Cyanobacteria (Blue-Green Algae)

What are blue-green algae?

Blue-green algae are microscopic organisms that are actually bacteria. They are commonly called blue-green algae because dense growths can turn the water any color from blue green to brownish-green. These algae are a natural part of lake ecology, but high nutrient levels in water can cause heavy growths (blooms), especially during warm weather.

What is the Issue?

There have been reports around the globe of blue-green algae producing toxins in fresh waters. These toxins can damage the liver or nervous system, produce gastrointestinal symptoms, or cause skin irritation. Many agencies in North America are paying increased attention to these toxins as more monitoring and research data are becoming available. Though conditions in Maine should make this problem uncommon, we have recently started to evaluate blue-green algal growth and toxin production in Maine water bodies.

What does a bloom look like?

A bloom is any dense growth of algae that discolors the water. Blooms not only turn the water murky and discolored, including neon green, pea green, blue green, or reddish brown color. They can also cause:

- Bad odors, usually musty in character

- Foam, scum or paint-like appearance

- Green or blue-green streaks on the shoreline

You may also see obvious accumulations of algae material floating on the surface, creating swirls when the water is disturbed.

What about toxic blue-green algae?

Not all blue-green algae or algae blooms are toxic. The reasons algae produce toxins at any given time are not well understood. Standard monitoring techniques cannot predict when a bloom has toxins in it. While heavy growths of blue-green algae often show detectable levels of toxins, only the most intense blooms like those above create a potential for significant toxin exposure for humans and animals. By far the most common and best known toxins are the various forms of Microcystins (MC), which are the focus of most monitoring world wide.

How toxic are these compounds?

Toxic reactions depend on a number of factors, including the degree of exposure (how much water is swallowed, how long the water is in contact, etc.), the concentration of toxins in the water and the sensitivity of the individual. The toxins are not readily absorbed through the skin and it is not clear if health problems can arise from inhaling water droplets with toxins. Though small amounts can cause mild reactions in sensitive individuals, significant human illness has been only rarely reported. However, severe reactions and death of pets or livestock drinking contaminated water have been reported from many locations outside of Maine . Few health-based exposure guidelines exist, but significant toxicity is not likely unless there is a serious bloom.

What about these toxins in Maine Lakes ?

Over the summers of 2008-09, DEP sampled 24 lakes that have histories of algae blooms. Of 91 samples, half were positive for MC but only 3 contained concentrations that were slightly above a health-based guideline for drinking water. No other toxins were found. In 2007, EPA sampled 32 lakes, only a few of which normally produce algae blooms. Only 6 of these had detectable concentrations of MC. All of these samples were below the World Health Organization recommended health-based guideline for recreational exposure. Samples of surface scums did contain moderate to very high concentrations of MC. While these data only p rovide a snap shot of toxin levels in our lakes, it is clear that conditions vary greatly, even within the same lake and from day to day. High concentrations of toxins are probably confined to lakes with intense algae blooms, but are probably detectable at low levels in many lakes that grow noticeable algae in the summer. Whenever surface accumulations of algae and scums occur, suspect a problem.  

What should I do to avoid problems?

While most adults will avoid green discolored water, a hot day can lure children and pets into the water.

1. Do not swim, water ski, or boat in areas where algae are visible (e.g., pea soup, floating mats, scum layers, etc), where water is discolored, or where musty odors are present.

2. Do not let pets or livestock swim or drink where the water is discolored or where you see foam, scum, or mats of algae on the water or where musty odors are present.

3. If you swim or wade in water that has dense algae present - rinse off with fresh water (and soap if available) as soon as practical. This is also an effective method of reducing skin exposure for your pets.

4. Do not drink lake water during a bloom. Well maintained domestic water treatment systems may make lake water safe to drink in many instances, but they are not guaranteed to remove algal toxins.

Who do I call with questions?

If you want to report a bloom, contact the DEP Lakes Staff at 207-287-3901. For information on health effects, contact the Environmental and Occupational Health Program (866-292-3474 in state). Out of State contact The World Health Organization (WHO).