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Texas Water Bodies: Toxicity

This completed project assessed the extent and severity of toxicity in ambient water and sediment in seven Texas water bodies.
photo of alligator bayou
Alligator Bayou

Counties: Brazos, Brewster, Cameron, Harris, Jefferson, Kinney, Maverick, Presidio, Terrell, Val Verde, Webb, Willacy, Zapata
Parameter: Toxicity in water and sediment
Basins: Neches-Trinity Coastal, San Jacinto River, Brazos River, Nueces–Rio Grande Coastal, Rio Grande
Segments: 0702A, 1007A, 1209A, 1209B, 2201, 2304, 2306

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Background and Goals

Water quality data assessed in 1999 indicated that toxic conditions might exist in the water or sediment of seven water bodies at various locations in Texas. Toxicity in water and sediment are among several conditions TCEQ evaluates to determine whether a water body can support a healthy aquatic community.

To determine the potential of water bodies to be toxic to aquatic life, sensitive aquatic organisms are exposed to water and sediment samples under laboratory conditions. These sensitive organisms serve as surrogates for the species indigenous to the water bodies being tested. However, there is not always a positive correlation between toxicity observed in the laboratory and actual toxic conditions in a water body being tested. Also, the laboratory tests used to determine possible toxicity do not identify the specific chemical toxicants responsible for the observed effects on aquatic life.

The goal of this project was to confirm whether toxic effects were present and to determine the causes, where present. 

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Summaries of Test Results

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Final Reports

Toxicity was verified in five of the seven water bodies (all except the Arroyo Colorado, Segment 2201, and the Rio Grande Below Amistad Reservoir, Segment 2304). Because the Rio Grande forms an international border, all plans to address toxicity in the river must be developed and coordinated with Mexico and with other U.S. state and federal agencies.

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The posters below were presented at the SETAC 24th Annual Meeting in North America, November 2003. 

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Contact the TMDL Program

Email, and mention the toxicity assessment project in the subject line. Or call us at 512-239-6682.

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