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.