Poop in the water? Why beaches had fecal bacteria closures, warnings.

Over the holiday weekend, many people looking to cool off from the summer heat were disappointed as some beaches were closed or authorities advised against swimming because of unsafe levels of bacteria.

The advisories and closures popped up across the East Coast, from Florida to Maine, along inland streams and rivers, and throughout the California coast. The culprit: fecal contamination detected in the water that presents a risk of illness.

For decades, beaches across the country have seen days, weeks and months of closures because of elevated levels of fecal bacteria, according to the Environmental Protection Agency. A recent report from the conservation group Environment America found that last year, 61% of beaches it tested nationwide had at least one day when bacteria levels were potentially unsafe.

More: Beaches across US close during Labor Day weekend due to fecal contamination

But what is causing the heightened contamination levels?

Experts told USA TODAY that stormwater runoff and sewage overflows were among the most likely causes, both of which are exacerbated by heavy rains, flooding and warming temperatures. Other contributing factors include animal and agricultural waste and failing septic systems.

Research shows that bacteria warnings are most prevalent in the summer, when most people are flocking to the beach and water temperatures are at their highest.

“These beach closures are not uncommon during warm seasons,” said Antarpreet Jutla, a professor of environmental engineering at the University of Florida, adding that while bacteria is a prevalent issue, most beaches are safe for most of the year. “Ninety-percent of all days are safe for beaches in the U.S., on both the East Coast and West Coast.”

What bacteria is being detected?

Experts say most agencies testing beaches and inland waterways for contaminants are looking for “fecal bacteria indicators” such as E. coli and enterococci bacteria, among others.

“In other words, they are testing for the presence of poop – that’s what we’re talking about here,” said John Rumpler, the clean water director at the nonprofit organization Environment America. He said the tests are done at beaches and freshwater sources like streams, lakes and ponds, especially in bodies of water that are popular among the public.

Other sources that lead to beach closures and advisories are algal blooms, according to the National Ocean Service. The USA TODAY Network – New England reported Aug. 29 that more than 20 beaches in Vermont were under bacteria advisories because of high cyanobacteria levels heading into Labor Day weekend.

Ingestion or general contact with these bacteria could cause a variety of illnesses and nasty symptoms, such as gastrointestinal illness, skin rashes, respiratory disease and ear and eye infections, according to the EPA.

Heavy rains and leaky sewage pipes

The causes of fecal bacteria in coastal and inland waters vary depending on the region, but in each case they’re worsened by heavy rains and extreme weather like hurricanes and tornadoes, experts said.

“Heavy rain will absolutely exacerbate sewage overflows and stormwater runoff,” Rumpler said.

Across the country, stormwater runoff can carry oil, grease, bacteria, dirt and waste into waterways. More rural parts of the country can see overflows from factory farms, leading to large amounts of animal waste and other pollutants in ponds, lakes and rivers.

Sanitary sewers, which are used in most of the country, can cause problems if they are undermaintained, cracked or become blocked. The EPA estimates such systems overflow as many as 75,000 times each year.

“There are billions of gallons of sewage overflows in many communities across the country,” Rumpler said.

Along with heavy rain, sprawling development and large building projects are “further destroying nature’s ability to absorb storm water,” he added.

How to stay safe

Jutla and Rumpler advised that people check their state’s website for beach closures and swimming advisories, though they noted there’s no standard signage to look for and not all beaches are monitored frequently.

People should avoid swimming in murky lakes, ponds and streams. Health authorities also said it’s important to avoid swimming after heavy rainfall or flooding, or if the water is an unusual color.

The Center for Disease Control and Prevention said people who have health problems or are taking medicines that affect their ability to fight germs should check with their health care provider before swimming in the ocean or other natural bodies of water.

Contributing: Thao Nguyen