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The Role of Microbial Mats within Wet Aeolian Systems in Barrier Island Geomorphology
Abstract
Barrier islands exist at the interface of land and water and as such are at the forefront of changing climatic conditions such as sea level rise. These environments are constantly shifting in response to internal and external forcings. Microbial mats are a common feature of these islands and as such makes them ideal locations to investigate how microbial mats may be influencing the geomorphic processes within the wet aeolian systems on barrier islands. To understand the role of microbial mats within these systems I evaluated the geomorphology for Padre Island, Texas, utilizing multi-temporal remote sensing data sets, field measurements and observations, and modeling to understand the processes controlling facies formation and island state change. Long-term island landcover was measured over 50 years with aerial imagery and seasonal fluctuations in facies were identified with satellite imagery over a full year. The long-term and season facies trends reveal the island is experiencing widespread stabilization of sediments as surfaces shift to vegetation and microbial mat covered. The changes are linked to the forcing factors of sea level rise and reduced sediment supply. The importance of elevation on barrier islands was evaluated and a strong connection between facies formation and elevation was detected. The faces-elevation link was then used to construct a new model for back-island sediment exchange which enabled the projection of future states of Padre Island under the dual threat of sea level rise and low sediment input. These projections reveal the vulnerability of the island to extensive narrowing in the coming decades if back-island accretion rates are unable to keep pace with sea level rise. This model is built around the ability of microbial mats to bind sediments, preventing their transport to other parts of the island. To evaluate this erosion measurements were made on the microbial mat morphologies at Padre Island to understand how their presence changed erosion thresholds. The different mat surfaces were shown to have varying erosion thresholds in aeolian and subaqueous settings. This result has implications for aeolian systems on barrier islands and studies on microbial mat preservation on Earth and other planetary surfaces.
Citation
Fisher, Kenton R (2022). The Role of Microbial Mats within Wet Aeolian Systems in Barrier Island Geomorphology. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198701.