• May resemble thick pea soup or spilled paint on the water’s surface
• May create a thick mat of foam along the shoreline
• Generally green or blue-green in color, but can be brown, purple, red or white
• Made of small specks or blobs floating at or below the water surface

• Stringy, bright grass-green, long strands that feel slimy or cottony—this is harmless green algae
• Mustard yellow in color—this is probably pollen

 

For photos of what is, and is not, a blue-green algae bloom:

 

Why should I be concerned about cyanobacteria?
General health effects caused by exposure to cyanobacteria cells (not their toxins) include rashes or skin irritation, allergy-like reactions such as a runny nose or a sore throat.  Additionally, some cyanobacteria may produce harmful compounds called cyanotoxins. When these toxins are swallowed in large amounts, they can cause serious health effects.

 

How can I protect myself from cyanobacteria?  Do not come in contact with surface scums of cyanobacteria or with water that is deep green, blue or white in color.

 

How we monitor and assess blue green algae at Lake Harwinton
Blue green algae affects the visual appearance and the clarity of water, and this is how we assess the category of an algae bloom and determine the level of concern.  We measure clarity using a Secchi disc and record how far down the disc can be seen.  We assess appearance using the three categories defined by the VT DPH (refer to Visual Assessment).

Category 1: Visible material is not likely cyanobacteria or the water is generally clear
Category 2: Cyanobacteria present in low numbers.  There are visible small accumulations, but the water is generally clear.  An advisory may be posted.
Category 3: Cyanobacteria present in high numbers.  Scums may or may not be present.  Water is discolored throughout.  Color assists to rule out sediment and other algae.  Beach closure may be posted.

Frequently Asked Questions
 (source: CT DPH Fact Sheet, October 2013)
What are blue-green algae?
Blue-green algae are simple organisms that exist naturally in marine waters, rivers, lakes, and ponds. Despite their name, blue-green algae are actually types of bacteria known as Cyanobacteria. These organisms can reproduce rapidly and a dense growth of these organisms is called a bloom.
What causes these organisms to form "blooms"?
In Connecticut, blooms occur in summer and early fall because the abundant light, high water temperature and nutrient content increase the chance for bloom formation. Under the right conditions a large bloom can form overnight.
What does a bloom look like?
Blue-green algae blooms can appear (or disappear) rapidly. Blooms can also disappear underwater or move to different parts of a pond or lake. Be mindful of any unusual look to the lake including a bright green color, abundant pea soup-like scum, or spilled paint-like appearance. Sometimes thick mats of algae are washed onshore.
Why should I be aware of blue-green algae blooms?
Some blue-green algae produce toxins that could pose a health risk to people and animals when they are exposed to them in large enough quantities. Exposure occurs when surface scums or water containing blue-green algae are ingested, contact the skin, or when airborne droplets containing toxins are inhaled while swimming, boating, and skiing. Symptoms of low-level exposure are short-lived and include; "allergic" type reactions, acute intestinal or respiratory problems, and skin irritations. However, swallowing relatively large amounts of the tainted water can cause serious illness such as liver damage and nervous system effects.
How can I prevent exposure to these toxins?
When you see an algae bloom, the safest course of action to take is to stay away from the water. Pay attention to posted advisories that limit recreational activities in and around a bloom. It is most important that pets and children are kept away from blue-green algae blooms as they may be less inclined to avoid contact with the tainted water.