The impact of urban pollution on metal contamination of selected forest pockets in Cape Town, South Africa

A heavy burden: Metal exposure across the land-ocean continuum in an adaptable carnivore

Urbanisation and associated anthropogenic activities release large quantities of toxic metals and metalloids into the environment, where they may bioaccumulate and threaten both wildlife and human health. In highly transformed landscapes, terrestrial carnivores may be at increased risk of exposure through biomagnification. We quantified metallic element and metalloid exposure in blood of caracals (Caracal caracal), an adaptable felid inhabiting the rapidly urbanising, coastal metropole of Cape Town, South Africa. Using redundancy analysis and mixed-effect models, we explored the influence of demography, landscape use, and diet on the concentration of 11 metals and metalloids. Although species-specific toxic thresholds are lacking, arsenic (As) and chromium (Cr) were present at potentially sublethal levels in several individuals. Increased use of human-transformed landscapes, particularly urban areas, roads, and vineyards, was significantly associated with increased exposure to aluminium (Al), cobalt (Co) and lead (Pb). Foraging closer to the coast and within aquatic food webs was associated with increased levels of mercury (Hg), selenium (Se) and arsenic, where regular predation on seabirds and waterbirds likely facilitates transfer of metals from aquatic to terrestrial food webs. Further, several elements were linked to lower haemoglobin levels (chromium, mercury, manganese, and zinc) and elevated levels of infection-fighting cells (mercury and selenium). Our results highlight the importance of anthropogenic activities as major environmental sources of metal contamination in terrestrial wildlife, including exposure across the land-ocean continuum. These findings contribute towards the growing evidence suggesting cities are particularly toxic areas for wildlife. Co-exposure to a suite of metal pollutants may threaten the long-term health and persistence of Cape Town's caracal population in unexpected ways, particularly when interacting with additional known pollutant and pathogen exposure. The caracal is a valuable sentinel for assessing metal exposure and can be used in pollution monitoring programmes to mitigate exposure and promote biodiversity conservation in human-dominated landscapes.

Effects of Excess Manganese on the Oxidative Status, and the Expression of Inflammatory Factors and Heat Shock Proteins in Cock Kidneys

Manganese (Mn) can have adverse effects on organisms as a result of heavy or chronic exposure, including neurological damage. This study examined the effects of chronic exposure to manganese chloride (MnCl₂) on various biochemical indices of inflammatory cytokines, antioxidant enzymes, and heat shock proteins (HSPs) in the kidneys of Hy-line cocks. The exposures were carried out using 600, 900, or 1800 mg/kg doses of MnCl₂ administered for periods of 30, 60, and 90 days. The exposure experiments indicated that Mn concentration in the kidneys increased over time and that Mn exposure potentially caused ultrastructural changes to the cells. Treatment with Mn was seen to increase the levels of various biomarkers, including protein carbonyl group content; DNA-protein cross-links (DPCs) and the mRNA expression of inflammatory factors such as tumor necrosis factor-α (TNF-α), nuclear factor-κB p50 (NF-κB p50), cyclooxygenase-2 (COX-2), and prostaglandin E synthase (PGES). The levels of other biomarkers were found to decrease as a result of Mn exposure, including the mRNA expression of oxidation indexes such as copper-zinc superoxide dismutase (CuZn-SOD), manganese superoxide dismutase (Mn-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT). Accompanying the above changes, Mn exposure was seen to result in the relative mRNA and protein expression of HSPs 90, 70, 60, 40, and 27 increasing significantly. Thus, in cock kidneys, HSPs attenuated the biological changes caused by toxic exposure to Mn. This mechanism needs further exploration.