The Massachusetts Department of Public Health is warning residents to avoid exposing themselves or their pets to algae on the Charles River after a report that a dog died from liver failure after being near the river.
DPH said the dog died after coming in contact with a potential cyanobacteria algae bloom in the river near Millennium Park. DPH has not confirmed that cyanobacteria exposure caused the dog’s illness or death, however.
DPH conducted a site visit on Tuesday, and is collecting water samples to test for test for cyanobacteria cells and the cyanotoxins. Laboratory results are expected on Thursday, and DPH will provide updated recommendations after reviewing the results.
But in the meantime, DPH officials and the Boston Public Health Commission are alerting residents to be careful around the Charles River between Kendrick Street in Needham and Newton and Bridge Street/Spring Street in Dedham and West Roxbury.
Julie Wood, climate resilience director of the Charles River Watershed Authority, said residents should be prudent around the river with their pets.
“I would say be cautious during these conditions where we’re in a drought and temperatures are pretty steadily high,” she said. “These are prime conditions for cyanobacteria. So if you do have a dog that likes to lap up the water, I would probably plan to bring your own water and and keep them away from the water.”
Residents should take precautions, Wood said, if they notice anything unusual about the water.
“When it comes to recreation or making decisions to go out on the water yourself, eyeball the water, take a look. Does it look unnaturally green? And then also check state resources to find out whether there is a bloom in place,” she said.
DPH has an interactive beach water quality dashboard that the public can use to check conditions.
Cyanobacteria occur naturally in freshwater, and blooms can develop, dissipate, or move within a waterbody over a short period of time on an annual basis, Wood said.
“We have a lot of fresh water and the cyanobacteria blooms are pretty common,” she said. “In the Charles, we typically see them in what we call the lower basin, the Boston-Cambridge area. They have happened in this upstream area by Millennium Park, or in West Roxbury Dedham,” she added.
Due to the prolonged drought in New England, dense layers of microorganisms called benthic mats have developed at the river bottom, said Wood..
“Cyanobacteria like hot water and they like stagnant water. They can really thrive there,” Wood said. “That might be why we’re seeing these benthic mats, which we haven’t seen in the past. You know, the water is pretty shallow, the sun can get all the way down to the bottom, and the algae can grow down there.”
Normally, Wood said the algae is suspended in the water, but in this case, DPH testers saw a benthic mat growing at the bottom of the Charles.
“As long as we’ve been tracking this issue, I don’t ever remember getting an alert ... from a situation where the algae was growing on the river floor,” she said.
Cyanobacteria produce toxins that can make people and pets sick, according to the Boston Public Health Commission. Residents are being urged to avoid contact with the water and any areas of algae concentration, even on shore.
When cyanobacteria multiply, they create harmful algal blooms, often forming visible accumulations that can cause the water to appear slightly discolored, cloudy, or resemble pea soup or paint.
Trash on the river
Even beyond the bacteria, Wood said another result of the long drought is stormwater runoff along the 80-mile long river.
She said that might explain the influx of trash seen along the Charles on Wednesday morning between the North Beacon Street bridge and the Arsenal Bridge.
“With this drought, it can mean that one rainstorm, there’s more buildup because there’s more dry weather in between these rainstorms, and then it can bring a bunch of pollution all at once,” Wood said.
Combined sewer overflows in the lower Charles is another problem.
“Those are also triggered ... when we get too much rain and in a combined sewer, the stormwater and the sewage are in the same pipe. It’s like an old system. It’s the way cities were built back in the late 1800s and before,” she said.
Wood said DPH is responsible for testing, and local health officials work in cooperation by sending out alerts.
“Local health departments are pretty good at getting signs up in regular contact areas where people get out on rivers. So just knowing about the issue and being cautious about it is important,” she said.
