bisi rt 2010 carbon and nitrogen stable isotope
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XIV Reunião de Trabalho de Especialistas em Mamíferos Aquáticos da América do Sul (RT) 8º Congresso da Sociedade Latinoamericana de Especialistas em Mamíferos Aquáticos (SOLAMAC)
Florianópolis (SC), 24 a 28 de outubro de 2010
Sociedade Latinoamericana de Especialistas em Mamíferos Aquáticos – SOLAMAC
CARBON AND NITROGEN STABLE ISOTOPE DIFFERENCES IN Sotalia guianensis DOLPHIN FROM RIO DE JANEIRO COAST, BRAZIL
Bisi, T. L.1,2,3; Lailson-Brito, J.3; Lepoint, G.4; Azevedo, A. F.3; Dorneles, P. R.2; Flach, L.5; Malm, O.2;
Das, K.4
1 Programa de Pós-Graduação em Ecologia (PPGE), Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brasil. [email protected]
2 Laboratório de Radioisótopos, Instituto de Biofísica, Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brasil
3 Laboratório de Mamíferos Aquáticos e Bioindicadores "Profa. Izabel Gurgel" (MAQUA), Faculdade de Oceanografia, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, Brasil
4 Centre MARE, Laboratoire d’Oceanologie, Université de Liége, Belgique
5 Projeto Boto-Cinza, Mangaratiba, Brasil Guiana dolphin (Sotalia guianensis) is a small delphinid that inhabits coastal waters from South and Central Americas, occurring from southern Brazil to Nicaragua. The species presents site fidelity to bays of Rio de Janeiro State, where the same individuals are found year round. In this study, carbon and nitrogen stable isotopes were measured in muscle of Guiana dolphins from Guanabara Bay (n=20), Sepetiba Bay (n=44) and Ilha Grande Bay (n=10), in order to investigate possible trophic distinctions among the three populations. Stable isotope measurements were performed on a V.G. Optima (Micromass) IR-MS coupled to an N-C-S elemental analyzer (Carlo Erba). Males and females were not significantly different in δ13C and δ15N values for dolphins from Guanabara (Mann-Whitney Test, Uδ13C =39, p=0.7; Uδ15N =43, p=0.9; nmale=11 and nfemale=8) and Ilha Grande bays (Mann-Whitney Test, Uδ13C =4, p=0.2; Uδ15N =5, p=0.3; nmale=6 and nfemale=3), suggesting that sex does not influence prey selection in these environments. On the other hand, females showed higher trophic level than males in Sepetiba Bay (mean δ15N: 14.5 and 13.8‰, respectively) (Mann-Whitney Test, U=79, p<0.002; nmale=32 and nfemale=12). Guiana dolphins from Guanabara (-14.0‰ ± 0.7) and Sepetiba bays (-14.6‰ ± 1.0) were significantly more 13C-enriched than those from Ilha Grande Bay (-16.6‰ ± 0.4) (ANOVA F2,71= 29.45, p<0.00001; Tukey HSD test, p<0.0001). Sepetiba and Ilha Grande Bays are two adjacent areas that are not separated by a physical barrier. However, our findings suggest the use of different feeding grounds by these two populations, which corroborates the pattern of residence and site fidelity described for the species. Regarding δ15N values, no differences were observed among Guiana dolphins from Guanabara (14.2‰ ± 0.9), Sepetiba (14.1‰ ± 0.6) and Ilha Grande bays (14.2‰ ± 0.65) (ANOVA F2,71= 0.38, p=0.68). Data from stomach contents showed that there was a partial overlap in Guiana dolphin prey species among the three bays, but there was difference regarding the most common preys in each environment. The trophic relationships between Guiana dolphins and their prey species in these bays should be further investigated for a better understanding of the results generated by the present study. Keywords: marine mammal, coastal waters, trophic relationship Financial support: CAPES (fellowship), “Pensa Rio” Program/FAPERJ (Proc. E-26/110.371/2007), APQ1-2009/1 - FAPERJ (Proc. E26-110.858-2009), Universal/CNPq (480701/2009-1) and Cetacean Society International grant.