Cyanobacteria Algal Blooms
When a dramatic increase in a cyanobacteria population occurs, this is called harmful algal blooms (HABs), or more accurately, cyanobacterial HABs (CyanoHABs). It often results in the waterbody turning bright green or blue-green, and forms a surface scum or a discoloration of the water column. CyanoHABs may also form a mat on the bottom sediments, which is more difficult to observe.
Health concerns associated with CyanoHABs vary depending on the type of cyanobacteria, the route of exposure, and the amount of cyanotoxins present. Ingestion is the primary concern since ingesting small amounts of cyanobacteria or cyanotoxin can cause gastrointestinal symptoms while larger amounts may cause liver or neurological damage. Contact with cyanobacteria can cause skin or eye irritation. Inhaling water spray containing cyanobacteria can cause asthma-like symptoms. Small children and pets are more susceptible to the effects of cyanotoxins than adults.
When a possible algal bloom is observed, the MA Dept. of Public Health (MDPH) recommends posting public advisories at all access points of the body of water to notify residents that water should be avoided. The MDPH Toxicology Program will conduct follow-up sampling once the bloom is no longer evident. The MDPH requires two samples below the guideline level to be taken one week apart to recommend rescinding the advisory.
The following should be avoided:
- Contact with the water
- Swimming (including pets)
Algae blooms can be caused by:
- Warm weather
- Excess nutrients in the water, such as fertilizer and human/animal waste
- Stormwater runoff
- Failing septic systems
Health concerns from harmful algae blooms vary depending on the type of exposure and the amounts:
- Contact with these algae can cause skin and eye irritation
- Ingesting small amounts can cause gastrointestinal symptoms. Ingesting large amounts of toxins may cause liver or neurological damage
- Inhaling water spray with algae in it can cause asthma-like symptoms
- Small children and pets are more susceptible to the effects of toxins than adults. Livestock and pet deaths from ingesting algal toxins have occurred. Dogs should be rinsed off immediately if they come into contact with an algae bloom
If you believe you or your pet came into contact with these algae, you should immediately wash yourself/pet with clean water and contact your primary care physician or veterinarian.
For more information on algal blooms, please visit: https://www.mass.gov/guides/cyanobacterial-harmful-algal-blooms-cyanohabs-water