The coastal wetlands at Aransas National Wildlife Refuge near Austwell, Texas, support the last migrating population of whooping cranes during the winter months (October through April). With a population currently at 216 individuals, these are the rarest cranes in the world. The wetlands in which they winter are a part of the San Antonio Bay system, a bay that receives constant fresh water flow from the Guadalupe River. Currently there is a plan for using water diverted from the Guadalupe River just before it enters San Antonio Bay as a water supply for the greater San Antonio metropolitan area located 200 km to the northwest. The Guadalupe River delivers nutrients and sediment into the estuary along with fresh water. Because of the importance of sediment within a tidal wetland ecosystem, it is imperative to understand the sediment budget and underlying forces that drive it if one is to ultimately grasp how this ecosystem functions. To document natural and anthropogenic factors exerting control over sediment movement in this system, three sites on tidal creeks near the boundary between marsh and bay were chosen. The Gulf Intracoastal Waterwayparallels the marsh edge. Over six, non-consecutive weeks water level and velocity were automatically monitored in the tidal creeks. Automated water samplers extracted water samples that were analyzed for suspended sediment. In addition, bedload traps were deployed in one creek to monitor sediment movement along the channel bottom. Inflow exceeded outflow during the study. As a result there was a net influx of suspended sediments into the marsh. Bedload material also moves with current direction, and it appears to move in response to barge induced outflow currents. Barges passing on the Gulf Intracoastal Waterway exert influence on water level, flow direction, and velocity within tidal creeks. Natural factors such as winds, tides, and freshwater input from upland runoff or river discharge also impact suspended and bedload sediments.

The following report describes the conception, pre-production, production, and post-production of the short film Yvonne & Clyde. Set in present day South East Texas, the film was shot in the Texas gulf towns of Bayside, Aransas Pass, and Port Aransas. The film follows the journey of the same two small time crooks named in its title as they drive towards the coast to extort money from an estranged relative. It’s an atmospheric piece centered on tone, setting, character, and performance rather than plot. It is a glimpse into the lives of these two long time friends on the last hundred or so miles of the trip. The majority of the writing contained in the report is a first-person narrative detailing the process of the film’s creation from its early genesis through to principal photography and into post-production. Included in the report is an early draft of the script. / text

Changes in freshwater inputs due to water diversions and increased urbanization may alter the function and properties of estuarine ecosystems in South Texas. Freshwater and nitrogen inputs from the Mission and Aransas rivers to the federally designated Mission-Aransas National Estuarine Research Reserve (Mission-Aransas NERR) have received considerable attention in the past few years. However, freshwater inputs from two rivers (the San Antonio and Guadalupe rivers) that combine and drain into a neighboring bay (San Antonio Bay) may also provide a substantial nitrogen source to Aransas Bay, which is within the boundaries of the Mission-Aransas NERR. In order to study the influence of the San Antonio and Guadalupe rivers, an oyster species, Crassostrea virginica, was chosen to provide time-integrated information about freshwater contribution as a nitrogen source within the bays. Chapter One addresses variations in isotope values ([delta]¹⁵N and [delta]¹³C) in oyster adductor muscle tissue from 2009-2011 along a sampling transect from the head of San Antonio Bay through Aransas Bay. Stable carbon isotope values increased linearly from approximately -25 % to -17 %, while stable nitrogen isotope values decreased from approximately +16 % to +10 % along this transect. The patterns in stable carbon and nitrogen isotope values are consistent with substantial mixing of river-supplied water and nitrogen from San Antonio Bay into Aransas Bay. Variations in nitrogen isotopic signature between periods of sustained drought and flood conditions were relatively small, suggesting that riverine nitrogen contributions were similar regardless of the amount of freshwater inflow observed during the time frame of this study. Chapter Two addresses the isotopic equilibration time for adult oyster adductor muscle tissue using a year-long transplant experiment (November 2010-November 2011). Full representation of ambient water isotopic composition in oyster adductor muscle tissues was determined to occur roughly a year after transplant. Oyster adductor muscle could therefore be useful for long-term monitoring of nitrogen contribution from freshwater sources, and would be valuable to include in concert with water sampling and analysis of other tissues that have shorter integration rates for a comprehensive view of an estuarine system. / text

Understanding the salt marsh ecosystem in the Guadalupe Estuary is needed because wetlands in this system support the endangered whooping crane (Grus americana). The marsh plant research and monitoring described herein were based in the salt marshes at Aransas National Wildlife Refuge (ANWR), which are utilized by the cranes each winter. Past research indicates that the Carolina wolfberry (Lycium carolinianum) contributes 21-52% of crane energy intake early in the wintering period (Chavez 1996). Beginning in Fall 2003, vegetation transects were sampled along an estuarine gradient at ANWR. Species diversity and composition was similar at the three sites, with all sites containing the same 6-7 common species. While Spartina alterniflora is only a minor part of this vegetation community, it dominates the few low inter-tidal, fringe areas present. Species composition exhibited little variability from Year 1 to Year 2 of the study. Densities and biomass of L. carolinianum were not significantly different between sites or years. L. carolinianum, while important to salt marsh ecology, accounts for only a small portion of the overall productivity. Based on correlation coefficients, L. carolinianum was found in association with some of the common species in the vegetation community, indicating that its growth and survival requirements are typical to the salt marshes at ANWR. Also beginning in Fall 2003, I repeatedly sampled L. carolinianum in permanent plots along the estuarine gradient. L. carolinianum exhibits strong temporal patterns. Leaf production peaked in early spring and again just prior to peak berry abundance. Flowering of L. carolinianum occurred in October and November. Peak berry abundance coincided with the cranes’ arrival in late October and early November. Berry production occurred in October, November, and December; berries were virtually non-existent in the marshes for the remainder of the year. Stepwise regression showed stem diameter alone was a good estimator of aboveground biomass of this species in ANWR marshes, accounting for 94% of the variability (p<0.001). Changes in aboveground biomass followed no distinct patterns in the year of monitoring, perhaps due to the woody stem of the plant. Spatial patterns in L. carolinianum were not explained by water quality parameters alone; it is suggested that soil properties may help to account for the spatial variability.

River export has a strong influence on the productivity of coastal waters. During storm events, rivers deliver disproportionate amounts of nutrients and organic matter to estuaries. Anthropogenic changes to the land use/cover (LULC) and water use also have a strong influence on the export of nutrients and organic matter to estuaries. This study specifically addressed the following questions: 1) How does river water chemistry vary across LULC patterns in the Mission and Aransas river watersheds? 2) How do fluxes of water, nutrients, and organic matter in the rivers vary between base flow and storm flow? 3) How do variations in nutrient/organic matter concentrations and stable isotope ratios of particulate organic matter (POM) in Copano Bay relate to river inputs? Water was collected from the Mission and Aransas rivers and Copano Bay from July, 2007 through November, 2008 and analyzed for concentrations of nitrate, ammonium, soluble reactive phosphorus (SRP), dissolved organic nitrogen, dissolved organic carbon, particulate organic nitrogen, particulate organic carbon (POC), and the stable C and N isotope ratios of the POM. The first half of the study period captured relatively wet conditions and the second half was relatively dry compared to long term climatology. Riverine export was calculated using the USGS LOADEST model. The percentage of annual constituent export during storms in 2007 was much greater than in 2008. Concentration-discharge relationships for inorganic nutrients varied between rivers, but concentrations were much higher in the Aransas River due to waste water contributions. Organic matter concentrations increased with flow in both rivers, but POM concentrations in the Aransas River were two fold higher due to large percentages of cultivated crop land. Values of [delta]¹³C-POC show a shift from autochthonous to allochthonous organic matter during storm events. Following storm events in Copano Bay, increases and quick draw down of nitrate and ammonium concentrations coupled with increases and slow draw down of SRP illustrate nitrogen limitation. Organic matter concentrations remained elevated for ~9 months following storm events. The [delta]¹³C-POC data show that increased concentrations were specifically related to increased autochthonous production. Linkages between LULC and nutrient loading to coastal waters are widely recognized, but patterns of nutrient delivery (i.e. timing, duration, and magnitude of watershed export) are often not considered. This study demonstrates the importance of sampling during storm events and defining system-specific discharge-concentration relationships for accurate watershed export estimation. This study also shows that storm inputs can support increased production for extended periods after events. Consideration of nutrient delivery patterns in addition to more traditional studies of LULC effects would support more effective management of coastal ecosystems in the future. / text

The respective kinetics of bacterial leucine aminopeptidase and [beta]-glucosidase activities were investigated to improve understanding of factors controlling activity and hydrolytic capacity in estuarine organic-poor sands. Depth distributions of enzyme activity and bulk organic matter content were determined in sediments of Aransas Bay and Copano Bay Texas, to investigate enzyme dynamics as related to the geochemical properties of the sediment. Vertical profiles of activity in sediment showed that the enzymes were more active at the surface and that the potential hydrolysis rate of leucine aminopeptidase was higher than that of [beta]-glucosidase. Vertical patterns of enzyme activity correlated (weakly) with variations in sediment organic matter (TOC, TN, and carbohydrates) content. Enrichments of sediment samples with monomeric organic compounds and inorganic nutrients did not affect leucine aminopeptidase and [beta]-glucosidase activities in short- and long-term incubations. Enzyme activity was independent of nutrient availability and suggested that microbial communities were not nutrient-limited. Time-course assays of bacterial hydrolysis of TOC, TN, and carbohydrates provided information about how substrate limitation may affect enzyme activity. Positive correlations between bulk TOC and TN content and enzyme activity indicated enzyme dependence on polymeric substrate content. Induction of enzyme activity after sediment enrichments with specific labile compounds confirmed the importance of available organic substrate to enzyme hydrolysis efficiency. A kinetic approach established the occurrence of enzyme inhibition and its effects on enzyme hydrolytic capacity. The addition of a specific-enzyme substrate to sediment samples modified enzyme parameters and indicated that a substrate-reversible type of inhibitor could reduce enzyme hydrolytic capacity. The addition of polyphenol, as a natural inhibitor of enzyme activity, to the sediment resulted in a concomitant reduction of leucine aminopeptidase activity and ammonium regeneration rate, and thus demonstrated a close coupling between enzyme activity and sediment ammonium regeneration. These research results demonstrate the dynamic nature of the hydrolytic enzymes, provide information about the mechanisms of induction and inhibition of activity, and demonstrate some implications of reducing the hydrolytic capacity to organic matter decomposition and nutrient regeneration rates. / text

Between July 2009 and October 2011, a new habitat was found for a rarely reported freshwater dinoflagellate species, Thompsodinium intermedium - Comal Springs (Comal County), Texas. In 2011, diel in-situ monitoring in monospecific blooms of this species revealed previously undetected negative impacts on endangered species habitat availability associated with conditions of low flow levels, recorded at the U.S. Geological Survey gage # 08169000 on Texas Commission on Environmental Quality river segment 1811 station 12655. During a period of low springflow in the summer of 2011, late afternoon and early morning measurements of dissolved oxygen and temperature and presence of dinoflagellate blooms were monitored at six sites. Significant differences in diel fluctuations were found in all of these parameters among sites with and without the planktonic blooms. These fluctuations increased risk of hypoxia and hyperthermia conditions at sites of planktonic bloom events. Arrays of in-situ continuous monitoring temperature/light probes were used inside and outside of blooms. Wildlife and human health implications are that hypoxia and hyperthermia are known to promote conditions favorable to harmful microbes which may be transported from springs to coastal bays. In-situ data demonstrated that T. intermedium blooms, hypoxia, and hyperthermia occurred in the upper Comal headwaters. These natural environmental stressors may be avoidable if adequate springflows are maintained to buffer against these impacts.