Jessica Kojadinovic - Academia.edu (original) (raw)

Papers by Jessica Kojadinovic

HAL (Le Centre pour la Communication Scientifique Directe), 2007

HAL (Le Centre pour la Communication Scientifique Directe), 2007

Proceedings of the 11th International Echinoderm Conference, 6-10 October 2003, Munich, Germany, 2004

Http Www Theses Fr, 2006

La presente etude s'inscrit dans une demarche d'acquisition de connaissances sur differen... more La presente etude s'inscrit dans une demarche d'acquisition de connaissances sur differents aspects de l'ecologie trophique de predateurs superieurs marins peuplant le sud-ouest de l'ocean Indien par l'analyse de teneurs en elements traces et de signatures isotopiques. Trois elements toxiques (cadmium, mercure et plomb) et cinq elements essentiels (cuivre, fer, manganese, selenium et zinc) ont ete doses dans six especes d'oiseaux marins (le Petrel de Barau, le Puffin de Bâillon, le Paille-en-queue a brins blancs, le Noddi Brun, le Noddi a bec grele et la Sterne Fuligineuse) et cinq especes de poissons pelagiques (l'Espadon, le Thon Jaune, le Listao, le Thazard Bâtard et la Dorade Coryphene Commune). De grands ecarts dans les teneurs en elements traces ont ete observes. Le cuivre est tres concentre dans le foie des Thons Jaunes peches autour de La Reunion, le fer et le zinc le sont dans les reins respectivement des Dorades et des Thons Jaunes collectes dans le Canal du Mozambique, et le mercure dans le foie et les reins des Petrels de Barau de La Reunion. Un ensemble de facteurs sont a l'origine de cette grande variabilite des teneurs. La bioaccumulation de ces elements traces est, en effet, influencee par l'organe ou le tissu considere, la condition nutritionnelle des animaux (dans le cas des elements essentiels), l'âge (etudie par l'intermediaire de la taille chez les poissons), le lieu geographique, les processus de detoxication, l'espece et le regime alimentaire. En revanche, il a peu de cas ou l'influence du sexe ou du statut reproducteur est observable.

Waterbirds, 2008

We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13... more We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13 C and δ 15 N analysis, based on a study of Barau's Petrels (Pterodroma baraui) and Whitetailed Tropicbirds (Phaethon lepturus). Samples were analyzed for stable isotopes before and after lipid removal. Lipid-free muscle and liver were significantly enriched in 13 C compared to those containing lipids (0.52 ‰ and 0.61 ‰ mean differences in δ 13 C respectively) implying that lipids should be extracted from these tissues to avoid effects of uncontrolled differential lipid content. However lipid extraction also slightly increased muscle δ 15 N values in tropicbirds. Researchers should thus run samples separately for δ 13 C and δ 15 N analysis, extracting lipids only in aliquots in which δ 13 C is measured, or apply arithmetic δ 13 C normalization methods on non lipid-extracted samples. Predictive models developed from our data, inferring δ 13 C values of lipid-extracted material from δ 13 C values and C:N ratios of non lipid-extracted material are presented and compared to five normalization methods taken from literature. Our models showed the best prediction efficiencies followed by that developed by McConnaughey and McRoy (1979). In feathers, no difference in stable isotopic measurements were noted between aliquots treated with sodium hydroxide or 2:1 chloroform:methanol. Both protocols seem suitable for preparing feather samples for isotopic analysis.

Science of The Total Environment, 2007

Breast feathers were used to estimate mercury levels in six marine birds nesting in the tropical ... more Breast 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.

Marine Ecology Progress Series, 2008

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine b... more Stable 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. KEY WORDS: Feeding behavior. Seabirds. Tunas. Dolphinfish. Top predators. Western Indian Ocean. δ 15 N. δ 13 C

Environmental Pollution, 2007

Trace elements were analyzed in fish of commercial interest to determine their importance in mari... more Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r 2 = 0.747) and Yellowfin Tunas (r 2 = 0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments. Metal bioaccumulation was quantified in four species of pelagic fish.

Archives of Environmental Contamination and Toxicology, 2006

Seabird tissues collected between 2002 and 2004 from Barau's Petrel (Pterodroma baraui), Audubon'... more Seabird 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.

Waterbirds, 2008

We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13... more We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13 C and δ 15 N analysis, based on a study of Barau's Petrels ( Pterodroma baraui ) and White-tailed Tropicbirds ( Phaethon lepturus ). Samples were analyzed for stable isotopes before and after lipid removal. Lipid-free muscle and liver were significantly enriched in 13 C compared to those containing lipids (0.52‰ and 0.61‰ mean differences in δ 13 C respectively) implying that lipids should be extracted from these tissues to avoid effects of uncontrolled differential lipid content. However lipid extraction also slightly increased muscle δ 15 N values in tropicbirds. Researchers should thus run samples separately for δ 13 C and δ 15 N analysis, extracting lipids only in aliquots in which δ 13 C is measured, or apply arithmetic δ 13 C normalization methods on non lipid-extracted samples. Predictive models developed from our data, inferring δ 13 C values of lipid-extracted material from δ 13 C values and C:N ratios of non lipid-extracted material are presented and compared to five normalization methods taken from literature. Our models showed the best prediction efficiencies followed by that developed by . In feathers, no difference in stable isotopic measurements were noted between aliquots treated with sodium hydroxide or 2:1 chloroform:methanol. Both protocols seem suitable for preparing feather samples for isotopic analysis.

Science of The Total Environment, 2007

Breast feathers were used to estimate mercury levels in six marine birds nesting in the tropical ... more Breast 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.

Marine Ecology Progress Series, 2008

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine b... more Stable 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.

Marine Biology, 2008

Over 6-million pairs of sooty terns Sterna fuscata breed once a year in the southwest Indian Ocea... more Over 6-million pairs of sooty terns Sterna fuscata breed once a year in the southwest Indian Ocean, mostly on three islands of the Mozambique Channel (Europa, Juan de Nova and Glorieuses) and in the Seychelles region. Seasonal reproduction in either winter or summer is the dominant strategy in the area, but nonseasonal reproduction also occurred in some places like at Glorieuses Archipelago. The feeding ecology of the sooty tern was investigated during the breeding seasons to determine whether terns showed signiWcant diVerences in their trophic ecology between locations. Regurgitations were analyzed to describe the diet of individuals when breeding, and stable isotopes and mercury concentrations were used to temporally integrate over the medium-term of the trophic ecology of both adults and chicks. Overall, the diet was composed of Wsh, Xying squid and Wsh larvae in diVerent proportions. At Europa and Aride in the Seychelles, where winter reproduction occurs, large epipelagic prey like Xying Wsh or squid dominated the diet. At Juan de Nova, sooty terns reproduce in summer and rely mostly on Wsh larvae. At Glorieuses (non-seasonal breeding), the diet was intermediate with Wsh larvae and Xying squid being important prey items. The stable-carbon and nitrogen isotope values in blood conWrm the diVerences observed in dietary analysis, and demonstrate diVerent feeding strategies between colonies. 13 C values of feathers showed spatial segregation between birds from the Mozambique Channel and the Seychelles region. Terns from the Seychelles had also higher 15 N values. Feather 13 C values also suggest a sig-niWcant shift from summer to wintering habitat for birds from Juan de Nova. This study emphasizes the high phenotypic plasticity of the species, which may explain its numerical dominance in all tropical waters of the World's Ocean.

Marine Biology, 2008

Nitrogen ( 15 N) and carbon ( 13 C) stable isotopes and contaminants, such as mercury, have been ... more Nitrogen ( 15 N) and carbon ( 13 C) stable isotopes and contaminants, such as mercury, have been widely used to characterise foraging ecology of temperate and polar seabirds. In this study, for the Wrst time, we used isotopic signatures and mercury levels of feathers and blood of eight tropical seabird species, that forage in a range-gradient between inshore and oVshore areas, to describe the foraging habits of a large tropical seabird community (from two neighboring islands of the Seychelles archipelago, western Indian Ocean) during both the breeding and interbreeding periods. Overall, we found a high overlap in both 15 N and 13 C signatures among species. The high inter-speciWc overlap in 15 N values was expected, given the similarities in the diet of the species from this community. However, several unexpected results, such as (1) the consistently higher 15 N signatures of white terns (Gygis alba), (2) the large variation in inter-speciWc diVerences in 15 N signatures among the sampling groups (season, age, island and tissue) and (3) the consistent low 15 N values of breeding birds during the northwest monsoon (austral summer), suggest that 15 N signatures cannot be used as indicators of seabird trophic levels in this community. The high inter-speciWc overlap in 13 C signatures and the absence, during the breeding season, of a 13 C gradient that follows the inshore-oVshore foraging gradient within the community can be explained by the habitat homogeneity of the Seychelles continental shelf and suggest that birds forage mostly within the limits of this "plateau". On the other hand, the similarities in 13 C values between the breeding and inter-breeding periods in species that are known to show post-breeding dispersal, strongly support the hypothesis of a lack of latitudinal variation in 13 C signatures of POM in the central Indian Ocean, and the consequent inaccuracy of 13 C values to track seabird movements within this geographic area. Inter-speciWc diVerences in mercury levels seem to be related to prey size, while consistent higher mercury concentrations in one of the studied islands suggest diVerent island mercury-backgrounds and possible segregation in foraging areas between the seabirds of the two islands. Communicated by R. Lewison.

Journal of Sea Research, 2014

In ecological systems, it is necessary to describe the trophic niches of species and their segreg... more In ecological systems, it is necessary to describe the trophic niches of species and their segregation or overlap to understand the distribution of species in the community. In oceanic systems, the community structure of top predators such as seabird communities has been well documented with many studies in several biogeographical areas. But for coastal habitats, very few investigations on the trophic structure have been carried out in avian communities. In this study, the trophic resource partitioning was investigated on eight of the most abundant species of a shorebird community on the central Atlantic coast of France. Our work comprised a comprehensive sample of birds with different ecomorphogical patterns and data on their main prey to encompass potential sources of overlap and segregation in this community. We examined the stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopic composition of blood to investigate the trophic structure (1) on a temporal scale by comparing migration and wintering periods; (2) on a spatial scale through inter-site comparisons; and (3) on the community level within groups of phylogenetically related species. Diets appeared different in several cases between periods, between sites and between juveniles and adults for the same sites. A clear trophic partitioning was established with four functional groups of predators in winter inside the community. The Grey Plover, the Bar-tailed Godwit, the Curlew and a majority of the dunlins were worm-eaters mainly feeding on Nereis diversicolor or Nephtys hombergii. Two species were predominantly deposit-suspensivorous mollusc-eaters, including the Red Knot and the Black-tailed Godwit feeding mainly on Macoma balthica. The Oystercatcher fed mainly on suspensivorous molluscs like Cerastodrema edule and two species including the Redshank and some dunlins adopted opportunistic behaviours feeding on mudflat and/or in marshes.

Environmental Pollution, 2007

Trace elements were analyzed in fish of commercial interest to determine their importance in mari... more Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r 2 = 0.747) and Yellowfin Tunas (r 2 = 0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments.

HAL (Le Centre pour la Communication Scientifique Directe), 2007

HAL (Le Centre pour la Communication Scientifique Directe), 2007

Proceedings of the 11th International Echinoderm Conference, 6-10 October 2003, Munich, Germany, 2004

Http Www Theses Fr, 2006

La presente etude s'inscrit dans une demarche d'acquisition de connaissances sur differen... more La presente etude s'inscrit dans une demarche d'acquisition de connaissances sur differents aspects de l'ecologie trophique de predateurs superieurs marins peuplant le sud-ouest de l'ocean Indien par l'analyse de teneurs en elements traces et de signatures isotopiques. Trois elements toxiques (cadmium, mercure et plomb) et cinq elements essentiels (cuivre, fer, manganese, selenium et zinc) ont ete doses dans six especes d'oiseaux marins (le Petrel de Barau, le Puffin de Bâillon, le Paille-en-queue a brins blancs, le Noddi Brun, le Noddi a bec grele et la Sterne Fuligineuse) et cinq especes de poissons pelagiques (l'Espadon, le Thon Jaune, le Listao, le Thazard Bâtard et la Dorade Coryphene Commune). De grands ecarts dans les teneurs en elements traces ont ete observes. Le cuivre est tres concentre dans le foie des Thons Jaunes peches autour de La Reunion, le fer et le zinc le sont dans les reins respectivement des Dorades et des Thons Jaunes collectes dans le Canal du Mozambique, et le mercure dans le foie et les reins des Petrels de Barau de La Reunion. Un ensemble de facteurs sont a l'origine de cette grande variabilite des teneurs. La bioaccumulation de ces elements traces est, en effet, influencee par l'organe ou le tissu considere, la condition nutritionnelle des animaux (dans le cas des elements essentiels), l'âge (etudie par l'intermediaire de la taille chez les poissons), le lieu geographique, les processus de detoxication, l'espece et le regime alimentaire. En revanche, il a peu de cas ou l'influence du sexe ou du statut reproducteur est observable.

Waterbirds, 2008

We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13... more We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13 C and δ 15 N analysis, based on a study of Barau's Petrels (Pterodroma baraui) and Whitetailed Tropicbirds (Phaethon lepturus). Samples were analyzed for stable isotopes before and after lipid removal. Lipid-free muscle and liver were significantly enriched in 13 C compared to those containing lipids (0.52 ‰ and 0.61 ‰ mean differences in δ 13 C respectively) implying that lipids should be extracted from these tissues to avoid effects of uncontrolled differential lipid content. However lipid extraction also slightly increased muscle δ 15 N values in tropicbirds. Researchers should thus run samples separately for δ 13 C and δ 15 N analysis, extracting lipids only in aliquots in which δ 13 C is measured, or apply arithmetic δ 13 C normalization methods on non lipid-extracted samples. Predictive models developed from our data, inferring δ 13 C values of lipid-extracted material from δ 13 C values and C:N ratios of non lipid-extracted material are presented and compared to five normalization methods taken from literature. Our models showed the best prediction efficiencies followed by that developed by McConnaughey and McRoy (1979). In feathers, no difference in stable isotopic measurements were noted between aliquots treated with sodium hydroxide or 2:1 chloroform:methanol. Both protocols seem suitable for preparing feather samples for isotopic analysis.

Science of The Total Environment, 2007

Breast feathers were used to estimate mercury levels in six marine birds nesting in the tropical ... more Breast 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.

Marine Ecology Progress Series, 2008

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine b... more Stable 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. KEY WORDS: Feeding behavior. Seabirds. Tunas. Dolphinfish. Top predators. Western Indian Ocean. δ 15 N. δ 13 C

Environmental Pollution, 2007

Trace elements were analyzed in fish of commercial interest to determine their importance in mari... more Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r 2 = 0.747) and Yellowfin Tunas (r 2 = 0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments. Metal bioaccumulation was quantified in four species of pelagic fish.

Archives of Environmental Contamination and Toxicology, 2006

Seabird tissues collected between 2002 and 2004 from Barau's Petrel (Pterodroma baraui), Audubon'... more Seabird 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.

Waterbirds, 2008

We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13... more We determined whether lipid extraction of seabird muscle, liver and feathers is required for δ 13 C and δ 15 N analysis, based on a study of Barau's Petrels ( Pterodroma baraui ) and White-tailed Tropicbirds ( Phaethon lepturus ). Samples were analyzed for stable isotopes before and after lipid removal. Lipid-free muscle and liver were significantly enriched in 13 C compared to those containing lipids (0.52‰ and 0.61‰ mean differences in δ 13 C respectively) implying that lipids should be extracted from these tissues to avoid effects of uncontrolled differential lipid content. However lipid extraction also slightly increased muscle δ 15 N values in tropicbirds. Researchers should thus run samples separately for δ 13 C and δ 15 N analysis, extracting lipids only in aliquots in which δ 13 C is measured, or apply arithmetic δ 13 C normalization methods on non lipid-extracted samples. Predictive models developed from our data, inferring δ 13 C values of lipid-extracted material from δ 13 C values and C:N ratios of non lipid-extracted material are presented and compared to five normalization methods taken from literature. Our models showed the best prediction efficiencies followed by that developed by . In feathers, no difference in stable isotopic measurements were noted between aliquots treated with sodium hydroxide or 2:1 chloroform:methanol. Both protocols seem suitable for preparing feather samples for isotopic analysis.

Science of The Total Environment, 2007

Breast feathers were used to estimate mercury levels in six marine birds nesting in the tropical ... more Breast 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.

Marine Ecology Progress Series, 2008

Stable nitrogen and carbon isotopes were used to investigate trophic ecology in tropical marine b... more Stable 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.

Marine Biology, 2008

Over 6-million pairs of sooty terns Sterna fuscata breed once a year in the southwest Indian Ocea... more Over 6-million pairs of sooty terns Sterna fuscata breed once a year in the southwest Indian Ocean, mostly on three islands of the Mozambique Channel (Europa, Juan de Nova and Glorieuses) and in the Seychelles region. Seasonal reproduction in either winter or summer is the dominant strategy in the area, but nonseasonal reproduction also occurred in some places like at Glorieuses Archipelago. The feeding ecology of the sooty tern was investigated during the breeding seasons to determine whether terns showed signiWcant diVerences in their trophic ecology between locations. Regurgitations were analyzed to describe the diet of individuals when breeding, and stable isotopes and mercury concentrations were used to temporally integrate over the medium-term of the trophic ecology of both adults and chicks. Overall, the diet was composed of Wsh, Xying squid and Wsh larvae in diVerent proportions. At Europa and Aride in the Seychelles, where winter reproduction occurs, large epipelagic prey like Xying Wsh or squid dominated the diet. At Juan de Nova, sooty terns reproduce in summer and rely mostly on Wsh larvae. At Glorieuses (non-seasonal breeding), the diet was intermediate with Wsh larvae and Xying squid being important prey items. The stable-carbon and nitrogen isotope values in blood conWrm the diVerences observed in dietary analysis, and demonstrate diVerent feeding strategies between colonies. 13 C values of feathers showed spatial segregation between birds from the Mozambique Channel and the Seychelles region. Terns from the Seychelles had also higher 15 N values. Feather 13 C values also suggest a sig-niWcant shift from summer to wintering habitat for birds from Juan de Nova. This study emphasizes the high phenotypic plasticity of the species, which may explain its numerical dominance in all tropical waters of the World's Ocean.

Marine Biology, 2008

Nitrogen ( 15 N) and carbon ( 13 C) stable isotopes and contaminants, such as mercury, have been ... more Nitrogen ( 15 N) and carbon ( 13 C) stable isotopes and contaminants, such as mercury, have been widely used to characterise foraging ecology of temperate and polar seabirds. In this study, for the Wrst time, we used isotopic signatures and mercury levels of feathers and blood of eight tropical seabird species, that forage in a range-gradient between inshore and oVshore areas, to describe the foraging habits of a large tropical seabird community (from two neighboring islands of the Seychelles archipelago, western Indian Ocean) during both the breeding and interbreeding periods. Overall, we found a high overlap in both 15 N and 13 C signatures among species. The high inter-speciWc overlap in 15 N values was expected, given the similarities in the diet of the species from this community. However, several unexpected results, such as (1) the consistently higher 15 N signatures of white terns (Gygis alba), (2) the large variation in inter-speciWc diVerences in 15 N signatures among the sampling groups (season, age, island and tissue) and (3) the consistent low 15 N values of breeding birds during the northwest monsoon (austral summer), suggest that 15 N signatures cannot be used as indicators of seabird trophic levels in this community. The high inter-speciWc overlap in 13 C signatures and the absence, during the breeding season, of a 13 C gradient that follows the inshore-oVshore foraging gradient within the community can be explained by the habitat homogeneity of the Seychelles continental shelf and suggest that birds forage mostly within the limits of this "plateau". On the other hand, the similarities in 13 C values between the breeding and inter-breeding periods in species that are known to show post-breeding dispersal, strongly support the hypothesis of a lack of latitudinal variation in 13 C signatures of POM in the central Indian Ocean, and the consequent inaccuracy of 13 C values to track seabird movements within this geographic area. Inter-speciWc diVerences in mercury levels seem to be related to prey size, while consistent higher mercury concentrations in one of the studied islands suggest diVerent island mercury-backgrounds and possible segregation in foraging areas between the seabirds of the two islands. Communicated by R. Lewison.

Journal of Sea Research, 2014

In ecological systems, it is necessary to describe the trophic niches of species and their segreg... more In ecological systems, it is necessary to describe the trophic niches of species and their segregation or overlap to understand the distribution of species in the community. In oceanic systems, the community structure of top predators such as seabird communities has been well documented with many studies in several biogeographical areas. But for coastal habitats, very few investigations on the trophic structure have been carried out in avian communities. In this study, the trophic resource partitioning was investigated on eight of the most abundant species of a shorebird community on the central Atlantic coast of France. Our work comprised a comprehensive sample of birds with different ecomorphogical patterns and data on their main prey to encompass potential sources of overlap and segregation in this community. We examined the stable carbon (δ 13 C) and nitrogen (δ 15 N) isotopic composition of blood to investigate the trophic structure (1) on a temporal scale by comparing migration and wintering periods; (2) on a spatial scale through inter-site comparisons; and (3) on the community level within groups of phylogenetically related species. Diets appeared different in several cases between periods, between sites and between juveniles and adults for the same sites. A clear trophic partitioning was established with four functional groups of predators in winter inside the community. The Grey Plover, the Bar-tailed Godwit, the Curlew and a majority of the dunlins were worm-eaters mainly feeding on Nereis diversicolor or Nephtys hombergii. Two species were predominantly deposit-suspensivorous mollusc-eaters, including the Red Knot and the Black-tailed Godwit feeding mainly on Macoma balthica. The Oystercatcher fed mainly on suspensivorous molluscs like Cerastodrema edule and two species including the Redshank and some dunlins adopted opportunistic behaviours feeding on mudflat and/or in marshes.

Environmental Pollution, 2007

Trace elements were analyzed in fish of commercial interest to determine their importance in mari... more Trace elements were analyzed in fish of commercial interest to determine their importance in marine systems of the Western Indian Ocean and their bioaccumulation patterns. The results are equivalent or lower than levels reported in ichthyofauna worldwide. Certain values of muscular Cd, Hg, Pb and Zn were, however, above thresholds for human consumption. Levels varied among tissues, species and fish length, but were seldom influenced by the nutritional condition of the fish, its gender and its reproductive status. Correlations between hepatic Hg and Se levels in Swordfish (r 2 = 0.747) and Yellowfin Tunas (r 2 = 0.226), and among metallothionein linking metals imply the existence of detoxification processes in these species. Level differences between fish from the Mozambique Channel and Reunion Island reflect differences of diets rather than differences of elemental availability in both environments.