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Lavaca Bay and Chocolate Bay

This completed project assessed support of aquatic life use in Lavaca Bay and Chocolate Bay.

Counties: Calhoun, Jackson, Victoria
Parameters: Mercury in water, dissolved oxygen
River and Coastal Basins: Bays and Estuaries, Lavaca River, Lavaca-Guadalupe Coastal Basin
Segment: 2453

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Background and Goals

This project addressed the concentrations of mercury and dissolved oxygen in Lavaca and Choclate bays. Mercury, a metal, accumulates in the tissue of aquatic species and is toxic if consumed in large quantities over an extended period of time. Oxygen, which dissolves in water, is essential for the survival of aquatic life. While the amount of dissolved oxygen in water fluctuates naturally, various human activities can cause unusually or chronically low dissolved oxygen levels, which may harm fish and other aquatic organisms.

In both bays, water quality testing indicated that dissolved oxygen concentrations and elevated mercury concentrations in the bays were not optimal for supporting aquatic life. People are advised to limit their consumption of fish and crabs from the bays because mercury concentrations in fish and crab tissue pose a risk to consumers. Oyster harvesting is restricted because of elevated bacteria concentrations.

Sampling results for dissolved oxygen and mercury in water indicated that TDMLs are not necessary for those parameters. Based on those results, TCEQ removed dissolved oxygen and mercury in water from the list of impairments for Lavaca Bay and Chocolate Bay on the Texas 303d List. Mercury in fish and crab tissue is being addressed by the Superfund Program. For more detailed project results, see the final reports in the Project Documents section.

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Description of Watershed

Lavaca Bay and Chocolate Bay, both included in Segment 2453, are part of the larger Matagorda Bay System located on the Texas Gulf Coast. Together these bays comprise 54.8 square miles. The average depth of both bays is four feet; however, Lavaca Bay can be as deep as seven feet naturally, and is 35–40 feet deep in dredged channels. The major tributaries to the bays are the Lavaca and Navidad Rivers. Venado, Garcitas, and Placedo Creeks are also important contributors of fresh water to the bays. Oyster beds and reefs are numerous, as are marshes and wetlands. Counties in the watershed include Calhoun, Victoria, and Jackson. Port Lavaca and Point Comfort are the major communities.

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Project Documents

The final reports are available in PDF.

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For More Information

Please email and mention the Lavaca Bay assessment project in the subject line. Or call us at 512-239-6682. 

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