DICKINSON — The soft currents of cool water making gentle waves along Dickinson Bayou might look inviting to swimmers on a hot and humid day.

Before taking a refreshing dip, however, it’s a good idea to see whether the county’s new bacteria warning signs suggest otherwise.

The Galveston County Health District installed the signs last week at two of the bayou’s boat ramps, just in time for the Memorial Day weekend. The signs are similar to the beach-watch signs in Galveston.

County Commissioner Stephen D. Holmes, who attended an April 30 meeting of the Dickinson Bayou Watershed Partnership, said he was concerned people weren’t being adequately warned about the potential for high concentrations of pathogens.

“As a result of some of those issues, people need to be aware if they see a body of water, they can’t just jump in,” Holmes said. “If the testing is good, then fine; but if not, they need to be discouraged from getting in the water and given fair notice.”

Ronnie Schultz, director of the district’s environmental health programs, said samples taken last month at boat ramps at state highways 146 and 3 were well below the state’s contact recreation standard for enterococci.

Although the triangular signs posted at boat ramps were open for all to see the warnings last week, the district said they were left opened in error.

“There was a miscommunication when the signs first came in, because the testing report has not come back yet. As a precaution, they were told to put them open until we got that in,” said Kurt Koopmann, a spokesman with the district.

A Texas Commission on Environmental Quality study from 1999 to 2006 revealed 13 of the bayou’s 17 monitoring stations exceeded the federal clean-water standard for bacteria up to 90 percent of the time.

Three bacteria, which are indicators of fecal pollution, can be found in high concentrations in parts of the bayou.

Three tributaries — Bensons Bayou, Bordens Gully and Geisler Bayou — had concentrations of E. coli that are nearly double the state’s contact recreation standard.

Swimming or coming into contact with the water in or near those tributaries of the bayou, where the state says harmful bacteria levels are the highest, increases your chance of becoming ill from an infection, a microbiology professor said.

Whether swimmers who ingest the diarrhea-causing E. coli pathogen become sick is mostly a matter of their immune system health, said Alfredo Torres, a microbiology professor at the University of Texas Medical Branch in Galveston.

“Not all E. coli in the environment are pathogenic,” Torres said. “It’s a really small number, but if the number exceeds the standard, there is a higher chance if you ingest the bacteria of getting infections.”

A young adult, for instance, would likely have a healthier immune system than someone 65 or older, and children 5 or younger don’t have a fully developed immune system, Torres said.

Dickinson Mayor Julie Masters said she grew up swimming on the bayou and would still swim in it except after a rainfall, which washes pollutants into the watershed.

Masters attended the April 30 meeting where the state revealed its study. She wants more information on the state’s findings before recommending anyone enter the water.

“There are too many variables to tell anyone whether it’s safe, but the people in that room wanted basic answers on whether it’s safe to swim in the bayou. I don’t think we got that answer,” Masters said.

The least E. coli polluted areas among the state’s samplings are at or near the state Highway 146 bridge and south of Friendswood near FM 528.

Those samples ranged from eight to 55 times below the state’s E. coli contamination standard.

At Holmes’ request, the county’s road department made the signs.

“They were fairly inexpensive, and it’s certainly my intention to continue to fund testing. It’s prudent on our part and good for the taxpayers to have the knowledge,” Holmes said.

The district will sample the bayou at the two boat ramps every other month and change the signs to reflect the outcome, Koopmann said.