4.0 Conclusions
A significant amount of sediment transport from the upstream watersheds occurred during Harvey in the GBES that significantly altered the nature and character of bed sediment relative to historical data. Qualitative and quantitative analyses conducted in the study provided strong evidence of the effect of this alteration on the metal distributions and the microbial community characteristics of the HSC-GB sediments. The difference in metal concentrations in sediment samples collected from the tidal part of the estuarine system compared to ones in deposited soil samples collected from the banks of freshwater bayous was indicative of associations to potential leaks from nearby active Superfund sites and entrainment of pollutants in industrial runoff. Locations with realtively high levels of toxic metals and nearby reported spills and leaks during Hurricane Harvey showed significant different diversity and richness in microbial communities (at the phylum level). Additionally, the relatively high abundance of ammonia-oxidizers and extremophile bacteria in samples confirms the importance of polluted sediment transport, caused by anthropogenic activities, from urban and rural areas into the estuarine system during Hurricane Harvey. Thus, it can be concluded that natural hazards change bed sediments in various ways and have a lasting impact on estuarine environments long after the event has passed. Quantifying sediment physical, chemical, and biological characteristics after natural hazards is critical towards understansing the long term sustainability and resilience of these important coastal environments.