Coastal wind-driven waves play an important role in transportation and exchange of mass and energy. The amount and intensity of wave energy determines the rate of erosion and deposition in estuarine systems. One limitation in many wave modeling studies is the lack of spatially robust wave measurements that can be used for validation since installing a large number of wave gauges, in any one site, is usually expensive. Wave modeling is a convenient approach for determining the pattern of waves in different spatial and temporal domains. This study aimed to evaluate the efficiency of a wind-generated wave model for Back Bay Biloxi, Mississippi in the Northern Gulf of Mexico. The SWAN model (Simulating Waves Nearshore) was coupled with the ADCIRC model (ADvance CIRCulation) to simulate wave height and period in order to capture the wave climate. Wind speed, wind direction, and a bathymetric mesh were used as input data to simulate the wave characteristics. Due to the complexity of the area, an unstructured bathymetric mesh was generated using the SMS model (Surface-water Modeling System). In this study, 35 relatively inexpensive “do-it-yourself” wave gauges were deployed to comprehensively measure wave parameters under a low energy system in Back Biloxi Bay.The measured data was used to validate the wave model. Consequently, this study will provide a novel validation method of a wave model using a spatially comprehensive wave measurement dataset.

A reliable understanding of wave climate is the prerequisite for all marine users. Safe navigation, coastal infrastructure establishment and maintenance, and understanding coastal morpho-dynamics are examples for which wave data are needed. Nearshore wave characteristics are highly affected by bathymetric features which are dynamic and usually not well resolved in shallow water areas. Moreover, observational data over the Northern Gulf of Mexico (NGoM) are mostly available at offshore stations, and few ones are available in shallow water with wave data. Long-term wave measurements are usually not available in the nearshore coastal environments and only occasional research measurements are available for shallow water stations. It is while, shallow water waves are a major parameter contributing to the wetland loss process. Based on a comprehensive analysis of the extent in land-water change throughout the coastal zone of the US, USGS reported that eighty-five percent of the coastal wetland loss in the contiguous United States occurs in the Gulf of Mexico. Therefore, numerical models are to be adopted to obtain reliable wave estimations over NGoM nearshore areas. Accurate simulated wind fields play the most important role in obtaining reliable wave simulations; something which are usually adopted from global and regional models. However, the global model data show considerable bias from observations near the land water interface. Hence, wind data correction may increase the wave model results, specifically over the estuarine environments. The present study aims to investigate nearshore wave characteristics over the NGoM waters. To this end, a wave model has been setup for the NGoM, with improved input wind data through a wind correction method approaches. The simulated wave data were verified against available real field observations. Hence, the shallow water wave characteristics are investigated in details in locations of interest over the Mississippi, Alabama and Louisiana coastlines.

Dissolved oxygen (DO) is often used as a water quality indicator and proxy for ecosystem health. Organic matter is remineralized in sediments by microbial and macrofaunal communities that consume DO in the process. DO consumption rate depends on the DO concentration of the overlying water but can also be enhanced by mixing and irrigating activities of sediment macroinfauna. DO in shallow coastal systems frequently exhibits a diel cycle, caused by photosynthesis increasing DO during the day and respiration drawing down DO at night. These recurring nightly drops in DO concentration may induce changes in DO consumption rates and macrofaunal behavior that affect total sediment oxygen consumption in unique patterns throughout the day/night cycle, and in different ways depending on the particular behavioral responses of macrofaunal taxa. However, most estimates of sediment metabolism are based on only a few DO consumption measurements, sometimes just one per day. If sediment DO consumption varies considerably throughout a diel cycle, current descriptions of sediment metabolism that use such limited measurements may be misestimating net metabolism rates, and therefore ecosystem health and function, over time. In this study, we addressed the questions, 1) do sediment DO consumption rates vary significantly over a diel cycle?, and 2) what influence do macrofauna have on sediment DO consumption throughout the diel cycle? We constructed in situ flow-through benthic metabolism chambers capable of producing a high temporal resolution time series of DO consumption associated with discrete patches of sediment and deployed them in shallow water off the Alabama coast. This research will enable better understanding of the connection between oxygen concentration and oxygen consumption, and improve our understanding of the role of macrofauna in modulating that relationship. Equipped with this knowledge, resource managers will be able to better track shifts in shallow marine ecosystem functioning and health.

Shallow coastal sediments and their burrowing invertebrate (infauna) communities are important for nutrient cycling and carbon storage. In the northern Gulf of Mexico, frequent storms disturb infauna and resuspend sediments. Re-consolidation of sediments following a storm impacts infaunal habitat suitability and community recovery, but this has been poorly studied. In this study, we compared how different geological and geotechnical properties of recently disturbed mud changed over time. We expected that post-disturbance changes to properties relating to mud cohesion would continue to occur after compaction stabilized. Cohesion is likely important in mud habitat suitability, thus may be a more relevant parameter in considering infaunal community recovery. We collected mud from 10m depth offshore of Dauphin Island, AL, and resuspended the top 5cm, simulating storm disturbance. At several timepoints following resuspension (1-30 days), we measured sediment properties providing metrics of compaction (sediment-water interface height, water content, acoustic sound speed and attenuation) and metrics of surface and subsurface cohesion (erodibility, fracture behavior, organic content, and exopolymeric substances (EPS)). Preliminary data suggest that sediment compaction occurred rapidly over the first 3 days after resuspension and stabilized within 7 days. Erodibility rapidly decreased over the first 3 days but began to increase from 14 to 30 days after disturbance, likely due to infaunal activity. This suggests mud compaction alone does not indicate overall restabilization, which is likely important to post-disturbance recovery of infauna communities.

The Mississippi Sound and Bight is a dynamic region to the east of the well-studied Texas/Louisiana shelf. Riverine input, variable winds, tidal exchange, and a complex coastal geography all play a role in the ecosystem dynamics of this economically important region. The Mississippi Sound and Mississippi Bight exchange coastal waters and represent an important pathway that links the freshwater dominated coastal waters with the open ocean shelf waters from the Bight. To understand this interlinked circulation and material exchange between the Mississippi Sound and Bight, a physical model was developed based on the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System. The Mississippi Sound and Bight Regional Ocean Modeling System (msbROMS) provides insights into the seasonal variations of the physical interactions in this coastal ecosystem that is heavily influenced by freshwater plumes. A high-resolution wind field that resolves the diurnal sea breeze is applied for this study and twin experiments with full resolution winds and filtered winds have been performed to investigate the influence of the diurnal sea breeze on the flushing of the region. Results from these numerical experiments provide a detailed perspective on residence times and the seasonal influence of the sea/land breeze circulation cycle and its impacts on the potential material exchange between the open ocean and coastal waters.