Have you ever experienced a woody, musty, earthy taste in your drinking water? Did you know that changes in taste can occur naturally in surface water? And what about the fish kill at Lake Granbury in February? That, too, was a result of natural changes.
One cause of these natural changes is algae and the other is technically a bacterium. When they bloom, the results can be quite bothersome. Both can be found in the Brazos River basin.
Texas has many types of algae occurring naturally in all surface water and any number of algae may exist in one waterbody at the same time. While most algae are not problematic, some types have the potential to produce toxins that are harmful to aquatic organisms and even humans, pets, livestock, and wildlife. Toxic algae events are called “blooms.”
An algal bloom is a sudden, massive growth of microscopic and macroscopic organisms that develop in surface water. Blooms can occur in warm freshwaters, cooler than normal freshwaters, marine waters, or brackish waters and are often associated with water bodies with ample nutrients.
A harmful algal bloom occurs when an alga, capable of producing toxins that can cause harm to aquatic organisms, animals, or people, grows rapidly.
According to the Centers for Disease Control and Prevention, harmful algal blooms are becoming more frequent with climate change. Water bodies with an ongoing bloom may look blue, green, brown, yellow, orange, or red.
There are two types of algal blooms found in the Brazos River basin: Cyanobacteria, also known as Blue-Green Algae and Golden Algae, which has historically been the biggest issue on Brazos River Authority system reservoirs.
Foul-tasting drinking water can be attributed to blue-green algae, sometimes called “pond scum,” a type of bacteria officially called cyanobacteria. When blue-green algae end their lifecycle, they emit an oily substance called geosmin, which has a distinctive earthy taste and smell that humans can detect even in small concentrations.
The unpleasant taste that shows up from time to time in our drinking water is normally due to the die-off of a portion of a waterbody’s population of algae. While this added flavor in drinking water can be annoying, it poses no health hazard.
The most effective way to improve water’s taste and odor is at the source by reducing the food supply to the algae that creates geosmin. The algae feed on nutrients that wash in from the surrounding watershed.
One source of those nutrients is fertilizer that washes into lakes from the lawns of lakeside property owners and others in the watershed. Limiting over-fertilization will reduce the amount of excess that washes into our streams and lakes during heavy rains.
Most blue-green algae are not harmful to animals; however, there are two types of blue-green algae, Anabaena sp. and Microcystis sp., known to occur in Texas that can produce toxins. These two blue-green algae species not only cause fish kills when toxic blooms occur, but their toxins can be harmful to humans, pets, livestock, and wildlife.
While blue-green algae have been known to happen in the Brazos River basin, fortunately, there have not been any recorded toxic blooms in more than 25 years.
If you’re on a water body, you will be able to identify there is an algal bloom happening; however, you wouldn’t be able to tell which type of algae it is unless you look at it under a microscope. Experts advise that if you see water with a “pea-soup” color and consistency, avoid it.
When it comes to fish kills, most people attribute them to a golden algae bloom and most of the time, they would be correct to do so.
Golden algae is the only species of algae in the Brazos River basin to have caused documented toxic events. Those past catastrophic golden algae blooms with fish kills were at Possum Kingdom Lake, Lake Granbury, and Lake Whitney in 2003 and 2005.
Localized blooms causing smaller, isolated fish kills have happened as recently as February and March of 2023 taking place at Lake Granbury. Small Threadfin Shad are often the first fish affected by a golden algae bloom.
According to Jenna Olsen, environmental programs manager at the BRA, the first golden algae bloom in Texas was in 1985 and we’ve been battling it for almost 40 years. That original golden algae bloom was found in the Pecos River area.
While golden alga is frequently present in the waters of the basin, they are in low concentrations. Olsen explains, “golden alga in central Texas thrives in cold, winter months, when water temperatures start getting below 86 degrees. That’s why we get excited when the weather warms up.”
The actual bloom is most likely causing fish kills, typically during cold weather events. A golden alga fish kill may last for days, weeks, or months, and may affect whole water bodies or isolated portions of water bodies.
Given the high frequency of wintertime golden algal fish kills, BRA aquatic scientists partner with the Texas Parks and Wildlife Department (TPWD) to take monthly samples during the fall and winter for early detection of potential golden alga issues on Possum Kingdom Lake and Lake Granbury.
Indicators of toxic golden algal blooms include:
- Water that appears to be tea-colored
- Impacts to small fish occur first, with larger fish impacted as the duration of the toxic event continues, expands in area, or increases in intensity. All species of fish can be affected.
- Fish may be gulping for air at the water’s surface because the toxin attacks their gills, and the gills no longer function appropriately.
- Fish swimming in irregular patterns or manners often appear to be intoxicated.
- Hemorrhaging is visible in the fish. It is first noticeable in the gills, head, and base of the fins, then moves into the tissue, giving the fish a pink to red appearance.
Although various research and studies done by the BRA, TPWD, Baylor University, Texas A&M University, the University of Texas at Arlington, and the United States Geological Survey have helped us understand golden algae better, none have found a treatment safe for water supply reservoirs. Olsen says, “Unfortunately, due to our reservoirs being in a natural system that is not closed, there is nothing that can be done to prevent or stop golden algae.”
When there is a report of dead fish in the Brazos River basin reservoirs or rivers, the BRA’s environmental team will assist the TPWD’s Kills and Spills Team in documenting the event and investigating the cause. The 24-hour communication center for TPWD can be reached at 512-389-4848.
In 2022, the BRA’s Environmental Services Department introduced a program to track fish kills caused by harmful algal blooms. The program, which is accessible to the public, allows citizens to report fish kills via an app that can then be researched to determine if golden algae are the cause.
People can report the time, date, location, and types and the number of fish observed through the free program, which also allows for uploading mobile phone photos. The BRA then provides tracking information to the Texas Parks and Wildlife Department to aid in their research. Use this link to Report a Possible Harmful Algal Bloom (HAB) (arcgis.com).
If you’re on a water body, you will most likely be able to see an algal bloom, but you will not be able to tell which type of algae without the use of a microscope.
Some of the signs of an algal bloom are:
- a strong odor
- discolored water
- algal mats or scum floating on the surface
- dead fish or other dead animals
No matter the cause, there are good standard practices to follow any time dead fish are in your area. Good practices include not swimming near dead or dying fish and not eating dead or dying fish. Only eat fish that appear healthy at the time they are caught.
Any algal bloom uses more oxygen to thrive, and cyanobacteria produce toxins that can be dangerous to all animals. Golden algae only impacts gill breathers and is not toxic to humans or pets.
Olsen stresses the importance of prompt reporting of fish kills. “Our biggest source of knowledge comes from the public being able to report fish kills through the survey link. Once we know, we can track it and retain that data for future use.”