Small cetaceans found stranded or accidentally captured in southeastern Brazil: Bioindicators of essential and non-essential trace elements in the environment

•Trace elements were analyzed in hepatic tissue of small cetaceans.•Some elements were significantly higher compared to other studies around the world.•CdxSe, CuxZn and HgxSe strong positive correlations were found for Guiana dolphins.•Differential elements accumulation was observed, probably due to feeding habits.•This is the first report of trace elements in pygmy killer whale liver.

Essential (Cu, Mn, Se and Zn) and non-essential (Cd and Hg) elements were analyzed in the hepatic tissue of 22 individuals of seven different species of small cetaceans (Feresa attenuata; Orcinus orca; Pontoporia blainvillei; Sotalia guianensis; Stenella frontalis; Steno bredanensis; Tursiops truncatus) accidentally caught in fishing nets or found stranded along the northern coast of the state of Rio de Janeiro, Brazil, between 2001 and 2010. Atlantic spotted dolphin (S. frontalis) showed the highest levels of Cd (20.23 μg g−1, dry weight), while rough-toothed dolphin (S. bredanensis) showed the highest levels of Hg (825.9 μg g−1 dw) and Se (221.9 μg g−1 dw). Killer whale (O. orca) presented the highest levels of Cu (64.80 μg g−1 dw) and Zn (2220 μg g−1 dw), and Guiana dolphin (S. guianensis), the highest level of Mn (13.05 μg g−1 dw). Cu, Hg, Mn and Zn in the hepatic tissue of killer whale (O. orca), Cu, Hg, Mn, Se and Zn in the hepatic tissue of rough-toothed dolphin (S. bredanensis) and Cd and Zn in the hepatic tissue of Guiana dolphin (S. guianensis) were significantly higher when compared to other studies with these species around the world. No significant correlations were observed between element accumulation and sex, sexual maturity and body length. An analysis of the interelemental relationships in the Guiana dolphin specimens showed strong positive correlations between Cd and Se, Cu and Zn, and Hg and Se. Differences were observed in the bioaccumulation of elements between the analyzed species, probably related to each species feeding habit, and differences between different element concentrations in the different dolphin species were probably due to the preference for certain preys and their bioavailability in the environment. Thus, the bioavailability of the analyzed elements in the marine environment should also be taken in consideration. This study also presents the first data ever reported for pygmy killer whale (F. attenuata) regarding trace element concentrations in hepatic tissue.

Graphical abstractThe higher the discharge of elements and contaminants in the oceans, the higher the intake of these in the food chain, causing harm to marine life and, consequently, to man.Figure optionsDownload full-size imageDownload as PowerPoint slide