Mercury Levels in Muscle of Six Species of Turtles Eaten by People Along the Rio Negro of the Amazon Basin

Abstract

Mercury levels in the Amazon River are generally high, but there are no published studies on Hg levels in turtles from the region. In this study, levels of Hg were examined in the muscle of six species of turtles in the Rio Negro in the Amazon basin of Brazil, including Podocnemis unifilis, Podocnemis expansa, Podocnemis erythrocephala, Podocnemis sextuberculata, Peltocephalus dumerilianus, and Chelus fimbriatus. It is important to analyze Hg levels in chelonians in this region because of the potential health risk to humans and other receptors that eat them, as well as their potential use as bioindicators. The effect of sex, weight, and carapace length on Hg concentrations in turtle muscle was examined to determine if the levels represent a health risk to riverine people. There was a significant interspecific difference in Hg levels but no differences as a function of size or gender. The highest Hg level was found in Chelus fimbriatus (mean = 432 ppb, standard deviation +/- 196 ppb), followed by Peltocephalus dumerilianus (106 +/- 41 ppb), Podocnemis expansa (62 +/- 49 ppb), P. sextuberculata (61 +/- 40 ppb), P. unilifis (35 +/- 17 ppb), and P. erythrocephala (33.1 +/- 17 ppb). Of the species studied, the piscivorous C. fimbriatus had the highest Hg level. Hg levels in turtles were similar to the levels found in fish from the same basin. Levels of Hg in the muscle of C. fimbriatus are sufficiently high to pose a potential risk to humans who consume them. This study represents the first comparative study of Hg levels in muscle of six species of turtles.

Mercury concentration in different tissues of Podocnemis unifilis (Troschel, 1848) (Podocnemididae: Testudines) from the lower Xingu River – Amazonian, Brazil

“…Finally, a negative correlation between Hg concentration and size, as in the result of this study, has been reported in similar studies with other Podocnemis species such as Podocnemis erythrocephala (Spix, 1824) and Podocnemis sextuberculata (Boulenger, 1889) (Schneider et al, 2009(Schneider et al, , 2010. The idea of changes in diet during growth as observed in Vogt and Benitez (1993) and Vogt (2008) could explain this result.…”

“…Results might reflect that Hg levels in P. unifilis are similar to levels found in herbivorous fish from other Amazonian basins (Lima et al, 2000;Barbosa et al, 2003). Similar Hg levels were found in P. unifilis from Negro River, a river with a natural occurrence of high Hg environmental contamination (Schneider et al, 2010). Thus, one can say that the lower Xingu River, like many other Amazon basin rivers, has occurrence of mercury in a bioavailable form for accumulation in organisms.…”

Assessment of non-invasive techniques for monitoring mercury concentrations in species of Amazon turtles

“…However, to our knowledge no one has studied the carapace morphology of C. fimbriatus. Interspecific differences in Hg concentrations might be due to differences in food and foraging behavior, which are discussed in Schneider et al (2010).…”

“…In our study, chelonian species of the Podocnemididae family are opportunistic omnivores, feeding primarily on plants. Yet C. fimbriatus is a carnivorous predator that feeds on fish and invertebrates (Schneider et al 2010). The lack of correlation between size of the animal and the concentration of Hg might be due to the low concentration of Hg, possibly because they are eliminating Hg to reach equilibrium.…”

Mercury Concentration in the Spectacled Caiman and Black Caiman (Alligatoridae) of the Amazon: Implications for Human Health

“…Although there has been considerable attention devoted to determining Hg concentrations in fish, turtles, and humans (Belger and Forsberg 2006;Malm et al 1995;Schneider et al 2009Schneider et al , 2010Schneider et al , 2011Silva-Forsberg et al 1999), no data have been published concerning Hg concentrations in caimans of the Amazon. This is remarkable given that caimans are top carnivores, Hg concentrations are expected to be high, and humans are consuming them.…”