Zooplankton protect viruses from sunlight disinfection

Area of Science:

• Environmental Microbiology
• Aquatic Ecology
• Virology

Background:

• Enteric viruses in water cause significant global health issues.
• Sunlight disinfection is a key natural process for inactivating waterborne viruses.
• The impact of zooplankton's dark biotic processes on viral sunlight disinfection is not well understood.

Purpose of the Study:

• To quantify the uptake of MS2 virus by the rotifer *Branchionus plicatilis*.
• To assess how rotifer filter feeding affects the subsequent sunlight inactivation of MS2 virus.
• To determine if active filter feeding, rather than passive presence, mediates viral protection.

Main Methods:

• Co-incubation experiments of MS2 virus with live and dead *Branchionus plicatilis* (rotifers).
• Exposure of MS2-rotifer systems to sunlight to measure viral inactivation.
• Quantification of viral removal and recovery from rotifer bodies.

Main Results:

• Rotifers removed 2.6 log of MS2 virus over 120 hours, with viable virus recovered from their bodies.
• Live rotifers protected MS2 virus from sunlight, reducing inactivation by 2-3 log compared to controls (4.5 log reduction).
• Dead rotifers did not provide the same level of protection, indicating active filter feeding is key.

Conclusions:

• Zooplankton filter feeding can shield viruses from sunlight disinfection in aquatic environments.
• Active zooplankton may act as vectors, reducing the effectiveness of natural sunlight disinfection processes.
• These findings are crucial for understanding viral fate in water and improving public health risk assessments.