Last updated Feb. 8, 2018

Overview

Nutrient pollution is a national concern that is caused by excess nitrogen and phosphorus in the air and water. Nitrogen and phosphorus are nutrients that are natural parts of aquatic ecosystems. However, when a wide range of human activities cause too much nitrogen and phosphorus to enter the environment, the air and water can become polluted. Nutrient pollution has impacted our waterways for the past several decades, resulting in serious environmental and human health issues and impacting the economy.

Too much nitrogen and phosphorus in the water causes algae to grow faster than ecosystems can handle. Significant increases in algae harm water quality, food resources and habitats, and decrease the oxygen that fish and other aquatic life need to survive.

Large growths of algae are called algal blooms and they can severely reduce or eliminate oxygen in the water, leading to illnesses in fish and the death of large numbers of fish. Some algal blooms are harmful to humans because they produce elevated toxins and bacterial growth that can make people sick if they come into contact with polluted water, consume tainted fish or shellfish, or drink contaminated water.

What are algae?

Algae are mostly aquatic, plant like organisms that can range in size from microscopic to giant kelp found in the ocean. Algae are photosynthetic organisms, meaning they use sunlight to process food and produce oxygen. In aquatic ecosystems, algae play a major role not only by producing oxygen but making up the base of the food chain.

What are harmful algal blooms (HABs)?

Any occurrence of rapid growth of algae in a water system, beyond normal levels, can be considered an algal bloom. Blooms are considered harmful when they have detrimental effects on aquatic ecosystems; or human, livestock or pet health. Effects may range from depleted oxygen levels to production of deadly toxins. 

What are blue-green algae?

Blue-green algae are not actually algae, but cyanobacteria. Like algae, these bacteria can “bloom” when the conditions are right. Cyanobacteria are especially concerning because they are capable of producing toxins that can be harmful, even lethal, to humans, livestock and pets.

What causes HABs?

Blooms occur when weather conditions are just right and there is an over-abundance of nutrients (mainly nitrogen and phosphorus) in a waterbody. Sources of nutrients include wastewater and run-off from farm fields and lawns. HABs typically take place during summer and early fall when the weather is warm and water temperatures are high. However, blooms can occur any time of the year if conditions are right.

Where are HABs found?

Blooms can be found throughout Missouri. Lakes and ponds are the most likely waterbody to experience blooms, but they can occur in streams, especially if they are slow moving or pooled. 

How will I know if a HAB is present?

Unfortunately, you cannot tell if an algae bloom is toxic just by looking at it. Higher levels of toxins are typically associated with algae blooms that appear as thick foam or scum on the water’s surface. They can be bright green, blue-green, white or brown in color. The water may look like pea soup or the surface may look as if green paint has been spilled on the water. If you come across areas of thick algae, take precaution by avoiding water contact and keeping pets out of the water. 

WHEN IN DOUBT, STAY OUT!

Last updated Feb. 8, 2018

What are the health risks if exposed to a HAB?

You can become sick if you swallow, have skin contact, or breathe in airborne water droplets while swimming, boating, waterskiing, tubing, bathing or showering in water that has harmful algae, or if you drink water that contains algal toxins. Skin irritation or rash is the most commonly reported health effect. Other symptoms range from diarrhea, cramps and vomiting to fainting, numbness, dizziness, tingling and temporary paralysis. The most severe reactions occur when large amounts of water are swallowed.

Inhalation of aerosolized toxins may result in allergy or asthma like symptoms. Individuals with respiratory illnesses such as asthma or other respiratory diseases are more susceptible to breathing difficulties and may experience more sever symptoms. Such individuals should consider avoiding exposure if possible. 

What makes blue-green algae dangerous? - video produced by the American Chemical Society discussing the cause of HABs, the most common toxins, the health risks and the chemistry behind them.

What should I do if I am experiencing symptoms?

If you are experiencing any of the symptoms mentioned above, it is best to seek medical attention. Let the medical personnel know that you have been in an area affected by a bloom and may have been exposed.

Is it safe to eat the fish?

Fish caught in affected waters pose unknown health risks and may have an undesirable taste. Because of the unknown risks, we recommend you do not eat fish from affected areas for two weeks after the bloom visually dissipates. If you choose to eat them, remove all fat, skin and organs before cooking because toxins are more likely to collect in these tissues. Always cook fish thoroughly.

Drinking water information

Missouri Department of Health and Senior Services

Is it OK for my pets and livestock to enter and/or drink the water?

There have been cases in Missouri of livestock and pet illness and/or death linked to HABs. If algae scum is floating on the water, block access to the affected water and provide another water source for them to drink. Pets should also be prevented from rolling in or eating scum that may have accumulated on shore, even if dried. Dogs can be affected by licking their fur after having been in contact with the scum. If your animal comes in contact with blue-green algae, wash them off with fresh water immediately.

What should I do if my pet or livestock have been in contact with affected waters?

If you are concerned your animal(s) may have been in contact with or ingested contaminated water, contact your veterinarian immediately.

Is it safe to eat the fish?

Fish caught in affected waters pose unknown health risks and may have an undesirable taste. Because of the unknown risks, we recommend you do not eat fish from affected areas for two after the bloom visually dissipates. If you choose to eat them, remove all fat, skin and organs before cooking because toxins are more likely to collect in these tissues. Always cook fish thoroughly.