Differential effects of two prevalent environmental pollutants on host-pathogen dynamics

Area of Science:

• Environmental Toxicology
• Ecotoxicology
• Aquatic Ecology

Background:

• Chemical pollutants, including microplastics and glyphosate-based herbicides, degrade freshwater habitats and cause species loss.
• While glyphosate impacts fish disease tolerance, microplastic effects on disease are unknown.
• Understanding pollutant interactions is crucial for aquatic ecosystem health.

Purpose of the Study:

• To investigate the individual and combined impacts of microplastics and glyphosate herbicide (Roundup®) on fish mortality and disease tolerance.
• To assess the effects on host-pathogen dynamics in a model fish system.

Main Methods:

• Utilized a model fish host-pathogen system to test polypropylene microplastics and Roundup®.
• Exposed fish to individual pollutants and combined pollutants under infected and uninfected conditions.
• Monitored host mortality and pathogen load metrics.

Main Results:

• Individually, microplastics increased and Roundup decreased mortality in uninfected fish, but combined exposure dramatically increased mortality (73%).
• In infected fish, microplastics had no significant effect, while Roundup increased mortality (55%); combined exposure showed synergistic effects (53% mortality).
• Microplastics prolonged infection, Roundup reduced pathogen load; combined, they additively reduced pathogen load.

Conclusions:

• Microplastics and Roundup interact to significantly increase fish mortality, both in uninfected and infected individuals.
• These pollutants individually and interactively alter host-pathogen dynamics, affecting disease progression and outcomes.
• The findings highlight the critical threat posed by combined microplastic and herbicide pollution to freshwater fish populations.