Heavy Metal Impacts: An Evaluation of Toxicological Concern in Stranded Odontocetes in Southern South America

Abstract

Heavy metals are ubiquitous elements of the Earth's crust. Due to their extensive use they are among the most common pollutants in marine ecosystems. Once in the aquatic system, heavy metals enter the food web and some are able to biomagnify, increasing concentrations in top predators. For animals located an the top of food webs, such as Odontocetes, they can reach extreme concentrations in their bodies and potentially constitute a toxicological threat. Stranding episodes provide opportunities to assess the occurrence and levels of pollutants in diverse tissues, including skin as a biomonitor organ. Here, tissular concentrations of heavy metals As, Ag, Cd and Hg in false killer whales are discussed. Studies have revealed a concerning amount of Hg and Ag in stranded specimens at the southern marine area of South America. The molar ratios of Se : Hg were assessed, aiding a potential protective effect of Se against Hg toxicity. The risks of As, Cd and Hg toxicities were evaluated by comparing measured concentrations with already known threshold benchmarks for marine mammals. The role of skin in marine mammals for pollution bioindication by analyzing biopsies extracted from living animals is discussed here with a focus on the use of this tissue as a proxy for free-range populations.