Metallic elements in aquatic herpetofauna (Crocodylia; Testudines) from a lentic Atlantic rainforest environment in northeastern Brazil

In the present study, Fe, Cu, Cr, Cd, Pb, Ni, and Al concentrations in Caiman latirostris and Testudines blood from the Tapacurá reservoir, Pernambuco, Brazil, were investigated. Blood was acid digested with HNO3, and metals were determined by ICP-OES and FAAS. Lead showed concentrations below the established limit of detection. Eighty animals were evaluated, forty from each group. The levels of all elements were statistically significant when compared between the two studied taxa (p < 0.05). In caimans, significant differences between young and adults were observed for chromium (p = 0.0539) and aluminum (p = 0.0515). Testudines showed no statistically significant differences for the variable age structure. Gender did not influence metal concentrations detected in the present study for either group. Differences between species of testudines were significant for Fe between Mesoclemmys tuberculata vs Phrynops geoffroanus (p = 0.0932) and Kinosternon scorpioides vs Phrynops geoffroanus (p = 0.063). The inter-elementary correlations showed statistically significant differences between the elements Cr vs Al (R2 = 0.52), Cr vs Cd (0.43), Cd vs Cu (R2 = 0.41), Ni vs Cu (R2 = 0.31), Ni vs Cr (R2 = 0.30), Al vs Cd (R2 = 0.27), and Cd vs Fe (R2 = 0.26). It is concluded that blood is an excellent predictor of metals in crocodilians and testudines in the Tapacurá reservoir, with statistically significant differences when correlated to concentrations such as size and species studied. In addition, it evidenced data that prove the exposure of these animals to metals, with strong inter-elementary correlations and opening doors for future studies that seek to understand possible biological effects caused in the studied taxa.