Heavy metals and trace elements in a threatened population of guanay cormorants (Leucocarbo bougainvilliorum) from an industrialized bay in the Humboldt Current System, Chile

Metal contamination from industrial and mining activities threatens coastal and marine ecosystems, leading to bioaccumulation in marine organisms and biomagnification through the trophic chain. The Guanay cormorant (Leucocarbo bougainvilliorum), an endemic species of the Humboldt Current System, is experiencing population declines and serves as a key bioindicator of heavy metal contamination due to its high trophic position, reliance on commercially exploited pelagic fish, and capacity to accumulate contaminants over time. This study analyzed the concentrations of five heavy metals (Hg, As, Pb, Cr, Cd) and three trace elements (Cu, Zn, Se) in liver, muscle, feathers, and kidney of 10 Guanay cormorants found dead in Mejillones Bay, Chile, a highly industrialized area. Feathers exhibited the highest concentrations of Cr (2.03 ± 0.63 mg/kg), Cu (19.72 ± 3.82 mg/kg), and Zn (109.84 ± 11.95 mg/kg), emphasizing their role in detoxification. Females showed significantly higher Cu and Pb concentrations in muscle and Cr in kidneys, likely due to physiological and hormonal differences related to reproduction. Correlations between metal concentrations across tissues suggest shared bioaccumulation mechanisms, while the Hg:Se molar ratio (e.g., 0.25 ± 0.04 in liver) indicated a protective role of Se against Hg toxicity. Metal concentrations were comparable to those reported in other marine cormorants but differed from freshwater populations, highlighting the influence of habitat on metal accumulation. Although current levels do not indicate acute toxicity, the ongoing population decline of Guanay cormorants underscores the need for long-term biomonitoring. Future research incorporating biochemical and enzymatic biomarkers is essential to assess potential sublethal effects and long-term ecological risks associated with heavy metal exposure in this species.