By Stephen Beech via SWNS
Even plankton refuse to clean up water contaminated by human poop, reveals new research.
The tiny, aquatic creatures are known to graze on bacteria in freshwater and saltwater.
But they won’t clean water contaminated with fecal microorganisms, according to a study published in the journal mSphere.
American researchers say their findings sheds light on the limitations of naturally occurring zooplankton for inactivating contaminated water.
Scientists at The University of Texas, El Paso, (UTEP) and Stanford University say a 2017 U.S. water quality inventory revealed that more than half of rivers, bays and estuaries were unsafe for at least one use, in many cases because of fecal contamination.
Study corresponding author Doctor Lauren Kennedy said: “When sewage is released into clean bodies of water and humans are exposed to it, it can lead to illness in humans.
“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?”
Dr. Kennedy, Assistant Professor of civil engineering at UTEP, explained that water from sewage and septic tanks can enter lakes and rivers as a result of accidents, inadequate water treatment or corroded infrastructure.
The research team hypothesized that zooplankton naturally present in water might graze on microorganisms from fecal contamination, inactivating the organisms and effectively “cleaning” the water.
To test their idea, the researchers added a virus called MS2 and the bacteria E.coli to samples of freshwater and saltwater taken from the San Francisco Bay area of California.
Dr. Kennedy said MS2 and E.coli are considered “useful proxies” for scientific research because they are present at high concentrations in sewage and their presence often indicates fecal contamination in the environment.
The water samples naturally contained both “large” particles such as zooplankton, sand and dirt, and “small” or dissolved particles like salt.
The researchers found that the large particles, including zooplankton, did not have a significant effect on the inactivation of the pathogen proxies.
But the small particles seemed to have a greater impact.
Dr. Kennedy said the pathogen proxies were inactivated at higher rates in high-salinity water, for example, ocean water taken from San Pedro Beach.
She added: “I am proud that we were able to provide another perspective to consider for surface water remediation efforts.”
Dr. Kennedy believes the study is an important step forward in understanding the limits of zooplankton as natural “cleaners” of contaminated water.
She says the next phases of the research will focus on the impact of salinity on pathogen survival in contaminated waters.
