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In September 1996 and again in September 1997, residents of Texas's coasts witnessed an increasing problem:
discolored, red patches of ocean waters and thousands and even millions of dead fish washed up on the shores. Red tides are produced when microscopic toxic algae increase in number and
"bloom," causing the telltale discoloration of the oceans. The type of red tide that has affected Texas's fish and shellfish is caused by an organism called Gymnodinium breve, which produces
a toxic affecting the central nervous system of fish.* In December of 2001, another red tide bloom affected the Corpus Christi Bay, causing the Texas Department of Health to ban shellfish harvesting for Aransas and Corpus Christi Bays for nearly a year.*
Another form of microscopic algae produces brown tide, which is not toxic to fish but does block out sunlight,
killing underwater plants and ultimately the fish themselves, which depend upon this vegetation. Brown tide has plagued the Corpus Christi area for several years by killing eelgrass and other
vegetation, ultimately destroying the fish habitat.* Brown tides have also affected the upper Laguna Madre, significantly affecting recreational fishing.
Still a third type of dangerous microscopic organism called pfiesteria was discovered in 1991 and has killed
millions of fish in North Carolina. Pfiesteria usually remain in a cystlike condition in the sediment of bays and estuaries, but when fish swim by, the organisms strike, using whiplike tails,
or flagella. Their increasing numbers have been tied to development along the North Carolina coast, which has led to an influx of pollutants rich in nutrients like nitrogen and phosphorus.
The growth in gigantic hog farms, leading to untreated hog feces and urine contaminating rivers, bays, and estuaries has also been linked to the increasing cases of pfiesteria.* This organism, however, has never been confirmed as occurring in Texas.
Golden alga is still another harmful algal bloom which has impacted Texas in recent years, although it has
impacted salty inland waters rather than bays and estuaries. Fish kills from the golden alga -- Prymnesium parvum -- have been documented since 1985, when waters of the Pecos River were
filled with dead fish which has come into contact with the toxins released from the golden alga. Since that time, most occurences of Golden alga have occurred in West Texas where waters are
more saline. Thus far, golden alga has caused fish kills in five major river systems, including the Canadian River, in the Lake Meredith stilling basin, along the Red River (the Wichita River
including Lake Kemp, Diversion Lake and the Dundee State Fish Hatchery), the Brazos River (Paint and California creeks, upper segments of the river, Lubbock City Lakes 1 thru 6, Possum
Kingdom Reservoir, Lake Granbury and Lake Whitney), the Colorado River (upper segments of the river, E.V. Spence Reservoir, Lake Colorado City, Moss Creek Lake and the river between E.V.
Spence and O.H. Ivy Reservoir), and the Pecos River (the entire river in Texas, Red Bluff Reservoir and the headwaters of Lake Amistad on the Texas-Mexico border).*
These so-called harmful algal blooms (HABs) can also affect humans who either handle or eat affected fish and
shellfish. For example, consumption of shellfish contaminated by Gymnodinium breve can lead to neurotoxic shellfish poisoning with symptoms such as tingling skin, nausea, vomiting, and some
loss of muscle control.* The consumption of finfish, crabs, and shrimp contaminated with red tide cells, however, does not appear to lead to these kinds of problems. Airborne toxins created by red tide can cause nose, throat, and eye irritations.* The eating or handling of fish contaminated by pfiesteria can cause open sores, nausea, memory loss, fatigue, dizziness and disorientation, and even near incapacitation.* Golden alga is not believed to impact non-aquatic species like cows or humans which drink the water, however, although caution when handling fish impacted by golden alga is recommended.
In September 1996, millions of fish in the Corpus Christi and Aransas bays washed up on shore. Following
extensive water and shellfish testing, the Texas Health Department issued an aquatic closure for oyster, clam, and mussel beds in both areas. The closure lasted until January 1997. In
September 1997, red tide struck again—this time farther south near South Padre Island, Padre Island National Seashore, and Mustang Island. In November and December, fish began dying from red
tide farther north in Oso and Corpus Christi bays and the Upper Laguna Madre. The high counts of red tide cells led to the closings of Corpus Christi and Aransas bays once again.* In late 2001 and early 2002, red tide reappeared, killing millions of fish in Corpus Christi, Aransas, Nueces and the Upper Laguna Madre Bay.* Unfortunately, there is little information on
exactly why red tide increases generally from August to February. While some posit climactic and hydrological conditions, others believe that increased nutrients and pollution from the shore
may be a factor.
The TPWD provides information about where red tide has been spotted or confirmed. To report a fish kill or find
out information on red tide, call the TPWD Kills and Spills Team at (512) 912-7055. Information is also available on their website (http://www.tpwd.state.tx.us) or on the
TPWD hotline at (800) 792-1112. Finally, the Texas Department of Health provides information about aquatic life closures or consumption advisories due to red tide. Call them at (800)
685-0361.
To deal with the problems of fish kills from alga blooms both along the coast and in inland waters, the Texas
Department of Health, TCEQ, TPWD, Texas Department of Agriculture, and several state universities have formed a workgroup known as the Harmful Algal Bloom Committee to help coordinate
research and mitigation efforts.
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