Oso Bay and the Laguna Madre: Assessing the Aquatic Life Use
Counties: Cameron, Kenedy, Kleberg, Nueces, Willacy
Parameter: Dissolved oxygen
Basins: Bays and Estuaries, San Antonio–Nueces Coastal Basin, Nueces River Basin, Nueces–Rio Grande Coastal Basin
Oso Bay is an enclosed, shallow body of water situated along the southern shore of Corpus Christi Bay, with a surface area of approximately seven square miles. The bay receives fresh water from Oso Creek, a stream whose flow is dominated by permitted discharges, and exchanges salt water with Corpus Christi Bay. Ecologically, Oso Bay provides habitat for many plants and animals, and plays an influential role in water purification and storm protection.
The Laguna Madre is one of only five hypersaline or negative estuaries in the world. The Laguna is a shallow, bar-built coastal lagoon with limited freshwater inflow and a surface area at mean high tide of 729 square miles. The Arroyo Colorado is primarily responsible for freshwater inflow to the lower Laguna Madre. Ecologically, the Laguna is characterized as exhibiting hypersaline conditions, barren shorelines with extensive wind-tidal flats, extensive submerged seagrass meadows, and a highly productive finfishery.
Water quality testing found that concentrations of dissolved oxygen are sometimes lower than the criterion established to assure a healthy aquatic ecosystem. 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.
The TCEQ’s TMDL Program assessed concentrations of dissolved oxygen and their effect on aquatic life in the two water bodies. Based on those results, the Standards Team prepared a use attainability analysis (UAA) for the bay.
In 2010, the TCEQ proposed revisions to the site-specific standards for dissolved oxygen in the bay. The EPA rejected those revisions as not adequately supported by the documentation. The Standards Work Group is carrying out additional assessment to support a change in the standard.
- Water Quality and Biological Characterization of Oso Creek and Oso Bay, Corpus Christi, Texas
- Oso Bay and Laguna Madre Phase III and IV Data Report
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