Cyanobacteria Outbreak Reported in the Charles River Lower Basin

Water samples collected Thursday, Aug. 25, confirmed a cyanobacteria, or blue-green algae, outbreak in the Charles River Lower Basin downstream of the Massachusetts Avenue Bridge, according to the Charles River Watershed Association.

The sampling showed concentrations of cyanobacteria exceeded 70,000 cells per milliliter of water, the water quality standard established by the Massachusetts Department of Public Health. The monitoring buoy operated by U.S. EPA near the Museum of Science also registered a spike in phycocyanin, an indirect measure of cyanobacteria, on Saturday. Public health officials recommend that people and pets avoid contact with the water in this area and rinse thoroughly in the event of contact.

When present in large numbers, cyanobacteria give the water a green, paint-like appearance and may produce toxins harmful to humans, dogs and wildlife. Exposure to these toxins can cause eye, ear, and skin irritation. Emerging science shows a possible link to neurodegenerative diseases and a possibility of exposure by inhalation. Because cyanobacteria are most likely to release toxins as they die off, the health risks persist for about two weeks after cell counts decline to safe levels. In addition to the public health risk, by preventing light and oxygen from entering the water, cyanobacteria can smother fish and other aquatic organisms.

The current bloom, the first documented this summer in the Lower Basin of the Charles, is part of an increasing trend as warmer summers and polluted

stormwater provide ideal conditions for cyanobacteriato thrive. The Charles has experienced one or more cyanobacteria blooms in nine of the past eleven summers. The growth of cyanobacteria is fueled by phosphorus pollution accumulated on roads and parking lots, which is discharged into the Charles River via storm drains.

An Aug. 22 rainstorm combined with the hot summer temperatures and the near record low flows in the river due to the extreme drought likely combined to cause this outbreak.

“The likely reason we did not see a cyanobacteria outbreak earlier in the summer is because of the severe drought,” said Bob Zimmerman, executive director of Charles River Watershed Association.

According to U.S. EPA, the relationship between high phosphorus levels from stormwater discharges to the Charles and the proliferation of cyanobacteria is well established. Phosphorus is present in the Charles at more than twice the level the river can safely handle.

“Green infrastructure solutions, such as rain gardens and constructed wetlands, reduce phosphorous pollution and also help to reduce flooding when it does rain,” Zimmerman said. “It is critical to implement EPA’s municipal stormwater permit, which some towns are now fighting, if we are serious about controlling phosphorus pollution and cyanobacteria.”

The Massachusetts Department of Public Health will continue testing for cyanobacteria in the Charles River.

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