Toxic Golden Algae in Texas
What is Golden Algae ?
The golden alga is a microscopic, free-floating, yellow-green algae. The golden alga, whose scientific name is Prymnesium parvum. Large concentrations of the golden alga color the water yellow to coppery-brown and may release the toxin prymnesin. Little is known about the cause of the blooms and toxin production. The toxin disrupts the functioning of the gills in fish and clams, killing them after extended exposure. Previous toxic blooms in Texas have killed hundreds of thousands of fish at a time, although aquatic insects, birds and mammals have not been impacted. The Texas Department of Health has stated that the golden alga is not known to harm humans; however, people should not collect dead or dying fish to eat.
Problem in Texas
5.1 million fish were killed at the Dundee Fish Hatchery during the 2001 production season. Many economically important fish have been affected, including largemouth bass, smallmouth bass, striped bass, catfish, crappie, and rainbow trout. In 1986 on the Pecos River, approximately 200 blue suckers and 3,600 Rio Grande darters were killed; both of these fish are on the Texas list of threatened animals. Several other state or federally endangered or threatened fish occur in areas of previous golden algal fish kills, and future blooms may affect these protected animals. Despite killing large numbers of fish, golden algal blooms do not permanently poison the water.
Does it Effect Humans ?
Blooms are not a public health threat. Unlike red tide, another toxic alga, toxins that golden algae produce appear to have no negative effect on other wildlife, livestock, or humans. However, as a common sense precaution, dead or dying fish should not be consumed.
Treatment for the Toxic Algae:
In aquaculture pond facilities, blooms are currently controlled primarily by the addition of chemicals possessing algicidal properties. These include ammonium sulfate, copper sulfate, and potassium permanganate. However, the concentrations of ammonium sulfate required to control the blooms may produce concentrations of un-ionized ammonia that can be toxic to some fish. Copper sulfate is effective in reducing the number of algal cells, but has no effect on their toxicity and may kill desirable algae along with the golden algae, as well as large numbers of invertebrate food organisms such as rotifers and cladocerans. In addition to using ammonium sulfate and copper sulfate to control the bloom, Chinese carp breeders have used suspended solids (mud), the addition of fertilizer (manure), and reduced salinity with varying degrees of success. Ultraviolet light and ozonation have been successfully used to control the bloom in small volumes of water, but these treatments may not be feasible for ponds and reservoirs due to the cost and required equipment.
What can be done to prevent it ?
To prevent the spread of golden algae from one body of water to another, the following precautions should be taken.
- Before leaving a lake or other body of water, drain all water from the bilge, live wells, and any other water-holding device of your watercraft.
- Rinse out the boat, bilge, live wells, and equipment with fresh water and, if possible, allow the equipment to dry for 2 to 3 days before using it at another body of water.
- For an extra precaution, it is recommended to spray the surface of equipment with a 10% bleach solution, allowing a 15-minute contact time before rinsing the area with clean water free of algae and allowing it to dry.
- Never move water, live animals, or plants from one body of water to another as you may also transplant undesirable species such as golden algae.