Final report : benthic samples taken from the Padre Island National Seashore

From March 1989 through January 1992 sediment samples were taken from subtidal areas within the boundary of the Padre Island National Seashore. These samples were taken as part of a large multidisciplinary study to determine how a hot, hypersaline estuary is able to maintain a large commercial finfishery harvest. ... This report is on just one component, the benthic component.From University of Texas at Austin, Marine Science Institute ... to United States Department of Interior, National Park Service, Padre Island National Seashore.September 1992Marine Scienc

Monitoring Hypoxia Conditions in Corpus Christi Bay – 2005

Hypoxia occurs predominantly in the southeastern region of Corpus Christi Bay in summer. During the summer of 2005, a moderate number of hypoxia events were found in spatial surveys in comparison to previous years. Disturbance by hypoxia did not significantly change over the nine year period sampled. Additional long-term sampling is needed to determine if disturbance caused by hypoxia is significantly changing over time in Corpus Christi Bay or if anthropogenic changes, such as the dredging of Packery Channel and brine discharge into Oso Bay will have an effect on the occurrence of hypoxic events.Coastal Bend Bay and Estuaries Program contract number 0528Marine Scienc

Matagorda Bay and Nearby Coastal Waters Dissolved Oxygen and pH TMDL Assessment Report

This project provides technical support to the Texas Commission on Environmental Quality (TCEQ) for the development of a Total Maximum Daily Load (TMDL). The TCEQ will lead an effort to assess the causes and sources of the following water quality problems identified in the 2002 Texas Water Quality Inventory and 303(d) List for Matagorda Bay/Powderhorn Lake (Segment 2451), which only partially supports the aquatic life use due to exceedence of the dissolved oxygen (DO) standard on the east half of the main bay; Tres Palacios/Turtle Bay (Segment 2452),which only partially supports the aquatic life use due to exceedance of the dissolved oxygen standard in the Palacios area assessment unit and Carancahua Bay (Segment 2456); which only partially supports the general use due to high pH in 9.2 square miles at the north end of the bay; and Carancahua Creek and Conn Brown Harbor (Segment 2483A), which does not support the aquatic life use in the entire harbor due to depressed dissolved oxygen. The goals of the current project were to develop a Quality Assurance Project Plan, to develop and implement a monitoring program to assess the DO conditions in Matagorda Bay, Tres Palacios Bay, and Conn Brown Harbor and the pH conditions in Carancahua Bay, and to assess the data collected from the monitoring plan and determine the cause of impairments that result in exceedence of the water quality criteria.Project Title: Total Maximum Daily Load (TMDL) AssessmentFinal Report Submitted To: Texas Commission On Environmental QualityUmbrella Contract No. 582-1-30479 (UTMSI) Total Maximum Daily Load Research Support Work Order No. 582-1-30479-07Marine Scienc

Final report : verification of bay productivity measurement by remote sensors

From University of Texas at Austin Marine Science Institute to Texas Water Development BoardInteragency cooperative contract TWDB contract no. IA03-483-003July 2004Ecosystem function in estuarine environments is known to be an important indicator of ecosystem health and productivity. There is a need to quantify estuarine ecosystem function variability and link to freshwater inflow to enable better management of ecosystem health and productivity. An important and quantifiable component of ecosystem function is ecosystem metabolism. Results indicate that open water methods were more appropriate than light-dark bottle methods for measuring net ecosystem metabolism in shallow water estuarine ecosystems because of the large contribution of benthos, which is ignored in water bottles. Spatial and temporal variability in net ecosystem metabolism was found. Spatial variability was attributed to differences in benthic habitats and/or station locations with respect to freshwater inflow point sources. Temporal variability in net ecosystem metabolism may be driven by differences in seasonal temperatures and freshwater inflow differences on seasonal time scales. Net ecosystem metabolism was directly related to amounts of freshwater inflow. The strength of this relationship depended on proximity to freshwater sources. Future studies of whole ecosystem metabolism in shallow estuarine ecosystems should employ open water methods and should strive to link other dynamic environmental conditions, such as temperature or irradiance, to ecosystem health, function, and productivity.Marine Scienc

Final report : effect of freshwater inflow on macrobenthos productivity and nitrogen losses in Texas estuaries

"The primary goal of the current research program is to define quantitative relationships between marine resource populations and freshwater inflows to the State's bays and estuaries. However, we know that there is year-to-year variability in the population densities and successional events of estuarine communities. This year-to-year variability is apparently driven by long-term, and global-scale climatic events that affect the rates of freshwater inflow. Therefore, this report documents long-term changes in populations and communities that are influenced by freshwater inflow. The best indicator of productivity is the change in biomass of the community. A secondary goal of the current research program is to quantify the loss of nitrogen in Texas estuaries. Nitrogen is the key element that limits productivity. A simple budget would account for nitrogen entering the bay via freshwater inflow, how it is captured and transformed into biomass, and finally how it is lost from the ecosystem. One aspect of nitrogen loss is very poorly understood: How much nitrogen is buried and lost from the system? We report here nitrogen content changes with respect to sediment depth. Presumably nitrogen is labile in the upper, biologically active, layers of sediment, and refractory at depth. Therefore, it is important to determine the sediment depth at which nitrogen content is at a low and constant value. This study is a continuation of freshwater inflow studies that began in 1984. The goals have evolved over the years to reflect the synthesis of new information and the management needs of the Texas Water Development Board (TWDB). The original studies (1984-1986) were designed to determine the effect of inflow on Lavaca Bay. One station used during that study is still being sampled. San Antonio Bay was studied in 1987, and the Nueces Estuary (Nueces and Corpus Christi Bays) were studied in 1988. Long-term studies of the Lavaca-Colorado and Guadalupe Estuaries began in 1990. Although, there is ten years worth of data in some cases, we have not sampled over two entire wet-dry cycles. We have sampled over one and one-half cycles. We are currently beginning to enter a dry cycle. The completion of this research will take about two more years and should end when we enter the next wet cycle, which will be heralded by the next El Nino event.From University of Texas at Austin Marine Science Institute ... to Texas Water Development BoardInteragency cooperative contract, TWDB contract no. 97-483-199December 1997Marine Scienc

Research technical final report : inflow needs assessment : effect of the Colorado River diversion on benthic communities

February 1994To Lower Colorado River Authority ... Austin, TexasThe Lavaca-Colorado Estuary has three major sources of freshwater inflow: the Lavaca, Tres Palacios, and Colorado Rivers. In 1991 the Colorado River was diverted to increase freshwater inflow into the east arm of Matagorda Bay. it was hypothesized that increased freshwater inflow would enhance productivity in the bay. The goal of this study was to determine the status of the bay and effectiveness of the water management program. Six stations were chosen along the major inflow gradients of the Lavaca and Colorado Rivers, and sampled quarterly for one year. Benthic macrofaunal abundance, biomass and community structure was measured. Observed salinity gradients at the stations indicated that marine water was diluted by freshwater near the mouthes of the rivers. Lavaca Bay and the east arm of Matagorda Bay had similar, low salinity characteristics. Both areas had similar community structure, and were typical of low salinity zones of Texas estuaries. However, there was an obvious enhancement of abundance, biomass and diversity in the east arm of Matagorda Bay (near the diversion of the Colorado River) relative to Lavaca Bay. These results indicate that the diversion probably has enhanced the productivity and health of Matagorda Bay. The only confounding factor is that the east end of Matagorda Bay also has less development than Lavaca Bay.Marine Scienc

Final report : effect of freshwater inflow on macrobenthos productivity in minor bay and river-dominated estuaries, FY01

The current contract is the first of a planned five-year study with the goal to determine the importance of freshwater inflow in maintaining benthic productivity in minor bays and river dominated systems. Minor bays are defined as those small bays that do not have direct freshwater inflow via a major river, but do have inflow from runoff or other indirect sources. Only a few rivers in Texas flow directly into the Gulf of Mexico, and these are also part of the subject study. The current project follows successful completion of a long-term study of large, or major open bays in Texas. The focus of this final report is on East Matagorda Bay. Biological data is added to a previous sediment study on nitrogen losses to compile a complete view of that system. Sampling was also begun for a long-term study of two river-dominated systems, the Rio Grande and Brazos River. The current report goes into lesser detail for this data as it will be subject to a fuller treatment in future.Benthos abundance, biomass, and diversity will be measured to assess inflow effects on ecosystem productivity. In addition, relevant water quality variables (i.e., salinity, temperature, dissolved oxygen, nutrients, and chlorophyll) will be measured during each sampling period to assess inflow effects on the overlying water, which affects benthos. The first year study was performed to initiate a long-term study of the two river estuaries (Brazos and Rio Grande) and complete a study of East Matagorda Bay, a minor bay.From University of Texas at Austin Marine Science Institute ... to Texas Water Development BoardInteragency cooperative contract, TWDB contract no. 2001-483-362October 2001"December 2001"--Cover leafMarine Scienc

How a Simple Question About Freshwater Inflow to Estuaries Shaped a Career

Chance and good luck led to a career studying how freshwater inflow drives estuary processes. In 1986, someone asked me: How much fresh water has to flow to a bay for it to be healthy? The question shaped my career. There is probably no better place on Earth to compare effects caused by inflow differences than the Texas coast, because the major estuarine systems lie in a climatic gradient where runoff decreases 56—fold from the Louisiana border in the northeast to the Mexico border in the southwest. This estuary—comparison experiment was used to study inflow effects. The science evolved from the idea in the 1990’s that organisms responded directly to inflow rates to the domino theory in the 2000’s of indirect effects where inflow drives estuary conditions and that organisms respond to those habitat conditions. Today it is hypothesized that climate drives hydrology, which drives estuary dynamics; and thus, climatic factors can indirectly shape estuarine structure and function. Assuming change along the inflow gradient is analogous to effects of altering estuaries over time, we can now predict ecosystem change with changing climate or land—use change

Final report : effect of freshwater inflow on macrobenthos productivity and nitrogen losses in Texas estuaries

"The primary goal of the current research program is to define quantitative relationships between marine resource populations and freshwater inflows to the State's bays and estuaries. However, we know that there is year-to-year variability in the population densities and successional events of estuarine communities. This year-to-year variability is apparently driven by long-term, and global-scale climatic events that affect the rates of freshwater inflow. Therefore, this report documents long-term changes in populations and communities that are influenced by freshwater inflow. The best indicator of productivity is the change in biomass of the community. A Secondary goal of the current research program is to quantify the loss of nitrogen in Texas estuaries. Nitrogen is the key element that limits productivity. A simple budget would account for nitrogen entering the bay via freshwater inflow, how it is captured and transformed into biomass, and finally how it is lost from the ecosystem. One aspect of nitrogen loss is very poorly understood: "How much nitrogen is buried and lost from the system?" We report here nitrogen content changes with respect to sediment depth. Presumably nitrogen is labile in the upper, biologically active, layers of sediment, and refractory at depth. Therefore, it is important to determine the sediment depth at which nitrogen content is at a low and constant value. ... The structure of this report is as follows. Chapter one is a manuscript which has been submitted for publication in the American Malacological Bulletin. This manuscript summarizes all biological data on mollusks taken to date and synthesizes current information on the biological effects of freshwater inflow on a key indicator taxanomic group. Chapter two is a compilation of biological and hydrographical data obtained during the last two years. Chapter three is a compilation of all the sediment data on nitrogen losses that has been collected to date. Chapter three also contains a brief narrative describing the data and drawing preliminary conclusions.From University of Texas at Austin, Marine Science Institute ... to Texas Water Development BoardInteragency Cooperative contract TWDB contract no. 94-483-003October 1994Marine Scienc