14.02.2024: Mercury is an environmental pollutant that raises concerns worldwide due to its toxicity and risks to both wildlife and human health – a point emphasized by the World Health Organization (WHO). This environmental toxin is found even in remote, untouched areas such as the Amazon, endangering the local wildlife. This is revealed in a recently published international study led by the Konrad Lorenz Institute for Comparative Behavioral Research (KLIVV) at the University of Veterinary Medicine Vienna, focusing on the poison frog Dendrobates tinctorius.

Artisanal and small-scale gold mining (ASGM) has become a major threat to South American forests. This method of gold extraction is a significant cause of small-scale deforestation and the largest contributor to mercury emissions into the atmosphere and freshwater systems worldwide. Previous studies have already highlighted the effects of mercury accumulation on various aquatic ecosystems and organisms. However, the consequences for other systems, such as small water-retaining plant structures (phytotelmata) and the organisms living within them, have gone unnoticed until now.

Focus on aquatic nurseries of Dendrobates tinctorius

A research team led by KLIVV at Vetmeduni (study's first author Lia Schlippe-Justicia; study's last author Bibiana Rojas) investigated this issue in French Guiana, focusing on the native poison frog Dendrobates tinctorius. The researchers focused on phytotelmata, small pools, for example, in the root area of plants, and other aquatic microenvironments, such as water in discarded containers.

High mercury levels from an early stage

In these typical breeding sites for Dendrobates tinctorius tadpoles, the researchers found high mercury concentrations. "In 17% of cases, we were able to detect very high mercury concentrations, particularly near known ASGM sites. However, we could not observe any influence of mercury concentration on the number of tadpoles in a given pool," says Lia Schlippe-Justicia. Tadpoles were also found in pools with extremely high concentrations, up to 8.68 ppm, suggesting that "D. tinctorius fathers do not seem to avoid pools with high mercury concentrations for tadpole deposition," according to Schlippe.

Negative effects on physical development

The research team also documented a significantly negative impact on amphibians, as reported by Bibiana Rojas: "Tadpoles in later developmental stages exhibited poorer body condition when growing up in pools with higher mercury concentrations. This underscores the need for further field and experimental studies examining the effects of mercury contamination on tadpole development and behavior, as well as the overall preservation of biodiversity in the Amazon."

 

The article „Poison in the nursery: Mercury contamination in the tadpole-rearing sites of an Amazonian frog“ by Lia Schlippe-Justicia, Jérémy Lemaire, Carolin Dittrich, Martin Mayer, Paco Bustamante and Bibiana Rojas was published in „Science of the Total Environment“.

Scientific article