Acoustic current meter data collected in the shallow ( 3m depth) Trinity Bay, (TB a sub-bay in Galveston Bay), TX, estuary were used to characterize locally generated windwaves. Significant wave heights, periods, and directions were estimated from dynamic pressure time-series (P; near bottom) and horizontal current velocities (U, V). Surface wave spectra were calculated from the pressure time-series and fitted to the empirical shallowwater Texel, Marsen, and Arsloe wave spectrum. The mean shape parameters used to define the TB wave spectra were:alpha = 0:016, gamma = 4:26, sigma-a = 0:063, sigma-b = 0:089. Waves heights were also hindcast using empirical and numerical models. The empirical formulas were derived from fetch-limited shallow water observations and follow the current proposed asymptotic limit to wave growth in shallow depth. The depth range for this empirical formulation is extended from 0.5–2m out to 3.5m. The model does not work for wind speeds less than 1m/s and during rapid wind direction changes. The Shallow WAves Nearshore numerical model was implemented in a Galveston Bay (GB; encompassing TB) computational domain. The model was forced with wind speeds and directions measured on-site and in four surrounding locations maintained by the NOAA PORTS. Currents measured on-site in TB and calculated bottom frictions were input homogeneously in space. The model was run in steady and unsteady conditions, and the modeled wave spectra were compared to the observations. The modeled wave spectra do not recreate the observed spectral shape for the steady and unsteady conditions. However, the total wave energy is represented in the unsteady conditions. In both the steady and unsteady cases, the wave period is underpredicted by one-half times the observed spectra and the model direction agrees with the observed wave directions.

The structure and function of coastal marshes results from a complex interaction of biotic and abiotic processes that continually influence the characteristics of marsh vegetation. A great deal of research has focused on how tidal processes influence vegetation dynamics along the Atlantic coast, but few studies have investigated the influence of similar processes in the marshes along the Gulf of Mexico. This study aims to identify the characteristic vegetation assemblages of the coastal marshes bordering the East Bay of Galveston Bay, Texas, and identify if elevation, inundation frequency and burning frequency are important to their structure. To identify characteristic vegetation assemblages, hierarchical cluster analysis was used. The cluster analysis resulted in seven statistically different vegetation assemblages that were used in diversity analysis and classification and regression analysis (CART) as dependent variables. Diversity measures were calculated at both the plot and assemblage scale using Shannon's diversity index and species richness. The resulting diversity measures were used as predictor variables in the CART analysis as well as regression analysis. Hydrologic modeling was accomplished using Mike 21, a flow and wave simulation model, along with a geographic information system (GIS), to model hourly inundation frequency at each of the sampled plots. The inundation frequency was then used as a predictor variable in the CART analysis and regression analysis. This study found that the main factor contributing to species richness was elevation. Vegetation assemblages at high elevations generally had high diversity, and assemblages at low elevations had lower diversity. Elevation and inundation frequency are inversely related, and the strong correlation between species richness and elevation also assumes that inundation frequency is important in structuring the marsh. Burn frequencies had no influence on diversity in general, but more frequent burning did result in monospecific stands of Spartina patens at Anahuac NWR.

Freshwater inflows are essential to the health of estuaries and minimum discharge levels must be maintained in order to sustain a healthy ecosystem. Due to the predicted 50% increase in urban population growth along the Texas coastline by the year 2050, water regulators and managers are faced with the challenge of meeting human needs, while maintaining essential freshwater inflows into estuarine ecosystems. Galveston Bay is of particular concern because 10 million people currently living within its watershed. Freshwater inflows into Galveston Bay during 2006 were determined by using daily discharge data from a United States Geological Survey (USGS) sampling gauge in the Trinity River. Changes in water quality parameters, primary productivity, and phytoplankton community structure in response to freshwater inflows, were monitored monthly to determine how the phytoplankton community responded to inflow events. Freshwater inflow into Galveston Bay during 2006 was indicative of a low-inflow year, with seven large (>7,000 ft.3 sec-1) inflow events occurring throughout the year. There were significant differences in phytoplankton biomass (Fm), photosynthetic efficiency (alpha), and photosynthetic potential (yield) of the phytoplankton community, between wet (January-April and October-December) and dry (May-September) months. Significant differences in the biomass of phytoplankton groups also occurred with cyanobacteria being present in higher concentrations during the dry months and diatoms & dinoflagellates during the wet months. Low flow periods favored cyanobacteria, which lead to decreased secondary productivity, while pulsed inflow events resulted in enhanced secondary productivity by favoring diatoms and dinoflagellates. Resource Limitation Assays (RLAs) indicated that nitrogen was a potential limiting nutrient in Galveston Bay during spring/summer, with light limitation of phytoplankton communities possibly occurring near the mouth of the Trinity River. This study demonstrates the role of freshwater inflows in determining the primary productivity and community composition of the phytoplankton in Galveston Bay over an annual cycle. Inter-annual studies are needed to elucidate the impact of freshwater inflows in years with higher inflows to Galveston Bay and determine which of these impacts need to be incorporated into water management decisions to maintain a healthy ecosystem.

Several flatfish species including southern flounder (Paralichthys lethostigma) recruit to estuaries during early life. Therefore, the evaluation of estuarine sites and habitats that serve as nurseries is critical to conservation and management efforts. I used biochemical condition and growth measurements in conjunction with catch-density data to evaluate settlement sites used by southern flounder in the Galveston Bay Estuary (GBE). In 2005, beam-trawl collections were made in three major sections of the GBE (East Bay, West Bay, Galveston Bay), and three sites were sampled in each bay. Within each sampling site, replicate collections were taken from 1) the marsh edge, 2) an intermediate zone, and 3) the open bay. The average size of southern flounder collected was between 12 and 19 mm standard length, and peak densities occurred in January and February. Catch data indicated that numeric densities of southern flounder were significantly greater in East Bay (2.75 per 100 m2) than in West Bay (0.45 per 100 m2) or in Galveston Bay (0.91 per 100 m2). Habitat-specific variation in density was not found. Otolith-based estimates of age indicated that the majority of southern flounder collected were 35-45 days old and derived from early December to early January hatch-dates. Growth rate differences were negligible across bays and habitats, with the average growth rate being 0.40 mm/day (range 0.21-0.76 mm/day). RNA:DNA ratios indicated that newly settled southern flounder in the GBE were in relatively high condition. Habitat-specific differences in RNA:DNA ratios were not observed; however, ratios were significantly lower in West Bay (average 8.0) than in East Bay (average 9.5) or in Galveston Bay (average 9.8), suggesting the condition of new recruits may vary across the GBE. Findings from this study indicate that southern flounder use a variety of habitats within the GBE during early life, and survival and recruitment success appear favorable regardless of settlement site. As a result, recruitment success of southern flounder may be less a function of the quality of nursery sites/habitats within the GBE than of other factors (e.g., larval supply to the estuary).

Knowledge of surface sediment distribution in Galveston Bay is important because it allows us to better understand how the bay works and how human activities impact the bay and its ecosystems. In this project, six areas of bay bottom were surveyed using acoustic techniques to make maps of bay bottom types and to investigate the types and extent of anthropogenic impacts. A total of 31 km2 was surveyed in six areas, one in Bolivar Roads (6.1 km2), one near Redfish Bar (3.1 km2), two in East Bay (12 km2), one southeast of the Clear Lake entrance (5.3 km2), and one in Trinity Bay (4.3 km2). Sidescan sonars (100 kHz and 600 kHz) were used to image the bay bottom, and a chirp sonar (2-12 kHz) was used to image subsurface sediment layers and bottom topography. In the side-scan records, objects as small as a few meters in extent were visible, whereas the chirp sonar records show a vertical resolution of a few tens of centimeters. The sidescan images display strong backscatter in some areas due to coarse sediments in addition to weak backscatter in areas of fine sediment. The bay bottom was classified using three levels of sonar backscatter ranging from high to low. Areas of differing sonar backscatter intensity were sampled with cores and grab-samples. High backscatter corresponded to coarse shell debris and oyster reefs, medium backscatter corresponded to a sand-silt-shell mixture, and low backscatter corresponded to silty loam. Chirp sonar records were classified as one of nine different bottom reflection types based on changes in amplitude and stratigraphy. Parallel, layered sediments are seen filling the bay valley and resting atop a sharp contact at which the acoustic signal fades out. Along the flanks of the valley fill the acoustic response revealed an absent or weakly laminated stratigraphy, whereas areas of high oyster productivity produced mounds, strong surface returns, and strong, shallow subsurface reflectors surrounding current oyster reefs. Anthropogenic features imaged with the sonar included sediment disruptions, such as the ship channels, dredge holes, gouges, and trawl marks, as well as debris, such as submerged boats, pipes, and unidentified objects.

A vessel-mounted ADCP study focusing on channel-scale flow patterns in Galveston Bay near the Houston Shipping Channel and Mid-Bay Island is described. Winds of 5-7 m/s at 215-230◦ from N were present during data collection. For both peak ebb and flood conditions, the tidal circulation forced flow in a direction opposing the wind, perhaps due to a large-scale flow divergence forced by Mid-Bay Island. The strongest such currents were measured closest the island. During peak flood flow, the shape of the along-channel velocity profile for the open water upwind of the channel at Mid-Bay Island indicated uniform flow, and the salinity profile indicated a well-mixed water column. The near-island along- channel velocity profile showed a near-linear trend, and the salinity profile indicated a stratified water column. This suggested that the stratification had some effect the velocity profile shape, but further research is needed to better quantify this effect. During peak ebb flow, the near-island along-channel velocities were highly variable with respect to the mean velocity, indicating an area of active turbulence. Salinity profiles collected in the open water and near-island both showed stratification, something that was not seen during flood conditions. Differences in observations between flood and ebb flows can possibly be attributed to the survey location with respect to the chain of dredge spoil islands. During flood flows Mid-Bay Island is the first of the islands, and the flows surrounding the island may part of a developing horizontal boundary layer. During ebb flows the island is last in the chain relative to the direction of flow, and therefore the surrounding flows are well back from the leading edge of a horizontal boundary layer. / text

The objective of this study was to deploy a conceptual framework developed by M. Forbes using a geographic information system (GIS) approach to assess the functionality of wetlands in the Galveston Bay Area of Texas. This study utilized geospatial datasets which included National Wetland Inventory maps (NWI), LiDAR data, National Agriculture Imagery Program (NAIP) imagery and USGS National Land Cover data to assess the capacity of wetlands to store surface water and remove pollutants, including nitrogen, phosphorus, heavy metals, and organic compounds. The use of LiDAR to characterize the hydrogeomorphic characteristics of wetlands is a key contribution of this study to the science of wetland functional assessment. LiDAR data was used to estimate volumes for the 7,370 wetlands and delineate catchments for over 4,000 wetlands, located outside the 100-yr floodplain, within a 2,075 square mile area around Galveston Bay. Results from this study suggest that coastal prairie freshwater wetlands typically have a moderate capacity to store surface water from precipitation events, remove ammonium, and retain phosphorus and heavy metals and tend to have a high capacity for removing nitrate and retainremove organic compounds. The results serve as a valuable survey instrument for increasing the understanding of coastal prairie freshwater wetlands and support a cumulative estimate of the water quality and water storage functions on a regional scale.

Benthic microalgal community composition on an ephemerally submerged sandflat at East Beach, Galveston Island, Texas was studied to determine the spatial and temporal variability of total biomass and community composition and its responses to experimental manipulations of two environmental factors (salinity and nutrients). Four field studies were conducted between August 2004 and February 2005. The community consisted of two major algal groups, diatoms, and cyanobacteria with two less abundant groups, green algae, and phototrophic bacteria. Spatial variability showed that patch sizes of 12 - 25 m were detected over larger scales with smaller scale (cm) patches of approximately 28 - 201 cm^-2 contained within the larger patches. The second study examined the spatio-temporal variability of BMA over a 21-month period in a 1,000 m^2 area. Sampling location and date explained a significant amount of the variability in the abundances of algal groups, which were positively correlated with the water content of the sediments and negatively correlated with temperature (sediment and water). All of the algal groups showed a seasonal pattern with higher abundances measured in the winter months and lower abundances found during the summer. BMA biomass (100 mg Chl a m^-2 or greater) maxima occurred at temperatures less than 22 degrees C and sediment water content greater than 15% (g water g sediment^-1). BMA response to different salinities and nutrient (N+P) amended sediments was assessed in four bioassays conducted over a 6-month period (Aug. 2004, Oct. 2004, Dec. 2004, and Feb. 2005). In the salinity study, the treatments that were either 100% or partially diluted with deionized water had the lowest BMA biomass over all. Chlorophyll a and fucoxanthin were significantly affected by salinity with higher abundances found in salinities that averaged 15 with a preference for salinities greater than 22. Chlorophyll b was affected by salinity with higher abundances measured in the treatments with lowest salinity (DL and DI); and was affected by the time of year. This would suggest that this algal group prefers an environment with salinity less than 2 but can easily adapt to environments with higher salinities. BMA abundances were not significantly affected by the nutrient amended sediment, but were significantly affected by stations with higher water content, and during the cooler months (Dec. 2004 and Feb. 2005).

Wetlands are one of the most productive ecosystems in the world, housing diverse biota and serving important functions as nursery habitat and feeding grounds. However, nearly 70% of coastal wetlands, including 21% of the salt marshes in Texas, have been lost since 1950, due primarily to coastal development and declines in water quality. Restoration of wetlands is essential to reestablish lost functions, but there is no standard method to assess the ecological health of restored salt marshes in Texas. Numerous recent salt marsh restoration projects in Galveston Bay have made it an ideal model system to develop and implement an ecosystem health assessment, known as a rapid assessment method (RAM). In this study, I modified an established RAM, the Mid-Atlantic Tidal Fringe Assessment, to compare the ecological health of representative reference salt marshes to restored marshes around Galveston Bay. I measured 14 biotic and abiotic characteristics at 12 restored and 6 reference sites around Galveston Bay, and then grouped those measurements into four functional groups: landscape/site characteristics, hydrology, wildlife habitat, and soil characteristics. I then developed a scoring system (minimum 0, maximum 100) to summarize the overall health of each site. Most of the restored salt marshes in this study scored lower than reference marshes. The average reference site score was 81.8 and the average restored site score was 69.7. Functional group values for landscape/site characteristics, soil, and wildlife habitat were significantly lower in restored than in reference sites. In particular, restored sites had more hydrological modifications, more fill material, and fewer macrobenthos than reference wetlands. The Galv-RAM effectively and efficiently identified restoration successes and weaknesses. With this information, management agencies can address restoration shortcomings by adapting management goals. The Galv-RAM will streamline monitoring protocols and facilitate long-term examination of restored wetland health. As a result, management decisions can be modified based on the scores received in different categories or variables to improve and or meet the goals of the project.

Galveston Bay is the second largest estuary in the Gulf of Mexico. The bay’s watershed and shoreline contains one of the largest concentrations of petroleum and chemical industries in the world, with the greatest concentration within the lower 15 km of the San Jacinto River/Houston Ship Channel (SJR/HSC). Extensive groundwater has been withdrawn to support these industries and an expanding population has resulted elevated land subsidence, with the highest land subsidence in the lower SJR/HSC, of over 3 m (3 cm yr^-1) and has decreased seaward throughout the bay to 0.6 cm yr^-1 near Galveston Island. Mercury (Hg) contamination is well documented throughout the bay’s sediments. Sediment vibra-cores were collected throughout the bay systems. 210Pb and 137Cs geochronologies from these cores was used to determine sedimentation rates and correlated to Hg profiles to estimate input histories. Relative Sea Level Rise (RSLR) is the sum of eustatic sea level rise and land subsidence. The results show sedimentation rates are high in areas with high rates of RSLR and the rates are of the same order of magnitude, however, in general, sedimentation rates are as much as 50% of RSLR, indicating that sedimentation has not kept pace with land subsidence, although they have the same relative order. Hg core profiles were correlated with radioisotope geochronologies and show significant input of Hg beginning around 1940, with a peak around 1971, and a dramatic drop off in concentration afterwards, demonstrating it to be a valuable geochronology tool. Hg concentrations were found to be dramatically higher proximal to the SJR/HSC and progressively decreasing seaward and to distal parts of the bay.