Lifetime Chronicles of Selenium Exposure Linked to Deformities in an Imperiled Migratory Fish

Aquatic ecosystems
worldwide face growing threats from elevated
levels of contaminants from human activities. Toxic levels of selenium
(Se) shown to cause deformities in birds, fish, and mammals can transfer
from parents to progeny during embryonic development or accumulate
through Se-enriched diets. For migratory species that move across
landscapes, tracking exposure to elevated Se is vital to mitigating
vulnerabilities. Yet, traditional toxicological investigations resolve
only recent Se exposure. Here, we use a novel combination of X-ray
fluorescence microscopy and depositional chronology in a biomineral
to reveal for the first time provenance, life stage, and duration
of toxic Se exposure over the lifetime of an organism. Spinal deformities
observed in wild Sacramento Splittail (Pogonichthys
macrolepidotus), an imperiled migratory minnow, were
attributed to elevated Se acquired through maternal transfer and juvenile
feeding on contaminated prey. This novel approach paves the way for
diagnosing sources, pathways, and potential for a cumulative exposure
of Se relevant for conservation.