Mercury content in commercial pelagic fish and its risk assessment in the Western Indian Ocean,” Sci.

Abstract As top predators of pelagic food webs, large fish naturally bioaccumulate mercury (Hg). Determining Hg burdens in commercialized fish is essential considering the concern about effects of contaminants on human health and the legal thresholds that are therefore set for local consumption and/or exportation. Total Hg levels were measured in the muscular tissue of 183 fish of five commercially important species from the tropical zone of the Western Indian Ocean. All individuals were measured and sexed in order to study the impregnation of Hg with size and sex within each species. Values of Hg found in this part of the Indian Ocean were comparable to Hg in muscular tissue of the same species studied in other areas. The highest Hg levels were noted in Swordfish (Xiphias gladius) caught in waters surrounding Reunion Island (3.97 ± 2.67 μg g − 1 dry weight). Following the Swordfish, in decreasing order of Hg content, were the Yellowfin Tuna (Thunnus albacares) and the Skipjack (Katsuwonus pelamis), then the Common Dolphinfish (Coryphaena hippurus) and the Wahoo (Acanthocybium solandri). In the North of the Mozambique Channel, Swordfish had higher Hg levels than Yellowfin Tunas, and Dolphinfish exhibited intermediate Hg levels. The size of a fish was a determining factor of its Hg burden, as was the species. Differences in size-normalized Hg levels were observed between the two study zones for Swordfish and Common Dolphinfish. Sex, in contrast, did not influence Hg levels suggesting that females and males have similar feeding habits. The muscular Hg levels presented here suggest that consumers of fish originating from theWestern Indian Ocean should limit themselves to one Swordfish based meal per week, or one fish meal a day if they choose to eat tuna or Common Dolphinfish

Écologie trophique de grands prédateurs marins de l'Océan Indien occidental tropical par l'étude conjointe de la bioaccumulation d'éléments traces et de rapports isotopiques

La présente étude s'inscrit dans une démarche d'acquisition de connaissances sur différents aspects de l'écologie trophique de prédateurs supérieurs marins peuplant le sud-ouest de l'Océan Indien par l'analyse de teneurs en éléments traces et de signatures isotopiques. Trois éléments toxiques (cadmium, mercure et plomb) et cinq éléments essentiels (cuivre, fer, manganèse, sélénium et zinc) ont été dosés dans six espèces d'oiseaux marins (le Pétrel de Barau, le Puffin de Bâillon, le Paille-en-queue à brins blancs, le Noddi Brun, le Noddi à bec grêle et la Sterne Fuligineuse) et cinq espèces de poissons pélagiques (l'Espadon, le Thon Jaune, le Listao, le Thazard Bâtard et la Dorade Coryphène Commune). De grands écarts dans les teneurs en éléments traces ont été observés. Le cuivre est très concentré dans le foie des Thons Jaunes péchés autour de La Réunion, le fer et le zinc le sont dans les reins respectivement des Dorades et des Thons Jaunes collectés dans le Canal du Mozambique, et le mercure dans le foie et les reins des Pétrels de Barau de La Réunion. Un ensemble de facteurs sont à l'origine de cette grande variabilité des teneurs. La bioaccumulation de ces éléments traces est, en effet, influencée par l'organe ou le tissu considéré, la condition nutritionnelle des animaux (dans le cas des éléments essentiels), l'âge (étudié par l'intermédiaire de la taille chez les poissons), le lieu géographique, les processus de détoxication, l'espèce et le régime alimentaire. En revanche, il a peu de cas où l'influence du sexe ou du statut reproducteur est observable.This study focuses on thé acquisition of knowledge of various aspects of thé trophic ecology of marine top predators from thé South-Western Indian Océan through thé analysis of trace élément levels and isotopic signatures. Three toxic éléments (cadmium, mercury and lead) and five essential éléments (copper, iron, manganèse, sélénium and zinc) were analyzed in six seabirds (Barau's Pétrel, Audubon's Shearwa'ter, White-tailed Tropicbird, Brown Noddy, Lesser Noddy and Sooty Tern) and five pelagic fishes (Swordfish, Yellowfin Tuna, Skipjack Tuna, Wahoo, Common Dolphinfish). A large range of trace élément levels were observed. Copper levels were high in thé liver of Yellowfin Tunas collected around Reunion Island, rénal iron and zinc levels were high, respectively, in Dolphinfish and Yellowfins sampled in thé Mozambique Channel, and mercury levels were highest in Barau's Pétrels liver and kidney. The large variations of trace élément levels were attributable to a combination of several factors influencing their bioaccumulation: thé organ or tissue considered, thé animais nutritional condition (for essential éléments), thé âge (determined through thé length for fish), thé geographical area, detoxification processes, thé species and thé diet.SAINT DENIS/REUNION-Droit Lettre (974112101) / SudocSudocFranceReunionFRR

Trace elements in three marine birds breeding on Reunion Island (Western Indian Ocean). Part 2 : Factors influencing their detoxification

International audienceSeabird tissues collected between 2002 and 2004 from Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni) and White-tailed Tropicbird (Phaethon lepturus) colonies on Reunion Island were analyzed for metallothioneins (MTs) and trace element content. The subcellular distribution between soluble and insoluble fractions of Cd, Cu, Fe, Mn, Se and Zn was determined in liver and kidney tissues. In both tissues, the soluble fraction of the cell concentrated most of the Cd and Se, whereas Fe, Mn and Zn were preferentially accumulated in the insoluble fraction. The distribution of these elements varied with the tissue, the age of the bird and the species. Furthermore, the distributions of Fe and Mn were somewhat influenced by the bird's physical condition. Metallothionein levels were measured in the soluble fraction after heat denaturation. The levels of these proteins varied from 5.5 ± 2.7 mg.g−1 d.w. to 11.4 ± 6.2 mg.g−1 d.w., depending on the species and the tissue considered. Metallothionein levels were significantly different between liver and kidney only in the White-tailed Tropicbird. In the three species, MT levels in kidney were significantly higher in adults than in juveniles. The bird's weight also had an influence on hepatic and renal MT levels, but not the gender nor the reproductive status. The implication of MTs in Cu and Zn homeostasis, and Cd and Hg detoxification are discussed. In addition, clues on Hg regulation by Se were found, especially in Barau's Petrel, where the levels of these two elements were very significantly correlated

Trace elements in three marine birds breeding on Reunion Island (Western Indian Ocean) Part 1: Factors influencing their bioaccumulation

This work aims to use seabirds as bioindicators of trace element levels in the tropical waters and food webs of the Western Indian ocean. The accumulation patterns of selected toxic (Cd and Hg) and essential (Cu, Fe, Mn, Se and Zn) elements were determined in liver, kidney and pectoral muscles of three species of 162 marine bird

Preliminary results on trace element levels in three species of seabirds from the western Indian Ocean

International audienceAs top predators of pelagic food webs, marine birds naturally bioaccumulate essential and non-essential elements. Levels of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), selenium (Se) and zinc (Zn) were determined in the liver, kidneys and muscles of three species of marine birds found on Réunion Island: Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni) and the White-tailed Tropicbird (Phaethon lepturus). The study of the 89 birds sampled put forth variations of the elemental levels between organs, age groups (juveniles versus adults) and species. Adult Barau's Petrels showed the highest values of Hg and Cd. This study offers a first glimpse of the levels of impregnation of eight trace elements in top predators of the western Indian Ocean and brings answers to certain questions related to the processes of bioaccumulation in marine top predators of the tropical Indian Ocean

Mercury in seabird feathers: Insight on dietary habits and evidence for exposure levels in the western Indian Ocean

International audienceBreast feathers were used to estimate mercury levels in six marine birds nesting in the tropical western Indian Ocean, i.e. Sooty Tern (Sterna fuscata), Brown Noddy (Anous stolidus), Lesser Noddy (Anous tenuirostris), Audubon Shearwater (Puffinus lherminieri bailloni), Barau's Petrel (Pterodroma baraui ) and the White-tailed Tropicbird (Phaethon lepturus). Juveniles consistently showed lower plumage mercury than adults. The lowest mean level was noted in juvenile Sooty Terns from the Glorioso Archipelago (0.05 μg.g−1). The highest levels were obtained for adult Barau's Petrels from Reunion Island (0.96 μg.g−1). An inter-site analysis of Sooty Tern showed higher mercury levels in birds nesting on Juan de Nova Island. Levels were low in comparison with values reported in the plumage of seabirds worldwide. The potential impacts of the size, the type (fish/cephalopod) and the origin (epi/meso-pelagic) of prey on mercury intake in birds are discussed. Although the diet composition of individuals within a species appeared to be quite variable, combining results on mercury levels with common knowledge of each species allowed additional information on their dietary and foraging habits to be unraveled

Trophic ecology of marine birds and pelagic fishes from Reunion Island as determined by stable isotope analysis

International audienceStable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine bird and fish communities from Reunion Island, western Indian Ocean. Firstly, isotope signatures in the liver of Barau's petrels Pterodroma baraui, Audubon's shearwaters Puffinus lherminieri bailloni, and white-tailed tropicbirds Phaethon lepturus were used to compare their trophic levels and determine whether they forage in the same areas while breeding on Reunion Island. Spatial and trophic segregations were noted among these seabirds. Barau's petrels seem to feed on prey of higher trophic levels than Audubon's shearwaters. Different isotopic signatures in adults and juveniles of these species suggest that these chick-rearing Procellariiformes adopt a dual food-provisioning strategy, making separate foraging trips to feed their fledglings and for their own maintenance. Satellite tracking should be undertaken to verify this hypothesis. Furthermore, novel data were obtained on the seabirds' interbreeding period by analyzing feather signatures. White-tailed tropicbirds are thought to change foraging areas during this season, although none of the birds seemed to shift diets. Secondly, isotopic signatures in the muscle of yellowfin tuna Thunnus albacares, skipjack tuna Katsuwonus pelamis, and common dolphinfish Coryphaena hippurus were used to gather information on their feeding behaviors in Reunion Island waters. Spatial and trophic segregations were also observed, particularly between common dolphinfish and the tuna species, where the former fed more on low trophic level coastal organisms under fish aggregating devices than did the latter. Finally, trophic interactions in bird and fish communities were investigated. Seabirds appear to be trophically more structured than fish, foraging in a wider range of areas. Our results confirmed feeding associations between Audubon's shearwaters and yellowfin tuna

Preliminary results on trace element levels in three species of seabirds from the western Indian Ocean

As top predators of pelagic food webs, marine birds naturally bioaccumulate essential and non-essential elements. Levels of arsenic (As), cadmium (Cd), copper (Cu), iron (Fe), mercury (Hg), manganese (Mn), selenium (Se) and zinc (Zn) were determined in the liver, kidneys and muscles of three species of marine birds found on Réunion Island: Barau's Petrel (Pterodroma baraui), Audubon's Shearwater (Puffinus lherminieri bailloni) and the White-tailed Tropicbird (Phaethon lepturus). The study of the 89 birds sampled put forth variations of the elemental levels between organs, age groups (juveniles versus adults) and species. Adult Barau's Petrels showed the highest values of Hg and Cd. This study offers a first glimpse of the levels of impregnation of eight trace elements in top predators of the western Indian Ocean and brings answers to certain questions related to the processes of bioaccumulation in marine top predators of the tropical Indian Ocean.Situés au sommet des réseaux trophiques pélagiques, les oiseaux marins bioaccumulent naturellement des éléments essentiels et non-essentiels tout au long de leur vie. La mesure des teneurs en arsenic (As), cadmium (Cd), cuivre (Cu), fer (Fe), mercure (Hg), manganèse (Mn), sélénium (Se) et zinc (Zn) a été effectuée dans le foie, les reins et les muscles de trois espèces d'oiseaux de l'île de La Réunion, le pétrel de Barau (Pterodroma baraui), le puffin de baillon (Puffinus lherminieri bailloni) et le paille-en-queue à brins blancs (Phaethon lepturus). L'étude des 89 oiseaux échantillonnés fait apparaître des variations des teneurs métalliques entre les organes, les classes d'âge (juvéniles vs adultes), ainsi qu'entre les espèces, les pétrels de Barau adultes ayant les plus fortes teneurs en Hg et Cd. Cette étude offre ainsi, un premier aperçu des niveaux d'imprégnation de 8 éléments traces chez des prédateurs supérieurs de l'Océan Indien occidental tropical et propose des éléments de réponses quant aux processus de bioaccumulation chez ces espèces.Ostrich 2007, 78(2): 435–44