On a busy Thursday afternoon, runners jogged on the Esplanade, while some walked their dogs and others sailed. Many of these people passed a bright yellow sign warning about a potentially harmful outbreak lurking in the Charles River nearby.
The Charles River Watershed Association says recent water tests revealed a cyanobacteria outbreak in the Lower Charles River.
"I probably wouldn't go paddleboarding in that part of the river," Elisabeth Cianciola, an aquatic scientist with the Watershed Association said Thursday. "Because we don't know exactly what the risks are at this point, we are trying to encourage people to take the problem seriously."
Ciancola says the outbreak was set up by an intense rainfall followed by an intense period of drought.
The blue-green algae can irritate the ears, nose and throat, according to experts. Dogs who drink or swimming in the Charles can become more sick.
"There is some concern that the toxins and bacteria can become airborne, so even if you aren't necessarily swimming or drinking the water, you still may be exposed to it," Cianciola said.
Experts say it's a good idea to try and avoid contact with the river. If you do, they say it is a good idea to shower as soon as you can.
"We would recommend showering thoroughly if you do choose to run along the Esplanade," Cianciola said.
The Watershed Association is expecting updated results as early as Friday, and expect the outbreak to last at least another two to four weeks.