Biomagnification and Burden of Organochlorinated Pesticides in Aquatic Ecosystem in the Zhalong Wetland, Northeastern China.

Trophic biomagnification of dichloro diphenyl trichloroethanes (DDTs) and hexachlorocyclohexane isomers (HCHs) were investigated in key components of the China's Zhalong Wetland. Current OCP exposure levels posed minimal risk to the red-crowned crane (Grus japonensis) and Oriental stork (Ciconia boyciana). However, significant trophic transfer and biomagnification effects were observed. The trophic magnification factor (TMF) for DDTs was 1.45 in the prey group but increased to 2.82 in the top predator group. Top predators (large fish and waterfowl) exhibited significantly elevated biomagnification factors (BMFs) for DDTs compared to prey species (F = 22.75, p = 0.003). While BMFs for benthic invertebrates and small fish were below 2, those for top predators ranged from 59 to 110. This trend indicates enhanced biomagnification at higher trophic levels and explains the detectable DDT residues found in G. japonensis and C. boyciana in recent years.