Heavy metal accumulation in lizards living near a phosphate treatment plant: possible transfer of contaminants from aquatic to terrestrial food webs

Abstract

We investigated the accumulation of heavy metals in Bosk's fringe-toed lizards (Acanthodactylus boskianus) living in Gabès region (southeastern Tunisia), in relation to habitat, diet, and distance from the Gabès-Ghannouche factory complex of phosphate treatment. More specifically, we compared the concentrations of cadmium, lead, and zinc in the stomach contents and samples of the liver, kidney, and tail from lizards living in four sites corresponding to different combinations of habitat (coastal dunes vs backshore) and distance from the factory complex (<500 vs 20 km). Examination of stomach contents showed that lizards living on the coastal dunes mainly feed on littoral amphipods, while those living in the backshore feed exclusively on terrestrial invertebrates. The concentrations of heavy metals in lizard tissues were overall positively correlated with those in the preys they ingested. Moreover, there was a general tendency towards increased concentrations of cadmium, lead, and zinc in the samples from lizards living on coastal dunes compared to those from the other sites, although some differences still lacked statistical significance. These results suggest that the highest contamination of lizards living on coastal dunes was probably related to the ingestion of contaminated amphipods. Thus, amphipods and Bosk's fringe-toed lizards seem to provide an important link between the marine and terrestrial food webs, with higher concentrations appearing to accumulate from materials released into the sea rather than the terrestrial environment. With regard to metal distribution among tissues, our results were overall in agreement with previous findings in other reptiles. In particular, cadmium was most concentrated in the liver samples, stressing once more the role of the liver as a storage organ of Cd. Moreover, high concentrations of the three assessed metals were found in the kidney samples, showing the role of the kidney as an active site of heavy metal accumulation.

The Broad-Scale Analysis of Metals, Trace Elements, Organochlorine Pesticides and Polycyclic Aromatic Hydrocarbons in Wetlands Along an Urban Gradient, and the Use of a High Trophic Snake as a Bioindicator

“…2 suggests there is a strong relationship between sediment and snake liver concentrations within sites. These results are consistent with the general pattern of fauna contaminated by metals increases if the population is exposed to a source of contamination (Nasri et al 2017), in this case the sediment. Therefore, our results support the use of tiger snakes as a bioindicators of wetland ecosystem health based on (1) the evidence that they accumulate a range of metals, (2) their long life expectancy of up to 24 years (Fearn and Norton 2011), (3) their small home ranges (~0.05 km 2 ) (Butler et al 2005) especially in wetlands isolated by urbanisation, and (4) their high trophic position in the food chain as adults (thus being exposed to all of their prey's contaminants).…”

Spatial Distribution and Source Identification of Heavy Metals in Surface Waters of Three Coastal Areas of Tunisia

“…Previous studies have shown high levels of heavy metals in the coastal sediments close to the industrial complexes [61][62]. Particularly high concentrations were recorded in the site where the effluents are released: Cd>100 µg l , and Cr 100-120 µg l -1 [59,61]. The most important Ni and Co concentrations were observed in station 1, situated close to the phosphoric acid and fertilizer plant.…”

“…Station 28 was near the commercial harbor and belonged to GA with a high concentration of Zn. The Gabes region in southeastern Tunisia, is a polluted area where such a situation is expected to contribute to the transfer of heavy metals from the marine to the bordering terrestrial ecosystems [59]. This area is nowadays considered as a pollution hotspot mainly due to the operation of the Gabes-Ghannouch factory complex of phosphate treatment for acid and fertilizer production since the early 1970s [60].…”

“…With the absence of scavenging processes and treatment plants for industrial wastes, persistent toxic elements and heavy metals find their way into the sea. Alarmingly, 10,000 to 12,000 tons of phosphogypsum, containing heavy metals (mainly Cd, Pb, Zn, Cu, and Cr), are released in the sea of GA per day [59][60][61]. Previous studies have shown high levels of heavy metals in the coastal sediments close to the industrial complexes [61][62].…”

Tissue distribution of tetrabromobisphenol A and cadmium in mixture inhalation exposure

“…Metals are known hazardous substances and have also been widely detected in various environmental media including air, water, soil/sediment, and food (Zheng et al, 2013). Metals can be transferred through food chains and accumulated in vital organs of the human body (Nasri et al, 2015). Heavy metal cadmium (Cd) is applied in electroplating, pigment manufacture, printing and photographic industries, alloy preparation, and Cd batteries.…”