Cyanobacteria, also known as blue-green algae, are naturally found in fresh water in the U.S. and in Lake Champlain and other Vermont waters. Cyanobacteria can multiply quickly to form surface scums and dense populations known as blooms, especially during the warm days of late summer and early fall. Some types of cyanobacteria can release natural toxins or poisons (called cyanotoxins) into the water, especially when they die and break down. Swimming in or swallowing water with cyanobacteria are present can cause sore throats, rashes, diarrhea, or more serious health problems.
Heavy precipitation events have been increasing, which sends nutrient runoff into water bodies and helps to feed cyanobacteria growth. Water temperatures have also been increasing, and cyanobacteria grow more rapidly in warm water. Warmer temperatures also strengthen water stratification, causing warm surface waters to float on top of colder water layers. Stratification can cause the release of additional nutrients stored in sediments at the bottom, and helps cyanobacteria stay afloat in the warm and sunny upper layer.
As temperatures in Lake Champlain and other fresh water bodies continue to warm due to climate change, and the frequency of heavy precipitation events increases, conditions will become more favorable for blooms to happen.
The health effects from cyanobacteria depend on the amount someone is exposed to, how they are exposed, whether toxins are being produced, and the type of toxin.
People may get rashes or other skin irritations from coming into contact with blooms. Usually these skin irritations are not associated with toxins, but from other compounds in cyanobacteria cells.
Breathing in water droplets with cyanobacteria or toxins may cause allergic-like reactions, runny noses or sore throats.
Swallowing water with high levels of cyanobacteria toxins may cause:
- Severe stomach problems like abdominal pain, diarrhea and vomiting
- Liver damage, which may take hours or days to show up in people or animals
- Numb lips, tingling fingers and toes, or dizziness
Anyone who has health concerns should talk with their health care provider.
Cyanobacteria can make the water appear dark green, and look like pea soup or spilled paint. Blooms can also appear as white, brown, red or purple.
It's important to know what cyanobacteria look like and to use your best judgment when thinking about swimming or doing other activities in the water. Watch a video to find out, and see more photos of what cyanobacteria look like and what are not cyanobacteria.
Check recent reports on the Cyanobacteria Tracker
- Read the Lake Champlain Basin Program’s 2015 State of the Lake Report to learn more about the health of Lake Champlain and factors affecting cyanobacteria blooms.
- Learn more about Vermont’s Clean Water Act (Act 64) passed in 2015 to help address water quality issues including excess nutrients in surface waters.
Here are some organizations that are working to improve water quality in Vermont and resources for you to help them:
- Smart WaterWays three-minute video—Chittenden County
- Make Some Waves—Lake Champlain Basin Program
- Get Involved—Lake Champlain Committee
- Low Impact Development Guide for Residential and Small Sites—Vermont Department of Environmental Conservation