Blue-green Algae

Blue-green algae bloom from October 14, 2021, at Rough Canyon.

NPS Photo / Rene Rios

While not very common at Amistad National Recreation Area, the reservoir does get occasional algal blooms. Read on to learn more about how to identify them, what causes them, and what effects they may have on you and on the lacustrine (lake-related) environment. If you see something in the park that you think matches this description, please contact the Visitor Center and provide contact information (so we can ask questions), location where algae was seen, a photo (if possible), and ask the information be forwarded to a park biologist.

What are blue-green algae?

Blue-green algae are also called “cyanobacteria” since they are biologically similar to bacteria in many ways. However, blue-green algae (Cyanophyta) are not classified with bacteria because they lack a nuclear membrane. One characteristic of these cyanobacteria is their ability to form blooms so thick it appears that blue-green paint covers the surface of the water. However, the toxins they create may be present days after the algae is no longer visible, so water quality testing is performed to verify water is safe to swim in.

Does Texas have blue-green algae?

Two forms of blue-green algae are found in Texas: Anabaena and Microcystis. These can produce toxins that are poisonous to fish and wildlife that drink water contaminated with the toxins. Furthermore, there are documented cases of blue-green algal toxins harming humans in other parts of the world through the consumption of poorly treated waters.

What causes algae blooms?

Blooms can be caused by several factors. An increase in nutrients can cause a dramatic increase in algae growth and reproduction, just as fertilizing a lawn makes grass grow faster. Or, there may be a change in water temperature, water quality, amount of sunlight, or some other environmental factor that gives some algae an advantage over other species of algae, which can result in a bloom of the algae that have the advantage. Harmful algal blooms need:

1. Sunlight.
2. Slow-moving water.
3. Nutrients (nitrogen and phosphorus).

What do blue-green algal blooms look like?

Blue-green algal blooms are often described as looking like pea soup or spilled green paint. However, blooms aren’t always large and dense and can sometimes cover small portions of the lake with little visible algae present. Blooms can also produce a swampy odor when the cells break down.

What are the possible health effects?

You can become sick if you swallow, have skin contact with, 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. If you become sick, you might experience vomiting, diarrhea, rash, eye irritation, cough, sore throat, and headache. Symptoms generally begin hours to two days after exposure.

Can animals be affected?

Pets, especially dogs, are susceptible to harmful algae because they are relatively small and tend to swallow more water while swimming and playing (e.g., retrieving a ball from the water). Dogs may ingest algae if they lick their coats after leaving the water. They are also less deterred by green, smelly water that may contain harmful algae. To reduce your animal's exposure to blue-green algae:

1. Don't let them swim or drink where there are noticeable algae in the water or scum on the shore.
2. If they swam in water that could have harmful algae, rinse them off with fresh water immediately. Don't let them lick their fur.

Animals can experience symptoms within minutes of exposure to the toxins. Symptoms they might experience include vomiting, diarrhea, weakness, difficulty breathing, and seizures. In the worst cases, animals have died. If your pet experiences these symptoms after exposure to algae, contact your veterinarian immediately.

The World Health Organization recommends the following for all freshwater-based recreation:

1. Avoid areas with visible cyanobacterial or algal concentrations and/or scums in the water as well as on the shore. Direct contact and swallowing appreciable amounts are associated with the greatest health risk.
2. Where no scums are visible, but the water shows strong greenish discoloration and turbidity, test if you can still see your feet when standing knee-deep in the water (after wading in without stirring up sediment). If not, avoid swimming— or at least avoid ingestion of water, i.e., submersion of your head. In such situations, avoid waterskiing because of potentially substantial exposure to aerosol toxins.
3. If sailing, sailboarding, or undertaking any other activity likely to involve accidental water immersion in the presence of cyanobacterial or algal blooms, wear clothing that is close fitting in the openings. The use of wet suits for water sports may result in a greater risk of rashes because cyanobacterial or algal material in the water trapped inside the wet suit will be in contact with the skin for long periods of time.
4. After coming ashore, shower or wash yourself to remove cyanobacterial or algal material.
5. Wash and dry all clothing and equipment after contact with cyanobacterial or algal blooms and scum.

Who responds to Harmful Algal Blooms?

Texas Parks and Wildlife Department (TPWD) has a Kills and Spills Team (KAST) that responds to an incident where fish or other animals have been harmed. These specially trained biologists collect water samples for analysis, record water quality and environmental data, and identify and estimate numbers of dead wildlife, among other tasks. They contact other agencies and personnel, including Texas Department of State Health Services if human health issues are suspected, Texas Commission on Environmental Quality for impacts to natural resources, and the governing authority that manages a particular area, like the National Park Service for issues with Amistad Reservoir. TPWD monitors harmful algal blooms as they progress and communicates with the public through the agency website and social media accounts. The county, city, river authority, or other agency in charge of an affected area is responsible for cleanup of dead wildlife.

Useful Websites:

Texas Parks and Wildlife Department (TPWD): https://tpwd.texas.gov/landwater/water/environconcerns/hab/

TPWD Kills and Spills Team (KAST): https://tpwd.texas.gov/landwater/water/environconcerns/kills_and_spills/index.phtml

Texas Department of State Health Services: https://www.dshs.texas.gov/

Texas Commission on Environmental Quality (TCEQ): https://www.tceq.texas.gov/

Environmental Protection Agency (EPA):https://www.epa.gov/nutrientpollution/harmful-algal-blooms#effect

 

Left image
Cyanobacteria is not immediately noticeable from boat ramp. These photos are taken only minutes apart.
Credit: NPS photo

Right image
Cyanobacteria becomes more apparent near the end of the same boat dock in the previous photo.
Credit: NPS photo

Blue-green algae blooms can happen quickly and may not be immediately apparent. Here are two photos from a recent algae bloom at Rough Canyon on August 30, 2023.