Algal blooms are naturally-occurring in lakes, ponds, rivers and oceans all throughout the country. Algal blooms are made up of tiny plant-like organisms. Certain species of these organisms can produce toxins that can make people and animals sick. When an algal bloom contains toxins or is comprised of a species that has the potential to produce toxins that are known to affect the health of people, animals, and the environment, they are known as harmful algal blooms (HABs).

HABs are made up of algae and cyanobacteria (often referred to as “blue-green algae”), and under the right conditions, these organisms can overgrow in natural waterbodies. HABs are typically observed during the warmer and drier months, and they can persist for several weeks. 

HABs can look like foam, scum, or thick layers of algae on the surface of water, or they can look bright green spilled paint or blue-green discoloration of the water. Algal blooms can look and smell bad and may cause the water to appear green, red, brown, or blue in color; however, algal blooms can't always be seen.

A general rule of thumb with any natural waterbody is, “When in doubt, stay out.”

It’s always recommended that individuals evaluate a waterbody before entering in it. If a waterbody looks discolored, has a foul odor, noticeable algal mats, or dead fish or other animals, it’s advisable to not enter the water or allow pets or animals near that water. Algae blooms can be very fast growing and become an issue before SCDES has been made aware of them. 

The major factors influencing the growth and reproduction of cyanobacteria are light, temperature and nutrients. HABs tend grow well with:

• ample sunlight
• slow-moving water
• excessive nutrients (nitrogen and phosphorus)
• relatively warm water temperature

HABs are more likely to occur in late spring to early fall when water temperatures are relatively high and are less likely to occur in winter months. Nutrient pollution can intensify algal blooms, resulting in more frequent and more severe blooms.

You can’t tell if a bloom is harmful just by looking at it, and not all blooms are easy to see. People or pets can get sick when they have contact with a harmful algal bloom by:

• swimming, kayaking, fishing, or wading through water
• breathing in tiny water droplets or mist that contains algal toxins
• drinking water affected by a harmful algal bloom
• eating seafood (fish or shellfish) affected by a harmful algal bloom
   

The EPA has developed health advisories for the cyanotoxins cylindrospermopsin and microcystin in drinking and recreational water.

South Carolina has adopted the recreational standards for these cyanotoxins. EPA’s drinking water health advisories are used as technical guidance.

Lyngbya wollei (now known as Microseira wollei) has been proven to produce toxins, but most of the scientific literature is still up to debate on whether it causes issues via contact, ingestion or inhalation. Some people have reported swimmer's itch and irritation with contact of the Lyngbya, so it's not recommended for people or pets to swim in or near these algal mats.

The most common symptoms associated with HABs are stomach pain, skin rash, headache, coughing and watery eyes. 

The U.S. Centers for Disease Control and Prevention recommends contacting a health care professional if you believe you’ve been exposed to a HAB. Be prepared to provide what waterbody you were in, and for how long you may have been in contact with the HAB.

If your pet experiences any of the symptoms listed below after coming into contact with a body of water, it's recommended to consult with your veterinarian.

• Physical: hypersalivation, weakness, labored breathing, seizures, other neurologic symptoms
• Chemical: elevated liver enzymes, low blood sugar, low protein, abnormal coagulation
   

HABs are a common occurrence and drinking water providers know how to monitor and safely treat their water for their customers, in compliance with state and federal drinking water standards. 

When SCDES is notified of a HAB in a waterbody that sources drinking water, we contact the water provider to communicate and share information. Water providers can provide details on the steps they’re taking specific to a HAB.

Some algal blooms and HABs can produce compounds that lead to odor or taste issues in drinking water. These compounds generally do not pose a health risk. 
 

Exposure to the toxins produced by a HAB occurs primarily through contact with or ingestion of the water where a HAB is located. In general, if you are boating in an area with a known HAB and water isn’t splashing or coming into contact with people on-board the boat, there is low risk.

As an added precaution, it is recommended to thoroughly rinse off a boat that was used in an area with a HAB to help limit the potential spread of the HAB.
 

In South Carolina, HABs are typically observed during the warmer and drier months, and they can persist for several weeks. Cooler temperatures, heavy winds and rain can sometimes contribute to HABs breaking up and dying off. Most HABs eventually disappear on their own, naturally.

There are some treatment options that local governments or lake associations may choose to explore for getting rid of a HAB. The EPA provides these resources: Preventative Measures for Cyanobacterial HABs in Surface Water.

Yes, SCDES tests ambient water quality, including lakes and rivers, on a monthly basis year-round, and the results of our statewide water sampling stations are available on our S.C. Watershed Atlas. The agency analyzes lake water throughout the State for cyanotoxins during the warmer months (May through October). SCDES also monitors water quality at ocean-facing beaches on a weekly basis from May 1 to Oct. 1.

SCDES's statewide monitoring stations, as well as current advisories and watches, and other information can viewed on our GIS Harmful Algal Bloom Monitoring App. 

Simply click on a highlighted waterbody to learn more about advisories or watches at that location or use the search feature to locate specific waterbodies on the map. 

The "About" pop-up provides additional guidance on what advisories or watches mean as well as additional resources. It's important to remember that any natural waterbody can pose some health risk, regardless of whether algae is observed. Natural waters are not sterile environments, and the presence of harmful bacteria, viruses and other organisms that can cause illness is always a possibility.