Cyanobacteria Blooms in Greater Boston Waterways
A dive into cyanobacteria blooms: what are they, where are they happening in the city, and who do they affect the most?
What are cyanobacteria blooms and what causes them?
While cyanobacteria are naturally occurring freshwater microorganisms, they bloom out of proportion in the presence of phosphorus-rich water, warm temperatures, and sunny days.
As they die and decompose, they release cyanotoxins posing a threat to public safety and wildlife. They can be fatal to pets and small children if ingested, cause skin rashes upon contact, and affect people’s respiratory systems posing special risk to those with preexisting conditions like asthma.
Today, stormwater runoff from rainfall or snow melt washing off pavement, roofs, parking lots, and other impermeable surfaces from residential, business, and industrial areas remains the biggest source of phosphorus fueling these blooms in rivers across the Greater Boston area. Impermeable surfaces act as a runway for phosphorus-laced water to enter natural water bodies without receiving any sort of treatment.
Because of climate change, these toxic cyanobacteria blooms are lasting longer and taking place more frequently – becoming an annual summer feature.
Where are these blooms happening?
Toxic cyanobacteria algal blooms are coating waterways across the U.S. from Alaska to Florida and everywhere in between.
Boston is no exception, with many of its rivers blooming annually during the summer months when the community comes out of hibernation and flocks to the water for much needed recreation.
The Charles, Mystic, Muddy, and Neponset rivers are all affected by cyanobacteria blooms, yet beloved by the communities they crisscross.
Alarmingly, there is no designated State agency overseeing the monitoring of Greater Boston’s waterways for cyanobacteria blooms.
However, thanks to the work of the Mystic River Watershed Association and the Charles River Watershed Association, there is some data available to analyze what happens in the Charles and Mystic rivers.
So... where exactly are cyanobacteria blooming along the Charles and Mystic rivers?
Left: Cyanobacteria blooms along Charles River (red dots) and Mystic River (yellow dots) between 2008-2015. Right: Same map showing Environmental Justice Communities within Greater Boston area.
More importantly... who are these toxic blooms affecting?
Cyanobacteria blooms and Greater Boston's Environmental Justice Communities.
Cyanobacteria blooms along the Charles and Mystic rivers within the Greater Boston area between 2008-2015. The blue bubble along the red (Charles bloom locations) and yellow (Mystic bloom locations) dots show Environmental Justice communities living half a mile from toxic blooms.
This map shows the exact locations where moderate to severe toxic algal blooms have taken place between 2008-2015 within 0.5 miles of Environmental Justice (EJ) communities .
Data analysis revealed that 34,116 people from EJ communities within the Charles River Watershed and 28,436 people from EJ within the Mystic River Watershed are affected by annual cyanobacteria blooms.
More data points along EJ communities are needed to determine whether EJ communities are disproportionately affected by toxic algal blooms. However, by definition, EJ communities face disproportionate environmental degradation. Nonprofits and state agencies should try to answer this question with more data.
Knowing where in the community cyanobacteria algal blooms are taking place can help Massachusetts agencies better cater to vulnerable populations by creating a set of protocols to alert the community when cyanobacteria blooms are present.
Vintage maps and modern vistas along the Charles (center left) and Mystic (center right) rivers.
