# Metal Concentrations (Mg, Fe, Zn, Cu, Cd, Pb) in the Plasma and Cell Concentrates of Chelonia mydas and Lepidochelys olivacea from Costa Rica

## TL;DR

This study measured metal levels in blood samples of green and olive ridley sea turtles in Costa Rica to assess marine pollution and health risks.

## Contribution

The study provides one of the earliest large-sample baselines for trace elements in sea turtle blood in the Eastern Tropical Pacific and Western Caribbean.

## Key findings

- Essential elements like Mg and Cu were higher in plasma, while Fe and Zn were higher in cell concentrates.
- Green turtles had higher Cu, Fe, and Zn levels in plasma, while olive ridleys showed higher Cd concentrations.
- Lead levels were low in both species compared to global data.

## Abstract

Sea turtles are widely used as bioindicators for assessing marine pollution, since they have a long lifespan, migrate across large oceanic areas and integrate into the environment over time. Measuring trace elements in their blood provides information regarding both environmental contamination and potential health risks. In this study, magnesium, iron, zinc, copper, cadmium and lead levels were measured in the plasma and red blood cells of green turtles (Chelonia mydas) and olive ridley turtles (Lepidochelys olivacea) from the Caribbean and Pacific coasts of Costa Rica. The blood was analyzed, since it reflects both recent exposure (plasma) and longer-term internal regulation (cell concentrates). The results were compared both between the blood compartments in the two species and with previously published data from other geographic areas and time periods. Essential elements showed different distributions between the plasma and the cell concentrates, confirming their physiological regulation in reptiles. Green turtles had generally higher iron and copper levels, likely related to diet, while olive ridleys showed higher cadmium concentrations, suggesting greater exposure in the Pacific basin. The lead concentrations were low in both species. This study provided baseline blood trace element data for sea turtles in Costa Rica and supported the usefulness of blood analyses for long-term environmental monitoring.

Sea turtles are increasingly being used as bioindicators of marine pollution, yet baseline data on trace elements in the blood are still limited. This study quantified magnesium (Mg), iron (Fe), zinc (Zn), copper (Cu), cadmium (Cd) and lead (Pb) in green turtles (Chelonia mydas) (55 plasma samples and 71 cell concentrate samples) and olive ridleys (Lepidochelys olivacea) (101 plasma samples and 65 cell concentrate samples) sampled off the Caribbean (Tortuguero) and Pacific (Ostional) coasts of Costa Rica in 2003–2004. The metals were measured using atomic absorption spectroscopy; whole-blood concentrations were derived from the plasma and the erythrocyte values. The present results were compared with published datasets to evaluate the spatial and temporal patterns of metal exposure over the past two decades. The essential elements showed matrix-specific distributions, with Mg and Cu higher in the plasma, and Fe and Zn higher in the cell concentrates in both species (p < 0.001). C. mydas generally exhibited higher Cu, Fe and Zn levels in the plasma (p < 0.001), whereas L. olivacea showed markedly higher Cd levels (p < 0.001). Overall, the Pb levels were low as compared with many other rookeries worldwide. These data provide one of the earliest, large-sample baselines for trace elements in sea turtle blood in the Eastern Tropical Pacific and Western Caribbean and underscore the value of blood-fraction analysis for long-term ecotoxicological monitoring.