Multigenerational effects of metals accumulate over three generations in the amphibian-killing fungus (Batrachochytrium dendrobatidis)

Exposure experiments within a single generation assess organisms’ sensitivity to pollutants but don't reveal long-term effects over multiple generations. We studied the multigenerational effects (MGEs) of copper (Cu), zinc (Zn), and their combination (Cu+Zn) on the amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) over three generations. Our goal was to determine if Bd's sensitivity to metals changes with continuous exposure, which should affect its long-term performance at metal-polluted sites. We conducted two experiments: (1) exposing three generations (F0-F2) of Bd to fixed, environmentally relevant metal concentrations, and (2) assessing how first-generation (F0) exposure influenced Bd's response to varying metal concentrations in F1, including no exposure to metals. Experiment 2 allowed us to estimate transgenerational plasticity (TGP), the extent to which F0 exposure influenced offspring performance without metals. We measured Bd's population growth rate, and the numbers of live zoospores, sporangia, and colonies. Continuous exposure to Cu and Zn led to a progressive decline in Bd performance over three generations, indicating accumulating negative effects. TGP was evident, with F0 metal exposure causing a decline in F1 performance without metals. TGP explained 20–80 % of the decline in population growth rate across generations with continuous metal exposure. Our findings suggest that continuous exposure to elevated Cu and Zn levels negatively impacts Bd, indicating that metal-polluted sites could serve as disease refugia for Bd-susceptible amphibians.