Dynamics, Biogeography, and Comparative Genomics of Microbial Communities in the Pamlico Albemarle Sound System (PASS)

Tropical cyclones impact the water quality and biogeochemistry of coastal North Carolina, and the frequency of these extreme storms appears to be increasing in recent decades. Notably we have little understanding of how they impact plankton and bacterioplankton. In this study, we examined the impact of Hurricane Florence on bacterioplankton abundance and bacterial community composition within the Neuse River Estuary (NRE) and Pamlico Sound (PS). As previous studies have shown, Florence led to a rapid decrease in salinity and a substantial increase in dissolved organic carbon (DOC) in the NRE. Furthermore, we observed a drop in picocyanobacterial and total bacterial abundance following the hurricane, particularly in the upper-middle stations of the NRE. However, the lower estuary did not exhibit such a drastic decrease in bacterial abundance. Alpha (a) and beta (b) diversity analyses revealed high bacterial abundance and greater dissimilarity in the upper-middle than lower estuary, especially post-Florence and during spring. Community change linked to shifts to winter-spring mirrored the effects of Hurricane Florence. Dominant Cyanobium taxa decreased due to Florence while members of clade hgcI (Actinobacteria) and Polynucleobacter (Betaproteobacteria) exhibited the largest and most significant increase in abundance post-Florence. Mantel correlations confirmed that bacterial dissimilarities post-Florence were similar to those observed in cold seasons (winter and spring). Overall, the results of this study provide new insights into changes in bacterial community composition and their responses to seasonal changes and extreme natural events in the NRE-PS. The upper-middle areas were more susceptible to diversity changes caused by Florence. Hurricane Florence and cold seasons had a similar impact on environmental parameters and estuarine bacterial communities, particularly affecting dominant genera, such as Cyanobium, and boosting the abundance of taxa common in cold seasons. The ASV data generated are valuable for future research to understand the microdiversity of these populations, metabolic capabilities, and resilience of the prevalent microbial communities in the NRE-PS.