Understanding Cyanobacteria

algae scum

What are Cyanobacteria?
Understanding Cyanobacteria Blooms

What Are Cyanobacteria?

Cyanobacteria (also called blue-green algae) are commonly found in the phytoplankton community of aquatic ecosystems. They help form the base of the food web of freshwater ponds.  The presence of cyanobacteria is natural and important.  

However, overabundant cyanobacterial growth (called blooms or harmful algae blooms (HABS)) and their release of cyanotoxins appear to be occurring more frequently across New England.  The reasons for this are under active investigation but appear to be at least partially due to excessive nutrients in ponds resulting from development around pond shores, and may also be due to warming global temperatures. Excessive growth of cyanobacteria and formation of blooms degrades habitats and impacts recreational use of waters.  Exposure to cyanotoxins can have serious health implications for humans, pets and wildlife.

Cyanobacteria blooms

Cyanobacteria can form harmful blooms (also called HABS)  in lakes, ponds, and rivers that make the water murky, and can sometimes make the water look like pea soup or swirls of paint in the water. The blooms may appear as green, blue or mustard-yellow areas of water with or without floating scum. Blooms are most common in summer and early fall when water temperatures are warm. Blooms in White Pond have increasingly been observed as early as late June or early July and often persist at some level until early fall.  


What causes cyanobacteria blooms?

  • Certain environmental conditions, such as warm weather, sunlight, and excess nutrients in the water help blue-green algae grow faster.
  • Phosphorus and nitrogen are two important nutrients used by blue-green algae in their growth. They are found in fertilizers and human and animal waste.
  • Excess levels of nutrients in water bodies often come from human-related sources.
  • Examples of sources that can input large amounts of nutrients to water bodies are septic systems, poorly managed storm water runoff, lawn fertilizers, pet and wildlife waste, and agricultural activities. Warm weather and lots of nutrients in the water help cyanobacteria grow faster

What Are the Possible Health Concerns of Harmful Algae Blooms? 

Cyanobacterial blooms sometimes produce toxins that can make pets and people sick. Toxins may be present within the algae cells or in the water column.  Health concerns from harmful algae blooms and their toxins vary depending on the type of exposure and the amounts and types of toxin present.

  • Contact with cyanobacteria can cause skin and eye irritation.
  • Ingesting small amounts can cause gastrointestinal symptoms. Ingesting large amounts of toxins may cause liver or neurological damage depending on the type of toxin present. .
  • 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. Pet deaths from ingesting algal toxins have occurred.
  • For humans, the primary concern is ingestion of water containing blue-green algae while swimming. Ingestion of blue-green algae can cause acute gastrointestinal symptoms, such as vomiting and diarrhea.  Of secondary concern is direct skin contact with the blue-green algae and inhalation of water droplets containing blue-green algae or toxins.  Contact can cause skin and eye irritation, and inhalation can cause respiratory irritation and exacerbate pre-existing respiratory conditions. Toxins are not absorbed through the skin.
  • For pets, the primary concern is the ingestion of water containing blue-green algae or scum that has washed ashore or gotten onto their skin or fur.  Dogs can get very ill and even die from licking algae off of their fur. Rinse dogs off immediately if they come into contact with a cyanobacteria bloom, and contact your veterinarian immediately  if you see any unusual symptoms or behavior after contact with a bloom.

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