Heavy metal concentrations suggest pollution risk varies between sea turtle species in the northwest Atlantic Ocean

Abstract

Heavy metal pollution poses an increasing threat to marine life globally. Due to bioaccumulation, the risks of heavy metal pollution are particularly acute for large species at high trophic levels although this will vary based on a species' diet and foraging location. Here, we assessed exposure risk to heavy metal pollution in three sea turtle species: the green (Chelonia mydas), Kemp's ridley (Lepidochelys kempii), and loggerhead (Caretta caretta) turtles. Specifically, we collected skin and scute samples from deceased turtles found after cold-stunning in Cape Cod Bay, Massachusetts, USA (green: n = 8, Kemp's ridley: n = 30, loggerhead: n = 17). Using ICP-MS, we analyzed samples for aluminum, arsenic, cadmium, cobalt, chromium, iron, manganese, nickel, lead, selenium, silver, and zinc concentrations. Across all species, heavy metal concentrations were predominantly higher and more variable in scute than skin. When comparing species, PCA analysis revealed loggerhead turtles had the least variability in metal heavy concentrations, potentially driven by a generalist foraging strategy, relative to green and Kemp's ridley turtles. Nevertheless, all three species had concentrations of As and Cd near values considered toxic in vertebrates with loggerhead turtles having the highest concentrations. These findings underscore the importance of considering inter-specific differences when assessing the risks of heavy metal exposure in sea turtles and highlight As and Cd as key pollutants of concern in the northwest Atlantic.