A cyanobacteria bloom was confirmed in the Charles River. Photo courtesy Charles River Watershed Association
September 20, 2024 (Boston, MA) – The Massachusetts Department of Public Health (DPH) confirmed on Thursday a cyanobacteria bloom in the Charles River downstream of the Longfellow Bridge – the river’s first major bloom in four years – and recommended a public health advisory.
Cyanobacteria, or blue-green algae, are naturally occurring microorganisms in rivers, lakes and ponds that can potentially release harmful cyanotoxins, exposure to which can be fatal to pets and young children. Direct contact with cyanobacteria-contaminated water can cause skin rashes, and inhaling airborne toxins can affect respiratory systems, especially for those with pre-existing conditions like asthma.
Due to these severe health risks, DPH has deemed the area unsafe for people and pets and has advised the public not to swim or swallow water in the area, to keep their pets away and to rinse off after having contact with the water.
DPH staff identified the bloom based on a visual assessment of the river, which was corroborated by water quality data from EPA’s Charles River buoy and by sampling and microscope analysis conducted by the Charles River Watershed Association (CRWA). CRWA identified the presence of cyanobacteria cells at levels exceeding DPH guidelines for recreational waterbodies in Massachusetts.
CRWA and Conservation Law Foundation (CLF) sued the Environmental Protection Agency in 2022 for not issuing permits that will reduce stormwater pollution in the Charles River. EPA admitted that permits are necessary to protect recreators’ health and water quality from stormwater pollution. But for years, EPA has not met any of its deadlines to issue the permits. Currently, the case is on hold until the end of November.
“Continued inaction by the Environmental Protection Agency has threatened the health of one of the most cherished symbols of Boston,” said CLF Staff Attorney Ameya Gehi. “This toxic algae bloom is evidence of the ongoing unregulated stormwater pollution issues in the Charles River. Any more delay by the EPA risks more cyanobacteria blooms that threaten this communal treasure.”
Cyanobacteria grow rapidly when bodies of water experience high phosphorus levels, hotter temperatures and stagnant conditions. In the Charles River, cyanobacterial blooms are a symptom of excess stormwater pollution and degraded ecology. Current stormwater regulations mandate an over 50% reduction in nutrient loading from watershed communities by the year 2038. While progress has been made, this bloom highlights the work to be done and the importance of addressing municipal stormwater runoff.
This bloom is particularly troubling as it comes amid Boston’s longest dry spell in 25 years, with no significant rainfall for more than three weeks. The decreased precipitation has led to lower water levels, which, coupled with the heat and increased phosphorus from stormwater runoff, creates ideal conditions for these toxic blooms.
For ongoing water quality updates, visit CRWA’s flagging webpage.
Experts are available for further comment.
###