Assessing the impact of chemical exposure on the health of endangered sea turtles through toxicokinetics and toxicodynamics

Abstract

The green sea turtle, Chelonia mydas, spends a considerable part of its life in coastal waters foraging on seagrass and/or algae, which brings it close to anthropogenic pollutant sources. Elevated concentrations of chemical contaminants from urban, industrial and agricultural run-off accumulate in coastal environments. These pollutants have the potential to cause serious harm to C. mydas populations. However, exposure and toxicity data are challenging to obtain for free-ranging, protected wildlife species like C. mydas. Furthermore, a lack of quantitative tools linking long-term external contaminant exposure, the uptake and tissue distribution of chemicals (toxicokinetics), and the biological pathway perturbations related to adverse health outcomes (toxicodynamics) hamper efforts by scientists and policymakers to quantify the risk of pollutants adversely affecting C. mydas health. Changes in C. mydas population abundance, in turn, may affect the marine seagrass ecosystems, which, by extension, could potentially also impact human health and animals that rely on seagrass habitats. The present thesis provided the means to research the hypothesis that land-based contaminants adversely impact the health of Australia’s resident green turtle populations. The following chapters in this thesis investigate the validity of this hypothesis. Valuable experimental toxicokinetic and toxicodynamic data are collected and described in Chapters 2 and 3. Chapter 4 used data from Chapter 3 to develop tools to confirm the initial hypothesis. Overall, this thesis describes the development of tools to aid risk assessors and policymakers in setting safe chemical exposure levels for green sea populations.