antonio. Data indicate that it concerns a resident but yet unknown population of bottlenose dolphins with a high commercial potential and an urgent need of conservation measurements. [less ▲]

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See detailOccurrence of perfluorooctane sulfonate and other perfluorinated alkylated substances in harbor porpoises from the Black Sea
Van de Vijver, Kristin Inneke; Holsbeek, Ludo; Das, Krishna ULg et al

in Environmental Science & Technology (2007), 41(1), 315-320

Perfluorooctane sulfonate (PFOS) and other perfluorinated alkylated substances (PFAS) were determined in liver, kidney, muscle, brain, and blubber samples of 31 harbor porpoises (Phocoena phocoena relicta ... [more ▼]

Perfluorooctane sulfonate (PFOS) and other perfluorinated alkylated substances (PFAS) were determined in liver, kidney, muscle, brain, and blubber samples of 31 harbor porpoises (Phocoena phocoena relicta) of different age and sex stranded along the Ukrainian coast of the Black Sea. In all individuals and in all tissues, PFOS was the predominant PFAS, accounting for on average 90% of the measured PFAS load. PFOS concentrations were the highest in liver (327 +/- 351 ng/g wet wt) and kidney (147 +/- 262 ng/g wet wt) tissue, and lower in blubber (18 +/- 8 ng/g wet wt), muscle (41 +/- 50 ng/g wet wt), and brain (24 +/- 23 ng/g wet wt). No significant differences could be determined between males and females, nor between juvenile and adult animals (p > 0.05). Perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanoic acid could be detected in liver tissue of approximately 25% of the individuals. Perfluorobutane sulfonate, perfluorobutanoic acid, and perfluorooctanoic acid were not detected in any of the porpoise livers. Although we investigated a potential intraspecies segregation according to the source of prey, using stable isotopes, no statistically significant correlation between PFOS concentrations and stable isotopes could be determined. It is, however, noteworthy that the contamination by PFOS in the Black Sea harbor porpoises is comparable to levels found in porpoises from the German Baltic Sea and from coastal areas near Denmark and, therefore, might pose a threat to this population. [less ▲]

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See detailVIABILITY OF THE NORTHEAST ATLANTIC HARBOUR PORPOISE AND SEAL POPULATION (GENETIC AND ECOLOGICAL STUDY)
Das, Krishna ULg; Drouguet, Olivier; Fontaine, Michaël ULg et al

Report (2007)

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) are far more abundant along our coast compared to the beginning of the nineties. Human impact on these species is however hard to ... [more ▼]

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) are far more abundant along our coast compared to the beginning of the nineties. Human impact on these species is however hard to establish, mainly due to lack of information on marine mammal population ecology, density, distribution and diversity. This project aims to gain further knowledge on the viability of the harbour porpoise and harbour seal populations in the North Sea (focusing mainly on its southern Bight) through - The characterisation of their genetic structure and diversity (through mtDNA and microsatellites in harbour porpoises) - A better understanding of their feeding ecology (through δ13C and δ15N measurements in muscles) - The assessment of their susceptibility of being trapped accidentally in fishing nets (post-mortem investigations) Harbour porpoise and harbour seal occupied the top trophic levels but displayed different feeding habits as inferred from their δ13C and δ15N mean values. Harbour porpoises displayed lower mean δ15N values suggesting a lower trophic position likely oriented towards small planktivorous fish such as herring and lesser sandeel. However, both their recent high abundance and their dietary preferences might lead to a higher susceptibility to by-catch as revealed by the significant emergence of net entrapment and net marks revealed by post-mortem investigations. The question rises about the sustainability of these incidental captures. Furthermore, genetic investigations revealed a higher fragmentation of the porpoises collected along the coast of France, Belgium and Netherlands. This apparent fragmentation is of particular importance from a conservation point of view and enhances the fact to protect in priority these last populations. Our study showed importance of multidisciplinary approaches (post-mortem investigations, stable isotope measurements (δ13C and δ15N measurements) and genetic investigations using mtDNA and microsatellites) to apprehend the question of marine mammal survival in our waters. [less ▲]

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See detailNew insights from metallic tracers on the feeding ecology of common dolphins in European waters
Lahaye, V.; Bustamante, Paco; Dabin, W. et al

Conference (2005)

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See detailEcological and pathological factors related to trace metal concentrations in harbour seal Phoca vitulina in the North Sea
Drouguet, Olivier; Siebert, Ursula; Jauniaux, Thierry ULg et al

Poster (2005)

During the last decade, recurrent epizootics have affected harbour seal (Phoca vitulina) populations in the North Sea. Recent data on their trophic habits and pollutant levels are of primary importance ... [more ▼]

During the last decade, recurrent epizootics have affected harbour seal (Phoca vitulina) populations in the North Sea. Recent data on their trophic habits and pollutant levels are of primary importance for their conservation. As isotopic composition of an animal is related to that of its prey, δ13C and δ15N were measured by mass spectrometry in the muscles of 66 harbour seals beached along the coasts of France (n = 10), Belgium (n = 30) and Netherlands (n = 26) between 1994 and 2004. Trace metals concentrations (Zn, Cu, Fe, Cd, Hg and Se) were also determined in liver, kidney and muscles by Inducted Plasma Spectrometry. δ13C and δ15N values remained similar between harbour seals from France (-15.7 0/00; 18.7 0/00, respectively), Belgium (-15.7 0/00; 19.0 0/00, respectively) and Netherlands (-14.7 0/00; 18.7 0/00, respectively). These data are in good agreement with their coastal and piscivorous life style. Isotopic value remained similar between males and females and between body conditions. Hg levels were significantly higher in seals from the southern North Sea when compared to previously published data from seals collected in Norway, probably due some geographical differential exposure. Hepatic Hg was positively correlated to hepatic Se, both increasing with the length of the seals. Such a relationship reflected an age accumulation process coupled to a detoxication mechanism involving antagonism between Hg and Se in the liver. No relationship between stable isotopes and Hg and Cd levels was observed. Increasing Zn and Hg hepatic levels were observed with degrading body condition of the harbour seals, which is reflected by decreasing blubber thickness and high hepatic to total body mass ratio. These observations tend to indicate a global redistribution of trace metals from muscle and blubber to liver, as a result of protein and lipid catabolism linked to disease and starvation. [less ▲]

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See detailTrace metal and stable isotope measurements (delta C-13 and delta N-15) in the harbour porpoise Phocoena phocoena relicta from the Black Sea
Das, Krishna ULg; Holsbeek, Ludo; Browning, Julie et al

in Environmental Pollution (2004), 131(2),

Stable carbon and nitrogen isotopes (delta(13)C and delta(15)N) and trace metals (Cd, Zn, Cu, Fe, Se, and Hg) were analysed in the tissues of 46 harbour porpoises (Phocoena phocoena relicta) caught in ... [more ▼]

Stable carbon and nitrogen isotopes (delta(13)C and delta(15)N) and trace metals (Cd, Zn, Cu, Fe, Se, and Hg) were analysed in the tissues of 46 harbour porpoises (Phocoena phocoena relicta) caught in fishing nets along the Ukrainian coasts between 1997 and 1998. Mean delta(13)C values differed significantly between male and female harbour porpoises suggesting a trophic segregation between sexes with a more coastal distribution for females at least during their gestation and nursing periods. Hepatic Hg was correlated to delta(13)C measurements, reflecting a different exposure linked to coastal vs offshore feeding habitats. A geographical comparison with existing data from other regions showed general low levels of Hg, Cd, Cu and Zn in the tissues of harbour porpoises from the Black Sea compared to other Atlantic and North Sea areas. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailEcological and pathological factors related to trace metal concentrations in harbour porpoises Phocoena phocoena from the North Sea and adjacent areas
Das, Krishna ULg; Siebert, Ursula; Fontaine, Michaël ULg et al

in Marine Ecology. Progress Series (2004), 281

There is growing concern about the health status of the harbour porpoise Phocoena phocoena in the North Sea and adjacent areas. The interaction between toxicological results (Zn, Cd, Cu, Fe, Se, Hg ... [more ▼]

There is growing concern about the health status of the harbour porpoise Phocoena phocoena in the North Sea and adjacent areas. The interaction between toxicological results (Zn, Cd, Cu, Fe, Se, Hg), stable isotope data (delta(13)C and delta(15)N) and the most common pathological findings, namely emaciation and lesions of the respiratory system, were investigated in 132 porpoises collected along the coasts of northern France, Belgium, Germany, Denmark, Iceland and Norway between 1994 and 2001. The body condition of harbour porpoises stranded on the French, Belgian and German coasts was poor compared to that of by-catch individuals from Iceland and Norway, as reflected by blubber thickness and hepatic to total body-mass ratio. High Zn and Hg concentrations were observed in some porpoises collected along the southern North Sea coast compared to by-catch individuals from Iceland, Norway and the Baltic Sea. Increasing Zn levels were observed with deteriorating health condition (emaciation and bronchopneumonia), while Hg increases were not significant. The increases were not related to shrinking liver mass which remained unchanged. These observations indicate a general redistribution of trace metals within the organs (muscles and blubber to liver), as a result of protein and lipid catabolism. Muscle delta(13)C and delta(15)N values remained unchanged with deteriorating body condition. Cd concentrations were associated only with age and low delta(15)N values, indicating that high Cd concentrations in Iceland and Norway porpoises may be partly diet-related, i.e. a result of Cd contaminated prey. [less ▲]

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See detailNorth Sea seabirds and marine mammals: pathology and ecotoxicology
Debacker, Virginie ULg; Coignoul, Freddy ULg; Das, Krishna ULg et al

Report (2004)

Les Bancs de Flandres accueillent, en hiver, une importante population d'oiseaux pélagiques. Dans le passé, ils étaient également largement fréquentés par les mammifères marins. De nos jours, on ne les ... [more ▼]

Les Bancs de Flandres accueillent, en hiver, une importante population d'oiseaux pélagiques. Dans le passé, ils étaient également largement fréquentés par les mammifères marins. De nos jours, on ne les observe que très rarement et, chaque année, quelques-uns d'entre eux et des centaines d'oiseaux sont trouvés échoués le long de la côte flamande. Ces espèces doivent être protégées, et le but de ce projet de recherche est d'étudier l'état de santé de leurs populations, son évolution temporelle, les pathologies observées et les contaminants associés, ainsi que les causes possibles de mortalités inhabituelles. La nuisance d'origine humaine la plus importante pour les oiseaux marins semble être la pollution par les hydrocarbures, mais les causes effectives des échouages des oiseaux qui ne sont pas mazoutés, et de la rareté des mammifères, restent inconnues (autres pollutions chimiques, diminution de la nourriture disponible, maladies... ?). [less ▲]

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See detailTrace metal variations in tissues of harbour seals (Phoca vitulina) stranded along Southern North Sea coasts
Drouguet, Olivier; Jauniaux, Thierry ULg; Holsbeek, Ludo et al

Poster (2004)

During the last decade, recurrent epizootics have affected harbour seal (Phoca vitulina) populations in the North Sea. The trace metal levels of the harbour seal in the Southern North Sea are poorly known ... [more ▼]

During the last decade, recurrent epizootics have affected harbour seal (Phoca vitulina) populations in the North Sea. The trace metal levels of the harbour seal in the Southern North Sea are poorly known. In this study, trace metal concentrations (Zn, Cu, Fe, Cd, Hg and Se) were measured in tissues (liver, kidney and muscle) of 72 harbour seals collected along the coasts of France, Belgium and Netherlands between 1994 and 2004. Hg levels were significantly higher in seals from the Southern North Sea than in seals from Norwegian waters (1) probably due to the amount of anthropogenic inputs in the North Sea. Hepatic Hg was positively correlated to hepatic Se, both increasing with the length of the seals. Such a relationship reflects an age accumulation process coupled to a detoxication mechanism involving antagonism between Hg and Se in the liver. Increasing Zn and Hg hepatic levels were observed with degrading body condition of the harbour seals, which is reflected by decreasing blubber thickness and high hepatic to total body mass ratio. Body condition was particularly poor in seals which died from infectious diseases. These observations tend to indicate a global redistribution of trace metals from muscle and blubber to liver, as a result of protein and lipid catabolism linked to disease and starvation. [less ▲]

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See detailMarine mammals from Northeast Atlantic: relationship between their trophic status as determined by delta C-13 and delta N-15 measurements and their trace metal concentrations
Das, Krishna ULg; Beans, Cristina; Holsbeek, Ludo et al

in Marine Environmental Research (2003), 56(3),

The relationship between trophic position through delta(13)C and delta(15)N and trace metal concentrations (Zn, Cd, Cu and Hg) was investigated in the tissues of six marine mammal species from the ... [more ▼]

The relationship between trophic position through delta(13)C and delta(15)N and trace metal concentrations (Zn, Cd, Cu and Hg) was investigated in the tissues of six marine mammal species from the Northeast Atlantic: striped dolphin Stenella coeruleoalba, common dolphin, Delphinus delphis. Atlantic white-sided dolphin Lagenorhynchus acutus, harbour porpoise Phocoena phocoena, white beaked-dolphin Lagenorhynchus albirostris, grey seal Halichoerus grypus stranded on French Channel and Irish coasts. White-beaked dolphins, harbour porpoises, white-sided dolphins, common and striped dolphins display the same relative and decreasing trophic position, as measured by delta(15)N values, along both the Irish and French channel coasts, reflecting conservative trophic habits between these two places. Hepatic and renal Cd concentrations were significantly correlated to muscle delta(13)C and delta(15)N values while Hg, Zn and Cu did not. These results suggest that Cd accumulation is partly linked to the diet while other factors Such as age or body condition might explain Hg, Zn or Cu variability in marine mammals. Combined stable isotope and trace metal analyses appear to be useful tools for the study of marine mammal ecology. (C) 2003 Elsevier Science Ltd. All rights reserved. [less ▲]

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See detailTrace metals in the harbour porpoise from the North Sea and adjacent areas: relationship with stable isotope measurements, the nutritional status, lesions of the respiratory system and parasitism.
Das, Krishna ULg; Siebert, Ursula; Fontaine, Michaël et al

Conference (2003)

Growing concern has been raised about the status and the long-term viability of the harbour porpoise (Phocoena phocoena) in the North Sea and adjacent areas. Sources of trace metal variations were ... [more ▼]

Growing concern has been raised about the status and the long-term viability of the harbour porpoise (Phocoena phocoena) in the North Sea and adjacent areas. Sources of trace metal variations were investigated using a multidisciplinary approach. Porpoises from the Belgian coasts were compared to individuals from the German North Sea and Baltic coasts, Denmark, Norway and Iceland. Toxicological results (Hg, Zn, Cu, Cd and Se) were confronted to most common pathological findings, namely emaciation, lesions of the respiratory system or parasitism. Influence of diet through stable carbon and nitrogen analysis (d13C and d15N), age and sex have also been considered. As expected, the nutritional status of stranded harbour porpoise from the Southern North Sea is poor compared to by-caught individuals from Norway and Iceland, as reflected by their blubber thickness, weight to length ratio and hepatic to total body mass ratio. The porpoises collected along the Southern North Sea coast display higher Zn and Hg concentrations compared to individuals collected in more preserved areas from the North Atlantic. Moreover, significant Zn, Hg and Se levels were observed with increasing emaciation severity. Porpoises displaying severe bronchopneumonia also have higher Zn concentrations probably due to the association previously described of emaciation and bronchopneumonia. Hg is clearly linked to parasitism. These increasing concentrations are not related to a shrinking of liver mass as it remains unchanged during the emaciation. As a result, hepatic trace metal load increases also. These observations tend to indicate a general redistribution of heavy metals within the organs (muscles to livers), which results from protein catabolism. Such a re-distribution could well be an additional stress for porpoises already experiencing stressful conditions (organochlorines, etc…). In contrast, Cu and Cd were never associated to emaciation. Other parameters such as age class or diet are more likely to be involved. [less ▲]

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See detailMarine mammal selenium linked mercury detoxifaction processes
Holsbeek, Ludo; Das, Krishna ULg; Bouquegneau, Jean-Marie ULg et al

Poster (2002, May 13)

New results confirm earlier findings on the importance of tiemannite acumulation on speciation and inter-tissue relationships. It is hardly surprising that, as opposed to what was concluded earlier, major ... [more ▼]

New results confirm earlier findings on the importance of tiemannite acumulation on speciation and inter-tissue relationships. It is hardly surprising that, as opposed to what was concluded earlier, major inter-regional differences in Hg accumulation can be demonstrated when comparing several populations of harbour porpoise on an age corrected basis. Important inter-species differences, probably depending on prey choice, are found, even after correction for "relative age". Regional differences are more important than the inter-species variability, at least within both classically described sub-orders of cetaceans. Based on actual estimates of MeHg exposure and tissue concentrations of Hg and MeHg in harbour porpoise from the Southern North Sea, Hg detoxification through precipitation of tiemannite is evaluated to neutralise on average 12% of the overall MeHg intake at age 7. Based on the idea of a 3 fold excess in toxicity of mercury over selenium and a 5 to 15 molar concentration excess of selenium over Hg in fish, Hg seems to play the major part in the mutual detoxification. The formation of tiemannite was previously described as resulting from a two-step accumulation mechanism appearing at a threshold level of Hg 100 g/g fw in liver. The reaching of an equimolar Hg to Se ratio can, however, be fully explained by the gradual increase of tiemannite levels in liver only. The new view is that molar Hg to Se hepatic ratios go towards equimolarity along with the slow nature of the tiemannite detoxification process, with tiemannite gradually taking the upper hand over MeHg, IHg2+ and a surplus of "free" selenium with the increase of the total Hg load. [less ▲]

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See detailNew findings on selenium related mercury detoxification processes.
Holsbeek, Ludo; Das, Krishna ULg; Bouquegneau, Jean-Marie ULg et al

Poster (2002)

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See detailMarine mammals from the North Sea: Insights in their feeding ecology and nutritional status from stable isotopes ratio and heavy metal concentrations
Das, Krishna ULg; Jauniaux, Thierry ULg; Holsbeek, Ludo et al

Poster (2001)

The relationship between trace metal levels, trophic position and health status has been investigated in North Sea marine mammals. Stable isotope ratio (15N and 13C, mass spectrometry) and trace metal ... [more ▼]

The relationship between trace metal levels, trophic position and health status has been investigated in North Sea marine mammals. Stable isotope ratio (15N and 13C, mass spectrometry) and trace metal analyses (Cd, Pb, Cu, Zn, Se, Hg, I.C.P Spectrometry and flameless atomic absorption) have been performed in tissues of 52 harbour porpoises Phocoena phocoena, 27 harbour seals Phoca vitulina, 9 white-beaked dolphins Lagenorhynchus albirostris, 6 grey seals Halichoerus grypus, 1 hooded seal Cystophora cristata, 2 white-sided dolphin Lagenorhynchus acutus, 7 sperm whales Physeter macrocephalus and 4 fin whales Balaenoptera physalus, found stranded on the Northern French, Belgian and Southern Dutch coasts. The lowest 15N value has been measured in fin whales, and the highest in white-beaked dolphins, grey and common seals, suggesting a higher trophic position. Sperm whales, white-sided dolphins and hooded seal have strongly negative 13C values and high renal cadmium levels (258, 88 and 62 µg Cd .g-1dw, respectively) indicating that they might feed, at least in part, on oceanic cephalopods. High Hg liver concentrations can be encountered in older animals and reflect a cumulative storage of detoxified HgSe over the whole life span rather than a bioamplification process. Zn, Cu and Hg concentrations were higher in harbour porpoises from the Southern North Sea compared to other areas. Some individuals were severely emaciated as shown by their muscle atrophy and reduced blubber thickness. Hepatic Zn and Se concentrations were significantly higher in emaciated juvenile porpoises than in normal animals suggesting a severe disturbance of the metal homeostasis. To conclude, within the North Sea, trace metal levels in marine mammals display strong intra- and interspecies variations due to geographic origin, age, diet, trophic position but also by nutritional status of the individuals, raising the question of the suitability of marine mammals as valuable bioindicators of trace metal pollution. [less ▲]

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See detailMarine mammals stranded on the Belgian and Dutch coasts: Approach of their feeding ecology by stable isotope and heavy metal measurements
Das, Krishna ULg; Debacker, Virginie ULg; Lepoint, Gilles ULg et al

Poster (2000, April)

The harbour porpoise Phocoena phocoena, the harbour seal Phoca vitulina and the white-beaked dolphin Lagenorhynchus albirostris are commonly found stranded on the Belgian and Dutch coasts. More ... [more ▼]

The harbour porpoise Phocoena phocoena, the harbour seal Phoca vitulina and the white-beaked dolphin Lagenorhynchus albirostris are commonly found stranded on the Belgian and Dutch coasts. More occasionally, oceanic species such as the white-sided dolphin Lagenorhynchus acutus, the sperm whale Physeter macrocephalus or the fin whale Balaenoptera physalus are also found stranded. For the last 10 years, trace analyses (Cd, Pb, Cu, Zn, Se, Hg) have been performed in their organs as well as complementary stable isotope ratio determinations (d15N and d13C) in order to trace their respective metal level and trophic position. Sperm whales, fin whales and white-sided dolphins display strong differences in their d13C and d15N values compared to harbour porpoises, harbour seals or white-beaked dolphins. The isotopic data from white-sided dolphins, sperm whales and fin whales suggest that they do not feed mainly within this area. On the contrary, porpoises, seals and white-beaked dolphins display close isotopic data reflecting a similar nutrition within the North Sea. However significant differences appear between these species: harbour porpoises display a significantly lower d15N (mean: 16.4 0/00 against 18.70/00 and 18.8 0/00 respectively) and d3C (mean-17 0/00 against –16 0/00 and –15.70/00 respectively) than harbour seals and white-beaked dolphins reflecting a lower trophic position of the porpoises.Moreover, Harbour porpoise isotopic compositions seem to have changed over the last five years, which could reflect a switch in their diet. In marine mammals, heavy metals are mainly absorbed through the diet and so potential relations between stable isotopes and heavy metals have been investigated. For example, it is suggested that harbour porpoises occasionally feed on cadmium contaminated preys as squids and that harbour seals and white-beaked dolphins are more restrictive on fish. [less ▲]

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See detailSpatial and interspecies variability of mercury accumulation in small cetaceans
Holsbeek, Ludo; Das, Krishna ULg; Joiris, C. R. et al

Poster (2000, April)

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See detailEcotoxicological and pathological studies of common guillemots Uria aalge beached on the Belgian coast during six successive wintering periods (1989-90 to 1994-95)
Debacker, Virginie ULg; Holsbeek, Ludo; Tapia, German et al

in Diseases of Aquatic Organisms (1997), 29(3), 159-168

During 6 successive wintering periods, 727 common guillemots Uria aalge were recovered from Belgian beaches. One-third of the birds were already dead; the rest passed through rehabilitation centres where ... [more ▼]

During 6 successive wintering periods, 727 common guillemots Uria aalge were recovered from Belgian beaches. One-third of the birds were already dead; the rest passed through rehabilitation centres where they eventually died. All birds were monitored for general condition (body mass, fat reserves), eventual status of oiling and pathological changes (cachexia, acute hemorrhagic gastroenteropathy); 339 birds were sampled for trace metals (total and organic Hg, Cu, Zn, Fe, Cd) and PCB (polychlorinated biphenyl) analysis. Oiling is still a major cause of death for wintering pelagic seabirds: half of the birds showed signs of external or internal oiling, probably a still greater number of oiled birds never reach the shores. Although a low body mass can be considered a normal winter condition for wintering guillemots, pathology results showed that three-quarters of the studied animals were in a state of cachexia with emaciated pectoral muscle and lowered muscle lipid content. Elevated levels of Cu, Zn, Hg and PCBs were linked to the state of cachexia and may well represent an additional stress factor leading to the debilitation and death of part of the wintering guillemot population. [less ▲]

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