Bioamplification and the Selective Depletion of Persistent Organic Pollutants in Chinook Salmon Larvae

Abstract

The maternal provisioning of yolk to eggs transfers significant quantities of persistent organic pollutants (POPs). As yolk utilization progresses via metabolic activity, there is a potential to realize further increases in POP concentrations if yolk lipids are depleted at a faster rate than POPs, a condition referred to as bioamplification. This study investigated the bioamplification of POPs in Chinook salmon (Oncorhynchus tshawytscha) eggs and larvae. Chinook eggs were sampled from the Credit River, ON, Canada, and brought to an aquaculture facility where they were fertilized, incubated, and maintained posthatch until maternally derived lipid reserves became depleted (approximately 168 days). The loss of chemicals having an octanol–water partition coefficient (log <i>K</i>_OW) greater than 5.8 was slow to negligible from days 0–135. However, during the increase in water temperatures in early spring, <i>K</i>_OW-dependent elimination of POPs was observed. Bioamplification was maximized for the highest log <i>K</i>_OW POPs, with an approximate 5-fold increase in lipid equivalents concentrations in 168 day old larvae as compared to newly fertilized eggs. This study demonstrates that later yolk-sac Chinook larvae (before exogenous feeding) are exposed to higher lipid equivalents POP concentrations than predicted by maternal deposition, which could lead to underestimates in the toxicity of critical life stages