What are blue-green algae?
"Blue-green algae” is the common name for several different types of algae. They are actually bacteria, which live in shallow, warm, slow moving or still water and use sunlight to create food and support life. The first recognized species were blue-green in color, which is how the algae got their name. Algae can range in color from olive-green to red.

What is an algae bloom?
A mass of algae in a body of water is called a “bloom.” When this mass rises to the surface of the water, it appears as a surface scum. They mostly appear in the hot summer months. Some blooms can look like foam, scum, or mats on the surface of fresh water lakes and ponds. The blooms can be blue, bright green, brown, or red. The water may resemble paint. As algae in a bloom die, the water may smell bad.
    

What causes blue-green algae?
Blue-green algae need warm temperatures, sunlight, phosphorus and nitrogen to grow. Phosphorus and nitrogen are found in animal and human waste and in fertilizers. Some common ways for phosphorus and nitrogen to enter lakes and streams are from agricultural and lawn runoff and improperly located septic systems. In addition, Zebra mussels have been implicated as a factor promoting the growth of harmful algae blooms in the Great Lakes region, particularly for low-phosphorus inland lakes.

  
How dangerous are blue-green algae?
Blue-green algae are a natural part of all waterways. There are many species of blue-green algae. Not all are poisonous, however some can produce poisonous toxins.

Is the water safe if it no longer appears to have a bloom in it?
It is likely that some concentration of the toxin will be present for several weeks following a scum forming bloom, although generally the amount of toxin will be much less than was present with the scum formation.

How does the toxin make people sick?

• Getting it on the skin can cause a rash, hives, or skin blisters (especially on the lips and under swimsuits).
• Inhaling water droplets can cause runny eyes and nose, a sore throat, asthma-like symptoms, or allergic reactions.
• Swallowing water that has toxins in it can cause abdominal pain, diarrhea and vomiting. It can also cause numb lips, tingling fingers and toes, or dizziness.

What should I do if I think I have been in contact with blue-green algae?
If you come into contact with a bloom, wash yourself thoroughly with clean water, paying special attention to the swimsuit area. If you develop symptoms like those listed above following contact with scummy water, contact your physician.

  
How can I protect my family and myself?

• Don’t swim, water ski, or boat in areas where the water is discolored or where you see foam, scum, or mats of algae.
• If you do swim in water that might have a bloom, rinse off with fresh water as soon as possible.
• Don’t let pets swim in or drink from areas where the water is discolored or where you see foam, scum, or mats of algae.
• If pets (especially dogs) swim in scummy water, rinse them off immediately—do not let them lick the algae off their fur.
• Don’t irrigate lawns with pond water that looks scummy or smells bad.
• Respect any water-body closures announced by local public health authorities.

How can I help reduce the occurrence of blooms?

• Reduce nutrient loading of local ponds and lakes by using only the recommended amounts of fertilizers and pesticides on your yard.
• Properly maintain your household septic system.
• Maintain a buffer of natural vegetation around ponds and lakes to filter incoming water.

Where can I learn more about blue-green algae?

NOAA Great Lakes Environmental Research Laboratory

Michigan Department of Environmental Quality (DEQ)

Centers for Disease Control & Prevention (CDC)