Monitoring Bacterial Contamination at Our Beaches

Participants at beach study.

High resolution (Credit: Univ. of Miami)

As beachgoers towel off and head home from beach vacations, water quality managers are taking note of a recently published study that found that bathers themselves, especially toddlers, carry a significant amount of bacterial contamination into the waves.

A new study, published in the journal Water Resources, is the first to measure the amount of fecal bacteria that comes from toddlers. It found that, in spite of their much smaller size, little children can carry as much fecal bacteria from their skin into a pool as adults.

Bacterial contamination is a main reason why health departments issue water advisories and close beaches to swimming.

A Beach is a Terrible Thing to Waste

Toddler in wading pool.

High resolution (Credit: Univ. of Miami)

As required by the Environmental Protection Agency, health departments test beach water for certain bacteria that signal the likely presence of disease-causing germs. These germs can come from human or animal feces, sewage spills, farm run-off, or heavy rains that flush them into the ocean.

Fecal bacteria can persist on skin, as well as inside the intestines where they help with digestion and are easily transferred by unwashed hands. Public health laboratories test for the presence of fecal bacteria on beaches to gauge whether disease-causing germs, which are notoriously difficult to grow in labs, could be present. When fecal bacteria in beach samples exceed a certain level, beaches are closed to protect public health.

Toddlers Spread More Germs Than Adults

Study researchers instructed 20 adults and 14 diapered toddlers to dip into large and small inflatable pools set up on a Miami beach. The children played in the sand for 15–30 minutes before their individual pool times.

Using traditional methods as well as the most advanced techniques, researchers analyzed water samples to determine how much bacteria was transferred into the water.

Toddler bather shedding research.

High resolution (Credit: Univ. of Miami)

The research showed that as the toddlers darted about and dug in the sand, they tended to leave bacteria behind and pick up more bacteria left by others. They spread germs far more efficiently than adults, who were more likely to sit in one spot on the beach.

Researchers from NOAA’s Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami helped analyze samples for this multi-agency study led by the Miami-Dade County Health Department and the University of Miami’s Oceans and Human Health Center. NOAA researchers Tomoyuki Shibata (now at the University of Northern Illinois), Christopher Sinigalliano and Maribeth Gidley contributed to this study, as did the University of Miami Department of Civil, Architectural and Environmental Engineering and the University of Miami Miller School of Medicine.

Clean Beaches Versus Closed Beaches

The Environmental Microbiology Laboratory within NOAA’s AOML conducts research on microscopic organisms in coastal ecosystems. Its scientists develop new methods to quickly detect and analyze microbial contamination of coastal and oceanic waters. They also study how microbes interact in the marine environment and their effect on human and ecosystem health.

This research is part of an ongoing effort to further understand the sources of bacterial contamination at sea- and lakeshores. With improved knowledge and better water analysis techniques, health departments could limit beach closings to those times when disease-causing pathogens are truly present — rather than when indicator bacteria suggest they might pose a health threat.

You can learn more about the water contamination study online. NOAA logo.