The majority of Texas estuaries have been experiencing a long-term decrease in alkalinity and pH. In particular, during a dry year (2014), an alkalinity loss occurred in the Mission-Aransas Estuary (MAE). Even though carbonate precipitation can reduce alkalinity, the alkalinity loss observed in the MAE could not be entirely explained by calcification of biological organisms. The reaction stoichiometry suggests that another process is responsible for creating this alkalinity sink. Possible explanations include sulfide discharge from groundwater, atmospheric deposition of acids from anthropogenic or natural sources, such as sulfur dioxide from ships, reverse weathering, or cyclic sediment behavior (redox) of sulfur or metal species, such as oxidation of iron sulfide-rich sediments, during periods of low precipitation and high salinity. To identify the cause of the alkalinity loss in MAE, sediment cores were collected from the system and incubated to examine benthic processes on overlying water alkalinity. Surface water samples were collected on a weekly basis and analyzed for calcium concentration and alkalinity. Based on reaction stoichiometry, a 2:1 ratio of calcium ion to alkalinity concentration would be expected if calcification were causing the alkalinity sink. Preliminary results revealed deviation from expected calcium ion to alkalinity ratios, which suggests presence of a seasonal sulfur and metal species cycle that could have been exacerbated by low precipitation and high salinity and may have caused the alkalinity sink observed in the MAE. Cyclical redox reactions occurring in sediment may have a major impact on estuarine alkalinity and biogeochemistry; these types of reactions should not be overlooked when studying carbonate chemistry of estuarine systems.

Water quality in rural areas can be negatively impacted by human activities despite lower population density. Indian Bayou, a part of the Pensacola Bay System, is sparsely populated with many unpaved red clay roads for the communities living along the Bayou shoreline. Recently, widening of the interstate, ditch clearing along the many unpaved roads, coupled with heavy rain events have led to increased sediment inputs. These impacts have led to local concern for the Bayou. This project conducted high frequency monitoring of water quality to examine variability within Indian Bayou. Sensors were placed off a dock in Indian Bayou to log the variability over an eight-week period. MiniDot Dissolved Oxygen and PAR sensors were used along with the HOBO Ware Conductivity sensor and Light tag sensors. The sensors were deployed on May 31st and discrete samples were collected in weekly intervals, along with downloading data from the data sensors, until July 27th. Each sensor logged data at frequencies ranging from once a second to once every fifteen minutes. Discreet water samples included YSI readings, water depth, Secchi depth, dissolved inorganic nutrients and chlorophyll a. Weekly YSI data readings were used to examine drift in sensors during the deployments. We examined how rain events affected salinity, light availability, nutrient distributions and phytoplankton biomass within Indian Bayou.

Monitoring of the carbonate system in the northwestern Gulf of Mexico’s Aransas Pass was conducted via deployment of in situ pH and partial pressure of CO2 (pCO2) sensors for a period of 10 months as well as monthly discrete sample collection for over four years. Temporal variability was assessed on both diel and seasonal scales. The daily range in pH at the site often exceeded the magnitude of average pH decrease that has occurred globally due to ocean acidification over the last century. Thermal and non-thermal controls on the carbonate system were assessed at both diel and seasonal time scales, and it was concluded that temperature exerts the primary control on diel variability of pCO2, but non-thermal controls, which may include tidal fluctuations and biological activity, exert the primary control on the system over longer time scales. Differences in calculations of CO2 flux resulting from these two different sampling methods are also reported to help suggest limitations and resulting uncertainties of current sampling methods for CO2 flux estimations. This study provides a step toward a better understanding of the highly variable carbonate chemistry of coastal ecosystems.

Anthropogenic influence from the increasing urbanization of the environment in estuarine watersheds affects the health of estuaries all over the world. Three urbanized bayous in the Pensacola Bay System; Bayou Texar, Bayou Chico, and Bayou Grande, are estuarine systems that are affected by anthropogenic effects of their surrounding watersheds. Land use in the Bayou Texar watershed is predominantly residential although commercial development has increased in recent years in the upper watershed. Bayou Chico’s lower watershed is mainly industrial, while the upper watershed is residential. In Bayou Grande, the watershed is divided between Naval Air Station Pensacola on one side and residential on the other. This study examines spatial and temporal variability of the water quality of these systems over the same time period in contrast to previous studies of these Bayous have analysed each system separately. Bimonthly sampling of water quality, nutrients, light attenuation, and phytoplankton biomass along with analysis of historical data will give perspective of how water quality has changed and responded to the increasing urbanization of the region. This research will compare these estuarine systems in close proximity to one another, and evaluate the impacts of different types of urbanization. We use mixing diagrams to examine the relationships between nutrients and chlorophyll a along the estuarine salinity gradient of each system. Restoration activity is occurring in this area and this information should provide relevant information for management of these systems.

Dissolved oxygen (DO), a major indicator of water quality, is also a critical component for the survival and success of aquatic organisms. A low concentration of dissolved oxygen for an extended amount of time (a condition known as “hypoxia”) can cause changes in behavior, physiological stress, and even death, significantly disrupting an ecosystem’s balance and functions. Hypoxia events occur when the measured oxygen concentration in the water falls below 2 mg/L. Two sites of Bear Point Bayou on the Gulf Park campus of the University of Southern Mississippi have been monitored for DO, pH, turbidity, nitrate and phosphate on a monthly basis for the past 12 months (and continues). The goal of this project is to calculate the apparent oxygen utilization (AOU) which estimates oxygen consumption by organisms in the water column and determine if water quality was more heavily impacted by biological vs. physical processes.

Global climate change has led to increased frequency of extreme weather events including droughts, floods and severe storms within the last century. In Texas, the greater Houston area has experienced multiple occurrences of such events within the last decade. The increasingly urbanized city of Houston is located within the watershed of Galveston Bay, an economically and ecologically important estuary on the northwest coast of the Gulf of Mexico. Extreme changes in freshwater inflow quality and quantity as a result of floods, droughts and storms (hurricanes) can impact the ecology of Galveston Bay. Monitoring campaigns designed to observe the extent of these ecological impacts have been conducted in Galveston Bay since 2010. Abiotic surface water quality parameters (temperature, salinity, dissolved oxygen, pH, conductivity, and water clarity) were assessed at discrete stations using a Secchi disk, refractometer and Hydrolab MS5 sonde. Water samples were collected for nutrient and phytoplankton pigment analyses. Phytoplankton community dynamics determined from these analyses serve as indicators of system-wide ecological response to changes in water quality. Contour maps facilitate the visualization of fine-scale gradients in each of the measured parameters along a transect from the San Jacinto River mouth to Gulf of Mexico throughout the period of study. Maps show that the ratios of pigments indicating Bacillariophyta and Dinophyta (estuarine and marine phytoplankton) compared to Chlorophyceae and Cyanophyta pigments (freshwater indicator phytoplankton) are largely influenced by both the magnitude and duration of freshwater inundation. Drought periods were dominated by Bacillariophyta. Prolonged flooding periods led to Chlorophyceae and Cyanophyta dominance in the northernmost stations of the transect which reflect that long-term climatological events can affect community-wide shifts. Ratios were nearly equal in the flooding period following a hurricane event supporting the assumption that Galveston Bay phytoplankton communities are resilient to short-term extreme weather events.

Estuarine organisms are adapted to variable water quality conditions created in estuaries by various forces including: freshwater inflows, anthropogenic nutrient loading, tidal fluxes, ground erosion or urbanization, and even extreme events such as hurricanes. At the end of August (2017), Hurricane Harvey made landfall over the southeast coast of Texas as a category 4 storm, and arrived in the Galveston Bay/Houston area as a tropical storm; releasing 33 trillion gallons of water over four days. Following this flood event, salinities in Galveston Bay decreased to 2-7 psu near the Gulf of Mexico compared to 25-30 psu reported pre-Harvey. In this study, we analyzed the fluctuations of the phytoplankton community in response to the increased freshwater inflows. Cell abundances and community shift in five phytoplankton groups found in the Bay were analyzed at the following time points: 7 days pre-Harvey, and daily for the 4-28 days post Harvey. The relative abundance of the groups shifted in response to changing freshwater inflows. The dinoflagellate relative abundance decreased from 80% pre-Harvey to 5% four days following Harvey. Freshwater cyanobacteria comprised 70% of the community immediately following the flooding event. The chlorophyte population remained lower than 5% up to 26 days after the storm and then increased to make up 35% of the community which decreased back to <5% on day 27. Diatom abundance increased 11-13 days after Harvey to 90-95% of the community but decreased to about 48% following a Euglena bloom 14 days post-Harvey. Percent abundance data displayed another increase of diatom cells 20-28 days post-storm to make up 85-90% of the community. A comparison of percent abundance data pre-Harvey (65% diatom, 35% dinoflagellate) to the 28 days post-Harvey (80% diatom, 15% dinoflagellate, 4% chlorophyte, 1% Euglena) was performed. By our observation, it was determined that the phytoplankton community primarily returned back to a diatom dominant system a month after the end of the storm.

Research has shown the importance of freshwater inflow as a driver of estuarine biogeochemistry and planktonic production. On the Texas coast, a sharp coastwide freshwater inflow gradient exists, which leads to diverse estuarine conditions ranging from river influenced, low salinity systems to semi-arid, hypersaline systems. Few studies have compared water quality and phytoplankton communities in estuaries spanning this freshwater inflow gradient however. In this study, we compare water quality and size-fractionated chlorophyll within and between three estuaries that differ in the magnitude of freshwater inflow; San Antonio Bay (river influenced), Nueces-Corpus Christi Bay (limited river influence, strong ocean influence), and Baffin Bay (no major rivers, frequently hypersaline). Our goal is to understand how freshwater inflow affects the biogeochemistry, phytoplankton biomass and community composition in Texas estuaries. Preliminary findings show strong seasonal and spatial differences in chlorophyll within estuaries, as well as differences between the estuaries. This presentation will elaborate on these differences, as well as potential causes and implications for freshwater inflow management in Texas.

Diatoms are known to produce copious amounts of polysaccharide chrysolaminarin, especially during the stationary phase of their growth, however their exact role is still unknown. Diatoms also tend to secrete a significant amount of polysaccharide into the environment, which can serve as a good organic carbon source for several bacterial species. The 2010 Deepwater Horizon oil spill exposed the Gulf of Mexico to substantial amount of oil that had a severe effect on the phytoplankton community. Here, we study the role of chrysolaminarin in the growth and physiology of an oil sensitive diatom Thalassiosira pseudonana and how it shaped the surrounding bacterial community and their activity in the presence of hydrocarbons. We found that inhibition of chrysolaminarin synthesis had a strong negative effect on the growth and recovery of T. pseudonana in the presence of hydrocarbons. This negative impact was presumably through feedback inhibition of the electron transport between the two photosystems by accumulating monosaccarides. Inhibition of chrysolaminarin synthesis also influenced the bacterial community and their exoenzyme activity. An increased abundance of members of hydrocarbon degrader Alcanivorax genus and higher lipase activity was observed in response to inhibition of chrysolaminarin synthesis and the presence of hydrocarbon. This in-turn seemed to have favored biodegradation of hydrocarbon. Overall, chrysolaminarin synthesis played a significant role in the survival of T. pseudonana in presence of hydrocarbon and had a significant effect on the community composition and activity of the surrounding bacteria.

Phytoplankton form the base of aquatic food webs and play an important role in carbon fixation and nutrient cycling. They are also among the first communities to respond to changes in environmental factors. The phytoplankton communities in the Atchafalaya-Vermilion Bay System (AVBS) have been quantified since 2016 to observe seasonal changes in abundance and community composition . Samples were analyzed using fluorometry to obtain chlorophyll a concentrations of the phytoplankton communities. Results from these analyses show overall dominance of the smaller size classes (< 20 µm) of phytoplankton throughout the year in this ecosystem. To further understand the composition and abundance of these small members of the plankton, preserved samples were analyzed using flow cytometry. These analyses allowed for enumeration of cells in different size classes (nano- and picoplankton) and functional groups (nanoautotrophs, nanoheterotrophs, picocyanobacteria, and picoeukaryotes) based on size and fluorescence. Picocyanobacteria had the highest abundances throughout the two year period with a maximum abundance in April 2017 and minimum abundance in January 2017. Nanoautotrophs showed the consistently lowest abundances, with minima in September 2016 and maxima in May 2017. Interestingly, however, nanoautotrophs showed the strongest correlation (r = 0.76) with the < 20 µm chlorophyll biomass throughout the study period. We are currently working to quantify how environmental factors (i.e. turbidity, nutrient availability, temperature, and salinity) may be influencing these members of the plankton community. Understanding these communities in the AVBS is needed, given their important roles in estuarine food webs and the potential for changes in their abundances to affect economically- and ecologically-important higher consumers.

In the Pensacola Bay system, seagrasses are a dominant habitat in the shallow estuarine region, particularly in Santa Rosa Sound and Big Lagoon. Many aquatic animals use seagrass beds to feed, breed and seek refuge. In the summer of 2017 the University of West Florida (UWF), Escambia and Santa Rosa County Sea Grant Extension began a partnership to enlist citizens and UWF students to monitor seagrass beds. Each month during the growing season, local citizens identify seagrass species and use quadrats to estimate to coverage of seagrass and macroalgae at different locations in Big Lagoon and Santa Rosa Sound. They also collect water samples that are brought back to the laboratory at UWF where students measure salinity and total suspended solids (TSS). In 2018, salinity range was 10.13 to 25.89 for Santa Rosa Sound and between 15.8 and 27.1 in Big Lagoon. TSS during this year was usually below 8 mg/L in Santa Rosa Sound and below 19 mg/L in Big Lagoon. Seagrass coverage from 2017, by the citizen scientists, was comparable to earlier UWF data from 2016. The goals of this program are to develop an active community of citizen scientists and develop long term monitoring of seagrass habitats in the Pensacola Bay system.

Coastal ecosystems are vulnerable to temporary or even perpetual alteration following intense and severe meteorological disturbances. After Hurricane Harvey, a category 4 hurricane, hit the Coastal Bend of Texas in August 2017, physical damage to seagrass beds was quantified in preliminary assessments of percent cover and blade length in 16 permanent monitoring stations in Redfish Bay. Immediately following the storm (1-month post hurricane), sampled seagrass beds exhibited an average loss of almost 40% of Thalassia testudinum percent cover. The continuing response of T. testudinum to the intense winds and wave action brought on by Harvey was compared between two categories of impact based on initial seagrass percent cover loss: high-impact stations (greater than 60% cover loss) and low-impact stations (less than 25% cover loss). At these stations, seagrass beds were sampled again (3-months post hurricane) for T. testudinum percent cover, above- and below-ground biomass, leaf area (blade length and width), blade density and shoot density. Percent cover in high-impact stations increased from 1-month to 3-months post hurricane but was still significantly less than the percent cover of T. testudinum in low-impact stations at the 3-month mark. High-impact stations observed significantly less above- and below-ground biomass than low-impact stations. Lower shoot density and leaf area were observed in high-impact stations, likely from direct removal of seagrass during periods of high winds and wave action during the storm. Drift algae was present in 88% of high-impact stations and 50% of low-impact stations suggesting that physical removal of seagrass blades from the water column may allow for the establishment of other submerged aquatic vegetation. Continued, sequenced monitoring of these T. testudinum dominated beds may reveal the initial structural perturbations, such as the observed loss of T. testudinum, as significant factors in predicting the recovery of seagrass communities following severe storms and wind events.

Disturbance has long been recognized as a driving force of diversity within ecological communities. Hurricanes are a major natural disturbance that frequently affect coastal communities and can cause physical damage as well as changes in water chemistry due to large freshwater inputs. Seagrass habitats are an important coastal marine community that provide nursery grounds to many juvenile species, sequester carbon, and provide sediment stabilization. Seagrasses may be especially vulnerable to hurricane disturbance because they inhabit shallow water and soft sediments. Hurricane Harvey was a category 4 hurricane that devastated the Central Texas coasts on August 25, 2017. Following the hurricane, seagrass cover was reduced within areas that experienced the highest intensity winds, although losses in seagrass were patchy. The objective of this study was to examine whether these losses in seagrass cover had cascading effects on seagrass faunal communities. To conduct this study, push net surveys were conducted along replicate 10 m transects at 16 sites that varied in their degree of seagrass loss within the Redfish Bay, Texas in November 2017. It was found that species richness was higher at low seagrass cover sites, but overall faunal abundance and biomass did not vary predictably with seagrass loss. Higher species richness at low seagrass cover sites most likely occurred as a result of the hurricane bringing in some species that would not typically be found in the local seagrass communities and are more often associated with unvegetated habitat. Additionally, we detected a minor shift in seagrass community structure with 14% of the variation in community structure across sites explained by seagrass cover post-storm. These results suggest that the hurricane disturbance may not have caused large losses in seagrass community abundance or diversity, but rather resulted in shifts in composition of seagrass communities post-storm.

Hurricanes, typhoons and cyclones are some of the greatest environmental drivers of change in shallow benthic communities. This study investigates the impacts of Hurricane Irma on seagrass and macroalgal communities in South Florida, specifically Florida Bay (FB) and the Florida Keys National Marine Sanctuary (FKNMS), by leveraging multi-agency environmental monitoring data. Regular monitoring of these habitats has been performed since 1996, and we utilized these long-term datasets to investigate the hurricane impacts in the context of recent and historical ecological baselines for the system. Longitudinal analyses were performed to examine changes in total seagrass (TSG) and total calcareous green macroalgae (TCAL) density across regional zones from 2012-2017. Three types of seasonal analyses were also performed to confirm that any changes to the benthos post-Irma were due to hurricane impacts rather than seasonal variability. We found a significant decrease in TSG in the Lower Keys (Bayside) of FKNMS, and in Manatee Bay of FB relative to previous years, but no significant differences in TCAL were found in either system. Seasonal analyses confirmed that for both FB and FKNMS, impacts from Hurricane Irma were greater than those observed due to regular seasonal variability. Most seagrass declines in FKNMS were due to direct impacts (i.e., physical impacts), whereas seagrass mortality in Manatee Bay (FB) was indirectly linked to Hurricane Irma through hyposalinity and low dissolved oxygen resulting from stormwater drainage. Our study provides an example of a single storm unleashing both direct and indirect impacts to the benthic community in very different (and not all) areas of the same system. Our results offer a preliminary assessment of post-Irma seagrass status and highlight the importance of long-term monitoring, not only as a historical benchmark, but also as the backbone for event-response monitoring in the aftermath of a disturbance.

Although seagrass beds provide many economically important ecosystem services worldwide, including mitigating the impacts of sea-level rise and enhancing commercial fisheries production, seagrass coverage is being lost at an average rate of 1.5% yr −1. The presence of excess atmospheric carbon and the resulting impacts make the capacity of seagrasses to sequester carbon of particular interest. Current seagrass coverage maps are generated by interpolating from samples taken by divers, making this method cost- and labor intensive. Recent research in resource management emphasizes the need for seascape-scale monitoring and planning. Remote sensing technology provides a versatile way for organizations to oversee large portions of landscapes, although the presence of water in coastal ecosystems provides unique challenges. Depth, water clarity, and water reflectance all influence the ability of sensors to provide valid imagery. The purpose of this project is to develop reliable, accessible methodology to assess seagrass coverage using aerial multispectral sensing techniques. Procedures for evaluating and mitigating the effects of water turbidity, water reflectance, and wave height will be investigated. The connection between canopy cover and belowground stored carbon is suspected but wide-scale data on this relationship is not readily available. The second goal of this project is to provide more comprehensive evidence for the link between seagrass coverage and stored belowground carbon so that carbon stocks may be reliably estimated using remote sensing.

Seagrasses are a relatively common group of rooted, marine angiosperms that provide essential habit for numerous commercially and recreationally important species. They also provide a number of freely available “ecosystem services” in the form of improved water quality, shoreline stabilization, and CO2 sequestration. Over the past several decades many species of seagrass have experienced decline and degraded environmental conditions across their range. A loss of seagrass can have severe impacts on marine biodiversity and the health of coastal ecosystems. Loss of diversity at the genetic level can also have major impacts, as various studies have shown a significant correlation between seagrass genetic (e.g. genotypic) diversity and resistance to environmental stress. Halodule wrightii is the most prominent species of seagrass on the Texas Gulf Coast. We used a DNA-based molecular marker assay to investigate genetic diversity in a population of Halodule wrightii from Oso Bay, near Corpus Christi, TX. We found low genotypic diversity (R = 0.20) and no evidence of a seed bank, but heterozygosity remains high (He = 0.73). Asexual reproduction appears to be the most common mechanism of reproduction in the northern portion of H. wrightii’s Texas range, though highly heterozygous genotypes appear to be favored.

Subsidence of marsh land as well as eustatic sea level rise causes high marsh plants, such as Spartina patens, to be increasingly inundated with seawater. Longer periods of submersion promote sulfate reduction by microbes among the roots of these plants allowing sulfide to increase to phytotoxic levels. In 2005 and 2010, Best Use Dredge Material from local shipping channels was used to elevate areas within the Salt Marsh Bayou in Southeast Texas with the goal of returning function to these areas which were suffering the phytotoxic and erosive effects of increased water inundation. Here, porewater analytes (sulfide, ammonium, sulfate, nitrate, pH, salinity) and sediment redox, water content and ash free dry mass (AFDM, a proxy for organic content), were monitored in winter and spring of 2018, at unstable declining sites, healthy stable sites, and restored sites. Water content and AFDM were highest at unstable sites, and least at restored sites. Phytotoxic levels of porewater sulfide (>1.0 mM) were found to be typical at unstable marsh sites. Salinity, however, was lowest at these unstable sites (9.7 ± 1.6 ppt; n=30) compared the restored sites (15.0 ± 2.2 ppt; n=30), contradicting the assertion that salinity, and hence sulfate, drives greater sulfate reducer activity and sulfide levels. Restored sites had the lowest values of sulfate and sulfide, especially in winter. Ammonium concentrations at unstable sites were over 12 times greater than at restored sites in winter, but less so in spring as soil temperatures warmed. Lower pH from winter to spring implies greater decomposition as sediment warmed, suggesting that plant uptake of ammonium is a probable cause for reduced concentrations. Stable site values for geochemical parameters have been relatively intermediate. Overall, BUDM marsh restoration is reversing geochemical conditions from those of unstable declining marsh sites.

Climate change is predicted to induce sea level rise and reduce the severity of freezing events on the Texas Gulf Coast; these changes are likely to lead to increased mangrove cover within the marsh-mangrove ecotone. The blue crab Callinectes sapidus is a commercially and ecologically important species within estuarine ecosystems along the Texas coast. It is a mobile invertebrate that feeds on a variety of organisms, and as an adult can be found foraging in both marsh and mangrove environments. A mobile prey item of the blue crab that is also found in marsh, mangrove, and open water habitats in Texas is the penaeid shrimp. The aim of this study was to determine if different vegetation types provide varying prey refuge values. Three habitat treatments were created within a 2-meter diameter tank. One treatment simulated mangrove pneumatophores, which were constructed from rigid wooden dowels. Another treatment contained plastic aquarium plants, which simulated flexible marsh grasses. The third treatment in the tank was a nonvegetated control. For each trial, five shrimp were placed in the tank for three hours. Five trials were conducted when the predator (Callinectes sapidus) was present, and five trials were conducted when the predator was absent. A GoPro Hero+ was mounted above the tank to record animal activity. Shrimp spent significantly less time in the mangrove treatment than the marsh treatment when the predator was absent, but the shrimp did spend significantly more time in the mangrove treatment than the marsh treatment when the predator was present. These results suggest that mangroves may provide more effective prey refuge than marsh vegetation.

Multiple studies have investigated the effects of atmospheric warming on mangrove range expansion into salt marsh; however, little is known about associated belowground processes in facilitating transgression. At the marsh-mangrove ecotone, we suggest that increases in estuarine water temperature may have pronounced effects on wetland soil temperature, thereby resulting in alteration of belowground biomass, biogenic accretion, plant productivity, species interactions, and plant community composition. To address this data gap, a tidal mesocosm experiment was established to investigate the effects of elevated seawater temperatures on key plant and soil responses. This design uses four vegetation treatments: Spartina alterniflora and Avicennia germinans grown both in monoculture and in mixture, plus unvegetated wetland soil. Unvegetated marsh soil and transplants of A. germinans and S. alterniflora were collected from areas adjacent to a companion warming experiment established at Guana Tolomato Matanzas National Estuarine Research Reserve, St. Augustine, Florida (GTM NERR). Semidiurnal tides were established to simulate the tidal frequency and and flooding depth at GTM NERR. Three estuarine water temperature regime treatments have been implemented to simulate current ambient seasonal water temperature fluctuations at GTM NERR plus two elevated water temperature regimes that range from approximately 2.5 to 5 degrees C above ambient temperatures in the summer and 5 to 10 degrees C above ambient temperatures in the winter. This type of controlled mesocosm approach in conjunction with companion field experiments can provide novel information on plant above- and belowground architecture and productivity, soil biogeochemistry, decomposition, and carbon dynamics that will advance our understanding of key environmental drivers of shifts in community composition and provision of ecosystem services under future warming scenarios.

In the Gulf of Mexico, black mangrove (Avicennia germinans) populations have been expanding into salt marsh dominated areas. Typically, mangrove populations in the Gulf of Mexico are restricted by occasional severe freezing events, but the rate and trajectory of recovery by these mangroves following freezing temperatures is poorly understood. In January 2018, winter storm Inga affected Galveston, TX; temperatures were less than -4°C for several hours. These conditions induced widespread mangrove damage. To assess the rate and trajectory of freeze recovery, trees with partially damaged and fully damaged canopies were tagged and monitored from January to July 2018. Within the two damage classes, trees were also divided into three different size classes: small (shorter than 0.5 meters), medium (between 0.5 and 1.4 meters, and large (taller than 1.4 meters). Of the 56 trees surveyed, eight exhibited no new growth and are presumed dead; all but one of the trees that exhibited no new growth were fully damaged in January. Less than 10% of the trees were flowering but all those that were flowering had undamaged leaves after the freeze and were in the medium and large size classes. Trees that had 100 percent leaf damage in January recovered an average of 48.5% of their pre-freeze heights the following July, while trees that were partially damaged recovered 75.3% of their pre-freeze height. Despite the severity of the freeze event, which brought temperatures below the previously documented threshold for tree mortality, some recovery and flower production suggest that other factors play a role in mangrove survival and recovery following severe freeze events. Soil properties, population genetic structure, and tree morphology should be analyzed to further study the resilience of mangrove individuals and populations to freeze events.

Coastal wetlands provide many services for the areas that surround them including structured habitat, water filtration through the sediment, and can dissipate storm surge effects. Increasing rates of wetland loss and loss of historic wetlands are causing concern in coastal communities. There has been increased efforts to restore and protect coast wetlands using living shorelines. One common method to first protect, and then facilitate wetland restorations, is to construct oyster reefs that can stabilize the shoreline. The objective of this study was to quantify the effects of restored subtidal oyster reefs on net sedimentation in the West Bay of Galveston Island. This data could help organizations with decision making regarding future projects as well as assist in acquiring funding in the future to sustain these projects. Sediment pins made of 7-foot-long PVC pipe were buried to a depth of 3 feet and an initial measurement of the elevation at the top was made to establish a baseline. These sediment pins were deployed at a restored oyster reef (n=6) and at a reference site (n=6), which lacks any restored reefs. Subsequent measurements of the sediment pin elevation, which were collected weekly between March-October 2018, provide a proxy for the net sedimentation in the area. Thus far, sedimentation rates have fluctuated less at the restored oyster reefs compared to the reference sites, with some interesting results at certain pin locations that have anomalous readings for their locations. The results of this study may be utilized to further direct management decisions for future restoration efforts of oyster reefs to further restore and protect coastal wetlands in the Galveston Bay system. Further research should include a longer study with a broader study area throughout the Galveston Bay ecosystem.

Billions of dollars will be spent on large-scale restoration of Gulf ecosystems over the coming decades, but there is no shared platform to guide assessment and reporting of restoration progress and effectiveness for the broad set of environmental, social, and economic goals. The diversity of these goals—including habitat restoration, water quality improvement, marine resource protection, community resilience, and economic revitalization—means a variety of metrics are needed to fully evaluate the effectiveness of restoration projects. A set of common restoration models and metrics relevant across projects, programs, and locations can facilitate effective project planning, evaluation, and measurement of success. This project will advance standardized metrics of restoration success by developing ecosystem service logic models with stakeholders from the five Gulf states, relevant federal agencies, and technical experts. Ecosystem service logic models trace the effects of restoration actions as they influence ecological and social systems to create important outcomes to people. In addition, evidence that accompanies these models can be used to clarify uncertainties that need to be considered and to identify critical research gaps. With local stakeholders and experts in each of the five Gulf states, we will develop site-specific ecosystem service logic models for restoration approaches commonly implemented across the Gulf. These will then be integrated into regional unified models that reflect the priorities of the local models. Using these regional models, priority metrics that effectively capture the outcomes of these restoration approaches will be identified. We will also assess the extent to which these metrics are already being monitored in the Gulf and where gaps in monitoring exist. We believe this project comes at a critical juncture for the Gulf and can help to inform investments in restoration so they will have the greatest possible positive impact on the Gulf economy, people, and ecosystems.

For over a century, populations of the eastern oyster, Crassostrea virginica, have dramatically declined due to increased anthropogenic pressure and other various natural stressors. Periodic large-scale storm events are one natural stressor that can largely reduce oyster populations over a short period of time from freshwater inputs and the upheaval, and subsequent deposition, of sediment. In response, resource managers are tasked with mitigating the loss of this valuable resource through constructing new reefs or dredging practices, which upheaves buried shells for settlement substrate. These dredging practices expose ‘black shell’, which are oyster shells that have been buried by sediment in an anoxic environment. However, the capability of these entombed ‘black shells’ to facilitate oyster larvae recruitment once they have been exposed is relatively understood. The objective of this study was to determine how oyster larvae will recruit to fresh black shell and sun cured black shell compared to traditional sun cured oyster shells used in restoration efforts. On restored bagged reefs in Sweetwater Lake, Galveston, Texas, these three different treatments were deployed during the end of May and retrieved at the end of August. In addition to comparing differences in treatments, recruitment was compared to background densities of the restored reefs, to understand how shell type influenced recruitment of larvae, with taking into consideration population structure on each restored reef. The results of this study may be utilized to further direct management decisions for future restoration efforts after large scale storm events that sediment in oyster reefs.

The role of polychaete tubes protruding through the benthic boundary layer in promoting or hindering erosion of fine-grained sediment was examined in laboratory experiments. Diver core samples of the top 10cm of sediment were collected west of Trinity Shoal off the Louisiana coast in 10-m depth. Some samples were sieved at a 0.5-mm to characterize the surficial macrobenthos and collect tubes created by macrobenthos for preservation. The remaining diver cores will be used in laboratory experiments conducted in a unidirectional flume. Tubes that were constructed by polychaetes, which comprised 70% of the species from the study area, were inserted in the core sediment surface and high-speed particle image velocimetry was used to determine the 3-D, 3-component fluid velocity at high temporal (100 Hz),and spatial (< 1mm vector spacing) resolution. The tubes that protruded above the boundary layer allowed vortices to be initiated. Tubes are made up of shell fragments and fine-grained sediment, allowing for some rigidity and resistance to the flow. Rigidity determines the resistance causing small-scale eddies to form. This turbulence incites erosion, allowing fine-grained particles to be suspended into the water and in some cases coarser particles to be mobilized. Less-rigid tubes succumb to the flow stream, allowing less eddies to form across the sediment boundary hindering erodibility and stabilizing the sediment. Results show that sediment dynamics are complicated by the effects of benthic biological activity

Oyster reefs provide environmental and economic services within coastal regions. Mapping the extent of these reefs and analyzing their composition can be highly beneficial for oyster management and restoration projects. This project examined the feasibility of the use of low-cost side-scanning sonar (SSS) systems and Unmanned Aircraft Systems (UAS) for mapping intertidal oyster reefs at two selected sites in Bastrop Bay and Bastrop Bayou complex following defined criteria that included the existence of intertidal oyster reefs and no aviation restrictions on the operation of UAS. The Hummingbird 1197c system was deployed when the minimum water depth was 2ft to allow vessel navigation and system deployment, while the UAS was deployed when shallow intertidal reefs were completely or partially exposed after meteorological events such as seasonal cold fronts which generate strong northerly winds produced water levels that were much lower than predicted low tide conditions. The SSS was used to collect bottom imagery that was processed using the SonarTRX platform to provide continuous coverage of the surveyed reefs. The UAS utilized during this study was used to collect visible images, which were post-processed using the Pix4D software to produce high-resolution orthoimages. The UAS images were superior to the side-scanning images in regards to quality, precision and the ability to differentiate reef composition. Classification techniques were used to identify different parts of the reef including exposed and submerged parts, while visual interpretation of images supported by field information on reef composition was used to classify different bottom categories (live and dead oyster, shell hash, mud bottom). We found that the UAS system is a useful tool for studying the distribution of intertidal reefs. However, the frequency of suitable meteorological and tidal conditions might limit the application of UAS systems for mapping intertidal reef.

The American Eel (Anguilla rostrata) is a catadromous panmictic species that provides important fisheries along the northeastern United States. There have been recent unsuccessful attempts to request listing of this species under the Endangered Species Act (ESA). Within Texas, American Eel is considered a species of greatest conservation need. In order to assess the current status of American Eel in Texas, life history information including their distribution, abundance, habitat use, and population structure throughout the Texas coast is being gathered using historical data and extensive field surveys. The current research program provides the first comprehensive assessment of juvenile American Eel populations that utilize coastal estuaries. During this first year of the project (September 2017-August 2018), fish community surveys utilizing multiple collection methods including fyke nets were conducted several times a month at multiple strategic monitoring locations in the lower portions of the river drainages. Using data gathered during year one of the study, a more directed effort will be used in the second year to focus sampling efforts during those months when juvenile recruitment is observed. Water quality, hydrology, and macrohabitat data is being collected to help better characterize American Eel migration, distribution, and abundance patterns. These data will be used to assist resource management agencies in determining the conservation need of American Eel and direct future projects that may impact the well-being and longevity of this species

An estimated 95% of commercially and 85% of recreationally important species utilize estuarine habitats and coastal wetlands at some point in their life cycle. Many fish species rely on estuaries as essential nursery habitats for maintaining population size and health. These “natural hatcheries” require certain environmental conditions to be viable habitats for juveniles. This study examines the freshwater inflows needed to sustain natural hatcheries, especially in times of drought. The quantity of freshwater inflow becomes increasingly important during droughts, or low flow periods, when the demand for water increases and water supply to estuaries decreases. Three communities were studied; benthic infauna, benthic epifauna, and nekton survey data to determine if low flows can sustain ecological health in natural hatcheries during times of drought. Both benthic invertebrates, which are good indicators of estuarine conditions and inflow because of their connection to productivity and relative immobility, and fisheries data was used to evaluate ecosystem health and stability to determine if small amounts of freshwater can maintain vital habitat. The TPWD sampling is to monitor whole bay systems, so a scheme was devised to downscale TPWD data to the areas of interest which include Colorado-Lavaca Estuary, Guadalupe Estuary, and Nueces Estuary. Multiple stations were aggregated to create a general area of similar salinity conditions within each study site. A target species list was developed to focuses on those species of epifauna and fish that recruit to upper marsh habitats. As human population, coastal development, and climate change increase, planning for future freshwater fluctuations will help prevent the negative impacts of drought on the health and productivity of Texas estuaries.

In Louisiana, coastal habitats that are essential for many fish species and productive fisheries are disappearing at an alarming rate. To mitigate habitat loss in coastal Louisiana, state agencies and conservation groups are conducting restoration and habitat creation projects, including the construction of inshore artificial reefs. Understanding how artificial reefs are used by juvenile red drum is of great importance to Louisiana fisheries, as red drum are highly targeted by recreational fishermen in Louisiana and across the Gulf of Mexico. To assess red drum use of Independence Island Reef, an artificial reef in Barataria Bay, LA, an acoustic telemetry array was used to track tagged juvenile red drum (n=15) from August 15, 2017 to April 25, 2018 at Independence Island and four adjacent habitat complexes. All but one fish were detected exclusively at the site where they were tagged. These results suggest that juvenile red drum in Barataria Bay have high site fidelity but are capable of traveling between habitat complexes within the estuary. Additionally, no fish were detected at the artificial reef sites. Based on this telemetry data, fish utilizing habitat complexes adjacent to Independence Island Reef do not use Independence Island.

Histamine fish poisoning is one of the most common seafood-borne illnesses throughout the world. The illness occurs after human consumption of fish containing high concentrations of histamine. Illness has been attributed to extended storage of fish catches at temperatures above 4.4°C, allowing histamine-producing bacteria (HPB) to grow and convert free histidine in fish tissues to histamine. However, other variables that may affect HPB are not well studied and the exact mechanisms of poisoning remain uncertain. To determine how the levels and identity of HPB vary in the aquatic environment and, in turn, affect concentrations of histamine in fish tissues during decomposition, we enumerated and identified HPB in marine and riverine water samples as well as in Spanish mackerel tissues incubated at 4°C, 15°C, and 30°C. The HPB were enumerated using a 3-tube most-probable-number (MPN) real-time PCR method, and isolated bacteria were identified using both API and 16S sequencing. The concentration of HPB in water samples ranged from <0.001 to 93 MPN/mL, and preliminary results suggest that variations in marine HPB concentrations have strong linear relationships with water temperature and dissolved oxygen, but not pH nor salinity. HPB isolated from marine water samples include Photobacterium damselae and Morganella morganii, high histamine producers that have been previously isolated from Gulf of Mexico fish, while HPB isolated from riverine samples included less common high histamine producers Plesiomonas shigelloides and Enterobacter aerogenes. In mackerel tissues, early findings suggest that HPB levels are not evenly distributed across fish sections, regardless of incubation time or temperature. The results from this ongoing experiment will enhance our understanding of natural HPB populations and the mechanism of histamine production in fish, aiding the development of regulations for prevention of this illness.

Low concentrations of pesticides are entering coastal environments through run-off from agricultural fields and residential areas. Once in coastal communities, these low doses of pesticides may not kill marine species, but they may negatively impact their foraging and behavior. Periwinkle snails (Littoraria irrorata) are influential consumers in coastal marshes because they forage on Spartina alterniflora grasses and can drastically reduce marsh production unless limited by predation or non-consumptive predator effects. Overconsumption of Spartina grasses can result in a loss of many ecosystem services such as sediment trapping that builds marsh land and nursery habitats for fish and invertebrates. Despite their importance to the maintenance of marsh ecosystems, few studies have examined whether pesticides may affect periwinkle foraging or behavior. Our study objective was to determine if insecticides influence periwinkle snail foraging and behavioral responses. To accomplish this objective, periwinkles (4 per bowl) were exposed to sub-lethal concentrations of the pesticides Carbaryl and Fipronil and we measured the amount of Spartina consumed. We also measured changes in periwinkle behaviors such as climbing (number of snails out of water), the time for periwinkles to emerge from their shells, and their responses to predator cues. We hypothesized that higher concentrations of Carbaryl and Fipronil will result in decreased foraging of Spartina due to avoidance of the pesticide laden water and that responses to blue crab chemical cues will be reduced due to pesticide exposure. These results will demonstrate if low concentrations of pesticides may alter marsh productivity by altering consumer foraging behavior.

Trophic cascades are important processes which regulate the structure and function of many marine communities such as salt marshes and seagrasses. The magnitude of these trophic cascades are dictated by a predator’s ability to successfully locate and consume its prey (consumptive effects) and the ability of prey to avoid being consumed (non-consumptive effects). Thus, anthropogenic impacts or other stressors which alter predator and/or prey behavior can influence the outcome and magnitude of trophic cascades. Pesticides that target insects frequently end up in streams and estuaries in low, sub-lethal concentrations where they may impact the biological functions and behaviors of non-target organisms, such as blue crabs and other crustaceans. As keystone consumers, blue crabs play an important role in structuring estuarine communities by feeding on and controlling the densities of periwinkle snails, which consume significant amounts of marsh grass. Without predation, the consumption of grass by periwinkles could cause the loss of important salt marsh habitats and encourage coastal erosion. However, little is known about how pesticides may influence blue crab behavior or their ability to consume prey and cause trophic cascades. To understand how sub-lethal concentrations of pesticides affect blue crab foraging and behavior, we conducted laboratory assays measuring coordination, aggression, and foraging of blue crabs (Callinectes sapidus) exposed to four concentrations (0, 10, 20, and 50 µg/L) of the insecticide carbaryl over three days. Before and after exposure, we measured the crabs’ positional righting time, interest in foreign stimuli, and the rate that crabs attack and consume periwinkles to simulate how pesticide exposure affects the crabs’ survival rate and foraging. The results of this study will provide insight on whether pesticide concentrations deposited in estuaries by the Mississippi River are significantly affecting the tropic interactions in estuarine ecosystems, as well as contributing to the coastal erosion in southern Louisiana.

Bivalves are useful biomonitors because they assimilate particles from their environment into tissue and shell. To determine if bivalves assimilate oil-derived elements into their shells as a possible retrospective bioindicator of exposure to oil or other contaminants, we conducted a controlled laboratory experiment exposing juvenile oysters to various oil types and concentrations during a 4 month period. Oysters were exposed to one of six possible treatments: Macondo 252 source oil; weathered oil from surface water; highly weathered tarballs from local beaches; water collected from an industrialized area in the Mobile River, Alabama; spiked oil of known elemental concentration (positive control); and filtered artificial seawater (negative control). Trace element profiles from the shells of a subset of exposed oysters were obtained using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). To incorporate the effects of multiple stressors, oysters were exposed to locally relevant low salinity stress (14) or standard estuarine salinity (25). Biological response to oil exposure and salinity conditions was monitored by measuring oyster survival and growth throughout the experiment. Preliminary data suggest oil exposure during the study did not have a significant effect on oyster growth or survival. This research tests a new technique to improve detection and tracing of oil and other contaminants in coastal waters and could be applied to enhance existing monitoring programs for damage and recovery assessment.

Ocean acidification is caused by the absorption of atmospheric CO¬2 by seawater and could impact organisms that utilize inorganic carbon for photosynthesis. Diatoms, a group of silicifying phytoplankton, play a key role in the marine carbon cycle due to their high primary productivity rates, their worldwide distribution, and their contribution to marine snow formation through the production of extracellular polymeric substances (EPS) and transparent extracellular particles. These polysaccharide-rich compounds help to aggregate organic material and transfer nutrients and carbon through the water column to either be consumed or stored long term in the sea floor sediments. Diatom EPS production can also be a stress response from harmful substances, such as spilled oil. While little is known about the effects of oil spills on phytoplankton, even less has been studied about these events under ocean acidification conditions. Using Thalassiosira pseudonana, a small centric diatom, roller tank experiments were conducted to replicate aggregation and sinking through the water column. Six treatments with three replicates were used to examine ocean acidification and oil spills effects on T. pseudonana marine snow production: control, enhanced pCO2 level, water accommodated fraction of oil (WAF), enhanced pCO2 and WAF, diluted WAF chemically enhanced with Corexit (DCEWAF), and enhanced pCO2 and DCEWAF. Samples were taken from the parent treatment stocks at the beginning time point and after three days from all the replicate roller tanks. Measurements included physiological responses of T. pseudonana, changes in oil concentrations and components, and water conditions. The results of this study will provide insights into how CO2 availability affects marine snow production and aggregation, and how phytoplankton may respond to harmful events such as oil spills in the future.

The Deepwater Horizon oil spill released four million barrels of crude oil into the Gulf of Mexico, altering conditions and initiating physiological responses for phytoplankton. Diatoms are single-celled phytoplankton that have a silica frustule and are abundant in coastal environments. Phaeodactylum tricornutum is a marine diatom that has previously shown resiliency in the presence of crude oil and the surfactant used for remediation after the spill. The purpose of this study was to investigate the role the silica frustule plays in protecting P. tricornutum against the potentially harmful effects of crude oil and surfactants. P. tricornutum was cultured in f/2 media both with and without silica for five weeks. Both P. tricornutum cultures were then inoculated into four treatments: a control (f/2 media), a water accommodated fraction of oil (WAF), a chemically enhanced (with surfactant) WAF (CEWAF), and a dilute CEWAF (DCEWAF). Each treatment had a silica replete and deplete counterpart. The experiment was sampled daily for one week to monitor changes in cell densities, the concentration of oil, macromolecular composition of cells, and photosynthetic efficiency using fluorescence induction and relaxation (FIRe) curve parameters (Fv/FM, σPSII, ρ, and t1). Results showed oil concentrations decreased over time across all treatments. SEM image analysis showed frustule deformation (but not complete loss) in silica starved cultures. Further, growth rates were more affected than photosynthetic efficiency by the pollutants, and each silica deplete treatment deviated lower than its silica rich counterpart. Results suggest that P. tricornutum protect their photosynthetic apparatus against harmful conditions, suppressing growth rates until oil concentrations decrease and conditions return to normal.

Marine snow are macroscopic aggregates that comprises of particles such as organic matter, dead and living microbes that sink through the water column providing carbon and energy to benthic ecosystems. The 2010 Deepwater Horizon oil spill contaminated the Gulf of Mexico (GoM) with an unprecedented amount of oil and large amounts of chemical dispersant were used as a remediation effort. Following this event, higher abundance of marine snow were observed in the Gulf suggesting oil and dispersant may have affected the process of marine snow formation. Moreover, higher concentrations of oil were associated with marine snow and nearly 1.8-14% of the oil spilled made its way to the sea-floor through its sinking process. Exoenzymes actively secreted by microbes excrete helps in breaking down exopolymeric substances to small monomers that provides nutrients (C, N and P) for microbial growth. Marine snow are hot-spots for exoenzymes activity that in-turn boost microbial activity. Therefore, we hypothesize that these exoenzymes might play a role in the formation and growth of marine snow. To study this, we conducted a time-course experiment using natural sea-water from GoM with and without chemical inhibitors of four major exoenzymes (α and β-glucosidase, alkaline phosphatase and leucine amino-peptidase) and exposed to oil and/or dispersant. Parameters such as exoenzyme activities, microbial growth and marine snow formation process were periodically monitored. These findings will be analyzed and the mechanism by which exoenzyme activity affected the marine snow formation process will be discussed.

Exposure to crude oil from Deepwater Horizon may have lasting impacts on the preservation of historic shipwrecks in the Gulf of Mexico. Submerged carbon steel structures, including shipwrecks, serve as artificial reefs which become hotspots of biodiversity in the deep-sea. Marine biofilms on submerged structures support settlement of micro and macro biota which enhance and protect against corrosion. Disruptions in the local environment, including those resulting from oil spills, may impact the role that biofilms play in preservation. To determine how the spill potentially impacted shipwreck biofilms and functional roles of biofilm microbiomes, experiments containing carbon steels disks (CSDs) were placed at five historic shipwreck sites located within and external to the seafloor footprint of the Deepwater Horizon spill and incubated for 16 weeks. Biofilms from CSDs and sediment and water microbiomes were collected and analyzed by 16S rRNA amplicon sequencing to describe communities and determine sources of taxa to biofilms. Metagenomes of biofilms were sequenced to compare differential gene abundances at spill impacted and reference sites. Biofilms were dominated by Zeta-, Alpha-, Epsilon- and Gammaproteobacteria. Sequences affiliated with the Mariprofundus and Sulfurimonas genera were prolific. Roseobacter, and Colwellia genera were also abundant. Sediment was the main known source of OTUs to biofilms. Differential abundance analysis revealed the two-component response regulator CreC, a gene involved in environmental stress response, to be downregulated at impacted sites compared to reference sites within the spill seafloor fallout plume. Genes for chemotaxis, motility and alcohol dehydrogenases were highly variable between reference and impacted sites. Metal loss on CSDs was elevated at sites within the fallout plume. Time series images revealed that metal loss at a heavily impacted site has accelerated since the spill. This study provides evidence that spill residues on the seafloor may impact biofilm communities and preservation of historic steel shipwrecks

Hurricane Harvey directly passed over Aransas and Copano Bays, TX on August 25, 2017 with wind speed over 130 mph as a Category 4, which caused tremendous resuspension and sediment redistribution within the bays. Knowing how the sedimentary geochemistry was affected by this hurricane is important for evaluating the ecosystem impacts. Using surface sediments (top 5 cm) collected before (June) and after (October) the hurricane, we measured a series of geochemical parameters, including grain size, organic carbon and nitrogen content, polycyclic aromatic hydrocarbons (PAHs), total hydrolyzable amino acids (THAAs) and n-alkanes. The sediment grain size within the bays overall became much coarser post-hurricane with certain stations increasing over 100 microns in median size. Together with the OC content, concentrations of PAHs decreased from a range of 59 to 1605 ng g-1 to 19 to 204 ng g-1, and 80-100% of the decrease was attributed to the loss of low molecular weight PAHs (2-3 rings). Similarly, concentrations of n-alkanes decreased from 1.3-19.9 to 1.1-9.3 μg g-1 post-hurricane. However, there was no obvious trend among the different n-alkanes, unlike the PAHs. The coefficients of variation of PAHs and alkanes became smaller after the hurricane, indicating that organic composition of surface sediments was more homogeneous after the hurricane. Overall, PAHs and n-alkanes are strongly correlated with grain size in sediments, and these results suggest that the storm surge strongly resuspended fine sediment particles that were concentrated in PAHs and alkanes, leading to the loss of these fine sediment particles and associated organic matter, either suspended in the water column or exported to coastal ocean. While some analyses such as THAAs are still ongoing, the preliminary data demonstrate the strong impact of Hurricane Harvey on sediment organic geochemistry of Aransas and Copano Bays.