An assessment of contaminant concentrations in toothed whale species of the NW Iberian Peninsula: Part II. Trace element concentrations

Abstract

Concentrations of Ag, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V and Zn were investigated in the liver and kidney of the five most common toothed whales off the Northwest Iberian Peninsula (NWIP), specifically common dolphin, long-finned pilot whale, harbour porpoise, striped dolphin and bottlenose dolphin. Differences were observed in the bioaccumulation of the above elements between the five species. The differences are probably related to biological factors such as age and sex and/or to ecological factors specific to each species such as feeding habits or bioavailability of the various elements. However, no significant relationship was observed between element accumulation and sex. Pilot whale and striped dolphin showed the highest concentrations of renal Cd and the highest concentrations of hepatic Hg and Se, while bottlenose dolphin showed the highest concentrations of Hg in kidneys. An analysis of inter-elemental relationships showed strong positive correlations between Hg and Se in the five species, however most individuals have Hg:Se molar ratio less than 1:1 indicating an excess of Se compare to Hg. This result, probably reflect the high proportion of young animals in the sample available for this study and/or that these animals had a good health status. We also observed a positive correlation in striped dolphins between Cd and Cu and between Cd and Zn in kidneys. In addition, comparing with other studies world-wide, the element concentrations (Hg and Cd) found in Iberian toothed whales indicate that these populations are not specially threatened by Hg and Cd exposure in the area.

Mercury and selenium status of bottlenose dolphins ( Tursiops truncatus ): A study in stranded animals on the Canary Islands

“…Moreover, the largest specimens may capture bigger prey, which are more likely to contain higher levels of Hg. Although essential trace elements are regulated via homeostasis in marine mammals (Mendez-Fernandez et al, 2014), Se levels in liver samples were notably higher in adults than in the youngest individuals ( Fig. 1) and were also correlated with animal length (r s = 0.764) in accordance with other studies (Woshner et al, 2001).…”

“…In the present study no influence of sex on Hg or Se accumulation was observed, as has been found in other marine areas of the North Atlantic Ocean (Mendez-Fernandez et al, 2014).…”

“…Se was in molar excess of Hg in 11 of 29 livers evaluated (37.9%). Other publications reported a similar levels of Se compared to Hg in both pelagic fish (Kaneko and Ralston, 2007) and cetaceans (Mendez-Fernandez et al, 2014), and the authors stated that this excess reflects the good health status of individuals or a high proportion of young animals. In the present study, individuals with a Se/Hg molar ratio above 1 were all included in older categories (Fig.…”

“…Furthermore, Se competes with Hg for its various biological targets, which also contributes to lowering the potential toxicity of Hg (Khan and Wang, 2009). Therefore, the Se/Hg molar ratio has been widely used (McHuron et al, 2014;Mendez-Fernandez et al, 2014;Squadrone et al, 2015;Vos et al, 2003), and many authors have established that Se, in a molar ratio of 1:1 or above with Hg, protects against the toxic effects of this metal (Ganther et al, 1972;Ralston and Raymond, 2013;Ralston et al, 2007;Ralston and Raymond, 2010;Sormo et al, 2011;Squadrone et al, 2015). However, paradoxically, this protective action can be harmful to the body because complex formation also results in the sequestration of both elements, causing them to become biologically unavailable (Martoja and Berry, 1980).…”

Th2 cytokine bias induced by silver nanoparticles in peripheral blood mononuclear cells of common bottlenose dolphins (Tursiops truncatus)

“…A variety of infections caused by intracellular pathogens in cetaceans have been reported and may be associated with the mass stranding events of cetaceans ( Cvetnic et al, 2016 ; Domingo et al, 1990 ; Domingo et al, 1992 ; Dubey et al, 2007 ; Dubey et al, 2008 ; Mazzariol et al, 2016 ; Mazzariol et al, 2017 ). In addition, previous studies suggested that Ag contamination exists in all aspects of the marine ecosystem, and cetaceans may have been negatively affected by Ag contamination ( Becker et al, 1995 ; Caceres-Saez et al, 2013 ; Chen et al, 2017 ; Dehn et al, 2006 ; Kunito et al, 2004 ; Li et al, 2018a ; Mendez-Fernandez et al., 2014 ; Reed et al, 2015 ; Rosa et al, 2008 ; Seixas et al, 2009 ; Woshner et al, 2001 ). The direct correlation between the infection of intracellular pathogens and the severity of Ag contamination in cetaceans is worth studying.…”