Long-term Benthic Data Informs Adaptive Management of Freshwater Inflow to the Texas Coastal Bend

Principal Investigator

Research

The purpose of this project is to analyze archived benthic (bottom-dwelling) samples to extend the long-term dataset of benthos community structure in samples collected from three Texas estuaries in the Texas Coastal Bend: Lavaca and Matagorda Bays (Lavaca-Colorado Estuary), San Antonio Bay (Guadalupe Estuary), and Nueces and Corpus Christi Bays (Nueces Estuary). Benthic organisms are ideal bioindicators of freshwater inflow effects on bays and estuaries, because they are fixed in space and integrate ephemeral processes in the overlying water column over long periods of time. Past studies have demonstrated that long-term hydrological cycles (which are driven by long-term climate cycles and change) affect freshwater inflow and water quality, and also regulate benthic abundance, productivity, diversity, and community structure.

Each Texas estuary is distinct, but they form at the mouth of a river, where freshwater flows into a secondary bay. The secondary bays are connected to primary bays, which are open to the Gulf of Mexico and influenced by tides. Thus, within each estuary there is a salinity gradient from lower salinity secondary bays to higher salinity primary bays. Sampling along the gradient was established in 1987 in all three systems. This time series has been intermittently funded, and while all water quality measurements (for salinity, dissolved oxygen, nutrients, and chlorophyll) have been made, many benthic samples have been archived because of a lack of funding.

The current study will extend documentation of benthic conditions by analyzing 1,056 archived samples. This will extend the time-series of water and sediment quality data from 1987 to 2019, which is a 32-year record. This data is necessary for the Senate Bill 3 adaptive management process, which calls for consideration of the ecological soundness of riverine, bay and estuary systems, and riparian lands (wetlands) in the water permitting process.

Project Objectives:

To support adaptive management of freshwater inflows to three Texas Coastal Bend estuaries: Lavaca and Matagorda Bays (Lavaca-Colorado Estuary), San Antonio Bay (Guadalupe Estuary), and Nueces and Corpus Christi Bays (Nueces Estuary).
To extend the long-term dataset of benthos community structure by analyzing archived benthic samples from the Coastal Bend from 2010 to 2016 and 2019 (7 years).
To engage with three Basin and Bay Area Stakeholders Committees (BBASCs) responsible for reviewing and adopting freshwater inflow standards in the Coastal Bend.
To publish and disseminate new knowledge about the long-term dynamics of water and sediment quality as it is affected by freshwater inflow in Coastal Bend estuaries. Results of the study will be presented to BBASCs, local stakeholder groups, and State agency personnel.