Non-Lethal Assessment of Potentially Toxic Elements Across Mammalian Trophic Levels in African Savannahs

Andrea B Webster,Nigel C Bennett,Andre Ganswindt,Javier F Callealta

doi:10.3389/fenvs.2021.794487

Abstract

South Africa is one of the most diverse countries in the world but the increase in agricultural, industrial and technological development to meet the needs of the growing human population has led to increased amounts of potentially toxic elements (PTEs) and other chemicals in the environment. As regional and global environmental processes influence local conditions to differing degrees, all organisms within a specific environment are exposed to highly complex, ill-defined PTE and chemical mixtures. Differences in feeding strategies within and between vertebrate trophic levels are likely to influence the degree to which individuals may be exposed to and affected by PTE presence. Using vertebrate faeces as a biological matrix, we investigate and compare quantitative differences in PTE concentrations in herbivorous, omnivorous and carnivorous terrestrial vertebrates from two protected areas in South African savannah. Of the eleven PTEs assessed [aluminium (Al), arsenic (As), barium (Ba), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb), antimony (Sb), tin (Sn), strontium (Sr), and vanadium (V)], the highest concentrations of Al, As, Cr, Pb, Sn, and V were found in carnivores. General patterns were evident between groups at each site for specific elements, but absolute values for the same elements were site-specific. This is the first study to non-invasively examine and compare PTE concentrations in a variety of free-ranging mammalian wildlife occupying different trophic levels within South African protected areas. Our results confirm that all individuals across trophic levels within these sites are exposed to multiple and varied PTE mixtures on a continuous basis. Whether PTEs at these concentrations cause synergistic or antagonistic disruption of physiological and biological systems alone or in combination in free-ranging African wildlife species is still unclear and requires further investigation.

Highlights

Toxic elements (PTEs) have no established biological or physiological function (Järup, 2003)
Overall potentially toxic elements (PTEs) concentrations varied between individuals and between animal groups (Figure 2)
“Heavy metal” pollution rated highest of 22 themes related to emerging chemical management issues in developing countries that are not covered by international treaties (STAP, 2012)

Summary

Introduction

Toxic elements (PTEs) have no established biological or physiological function (Järup, 2003). Even when concentrations are too low to be individually effective, the combined action of multiple PTEs at low concentrations alone and in combination with other organic and synthetic chemicals can result in adverse effects (Rhind, 2009; Martin et al, 2021). The sequential and simultaneous exposure of wildlife to mixtures of synthetic compounds and PTEs from direct, indirect, past or contemporary exposures that interact in additive or synergistic ways, can disrupt various physiological systems resulting in subsequent negative cascading effects (Kortenkamp and Faust, 2018; Martin et al, 2021). The chemical form and abundance at which an element is present in the environment influences its availability for uptake by an organism (Kabata-Pendias, 2011; Olaniran et al, 2013)

Methods

Results

Conclusion