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Sea level rise and changing storm frequency and intensity resulting from climate change create tremendous amounts of uncertainty for coastal species. Intertidal species may be especially affected since they are dependent on daily inundation and exposure. The eastern oyster Crassostrea virginica is an economically and biologically important sessile intertidal species ranging from Canada to the Gulf of Mexico. Declines and changes in distribution of oyster populations has forced commercial harvesting to spread from subtidal to intertidal reefs. We investigated the potential responses of intertidal C. virginica to sea level rise, and the response of larval settlement to sedimentation which is likely to increase with higher water levels and storm frequency. Inundation was used as a proxy for sea level rise. We hypothesized four possible outcomes for intertidal oyster reefs as a result of changes in inundation due to sea level rise: (a) intertidal reefs become subtidal and remain in place, (b) intertidal reefs will be lost, (c) intertidal reefs migrate shoreward upslope and remain intertidal, and (d) intertidal reefs will grow in elevation and remain intertidal. To test the plausibility of these four outcomes, oyster ladders were placed at two sites within Apalachicola Bay, Florida, USA. Ladders supported oyster recruitment mats at five heights within the range of intertidal elevations. The bottom-most mat was placed near mean low tide, and the top mat near mean high tide to investigate the effect of tidal inundation time on C. virginica. Sediment traps were attached to ladders with openings at equal elevation to the oyster mats. Ladders were deployed for one year starting in June 2012, and again in June 2013, during peak oyster recruitment season. Monthly for six months during year one, sediment was collected from traps, dried to constant weight and weighed to obtain a monthly average for total sediment at each elevation. At the end of one year, oyster mats were collected from the field and examined for the following responses: live oyster density, mean oyster shell length of live oysters, mean oyster shell angle of growth relative to the benthos, and mean number of sessile competitors. We used AICc to identify the most plausible models using elevation, site, and year as independent variables. Oyster density peaked at intermediate inundation at both sites (maximum 1740 oysters per m2), it decreased slightly at the mean low tide, and sharply at the mean high tide. This response varied between years and sites. Mean oyster shell length peaked near mean low tide (6.7 cm), and decreased with increasing elevation. It varied between years and sites. Oyster shell angle of growth relative to the benthos showed a quadratic response for elevation; site but not year affected this response. Sessile competitor density also showed a quadratic response for elevation and varied between sites and years. Barnacles were the primary spatial competitor reaching densities of up to 28,328 barnacles per m2. Total monthly sedimentation peaked at the lowest elevations, and varied by site, with an order of magnitude difference between sites. Sediment increased with decreasing elevation. Outcomes a, c, and d were found to be viable results of sea level rise, ruling out complete loss of intertidal reefs. Outcome (a) would be associated with decrease in oyster density and increase in oyster length. Outcome (c) would require the laying of oyster cultch upslope and shoreward of current intertidal reefs, as well as the removal of any hard armoring or development. Outcome (d) remained possible, but is the least likely requiring a balance between sedimentation, oyster angle of growth, and recruitment. This should be further investigated. A laboratory experiment was designed to test relative impact of varying sediment grain sizes on settlement of C. virginica larvae. Previous studies showed that suspended solids resulted in decreased larval settlement when using mixed sediment grain sizes. Predicted storm levels and hurricane levels of total suspended solids were used in flow tanks. Sediment from the field experiment was sieved into seven size classes, the most common five of which were used in the experiment since they represented 98.8% of total mass. Flow tanks were designed and built that held 12 aged oyster shells, instant ocean saltwater, and sediment. Oyster larvae were added to the flow tanks and allowed one hour to settle on shells. Each run utilized one of the five size classes of sediment at either a high or low concentration. Following the one-hour settlement period, oyster shells were removed from the flow tank and settled larvae were counted under a dissecting microscope. Settlement was standardized by settlement area using Image J. AICc model selection was performed and the selected model included only grain size, but not concentration. A Tukey's post hoc test differentiated < 63 µm from 500 – 2000 µm, with the < 63 µm grain size having a negative effect on oyster larval settlement. This indicates that the smaller grain sizes of suspended solids are more detrimental to oyster larval settlement than larger grain sizes. The oyster ladder experiment will help resource managers predict and plan for oyster reef migration by cultch laying, and or associated changes in oyster density and shell length if shoreward reef growth is not allowed to occur. The laboratory experiment will help to predict the impacts of future storms on oyster larval recruitment. Together this information can help managers conserve as much remaining oyster habitat as possible by predicting future impacts of climate change on oysters.

Sea level rise (SLR) has the potential to affect coastal environments in a multitude of ways, including submergence, increased flooding, and increased shoreline erosion. Low-lying coastal environments such as the Northern Gulf of Mexico (NGOM) are particularly vulnerable to the effects of SLR, which may have serious consequences for coastal communities as well as ecologically and economically significant estuaries. Evaluating potential changes in tidal hydrodynamics under SLR is essential for understanding impacts to navigation, ecological habitats, infrastructure and the morphologic evolution of the coastline. The intent of this research is to evaluate the dynamic effects of SLR and coastal geomorphology on tidal hydrodynamics along the NGOM and within three National Estuarine Research Reserves (NERRs), namely Grand Bay, MS, Weeks Bay, AL, and Apalachicola, FL. An extensive literature review examined the integrated dynamic effects of SLR on low gradient coastal landscapes, primarily in the context of hydrodynamics, coastal morphology, and marsh ecology. Despite knowledge of the dynamic nature of coastal systems, many studies have neglected to consider the nonlinear effects of SLR and employed a simplistic "bathtub" approach in SLR assessments. More recent efforts have begun to consider the dynamic effects of SLR (e.g., the nonlinear response of hydrodynamics under SLR); however, little research has considered the integrated feedback mechanisms and co-evolution of multiple interdependent systems (e.g., the nonlinear responses and interactions of hydrodynamics and coastal morphology under SLR). Synergetic approaches that integrate the dynamic interactions between physical and ecological environments will allow for more comprehensive evaluations of the impacts of SLR on coastal systems. Projecting future morphology is a challenging task; various conceptual models and statistical methods have been employed to project future shoreline positions. Projected shoreline change rates from a conceptual model were compared with historic shoreline change rates from two databases along sandy shorelines of the. South Atlantic Bight and NGOM coasts. The intent was not to regard one method as superior to another, but rather to explore similarities and differences between the methods and offer suggestions for projecting shoreline changes in SLR assessments. The influence of incorporating future shoreline changes into hydrodynamic modeling assessments of SLR was evaluated for the NGOM coast. Astronomic tides and hurricane storm surge were simulated under present conditions, the projected 2050 sea level with present-day shorelines, and the projected 2050 sea level with projected 2050 shorelines. Results demonstrated that incorporating shoreline changes had variable impacts on the hydrodynamics; storm surge was more sensitive to the shoreline changes than astronomic tides. It was concluded that estimates of shoreline change should be included in hydrodynamic assessments of SLR along the NGOM. Evaluating how hydrodynamics have been altered historically under a changing landscape in conjunction with SLR can provide insight to future changes. The Grand Bay estuary has undergone significant landscape changes historically. Tidal hydrodynamics were simulated for present and historic conditions (dating back to 1848) using a hydrodynamic model modified with unique sea levels, bathymetry, topography, and shorelines representative of each time period. Changes in tidal amplitudes varied across the domain. Harmonic constituent phases sped up from historic conditions. Tidal velocities in the estuary were stronger historically, and reversed from being flood dominant in 1848 to ebb dominant in 2005. To project how tidal hydrodynamics may be altered under future scenarios along the NGOM and within the three NERRs, a hydrodynamic model was used to simulate present (circa 2005) and future (circa 2050 and 2100) astronomic tides. The model was modified with projections of future sea levels as well as shoreline positions and dune elevations obtained from a Bayesian network (BN) model. Tidal amplitudes within some of the embayments increased under the higher SLR scenarios; there was a high correlation between the change in the inlet cross-sectional area under SLR and the change in the tidal amplitude within each bay. Changes in harmonic constituent phases indicated faster tidal propagation in the future scenarios within most of the bays. Tidal velocities increased in all of the NERRs which altered flood and ebb current strengths. The work presented herein improves the understanding of the response of tidal hydrodynamics to morphology and SLR. This is beneficial not only to the scientific community, but also to the management and policy community. These findings will have synergistic effects with a variety of coastal studies including storm surge and biological assessments of SLR. In addition, findings can benefit monitoring and restoration activities in the NERRs. Ultimately, outcomes will allow coastal managers and policy makers to make more informed decisions that address specific needs and vulnerabilities of each particular estuary, the NGOM coastal system, and estuaries elsewhere with similar conditions.

The Gulf of Mexico dune system is a broad and dynamic environment that varies greatly in geomorphology and vegetative composition across the Gulf coastline. Beach mice (Peromyscus polionotus spp.) are an endangered species that rely on coastal habitat structure. I hypothesized that beach mouse occupancy would be dependent upon coastal dune land cover and landform features. I identified coastal landforms using high-resolution elevation data and landform models in GRASS GIS and identified coastal dune vegetation classes using high-resolution aerial imagery and object oriented vegetation classification. These features were used to create a dynamic occupancy model to determine occupancy patterns in three subspecies of beach mice over multiple years of sampling. Beach mice demonstrated no distinct pattern in habitat occupancy over the study period. However, dynamic occupancy models demonstrated that habitat occupancy varied between individual sites, indicating that habitat selection may be population specific.

Oyster reefs in the western Mississippi Sound (WMS) are dependent on the salinity moderation by freshwater input. However, freshwater brings in high amount of pollutants, which affect the oysters negatively. Oyster diebacks happened as a result of hypoxia caused by excessive organic matter input to WMS in summer 2017. Colored dissolved organic matter (CDOM) is widely used as a proxy for determining organic matter distribution. In this study, hyperspectral and multispectral remote sensing data collected using unmanned aerial systems and in situ CDOM data were used to develop algorithms in order to retrieve CDOM remotely. Collected physical and biogeochemical parameters were used to understand the carbon fluxes regulating the quality and quantity of CDOM. Developed algorithms showed high accuracy after accounting for seasonal variations of CDOM. Further, seasonal induced photodegradation, photosynthesis, calcification, and exchange of CO2 were identified as possible factors that affect the carbon dynamics in the study area.

No description available.

<p>St. Joseph peninsula is situated on the panhandle of Florida west coast in the northeastern Gulf of Mexico at N29°50‘ and W85°20‘ and is located at the west edge of the westernmost portion of the Apalachicola Barrier Island Complex (ABIC) on the Gulf of Mexico shoreline. Three vibra-cores were collected on Saint Joseph Bay side of Cape San Blas which is part of St. Joseph peninsula to determine its evolution in context of previous work by Rink and Lopez (2010). The study uses detailed textural analysis (PSD - Particle Size Distribution plots), multivariate statistics on the PSDs (Q-mode cluster analysis) and organic matter geochemistry (C/N and δ13C). In addition, Ground Penetrating Radar (GPR) profiles are used to provide broader stratigraphic context.</p> <p>The stratigraphic analysis found that CSB has an older nucleus of strandplain deposits dating to >12 Ka that were subsequently flooded and modified through Holocene sea-level rise at ≈ 2.2 Ka. Actual barrier formation began sometime between 2.2. Ka and 0.6 Ka which is the oldest beach ridge measured by Rink and Lopez (2010). Progradation of the barrier on the St Joseph Bay side began at least by 0.3 Ka and likely earlier. There is no evidence to indicate a higher than present sea-level in our core data and our data follows that of other sea-level studies using submerged offshore samples</p> / Master of Science (MSc)

Ocean acidification is the reduction in seawater pH due to the absorption of anthropogenic carbon dioxide by the oceans. Reductions in seawater pH can inhibit the precipitation of aragonite, a calcium carbonate mineral used by marine calcifiers such as corals. Lophelia pertusa is a cold-water coral that forms large reef structures which enhance local biodiversity on the seafloor, and is found commonly from 300-600 meters on hard substrata in the Gulf of Mexico. The present study sought to investigate the potential impacts of ocean acidification on L. pertusa in the Gulf of Mexico through combined field and laboratory analyses. A field component characterized the carbonate chemistry of L. pertusa habitats in the Gulf of Mexico, an important step in establishing a baseline from which future changes in seawater pH can be measured, in addition to collecting in situ data for the design and execution of perturbation experiments in the laboratory. A series of recirculating aquaria were designed and constructed for the present study, and support the maintenance and experimentation of live L. pertusa in the laboratory. Finally, experiments testing L. pertusa's mortality and growth responses to ocean acidification were conducted in the laboratory, which identified thresholds for calcification and a range of sensitivities to ocean acidification by individual genotype. The results of this study permit the monitoring of ongoing ocean acidification in the deep Gulf of Mexico, and show that ocean acidfication's impacts may not be consistent across individuals within populations of L. pertusa. / Biology

Tidal marsh and its bird community across the northern Gulf of Mexico are subject to numerous disturbances such as oil spills, hurricanes, habitat loss from land use change, and high relative sea level rise rates looming in the future. Baseline population data and landscape associations are greatly needed to assess the current distribution and the future impact of perturbations on marsh birds across the Mississippi Gulf Coast. Using a standardized sampling design and point count survey protocol, we determined the abundance and population size of Clapper Rails, Common/Purple Gallinules, Least Bitterns, Marsh Wrens, Seaside Sparrows, Red-winged Blackbirds, and Common Yellowthroats across the Mississippi Gulf Coast. With abundance models for each species in 2021 and 2022, we further investigated the impact of important fine and broad scale landscape variables that affected species-specific abundance across variable marsh complexes. Finally, we generated species distribution maps based on our spatially-explicit baseline population estimates.

Sandstone modal compositions and detrital zircon U-Pb analysis of the Paleocene-Eocene Wilcox Group of the southern Gulf Coast of Texas indicate long-distance sediment transport primarily from volcanic and basement sources to the west, northwest and southwest. The Wilcox Group of south Texas represents the earliest series of major post-Cretaceous pulses of sand deposition along the western margin of the Gulf of Mexico (GoM). Laramide basement uplifts have long been held to be the provenance of the Wilcox Group, implying that initiation of basement uplifts was the driving factor for this transition from carbonate sedimentation to clastic deposition. To determine the provenance of the Wilcox Group and test this conventional hypothesis, 40 thin sections were point-counted using the Gazzi-Dickinson method to determine sandstone composition and 10 detrital zircon samples were analyzed by LA-ICP-MS to determine U-Pb age spectra for each of the sampled areas. Modal data for sand grain populations suggest mixed sources including basement rocks, magmatic arc rocks and subordinate sedimentary rocks for the Wilcox Group. Zircon age spectra for these sandstones reveal a complex grain assemblage derived from older sediments and crystalline rocks ranging in age from Archean to Cenozoic. Sediment was primarily derived from Laramide uplifted crystalline blocks of the central and southern Rocky Mountains, the Cordilleran arc of western North America, and arc related extrusive and intrusive igneous rock of northern Mexico. Comparisons of Upper and Lower Wilcox zircon age spectra show that more arc related material was deposited in the Lower Wilcox, whereas more basement material was deposited in the Upper Wilcox. / text