Heavy metal contaminants in eggs and hatchlings of olive ridley turtles (Lepidochelys olivacea) at a mass nesting rookery in India

Abstract

Heavy metal pollution has emerged as a prominent threat in recent times with high metal levels widely reported in species across ecosystems. The threat of rapid biomagnification is particularly enhanced in species such as olive ridley turtles, which occupy a higher trophic position, increasing their exposure to heavy metals. In the current study, we examine the presence of heavy metals in adults, in-utero and oviposited eggs, hatchlings as well as the nesting beach at two important olive ridley rookeries in India – Devi and Rushikulya. We collected muscle and in-utero egg samples from stranded adult olive ridleys at the two rookeries, while oviposited eggs, hatchling and sand samples were obtained from hatchery nests at Rushikulya. We compared concentrations of 9 heavy metals (Cr, Mn, Ni, Co, Cu, As, Se, Cd, and Pb) across different sample types in an Inductively Coupled Plasma Mass Spectrometer (ICP-MS). We found mean metal concentrations of sand to be highest among all samples analysed, followed by muscle tissue. Arsenic was the most prominent metal in adult turtles suggesting bioaccumulation, while Selenium was found to be higher in egg components. Heavy metals (HM) were found in-utero eggs, providing evidence of maternal transfer. Most HMs were similar for in-utero and oviposited eggs, though a few metals were higher in in-utero eggs suggesting potential leaching out during development. Sand and hatchling samples show a high correlation for Mn suggesting potential environmental transfer. These findings emphasise the risk posed by heavy metals to adult and early life stages of olive ridleys and highlight the urgent need for mitigation of these threats.