Egg yolk and albumen as biomonitoring tissues for organic pollution: Estimating mother-egg partitioning

The composition and concentration of chemical cocktails are often poorly established in marine environments particularly beyond the coastal zone. Marine migratory species could act as biomonitors to represent the exposure of associated communities, provided that suitable tissues for biomonitoring are available. Sea turtles could present suitable biomonitors because they integrate pollution across their long lifespan and wide migrations. They also do not feed during their nesting migrations, making their eggs potentially suitable biomonitoring tissues to reflect pollution in maternal foraging grounds. We investigated maternal transfer among 56 PCB, 12 OCP and 34 PBDE compounds from coupled samples of loggerhead turtle maternal plasma and replicate egg yolk and albumen. We applied robust Regression on Order Statistics to calculate summary statistics among samples with measured concentrations below detection limit. Wet weight concentrations of compounds were lower and more variable among replicate samples in albumen than yolk. Additionally, the correlation with plasma concentrations was lower for albumen than yolk, which discourages the use of albumen as a model tissue for maternal burdens at the current moment. By contrast, lipid-normalized concentrations of PCB and OCP were positively correlated between plasma and yolk, and overlapped with previous observations between whole blood and whole egg for leatherback and green turtles. The maternal transfer rate between yolk and plasma indicated that lipid normalized concentrations in yolk were on average 6.6 times lower than those in plasma. Nevertheless, this maternal transfer rate varied between compounds suggesting compound-specific transfer, and negatively related with compound lipophilicity as estimated by the octanol-water partitioning coefficient, K _ow. Dioxin-like PCB 118 was among the three PCB with highest concentrations in yolk, and obtained a high log ₁₀ maternal transfer ratio of -0.30. Regarding OCP, p,p`DDE was the most prevalent compounds in yolk, albumen and plasma, and obtained a near-equilibrium log ₁₀ maternal transfer ratio of 0.01. Our results indicate that yolk could offer a suitable biomonitoring tissue which relates to maternal body burdens. Nevertheless, compound-specific maternal transfer rates need to be considered when translating yolk levels back to maternal pollution burdens, and when assessing the risk to the subsequent generations of turtle embryos.