| dc.description.abstract | Microorganisms account for ~70% of the total biomass of the ocean and fill many necessary roles within the ecosystem. However, little is known about how the marine microbial communities respond and recover from environmental stressors such as hurricanes. Hurricanes bring sudden changes to the marine ecosystem such as drops in salinity and temperature and influx of terrestrial sediment. All of these changes may impact the marine microbial community structure and genomic composition. Hurricane Harvey hit the Texas Gulf Coast on August 25th, 2017 as a category 4 hurricane and brought a record-breaking amount of rainfall to the Houston area. Storm water run-off from Hurricane Harvey brought excess freshwater and sediment to Galveston Bay. Here, we characterized how Hurricane Harvey altered the microbial communities within Galveston Bay. This was achieved through the following three objectives: 1) describe the change in microbial community structure, 2) identify how the genomic composition and metabolic potential of the microbial community changed and 3) demonstrate the role of viruses in ecosystem recovery by showing how the viral community adapts and changes with host abundances following Hurricane Harvey. These objectives were accomplished through sampling four stations along a transect in Galveston Bay once a week for five weeks. The microbial communities were identified using 16S ribosomal RNA gene sequencing for the hosts and metagenomics for the hosts and viruses. Viral production experiments were used to characterize viral activity. The results show that the microbial community transitioned from an ecosystem that was dominated by marine microorganisms (e.g., Cyanobacteria and Acidimicrobiia) prior to Hurricane Harvey to a system dominated by microorganisms that were terrestrially derived (e.g., Actinobacteria and Verrucomicrobiota) after landfall. The genomic composition and metabolic potential of the community changed after Hurricane Harvey with an increase in genes involved in nitrogen and sulfur metabolisms and a decrease in genes involved in photosynthetic metabolisms. Common marine viruses such as Podoviridae and Myoviridae were removed from the ecosystem and there was an increase in auxiliary metabolic genes associated with nitrogen, sulfur and methane metabolisms. While the prokaryotic community almost recovered, the viral community did not recover to pre-Hurricane Harvey conditions within five weeks, when comparing to pre-Harvey conditions. With climates changing, it is predicted that hurricane and rainfall intensities are going to increase over the years; therefore, it is important to understand how pulse disturbances like large rain event impact the marine microbial community, how the ecosystem recovers, and the impact of the changes on the global ecosystem. | en |
