Blog - Charles River Watershed Association

9 Ways to Combat Cyanobacteria Blooms in the Charles River

Posted by Allie Rowe

10/10/16 3:48 PM

What is cyanobacteria? Why is it a concern?


Cyanobacteria bloom in a freshwater pond
Source: Christian Fischer | CC BY-SA 3.0

Cyanobacteria, also known as blue-green algae, are microorganisms that obtain their energy through photosynthesis and live in aquatic environments. Cyanobacteria populations can grow rapidly in fresh water, brackish water, or seawater during events known as “blooms.” Blooms often appear as dense green mats floating on or just below the water’s surface. Cyanobacteria blooms can produce toxins that harm humans, dogs, and wildlife. Exposure to these toxins may irritate the eyes, ears, and skin, and can also damage to the liver and nervous system. Emerging science shows a possible link to neurodegenerative diseases and a possibility of exposure through inhalation. Thick mats of cyanobacteria block sunlight and oxygen from entering the water, smothering fish and other aquatic organisms.


What causes cyanobacterial blooms in the Charles?

Phosphorous pollution fuels the growth of cyanobacteria. Phosphorus, a nutrient, is present in the Charles at more than twice the level the river can safely handle. Sources of excess phosphorus include fertilizers, car exhaust, animal manure, wastewater, some soaps and detergents, eroded soil and leaf litter. When rain falls or snow melts on developed areas, water flowing over impervious surfaces (rooftops, roads, and parking lots) can't soak into the ground. This water, known as stormwater runoff, picks up phosphorous pollution and dumps it into the Charles River through storm drains and outfalls.


Cyanobacteria blooms in the Charles River

This summer, water sampling confirmed a large cyanobacteria bloom in the Charles River downstream of the Massachusetts Avenue bridge. During the ongoing outbreak, public health officials recommend that people and pets avoid contact with the water, rinse thoroughly in the event of contact, and refrain from boating in affected areas. Cyanobacteria blooms are unfortunately increasing in the Charles River due to stormwater pollution and warmer water temperatures. The blooms are also lasting longer and covering larger portions of the river. 


You can help combat cyanobacteria blooms! Here’s how:

rain garden

Rain Garden at U.S. Naval Academy
Source: Chesapeake Bay Program | CC BY-NC 2.0

Reduce your phosphorous footprint

  1. Pick up after your dog and properly dispose of the waste in the garbage.
  2. Visit a car wash, where water is treated and recycled, instead of washing your car in the driveway. This saves water too!
  3. Avoid using fertilizers that contain phosphorous on your lawn or garden beds—compost is a great alternative. Soil testing will help determine the nutrients your landscape needs.

Manage stormwater on your property with green infrastructure

  1. Install a rain barrel. Rain barrels are containers used to collect rainwater from the roof of a building. The collected water can be used to water gardens or lawns, wash cars, fill swimming pools, or do other household chores. Rain barrels conserve water and reduce stormwater runoff.
  2. Plant a rain garden. Rain gardens are landscaped areas that collect stormwater and filter it through layers of mulch, soil and plant root systems and into the ground.
  3. Replace driveways and patios paved with non-porous asphalt or concrete with alternatives that allow water to percolate into the ground such as permeable pavers or  permeable pavement

Get involved in your community

  1. Ask your city or town to implement green infrastructure including rain gardens, vegetated swales, stormwater planters, and tree pits. Check out what other cities and towns are doing to keep pollution out of the Charles River including the rain gardens in Franklin and a porous alley in Boston. 
  2. Encourage the shops and other service-providers you patronize to manage stormwater on their properties with green infrastructure.
  3. Become a citizen scientist! Help CRWA and the Northeast Cyanobacteria Monitoring Program monitor cyanobacteria blooms near you. With the new BloomWatch app, easily submit a picture and report a bloom. Find the bloomWatch app on Google PlayTMor on the App Store.


Thank you on behalf of CRWA, and all of us who share the Charles River Watershed!


Topics: Charles River, Stormwater, Stormwater Management, Green Infrastructure, Pollution, Charles River Pollution, Stormwater Runoff

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About Charles River Watershed Association:

One of the country's oldest watershed organizations, Charles River Watershed Association (CRWA) was formed in 1965 in response to public concern about the declining condition of the Charles. Since its earliest days of advocacy, CRWA has figured prominently in major clean-up and watershed protection efforts, working with government officials and citizen groups from 35 Massachusetts watershed towns from Hopkinton to Boston. Initiatives over the last fifty years have dramatically improved the quality of water in the watershed and fundamentally changed approaches to water resource management.