Dining on disease: how interactions between infection and environment affect predation risk

Area of Science:

• Ecology
• Parasitology
• Aquatic Ecology

Background:

• Ecological interactions between predators and pathogens are increasingly recognized.
• Few studies have experimentally tested how infection impacts host predation risk.
• Environmental conditions can influence predator-prey-pathogen dynamics.

Purpose of the Study:

• To investigate the impact of chytrid infection (Polycaryum laeve) on Daphnia susceptibility to fish predation.
• To determine how environmental factors, specifically dissolved organic carbon (DOC), moderate this predator-prey-pathogen interaction.

Main Methods:

• Combined mesocosm experiments with in situ foraging data and lake surveys.
• Assessed fish predation preference for infected versus uninfected Daphnia.
• Correlated infection prevalence with environmental characteristics like DOC and light penetration.

Main Results:

• Fish (bluegill, yellow perch) preferentially preyed on infected Daphnia (2-10 times higher risk).
• Higher infection intensity increased predation risk for infected Daphnia.
• Selective predation on infected Daphnia was eliminated in high DOC water.
• Chytrid infections were more prevalent in lakes with higher DOC and lower light penetration.

Conclusions:

• Parasitism significantly alters host predation risk, with infection intensity being a key factor.
• Water color (high DOC) can mask the increased visibility of infected hosts, thereby reducing selective predation.
• Infected Daphnia are more likely to inhabit environments that reduce their conspicuousness, illustrating a strong interplay between parasitism, predation, and environmental conditions.