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Habitat restoration efforts are often limited by cost, making it important that available funds are used efficiently and effectively to achieve desired restoration goals. In this study, we evaluate habitat provision for oysters and motile epifauna on restored oyster reefs in a northwestern Gulf of Mexico estuary constructed with discrete high vertical relief (~0.6m "reef mounds") or continuous low vertical relief (<0.08 m "reef flats"). Habitat provision on reef mounds exceeded that on reef flats within one month of construction and supported 0.75x higher oyster density, 2x higher motile epifauna biomass, and 3.6x higher motile epifauna density one year after construction. Oyster density on reef mounds remained relatively high throughout the study period, with ~2x higher oyster densities than reef flats 18 months after construction and ~1.5x higher oyster densities by the end of the study. Both reef mounds and reef flats increased oyster and epifaunal densities compared to unrestored areas. Although on-reef oyster densities were higher on reef mounds than reef flats, the total restored oyster areal density and volumetric density was higher in restored reef flat areas, primarily because the restored flats area had no gaps within its restoration boundaries. Our findings have practical value for better predicting restoration outcomes and achieving desired restoration goals based on restored oyster reef height, with reef mounds maximizing on-reef oyster and epifaunal densities and reef flats maximizing the total number of oysters per area restored or volume of substrate purchased. Understanding the benefits and tradeoffs between restoration designs will allow resource managers to improve cost-efficiencies in future restoration projects. [ABSTRACT FROM AUTHOR]

Objective: The Atlantic Tripletail Lobotes surinamensis is a globally distributed subtropical and tropical fish species that inhabits estuaries throughout the northern Gulf of Mexico (GOM), particularly during warm months. Little is known about distribution and residency patterns within estuaries, as the species is rarely caught in the recreational fishery, and virtually no commercial fishery exists for the species in the GOM. Methods: We used data from a long‐term fishery‐independent gill‐net survey to model estuarine distribution throughout Texas and to relate environmental variables to the Atlantic Tripletail catch. Result: Although there were no observable temporal trends in catch over the time series (1990–2022), the most recent 6 years included record catch in six of the 10 major Texas estuaries, possibly indicating a recent pulse in abundance. Catch throughout the time series was spatially aggregated in a small number of "hot spots" observed coastwide. Latitude was the best predictor of catch, although wind fetch and wind aspect (wind direction in relation to shoreline direction) were important predictors, and catch was highest near GOM inlets. The Texas Parks and Wildlife Department gill‐net sampling program caught a range of Atlantic Tripletail between 171 and 880 mm total length, indicating a potential gear bias against juveniles. Conclusion: Despite this gear bias, these data shed light on the factors that drive Atlantic Tripletail estuarine distribution and abundance in the northwestern GOM. Wind‐driven passive movements in the estuary, combined with active selection of polyhaline habitats near GOM inlets, might be primary drivers of Atlantic Tripletail catch, thus supporting findings from previous studies. Impact statementAtlantic Tripletail are a popular recreational fishing species throughout the Gulf of Mexico. In Texas estuaries, Atlantic Tripletail are clustered in hot spots, which are typified by windward shorelines, and present mainly during the high‐use fishing season. They are rarely observed at water temperatures below 20°C. [ABSTRACT FROM AUTHOR]

The impact of surface wave assimilation on hurricane track and intensity forecasts has been investigated using a fully coupled air-ocean-wave tropical cyclone data assimilation and forecast modeling system. A new 3DVAR wave assimilation method in the Navy Coupled Ocean Data Assimilation system (NCODA) maps the 1D wave energy spectra from buoys to 2D directional wave energy spectra using the maximum likelihood method (MLM) and corrects the wave model forecast component directional wave energy spectra. The Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclone Prediction (COAMPS-TC) is used to conduct three Hurricane Harvey (2017) airocean-wave coupled data assimilation and forecasting experiments with and without the wave data assimilation. Hurricane Harvey traversed through the Western Gulf of Mexico from 24 August to 1 September, 2017 and made landfall in the Texas and Louisiana coast. Validation of track, maximum wind speed, significant wave height, and mean absolute wave periods show wave assimilation of the 1D wave energy spectra from 13 National Data Buoy Center (NDBC) buoys reduced the forecast errors of these parameters compared to experiments without the wave assimilation. In spite of this positive outcome, the wave assimilation is unable to reduce Harvey's 0-120 h forecast mean wave direction errors and correlation compared to the NDBC buoy time series. [ABSTRACT FROM AUTHOR]

This article focuses on developing models that estimate suspended sediment concentrations (SSCs) for the Lower Brazos River, Texas, U.S. Historical samples of SSCs from gauge stations and satellite imagery from Landsat Missions and Sentinel Mission 2 were utilized to develop models to estimate SSCs for the Lower Brazos River. The models used in this study to accomplish this goal include support vector machines (SVMs), artificial neural networks (ANNs), extreme learning machines (ELMs), and exponential relationships. In addition, flow measurements were used to develop rating curves to estimate SSCs for the Brazos River as a baseline comparison of the models that used satellite imagery to estimate SSCs. The models were evaluated using a Taylor Diagram analysis on the test data set developed for the Brazos River data. Fifteen of the models developed using satellite imagery as inputs performed with a coefficient of determination R2 above 0.69, with the three best performing models having an R2 of 0.83 to 0.85. One of the best performing models was then utilized to estimate the SSCs before, during, and after Hurricane Harvey to evaluate the impact of this storm on the sediment dynamics along the Lower Brazos River and the model's ability to estimate SSCs. [ABSTRACT FROM AUTHOR]

A three-dimensional coupled hydrodynamic–biogeochemical model with multiple nutrient and plankton functional groups was developed and adapted to the Gulf of Mexico to investigate the role of nutrients and the complexity of plankton community in dissolved oxygen (DO) dynamics. A 15-year hindcast was achieved covering the period of 2006–2020. Extensive model validation against in situ data demonstrates that the model was capable of reproducing vertical distributions of DO and spatial distributions of bottom DO concentration, as well as their interannual variations. The study demonstrates that bottom DO dynamics and hypoxia evolution are significantly influenced by both physical processes and local biochemistry, with sedimentary oxygen consumption and vertical diffusion identified as key contributors. Summer hydrodynamics play a critical role in nutrient distribution and limitation: a notable expansion of Si limitation was simulated when coastal currents shifted eastward or northward. This effect, especially pronounced on the western part of the Louisiana–Texas shelf, underscores the importance of nutrient limitation in shaping DO dynamics. The model identifies a bi-peak primary production pattern in spring and early summer, aligned with satellite chlorophyll a variations, attributed to the complexity of the plankton community and interactions among different plankton groups. Our findings emphasize the necessity of integrating sophisticated plankton community dynamics into biogeochemical models to understand primary production variability and its impact on bottom hypoxia. [ABSTRACT FROM AUTHOR]

Objective: Crevalle Jack Caranx hippos are important coastal predators and support an increasingly popular catch‐and‐release sport fishery. However, population declines have recently been perceived by stakeholders in parts of the species' range. Here, we aimed to provide distribution and harvest trends for Crevalle Jack in the northwestern Gulf of Mexico. Methods: Long‐term fishery‐independent and fishery‐dependent data were collected by the Texas Parks and Wildlife Department from 1983 to 2021. Bag seine, bay trawl, and gill‐net samples were collected in conjunction with angler creel surveys. Crevalle Jack that were observed in fishery‐independent sampling were used to assess patterns in both juvenile and adult relative abundance, distribution, and seasonality. In addition, boosted regression tree models were used to highlight important predictors of Crevalle Jack presence. Crevalle Jack harvest observed during angler surveys was used to describe the fishery, including differences in inshore and offshore catch patterns. Relative abundance of both juveniles and adults was variable across years but displayed no trend throughout the time series. Result: Crevalle Jack of all sizes were found within inshore waters, with subadults and large adults particularly reliant on estuarine systems. Recruitment peaked in early summer, with juveniles occupying all major estuaries along the coast. Shifts in recruitment were evident in bag seines, as the mean date of catch trended almost 2 weeks earlier over the study period. The Crevalle Jack fishery was spread across inshore and offshore waters, with significantly larger fish harvested offshore during summer. The majority of anglers who harvested Crevalle Jack stated that they were specifically targeting other species, thus supporting the notion that the targeted fishery is mainly catch and release. Conclusion: As Crevalle Jack declines have been noted elsewhere in the species' range, these results could help to inform future management decisions in Texas. Impact statementCrevalle Jack are an important sport fish in the eastern Gulf of Mexico. However, anglers have noted population declines in parts of their range. Here, we examined seasonality, distribution, and recruitment of Crevalle Jack in Texas. Results indicate that populations are stable and provide important insights into Crevalle Jack ecology. While the fishery is largely catch and release, the reliance of large Crevalle Jacks on estuaries and nearshore waters could see them increase in popularity as an accessible sport fish. These findings will be important to inform future management decisions. [ABSTRACT FROM AUTHOR]

Whitehead, S.J.; Yeager, K.M.; Feagin, R.A.; Huff, T.P.; Paine, J.G.; Schindler, K.S., and Dixon, T.S., 2024. Growth fault–induced effects on tidal marsh surficial processes and landscape conversion in the Slop Bowl, Brazoria National Wildlife Refuge, Texas. Journal of Coastal Research, 40(1), 64–79. Charlotte (North Carolina), ISSN 0749-0208. The Slop Bowl marsh, located in the Brazoria National Wildlife Refuge on the Texas coast, is an anthropogenically influenced tidal marsh setting that has experienced rapid rates of landscape conversion and loss over the last ∼70 years. This tidal marsh has been affected by recently active faults and several hydrologic barriers (roads, pipeline channels, and active hydrocarbon-extraction well pads). Geophysical field methods and sedimentological analyses were conducted to better understand the effects of these developments on marsh surficial processes. Lithostratigraphy, shallow geophysical data, GPS surveys, radionuclide dating, and organic matter analyses all exhibited influences connected to growth-fault motion. The location and activity of a major growth fault were identified as contributing to subsidence on the downthrown fault block and causing vertical displacement of the marsh surface. Fault motion, in conjunction with the construction of roads, has disrupted the natural hydrologic pathways that once existed. Their combined effects resulted in transition of the land cover over the past several decades from a saline coastal prairie to a tidal marsh–dominant landscape, with continued future submergence anticipated. As the natural laboratory of the Slop Bowl demonstrates, anthropogenic development, neotectonics, and hydrocarbon extraction can have outsized effects on sedimentation processes, with implications for the long-term sustainability of coastal wetland environments in the northern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Objective: We analyzed a fishery‐independent catch time series in the context of predicted historical age structure of Red Drum Sciaenops ocellatus for the years 1980–2019. This time series roughly coincided with closure of the commercial fishery in Texas (in 1981) and federal waters (in 1987). Changes in size and age were used to estimate changes in mortality and offshore escapement. Methods: Otoliths collected from Red Drum between 1997 and 2015 in Texas were used to create seasonal length‐at‐age growth functions, which were then used to estimate ages (based on total length) of all Red Drum encountered in fishery‐independent gill‐net samples collected by the Texas Parks and Wildlife Department during 1980–2019 (total n = 311,150). Temporal changes in observed body size and overall catch were used to predict annualized changes in mean age, mortality, and offshore escapement of the estuarine population. Result: The initial 14‐year period (1980–1993) was characterized by rapid increases in mean catch per hour and mean total length (mm) in fishery‐independent samples, followed by relative stability for the remainder of the time series. There was a 55% increase in estimated mean age of Red Drum when comparing 1980 (mean age = 0.84 year) to 2019 (1.30 years). There were also rapid and significant declines in total mortality (Z; estimated via catch curves) and increases in offshore escapement (estimated indirectly from mortality) in the initial recovery period. Conclusion: The current estuarine population of Red Drum in Texas is significantly larger and older than it was at the onset of fishery management measures, and offshore escapement is annually well above the current target level of 30% set by the federal fisheries management plan. These findings suggest that regulations put into effect starting in the 1980s have succeeded in recovering the estuarine Red Drum population in Texas. Impact statementFisheries management regulations set into place starting in the 1980s in Texas and the greater Gulf of Mexico have had a measurable, positive impact on the age and size structure of Red Drum populations. These changes have resulted in a more valuable fishery that is accessible for a greater number of Texas estuarine anglers. [ABSTRACT FROM AUTHOR]

Carbon dioxide capture and geologic storage (CCS; geologic sequestration) is a promising technology for reducing anthropogenic greenhouse gas emissions to the atmosphere from industrial point sources. Aspects of CCS have been investigated for over two decades, and many large‐ and small‐scale geologic storage field demonstration projects are now underway globally. Interest in offshore CCS has been increasing in recent years (e.g., European Union, Australia, Japan, and the United States). Deep geologic storage in offshore settings is analogous to onshore CCS activities in many respects (i.e., geologic and geotechnical aspects), but is distinct from previously explored seabed sediment CO2 storage) or deep marine dissolution). Given the large subsurface geologic storage volumes available in offshore settings, much discussion of offshore CCS is focused on the benefits and risks of such activity compared to onshore settings. Similar to onshore settings, existing (legacy) wells likely present the most direct migration pathway and largest risk of noncontainment in offshore settings. As part of current studies to evaluate geologic storage options in offshore settings along the Texas coast and greater Gulf of Mexico (GoM), mapping of the geographic distribution and ages of wells in a region containing coastal counties and extending 30 miles offshore Texas indicates that both well spatial density and well age decrease moving from onshore to offshore. Results suggest reduced risk of leakage owing to more rigorous and documented well completion and abandonment practices for these generally younger wells (although many are decades old). A result of decreased well density is that larger areas are available for leasing for CCS projects that avoid legacy wells altogether (> 1 mile from any existing well). The one‐mile designation is used as an arbitrary convention, and while it is recognized that this is smaller than a typical area of review (AoR) for permitting, each site will have a different AoR radius for consideration. The combination of large subsurface storage volumes under control of a single landowner and reduced risks from legacy wells makes offshore CCS attractive in the GoM. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Human-fortified ship channel inlets can represent the only connection between estuarine and coastal waters for tens of kilometers in some areas of the Northern Gulf of Mexico, making them bottlenecks for fish movement. A variety of fishes associate with the jetties that fortify ship channel inlets, and the deep depths of channel inlets relative to surrounding waters may provide a unique type of habitat. To understand variability in fish biomass in these vital areas, 49 hydroacoustic surveys of the Aransas Channel Inlet, Texas were conducted and paired with environmental (e.g., temperature) and meteorological (e.g., barometric pressure) data between January 2018 and February 2020. Fishery-independent and fishery-dependent data from the surrounding area were employed to provide context to variability in fish backscatter (i.e., volume backscattering strength, sv, a proxy for fish biomass). Generalized additive models indicated that variation in fish backscatter was best explained by variation in temperature, change in barometric pressure, and salinity (adj.-R2 = 0.71). There were two dimensions to these effects. In the first, variation in temperature tracked seasonal shifts in the relative abundance of pelagic fishes, which were well sampled by acoustic technologies relative to demersal fishes. In the second, episodic cold fronts (i.e., high pressure systems) were associated with high values of fish backscatter — likely because the Aransas Channel Inlet is far deeper than surrounding areas and protected by jetties, making it less affected by physical disturbances and rapidly changing air temperatures or precipitation. Thus, disturbances in the Aransas Channel Inlet (e.g., dredging and construction, shipping traffic) are likely to be most impactful to non-demersal fishes when temperature and salinity are low (< c.a. 15 °C and < c.a. 28 psu) and frontal systems are likely to affect the area (barometric pressure increase > c.a. 3 mb or decrease > 7 mb over 24 h). [ABSTRACT FROM AUTHOR]

Mangrove ecosystems with high sediment deposition and active carbon cycling are a source of methane (CH4) to the coastal atmosphere. We investigated diurnal and seasonal variations in CH4 emissions from a subtropical mangrove estuary in southern Texas, northwest Gulf of Mexico. Tidal processes, amplitude (spring vs. neap tides) and topographic characteristics are crucial factors controlling CH4 cycling in mangrove creeks. Higher CH4 concentrations were observed during the ebb in spring tides due to the combination of processive export of CH4 along the creeks during ebb tides and the addition of porewater CH4 in upper intertidal sediment under water inundation in spring tides. The annual CH4 emissions offset approximately 0.15% of the carbon stock in normal years, indicating that these mangrove creeks are a weak CH4 source. However, significantly elevated CH4 emissions were observed from mangrove dieback after the extreme cold‐freezing event in February 2021. The average CH4 flux from the mangrove creeks (126.1 ± 128.3 μmol [m2·d]−1) increased 45% in 3 months after mangrove die‐off in comparison with the overall average in normal years (87.0 ± 64.4 μmol [m2·d]−1). It is obvious that the previous small CH4 offset of the healthy mangrove forest was enlarged by the dieback event. Because the mangrove forests in this study live close to the limit of their survival range, our study highlights the important management considerations for blue carbon projects in vulnerable areas. [ABSTRACT FROM AUTHOR]

Numerical mixing, the spurious mixing primarily generated by the discretization of advection, is often significant in estuarine and coastal models due to sharp, energetic fronts. We compare on‐ and offline estimates of numerical mixing in a submesoscale‐resolving realistic simulation of the ocean state over the Texas‐Louisiana continental shelf. While offline estimates of numerical mixing differ from online estimates, offline methods may be the only analysis available. We use two methods to estimate numerical mixing offline based on the residuals of the salinity squared s2 and volume‐mean salinity variance s′2 ${s}^{{\prime }^{2}}$ budgets. The s′2 ${s}^{{\prime }^{2}}$ budget overestimates the time‐averaged online numerical mixing by 60% at hourly output. The s2 budget compares poorly due to large truncation errors associated with the tendency and advection terms. The residual of the s2 budget starts to converge to the s′2 ${s}^{{\prime }^{2}}$ budget as output frequency increases to 10 min—an unrealistic frequency for long‐term coastal ocean simulations—but neither method unconditionally converges to the online method and therefore cannot be recommended for generic analysis of numerical mixing. We also investigate the effects of horizontal resolution on numerical mixing using a two‐way nested grid with the online method. The volume‐integrated numerical mixing constitutes 57% of the bulk physical mixing—the mixing prescribed by the turbulence closure scheme—in the coarse model and may exceed the physical mixing by half an order of magnitude. We find numerical mixing is reduced by 35% on average in the nested model, likely due to new dynamical processes that emerge in the nested simulation. Plain Language Summary: Numerical models are powerful tools for studying the general circulation of the ocean, allowing us to examine the ocean's complex relationship with Earth's weather and climate in greater detail than observations allow. However, numerical ocean models are prone to several types of numerical errors because they represent physical processes with discrete approximations. One of these errors is numerical mixing, a process by which the discretized transport of tracers by currents generates spurious mixing. Recent studies suggest numerical mixing can be as large as the physical mixing prescribed by a parameterization, especially in regions with strong tracer gradients, such as in estuaries or the coastal ocean. In this study, we examine numerical salinity mixing using a combination of on‐ and offline methods in a model of the ocean state over the Texas‐Louisiana continental shelf in the Gulf of Mexico. Offline methods rely on existing model output and are often easier to implement than online methods. However, offline methods trade numerical accuracy for convenience because online methods require modifying a model's source code and re‐running it. We find offline estimates of numerical mixing should not be used because they may be inaccurate even at impractically high resolution. Key Points: We use offline salinity variance budgets to quantify numerical mixing due to the discretization of advection in a coastal ocean modelNumerical mixing estimated from s2 and s′2 ${s}^{{\prime }^{2}}$ budgets does not converge to the online method at high model output frequenciesOnline analysis indicates the volume‐integrated numerical mixing exceeds the physical mixing for a significant portion of the simulation [ABSTRACT FROM AUTHOR]

Feeding patterns of sheepshead, Archosargus probatocephalus, in the northwest Gulf of Mexico were examined from samples collected at two locations in Texas, USA; Galveston and Port Aransas. A total of 53 sheepshead stomachs (Galveston, n = 35; Port Aransas, n = 18) had their contents analyzed along with tissue samples from the muscle and liver for a stable isotope analysis (δ13C, δ15N, and δ34S) because they provide a contrast between short-term (liver) and long-term (muscle) measurements. Multiple species of amphipods made up the majority of the prey items in sheepshead from Galveston (%IRI = 61.79), whereas barnacles were the primary diet item for sheepshead collected in Port Aransas (%IRI = 39.53). We observed diet shifts prior to and during the spawning season. MANOVA revealed significant differences in δ13C, δ15N, and δ34S stable isotope values from the muscle and liver tissue of sheepshead based on the location. In both muscle and liver samples, δ13C values were lower in Galveston than Port Aransas, but δ15N and δ34S values were higher in Galveston than Port Aransas. Niche size and overlap also differed between sheepshead from both locations and tissue types. Sheepshead collected in Galveston had a larger niche size in the muscle and liver samples ((mean ± SD) 479.3 ± 131.2, muscle; 433.3 ± 120.3, liver) than Port Aransas (178.8 ± 54.3, muscle; 270.0 ± 80.9, liver). The trophic niche of sheepshead from Galveston overlapped Port Aransas in muscle samples by 16.47% and 18.56% in liver samples. The trophic niche overlap of sheepshead from Port Aransas measured in muscle samples overlapped with sheepshead from Galveston by 18.49% and by 39.17% in liver samples. This study shows that there are subtle but significant differences between the diets of sheepshead along the Texas coast, with the majority of the differences potentially attributable to differences in the prey field along the natural salinity gradient of the Texas coast. This work provides an insight into the widely generalist grazing behavior of sheepshead, which potentially changes during the springtime spawning season. [ABSTRACT FROM AUTHOR]

In recognition of the unique hydrologic functions they serve, certain stream segments in Texas have been designated as ecologically significant. In this study, we evaluated low flow trends in seven hydrologically unique stream segments spanning three climatic divisions in Texas from 1970 to 2019. Despite increasing mean annual temperatures, there are no trends in low flows or other hydrologic variables in the East Fork of the San Jacinto River in the Upper Coast climatic division, likely due to local moisture surplus effects from the Gulf of Mexico. In the Edwards Plateau climatic division, annual low flows and annual baseflows are decreasing in the South Fork of the Guadalupe River, the Sabinal River and the Frio River. While increasing mean annual temperatures appear to have a role in the drying of all three of these stream segments, increasing annual potential evapotranspiration may be an additional driver in the Sabinal and Frio Rivers. Analysis of the Standardized Streamflow Index indicates that all seven stream segments experienced their worst streamflow droughts in the 2010s. As such, the watersheds draining to the gages on these stream segments have minimal anthropogenic impacts, suggesting the influence of climate on the observed stream drying. [ABSTRACT FROM AUTHOR]

Connectivity along the coastline is important for applications including pollutant, larvae, and phytoplankton transport, particularly between bays which can act as sources or sinks of these materials. This study presents the results of a high-resolution numerical model (500 m–2 km with 30 vertical layers) of the northwest Gulf of Mexico to simulate surface drifters, and the calculation of alongcoast connectivity by tracking drifter crossings of 5 km by 5 km analysis boxes along the coastline. Seasonal results show the detailed connectivity relationships between locations, particularly strong downcoast (toward Mexico from Louisiana) connectivity in winter and both up- and downcoast connectivity in summer, tied to winds as well as the presence of the Mississippi-Atchafalaya river plume. The likelihood of any connectivity between nine bays and notable locations along the Texas–Louisiana coastline is summarized and shows particular connectivity from Galveston downcoast to Port Aransas, especially in the winter. The details of likelihood of any connectivity as well as the timing over 30 simulation days are presented for transport from and to each of the nine locations. The Louisiana locations are more isolated from the Texas locations, though they can have downcoast transport to Texas in the winter. Texas sites can be connected both up- and downcoast, especially with other Texas sites. These results can be used to read the minimum transport time between locations as well as detailed likelihood over time by season for determining the possibility of transport of, for example, a harmful algal bloom from one known location to other vulnerable sites. [ABSTRACT FROM AUTHOR]

Coastal wetlands are predicted to undergo extensive transformation due to climate and land use change. Baseline maps of coastal wetlands can be used to help assess changes. Found in the upper portion of the estuarine zone, high marsh and salt pannes/flats provide ecosystem goods and services and are particularly important to fish and wildlife. We developed the first map of high marsh and salt pannes/flats along the northern Gulf of Mexico using regional models that included spectral indices related to greenness and wetness from optical satellite imagery, elevation data, irregularly flooded wetland probability information, and synthetic aperture radar backscatter. We found the greatest relative coverage of high marsh along the Texas coast (30% to 65%) and the Florida Panhandle (40%), whereas the greatest relative coverage of salt pannes/flats was along the lower Texas coast (74%) and the middle Texas coast (15%). As part of this effort, we also developed a map that highlighted irregularly flooded wetlands dominated by Juncus roemerianus (black needlerush) for part of the study area. Both maps had an overall accuracy of around 80%. Our results advance the understanding of estuarine marsh zonation and provide a baseline for assessing future transformations. This is the first map of high marsh and salt pannes/flats along the northern Gulf of Mexico and provides a baseline for understanding transformations predicted to occur with climate change. Due to high elevation uncertainty in wetlands, we used a map of irregularly flooded wetland probability that was created using elevation error assumptions. Irregularly flooded wetland probability, synthetic aperture radar backscatter, and spectral indices related to greenness and wetness were important predictor variables. Differences in wetland zonation and species composition along the study area led to variation in models by region. The framework presented here could be adapted to other areas. [ABSTRACT FROM AUTHOR]

Tidal datums are key components in NOAA's Vertical Datum transformation project (VDatum), which enables effective vertical transformation of the water level between tidal, orthometric, and ellipsoid -based three-dimensional reference systems. An initial application of modeling tidal datums was developed for the coastal waters of Texas and western Louisiana in 2013. The goals of the current work include: (1) updating the tidal model by using the best available shoreline, bathymetry, and tide station data; (2) implementing a recently developed statistical interpolation method for interpolating modeled tidal datums and computing tidal datum uncertainties; and (3) using modeled tidal datums to upgrade non-tidal polygons for enhancing the quality of the VDatum marine grid population. The updated tidal model outperformed the previous tidal model in most cases. The statistical interpolation method is able to limit the interpolated tidal datums to within a user-defined model error (0.01 m in this work) and produce a spatially varying uncertainty field for each interpolated tidal datum field. The upgraded non-tidal polygons enhanced the quality of the VDatum marine grid population. This paper will introduce the detailed procedures of this modeling work, present and discuss the obtained results, share the effective methods used for improving model performance and lessons learned in the model assessments, and analyze the improvement of the current tidal model in comparison with the previous tidal model. [ABSTRACT FROM AUTHOR]

Low bottom water dissolved oxygen conditions (hypoxia) occur almost every summer in the northern Gulf of Mexico due to a combination of nutrient loadings and water column stratification. Several statistical and mechanistic models have been used to forecast the midsummer hypoxic area, based on spring nitrogen loading from major rivers. However, sub-seasonal forecasts are needed to fully characterize the dynamics of hypoxia over the summer season, which is important for informing fisheries and ecosystem management. Here, we present an approach to forecasting hypoxic conditions at a daily resolution through Bayesian mechanistic modeling that allows for rigorous uncertainty quantification. Within this framework, we develop and test different representations and projections of hydrometeorological model inputs. We find that May precipitation over the Mississippi River basin is a key predictor of summer discharge and loading that substantially improves forecast performance. Accounting for spring wind conditions also improves forecast performance, though to a lesser extent. The proposed approach generates forecasts for two different sections of the Louisiana–Texas shelf (east and west), and it explains about 50 % of the variability in the total hypoxic area when tested against historical observations (1985–2016). Results also show how forecast uncertainties build over the summer season, with longer lead times from the nominal forecast release date of 1 June, due to increasing stochasticity in riverine and meteorological inputs. Consequently, the portion of overall forecast variance associated with uncertainties in data inputs increases from 26 % to 41 % from June–July to August–September, respectively. Overall, the study demonstrates a unique approach to assessing and reducing uncertainties in temporally resolved hypoxia forecasting. [ABSTRACT FROM AUTHOR]

The US Gulf of Mexico coastal region has repeatedly been subjected to major flood events. Local geotechnical site characteristics and geomorphology can change due to sediment transport processes during such events. However, field measurements during extreme conditions are challenging. This paper discusses initial attempts at a combined geotechnical and geophysical site investigation of the uppermost layers of riverbeds following severe flooding events at three different rivers in Texas: the Guadalupe, Brazos, and Colorado Rivers in terms of sediment strength derived from a portable free fall penetrometer, backscatter intensity recorded by a chirp sonar, and soil sample characterization. Results show low strength sediments (<40 kPa) along the investigated sections of the Guadalupe and Brazos riverbanks. Although sediments in the center of the Brazos River were characterized with higher strength (>50 kPa) and larger grain sizes (d 50 ∼ 0.3 mm), sediment strength of the Guadalupe and Colorado Rivers displayed more variations around bridge piers. The spatial variations likely resulted from sediment remobilization processes and local scour under severe hydrodynamic conditions. Both, geotechnical and geophysical results, reflected the observed variations in the riverbed sediments; nonetheless, a quantitative correlation among the rivers was impeded by challenges primarily related to limitations of spatial accuracy and the significant riverbed heterogeneity, as well as shallow water limitations of the chirp sonar. • Combined geotechnical and geophysical site characterization at three Texas river sections • Measurements from small vessels and in areas of unknown riverbed conditions • Sediment dynamics were reflected in geotechnical and geophysical data • Qualitative relationship between portable free fall penetrometer and chirp sonar • Three river sections differed significantly in local sediment properties [ABSTRACT FROM AUTHOR]

The eastern oyster, Crassostrea virginica, is divided into four populations along the western North Atlantic, however, the only published mitochondrial genome sequence was assembled using one individual in Delaware. This study aimed to (1) assemble C. virginica mitochondrial genomes from Texas with pooled restriction-site-associated DNA sequencing (ezRAD), (2) evaluate the validity of the mitochondrial genome assemblies including comparison with Sanger sequencing data, and (3) evaluate genetic differentiation both between the Delaware and Texas genomes, as well as among three bays in Texas. The pooled-genome-assembled-genomes (PAGs) from Texas exhibited several characteristics indicating that they were valid, including elevated nucleotide diversity in non-coding and the third position of codons, placement as the sister haplotype of the genome from Delaware in a phylogenetic reconstruction of Crassostrea mitochondrial genomes, and a lack of genetic structure in the ND4 gene among the three Texas bays as was found with Sanger amplicons in samples from the same bays several years prior. In the comparison between the Delaware and Texas genome, 27 of 38 coding regions exhibited variability between the two populations, which were differentiated by 273 mutations, versus 1–13 mutations among the Texas samples. Using the full PAGs, there was no additional evidence for population structure among the three Texas bays. While population genetics is rapidly moving towards larger high-density datasets, studies of mitochondrial DNA (and genomes) can be particularly useful for comparing historic data prior to the modern era of genomics. As such, being able to reliably compile mitochondrial genomes from genomic data can improve the ability to compare results across studies [ABSTRACT FROM AUTHOR]

Continuous monitoring and early warning together represent an important mitigation strategy for harmful algal blooms (HAB). The coast of Texas experiences periodic blooms of three HAB dinoflagellates: Karenia brevis, Dinophysis ovum, and Prorocentrum texanum. A plankton image data set acquired by an Imaging FlowCytobot over a decade of operation was used to train and evaluate two new automated image classifiers. A 112 class, random forest classifier (RF_112) and a 112 class, convolutional neural network classifier (CNN_112) were developed and compared with an existing, 54 class, random forest classifier (RF_54) already in use as an early warning notification system. Both 112 class classifiers exhibited improved performance over the RF_54 classifier when tested on three different HAB species with the CNN_112 classifier producing fewer false positives and false negatives in most of the cases tested. For K. brevis and P. texanum, the current threshold of 2 cells.mL−1 was identified as the best threshold to minimize the number of false positives and false negatives. For D. ovum, a threshold of 1 cell.mL−1 was found to produce the best results with regard to the number of false positives/negatives. A lower threshold will result in earlier notification of an increase in cell concentration and will provide state health managers with increased lead time to prepare for an impending HAB. [ABSTRACT FROM AUTHOR]

A multi-decadal simulation of ocean circulation in the northern Gulf of Mexico produces strong submesoscale instabilities in the Mississippi/Atchafalaya plume fronts. The model skill in reproducing these submesoscale frontal eddies over the Texas-Louisiana shelf is assessed using simulated and observed salinity and velocity fields as a way to investigate simulation accuracy and quantify the variability of frontal eddies. The model successfully reproduces mean salinity structure observed in multi-year densely sampled CTD profiles. Variability associated with submesoscale eddies is the largest source of error in predicted salinity. On the other hand, the model is statistically able to reproduce the magnitude and characteristics of frontal eddies; metrics for eddy kinetic energy are similar between the observations and simulation, and observed horizontal salinity gradients have similar occurrence rates in the model when sampled in a manner similar to the observations. Seasonal and inter-annual variability of frontal eddies is associated with the volume of freshwater onto the shelf and wind stress. Wind stress, the highest in winter and lowest in summer, contributes to the suppression of baroclinic instability during non-summer seasons. River streamflow, highest in spring, creates strong horizontal and vertical density gradients. These strong horizontal density gradients, along with weak seasonal upwelling-favorable winds that tend to broaden the plume, are the primary factors in exciting submesoscale instabilities during summer on the Texas-Louisiana shelf. At decadal scales, streamflow, EKE, and salinity gradients have a positive correlation suggesting that long-term variability of frontal eddies may be influenced remotely by inter-annual variability in the Mississippi River outflow. [ABSTRACT FROM AUTHOR]

This paper provides an evidence-based contribution to understanding coastal governance in response to hurricane hazards. It uses the five-part conceptual framework for coastal governance, which includes 1) complexity, 2) vulnerability, 3) adaptive management, 4) stakeholder participation, and 5) the integration of technical knowledge in decision-making. A case study of the Harvey-impacted Texas communities in the Gulf of Mexico is presented within this framework. This particular case is important because of current high level discussions that suggest subnational, state-centric policy response to hazards may be the new model for disaster response moving forward. This study presents insights on the current trends toward devolved, subnational policy response to disasters, as well as a revised framework for coastal governance, where resilience is linked to all concepts in the governance framework as an outcome. Several major findings are discussed. First, higher scales of government take much longer than is necessary to respond to hazards because of their complex administrative policies and procedures. This is worsened in places that have not experienced hazards in recent decades. Innovative adaptation by subnational policy-makers may be one pathway to quicken policy response, as are the commendable but fragmented efforts of charities and voluntary groups. However, devolved policy responses may face their own challenges in implementation, increasing adaptive capacity but decreasing resilience. This study found that participatory, multi-stakeholder processes enhance resilience through disaster simulation exercises and participatory planning processes. These participatory processes enhance learning and the capacity to implement recovery-focused public policy within the constraints of the disaster. [ABSTRACT FROM AUTHOR]

Beach and dune morphology are spatially and temporally variable, changing over a broad range of scales simultaneously. Strong wind, waves, and storm surge from Hurricane Harvey substantially eroded the beach and dunes along the Texas coast, causing significant scarps and berms. This paper presents information about how anthropogenic activity, such as driving on the beach, affected the response and recover of a barrier island with regard to the post-storm resiliency along the Texas-Gulf of Mexico coast by comparing two adjacent 7 km stretches of coast: a driving section and a limited-access section. A collection of field photos, aerial imagery, and a September 2016 LiDAR-derived digital elevation model (DEM) dataset provide information on pre-storm morphology, while field photos, taken only 3 days after Hurricane Harvey made landfall, and a structure-from-motion (SfM)-derived DEM and imagery provide qualitative and quantitative information about the post-storm morphology. While beach and dune erosion in the non-driving section was restricted entirely to the beach and incipient dune system, the driving section exhibited complex patterns of erosion and deposition along the beach and the entire foredune profile was altered. Despite the hurricane making landfall north of the study site and closer to the non-driving section, beach-dune erosion and scarping was greatest in the southern section which is accessible to public vehicles. Results demonstrate that human activity affects the response and recovery of the beach-dune system along the Gulf side of the island by decreasing alongshore variability in erosion-deposition and limiting vegetative and geomorphic recovery. Unlabelled Image • Driving on the beach affects beach-dune response to and recovery following a storm. • Non-driving areas show substantial evidence of recovery within 6 months post-storm. • Driving on the beach limits incipient foredune development and recovery. • Limiting low dune recovery can reinforce the effects of framework geology. [ABSTRACT FROM AUTHOR]

The Louisiana and Texas Rigs-to-Reefs programs enjoy widespread public, industry, and government support and have become models for similar programs around the world. Louisiana's Rigs-to-Reefs program is the largest in the world, and since its inception in 1986 about 363 oil and gas platforms have been donated, or on average about 12 structures per year. Texas's Rigs-to-Reefs program started in 1990, and since this time about 154 structures have been donated, or about six structures per year. A summary update of the Louisiana and Texas reef programs is provided, along with recent changes in legislative activity. Donation trends and statistics are reviewed. The Rigs-to-Reefs programs are unlikely to see donation activity above historic levels, and both programs should start planning for a future where the income generated from future projects diminishes. [ABSTRACT FROM AUTHOR]

The hypoxic zone on the Louisiana-Texas shelf varies in its area, volume, and vertical distribution. Vertical movement to avoid hypoxia (dissolved oxygen (DO) concentration < 2 mg/L) can be important to understanding fish exposure to low DO. Fish movement was simulated in 2-D (bottom layer) and 3-D with movement algorithms that depended on DO fields generated by a 3-D coupled hydrodynamic-water quality model. Fish exposure to low DO was simulated using two alternative movement algorithm groups, good and bad avoidance competency, and three perception ranges for detecting DO. The algorithm groups (default and avoidance) differed in whether the default movement included a downward bias. Avoidance competencies differed in the degree of random variation imposed on the avoidance movement. Fish exposures to low DO were simulated in 2-D and 3-D for July 24 to August 2 of 2002 during which hypoxia showed both horizontal and vertical variations. The addition of vertical movement (3-D) resulted in mean cumulative hypoxia exposures (days with DO< 2 mg/L) typically about 8 times lower than the 2-D movement results (e.g., ∼0.1 days versus 0.8 days with good avoidance), but vertical avoidance did not decrease the cumulative days of exposure of fish to moderate hypoxia (2–4 mg/L). The differences between the 2-D and 3-D model results, coupled with the limited data on vertical fish movement in response to hypoxia, suggest that 3-D movement could affect exposure to hypoxia and should be considered for spatially complex habitats. [ABSTRACT FROM AUTHOR]

A 3-D unstructured-grid hydrodynamic model for the northern Gulf of Mexico was developed, with a hybrid s – z vertical grid and high-resolution horizontal grid for the main estuarine systems along the Texas–Louisiana coast. This model, based on the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM), is driven by the observed river discharge, reanalysis atmospheric forcing, and open boundary conditions from global HYCOM output. The model reproduces the temporal and spatial variation of observed water level, salinity, temperature, and current velocity in Galveston Bay and on the shelf. The validated model was applied to examine the remote influence of neighboring large rivers, specifically the Mississippi–Atchafalaya River (MAR) system, on salinity, stratification, vertical mixing, and longshore transport along the Texas coast. Numerical experiments reveal that the MAR discharge could significantly decrease the salinity and change the stratification and vertical mixing on the inner Texas shelf. It would take about 25 and 50 d for the MAR discharge to reach the mouth of Galveston Bay and Port Aransas, respectively. The influence of the MAR discharge is sensitive to the wind field. Winter wind constrains the MAR freshwater to form a narrow lower-salinity band against the shore from the Mississippi Delta all the way to the southwestern Texas coast, while summer wind reduces the downcoast longshore transport significantly, weakening the influence of the MAR discharge on surface salinity along Texas coast. However, summer wind causes a much stronger stratification on the Texas shelf, leading to a weaker vertical mixing. The decrease in salinity of up to 10 psu at the mouth of Galveston Bay due to the MAR discharge results in a decrease in horizontal density gradient, a decrease in the salt flux, and a weakened estuarine circulation and estuarine–ocean exchange. We highlight the flexibility of the model and its capability to simulate not only estuarine dynamics and shelf-wide transport, but also the interactions between them. [ABSTRACT FROM AUTHOR]

Caudle, T.L. and Paine, J.G., 2017. Applications of coastal data collected in the Texas High School Coastal Monitoring Program (THSCMP). The Texas High School Coastal Monitoring Program (THSCMP) engages students and teachers who live along the Gulf of Mexico in the study of their natural environment. Scientists from the Bureau of Economic Geology (BEG) at The University of Texas at Austin show middle and high school students and teachers how to measure topography, map vegetation lines and shorelines with GPS, and observe weather and wave conditions. The students are active participants in the research project, which has the dual benefit of enhancing their science education while providing valuable data on the dynamic coastline. Students collect critical scientific data that help scientists and managers address coastal issues and gain a better understanding of dune and beach dynamics on the Texas coast. Since the THSCMP began in 1997, data collected by students have been applied by scientists to investigate beach, dune, and vegetation-line recovery following several tropical cyclones, including Hurricane Ike in 2008. Student-collected data are used to monitor the effects of nourishment projects on South Padre Island, foredune changes on Mustang Island, geotextile tubes on Galveston Island, and jetty construction on Matagorda Peninsula. Student data are also used in verifying shoreline positions for updates of Texas' long-term shoreline change rates. Through these real-world examples of scientific observations, students gain a better understanding of environmental issues affecting their communities. [ABSTRACT FROM AUTHOR]

Severe and persistent bottom-water hypoxia (≤2 mg O2 L−1) occurs on the Louisiana/Texas continental shelf from mid-May through mid-September over a large area (up to 23,000 km2 in mid-summer). Benthic infauna are less mobile than demersal organisms and become stressed by the low dissolved oxygen; benthic community composition, abundance, diversity, and biomass become altered. From the 1950s to the early 1970s, when sediment core indicators identified the initiation and subsequent worsening of dissolved oxygen conditions, there were no hydrographic data or benthic infaunal studies within the current area of frequent bottom-water hypoxia. This study highlights the impacts of severe hypoxia on benthic macroinfaunal communities and how they may have changed from less-hypoxic periods. Polychaetes were and are the dominant taxa in the available studies, but polychaete species richness in summer is now curtailed severely beginning with our 1985–1986 data. Species richness of polychaetes in summer hypoxia (1985–1986 and 1990–1991) was about 60% less than comparable taxa in 1972–1973. Abundance of polychaetes was much less in summer than spring, and recent infaunal biomass in summer was only 15% of what was found in spring. The result is less prey for demersal penaeid shrimp and fishes. Over the period of our comparison, infaunal feeding modes shifted from subsurface deposit feeders and surface deposit feeders to primarily surface deposit feeders (i.e., 95.5% of all polychaetes). Most were opportunistic, hypoxia tolerant, and recruited in high numbers following hypoxia abatement, some in fall and winter but most in spring. As benthic communities succumb to the stress of severe and continued seasonal low oxygen, they occupy the few upper centimeters of the sediment profile above the redox discontinuity layer with negative feedbacks to the water column by way of altered biogeochemical processes. [ABSTRACT FROM AUTHOR]

Environmental-DNA (eDNA) for metabarcoding is a rapid and effective means to investigate microplankton community composition and species diversity. The objective of this study was to examine the genetic diversity of the phytoplankton community in the Gulf of Mexico, with particular emphasis on harmful algal bloom species. Samples were collected at stations along the coast of Texas in September-October 2017 that were inundated by low salinity waters in the aftermath of Hurricane Harvey. Metabarcodes were generated from the eDNA targeting both the V4 and V8-V9 regions of the 18S rDNA gene. Evaluation of the metabarcodes revealed an unexpectedly high number of harmful algal species during this short period, including five that had not been documented in this region previously. A total of 36 harmful algal species could be differentiated based on V4 and V8-V9 metabarcode markers. Using a phylogenetic approach, the taxonomic resolution of each marker differed and not all species could be differentiated using solely one marker. The V4 region resolved species within some genera (e.g., Heterocapsa), while the V8-V9 marker was necessary to resolve species within other genera (e.g., Chattonella). In other cases, species differentiation within a genus required a combination of both markers (e.g., Prorocentrum, Karenia), or another marker will be needed to resolve all species (e.g., Alexandrium, Dinophysis). We conclude that no single marker can delineate all species, so it is recommended HAB monitoring programs use more than one marker. Overall, the observed diversity of HAB species along the Texas coast using metabarcoding exceeded reports from other parts of the world., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Changing environments of temperature, precipitation and moisture availability can affect vegetation in ecosystems, by affecting regeneration from the seed bank. Our objective was to explore the responses of soil seed bank germination to climate-related environments along geographic gradients. We collected seed banks in baldcypress (Taxodium distichum) swamps along the Mississippi River and the Gulf of Mexico Coast in the United States, which have distinct temperature and/or precipitation gradients, and germinated them in a greenhouse. The frequency, richness and seed density of species germinated from the seed bank were compared between various geographic locations, experimental water regimes (saturated, flooded) and wetland types (tidal, non-tidal and inland swamps). We also analyzed the relationship of seed density to the environment by using a Non-metric Multi-dimensional Scaling (NMDS) model. Sixty-one species germinated from the seed bank, differing in pattern by geographic location, experimental water regime and wetland type. The foundation species (i.e., T. distichum and Cephalanthus occidentalis) germinated with a niche affinity for the northern part of the latitudinal gradient (Tennessee and Illinois) and these species may shift northward with climate change. Some species had higher seed density in the locations that were subject to more persistent drought conditions (e.g., Texas) including Cyperus rotundus and Gratiola virginiana, indicating that these species may be better adapted to sites with high temperature and low precipitation. In contrast, certain species including Saururus cernuus and Ludwigia palustris were present throughout the range of these gradients, and so may be more resilient to any future climate shifts. We found that the regeneration potential of baldcypress swamps might be altered by changes in local and climate environment because of nuances of responses of seed banks to climates along latitudinal and longitudinal gradients. Our study can help predict vegetation regeneration potential to climate change environments depending on the ability of these species to disperse and maintain seed banks., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Framework-forming scleractinian (FFS) corals provide structurally complex habitats to support abundant and diverse benthic communities but are vulnerable to environmental changes and anthropogenic disturbances. Scientific modeling of suitable habitat provides important insights into the impact of the environmental conditions and fills the gap in the knowledge on habitat suitability. This study presents predictive habitat suitability modeling for deep-sea (depth > 50 m) FFS corals in the GoM. We first conducted a nonparametric estimate of the observed coral point process intensity as a function of each numeric environmental variable. Next, we performed species distribution modeling (SDM) using an assemble of four machine learning models - maximum entropy (ME), support vector machine (SVM), random forest (RF), and deep neural network (DNN). We found that most important variables controlling the coral distribution are super-dominant gravel and rock substrata, SW and SE aspects, slope steepness, salinity, depth, temperature, acidity, dissolved oxygen, and chlorophyll-a. Highly suitable habitats are predicted to be on the continental slope off Texas, Louisiana, and Mississippi and the shelf and slope of the West Florida Escarpment. All the four models have outstanding prediction performances with AUC values over 0.95. DNN model performs best (AUC = 0.987). The study contributes to coral habitat modeling research by presenting unique methods including nonparametric function of coral point process intensity, DNN and SVM models that have not been used in coral SDM, post-classification model assembling, and percentile approach to determine a threshold value for classifying a suitability score map into a binary map. Our findings would help support conservation prioritization, management and planning, and guide new field exploration., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)