Researchers from The University of Texas at El Paso and Stanford University found that zooplankton, tiny aquatic animals known for grazing on bacteria, do not effectively clean water contaminated with fecal microorganisms. Their findings, published in the journal mSphere, have significant implications for water quality and public health.
In an unexpected twist, scientists from The University of Texas at El Paso (UTEP) and Stanford University have discovered that zooplankton, minute aquatic creatures known for their bacterial grazing habits, fail to clean water contaminated with fecal microorganisms.
Published in the journal mSphere, the study provides groundbreaking insights into the limitations of relying on natural zooplankton communities for treating bodies of water contaminated with sewage. Over half of the U.S. rivers, bays and estuaries were deemed unsafe for at least one use, mainly due to fecal contamination, according to a 2017 water quality inventory.
“When sewage is released into clean bodies of water and humans are exposed to it, it can lead to illness in humans,” corresponding author Lauren Kennedy, an assistant professor of civil engineering at UTEP, said in a news release. “Our research seeks to understand what factors can render pathogens unable to infect people. In other words, how long does it take for the water to become safe for recreation again without any forms of outside intervention?”
Kennedy elaborated on how water from sewage and septic tanks might accidentally enter freshwater systems due to accidents, inadequate treatment facilities or corroded infrastructure.
The research team hypothesized that naturally occurring zooplankton in freshwater and saltwater might graze on pathogens from fecal contamination, thus purifying the water. To test this, they introduced MS2 virus and E. coli bacteria — both proxies for contaminants prevalent in sewage — into water samples from the San Francisco Bay area.
The findings were surprising. The larger particles in the samples, which included zooplankton, had little to no effect on inactivating the pathogen proxies. However, smaller particles, such as dissolved salts, showed a higher rate of inactivating the pathogens, particularly in saline locales like San Pedro Beach.
“I am proud that we were able to provide another perspective to consider for surface water remediation efforts,” added Kennedy.
The study highlights the need for rethinking current assumptions about the ecological roles of zooplankton in contaminated water bodies, she added.
As the scope of this research expands, future phases will delve deeper into how salinity impacts pathogen survival in contaminated waters, aiming to inform better strategies for water quality management and public health safety.