Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2023

Can environmentally relevant concentrations of copper and zinc impact the viability and transgenerational effects of amphibian-killing fungus Batrachochytrium dendrobatidis? (#108)

Milad Esmaeilbeigi 1 , Simon Clulow 2 , Richard Duncan 2 , Tariq Ezaz 2 , Ben Kefford 1
  1. Centre for Applied Water Science, Institute for Applied Ecology, Faculty of Science and Technology , University of Canberra, Canberra, Bruce, 2617, ACT, Australia
  2. Center for Conservation Ecology and Genomics, Institute for Applied Ecology, Faculty of Science and Technology , University of Canberra, Canberra, Bruce, 2617, ACT, Australia

The amphibian-killing fungus Batrachochytrium dendrobatidis (Bd) has caused declines in many amphibian species since the 1970s. Small populations of Bd-susceptible frogs have managed to survive in metal-polluted sites, giving rise to a hypothesis that frogs can better survive with Bd in metal-polluted environments than in unpolluted sites because Bd is inhibited by the metals. To test this, we exposed Bd zoospores, the life-stage that infects amphibian hosts, to environmentally relevant elevated concentrations (ERECs) of copper (Cu), zinc (Zn), and their combination (Cu+Zn) and examined their survival over 96 hours. We further investigated transgenerational effects of metals on Bd over three generations after 14 days incubation by measuring the fecundity and population size responses. The survival of Bd zoospores was significantly impacted by exposure to Cu, Zn, and Cu+Zn, with adverse effects detected at lowest concentrations 0.5, 5, and 0.5+5 µg/L, respectively. Bd was more sensitive to Cu (96h LC50: 0.6 µg/L) than most amphibians (96h LC50: 17-8000 µg/L) reported in the literature. There was a synergistic effect of Cu and Zn on survival of Bd zoospores after 96 hours. There was also a reduction in the fecundity of Bd in terms of zoospores produced and population size when exposed to these metals over one generation. These reductions persisted for at least two generations, after transferring the first-generation zoospores to the second and third generations with no metals. Therefore, both Cu and Zn were shown to be toxic to Bd zoospores at ERECs which are unlikely to acutely harm most amphibian species. Our findings support the hypothesis that Bd is metal sensitive relative to amphibians and could be impacted by ERECs, which could therefore mitigate Bd virulence in amphibians, although future experiments are required to confirm the potential benefits for amphibians.