Trophic ecology of marine top predators from the Western Indian Ocean through the study of trace element bioaccumulation and stable isotope ratios.


French version

Jessica KOJADINOVIC

University of La Réunion
2003 / 2006

Research advisor: Paco Bustamante, Associate Professor at La Rochelle University, CRELA UMR 6217.

Scientific advisors: Matthieu Le Corre, Associate Professor at La Reunion University, ECOMAR, and Richard P. Cosson, Senior researcher at Nantes University, EMI EA 2663.

This work is funding by the Conseil Régional de La Réunion and the European Social Fund.

  Trophic ecology, Seabirds, Pelagic fish, Bio-indicators, Tropical ecosystems, Trace elements, Bioaccumulation,  Detoxification, ?¹³C, ?¹⁵N, Trophic levels.

  Knowledge on the biology and ecology of tropical marine species from the southern hemisphere is poor compared to that acquired in other regions of the world. This is true regarding the trophic ecology of marine birds and large pelagic fish from the Western Indian Ocean.  The trophic ecology of these top predators is difficult to study using traditional methods (such as stomach content analysis, observation...) because of their pelagic behavior and the great distances they cover. Researchers thus increasingly turn to bio-markers, such as trace elements and stable isotopes, to investigate on such animals.

The Western Indian Ocean is considered as pristine because of its geographical isolation. It is consequently an interesting “laboratory site” for tracking potential variations in environmental trace element levels, whether these variations be natural or anthropogenic.  

u      Obtain baseline levels of trace elements in marine ecosystems of the Western Indian Ocean through the study of bio-indicators (i.e. seabirds and pelagic fish).

u      Investigate on the potential health hazard for Man of element levels in large pelagic fish of commercial importance.  

u      Study bioaccumulation and detoxification processes of mercury (Hg), lead (Pb), cadmium (Cd), copper (Cu), iron (Fe), manganese (Mn), selenium (Se) and zinc (Zn) in five species of fish (Xiphias gladius, Tunnus albacares, Katsuwonus pelamis, Coryphaena hippurus et Acanthocybium solandri) and six species of seabirds (Sterna fuscata, Anous stolidus, Anous tenuirostris, Puffinus lherminieri, Pterodroma baraui et Phaeton lepturus).

u      Study the trophic ecology of the predatory species mentioned above, using trace elements and stable isotopes as bio-markers.

  • Sampling : Sampling of seabirds on Reunion Island, in Seychelles, in the Glorieuses Archipelago, on Juan de Nova and on Europa. Sampling of fish in waters surrounding Reunion Island and in the North of the  Mozambique Canal.

    • Trace elements : Top predators are exposed to trace elements through their prey. Studies have shown that predators feeding preferentially on fish have higher mercury levels than those which feed on squid, which in turn are vectors of cadmium transfer to higher trophic levels. The analysis of trace element levels in various tissues characterized by different turnovers (liver, kidney, muscle and bird feathers) have provided new information on the diets of the animals considered in my thesis. This knowledge is complementary to that acquired by researchers of the ECOMAR and IRD laboratories using traditional methods.

Furthermore, I have focused on better understanding the fate of mercury, lead, cadmium, copper, iron, manganese, selenium and zinc in each species through the understanding of their bioaccumulation and detoxification patterns.

   • Stable isotopes : The use of stable isotopes in ecology lies on the comparison of the following ratios, ¹³C/¹²C (?¹³C) and ¹⁵N/¹⁴N (?¹⁵N), in the proteins of the predators tissues with those of prey tissues. ?¹³C, which is hardly enriched from one trophic level to another (1‰), informs on the food chain source of carbon and characterizes water masses. This approach enabled me to glean comparative information on the foraging areas of the different species. Conversely, ?¹⁵N is enriched by 3 to 4‰ at each trophic level and, hence, informs on the predator's trophic level.

In the light of these two markers, I work on better understanding the trophic relationships that exist between top predators of various ecosystems of the tropical Western Indian Ocean.

Peer reviewed international journals

Ø       J. Kojadinovic, M. Potier, M. Le Corre, R.P. Cosson and P. Bustamante (2006), Mercury content in commercial pelagic fish of the Western Indian Ocean. The Science of the Total Environment, 21 pages, in press.

Ø       J. Kojadinovic, M. Le Corre, P. Bustamante, R.P. Cosson and M. Salamolard (2006) Preliminary results on trace element levels in three species of seabirds from Reunion Island (Western Indian Ocean). Ostrich, 13 pages, in press.

National journals

Ø       Kojadinovic J., Falquet M-P. and Conand C. (2004) Acanthaster planci on La Reunion reefs. Reef encounter, 32: 26-27 (Australia).

Submitted journals

Ø       J. Kojadinovic, M. Le Corre, R.P. Cosson and P. Bustamante (2006) Trace elements in three marine birds breeding on Reunion Island (Western Indian Ocean) – Part 1: Factors influencing their bioaccumulation, 26 pages, submitted for second review in Archives of Environmental Contamination and Toxicology.

Ø       J. Kojadinovic, P. Bustamante, M. Le Corre, and R.P. Cosson (2006) Trace elements in three marine birds breeding on Reunion Island (Western Indian Ocean) – Part 2: Factors influencing their detoxification, 20 pages, submitted for second review in Archives of Environmental Contamination and Toxicology.

Ø       J. Kojadinovic, M. Potier, M. Le Corre, R.P. Cosson and P. Bustamante (2006) Bioaccumulation of trace elements in pelagic fish from the Western Indian Ocean, 36 pages, submitted at Environmental Pollution.

Peer reviewed international conference acts

Ø       J. Kojadinovic, M-P. Falquet, P. Mangion, C. Conand (2004) Distribution, abundance and asexual reproduction of Asterina burtoni (Asteroidea: Echinodermata) from La Reunion reefs (Western Indian Ocean). In: Echinoderms: München - Heinzeller and Nebelsick (eds) - Taylor and Francis Group, London, p 225-229.

  Oral communications

Ø       Bioaccumulation of metals in three species of marine birds from Reunion Island (Western Indian Ocean). J. Kojadinovic, P. Bustamante and M. Le Corre - 11^th Pan Africain Ornithological Congress, 2004, Djerba, Tunisia.

Ø       Bioaccumulation de métaux dans les grands prédateurs marins de La Réunion (Océan Indien): cas de trois espèces d'oiseaux. J. Kojadinovic, P. Bustamante, M. Le Corre, R.P. Cosson & M. Salamolard - ``Jounées d'Ecologie Marine'' organised by the Société Française d'Ecologie, 2004, Nantes, France.

Ø       Distribution, abundance and asexual reproduction of Asterina burtoni (Asteroidea : Echinodermata) from La Reunion reefs (Western Indian Ocean), J. Kojadinovic, M-P. Falquet, P. Mangion & C. Conand - 11^th International Echinoderm Conference, 2003, Munich, Germany - Participation as chairman.

Ø       Oral communication on the Crown of Thorns starfish Acanthaster planci in a meeting organised by the association Vie Océane. J. Kojadinovic & M-P. Falquet, 2002, La Réunion, France.

Posters

Ø       Mercury levels in four species of fish from the Mascarene Archipelago and the Mozambique Channel (Western Indian Ocean). J. Kojadinovic, M. Potier, M. Le Corre, R.P. Cosson and P. Bustamante, 4^th Western Indian Ocean Marine Science Association (WIOMSA) Scientific Symposium, 2005, Grand Baie, Mauritius.

Ø       Influence of age, diet and reproductive status on trace element levels in three seabirds from Reunion Island (Western Indian Ocean). J. Kojadinovic, P. Bustamante, M. Le Corre and R.P. Cosson, Society of Environmental Toxicology and Chemistry (SETAC) Europe, 15^th Annual Meeting, 2005, Lille, France.