Award: OCE-1902496

During the 2018 Hurricane Season, large amounts of storm-related rainfall were deposited along the East Coast of the United States. Wind gusts associated with Hurricane Florence, one of the largest storms of the season, reached up to 106 mph and deposited 20+ inches of rainfall along the North Carolina coast where it made landfall and to the right of the track of the center. The excessive rain initially eroded sediments from land and other types of organic matter, that were visible from satellite images. This research project hypothesized that Hurricane Florence may have introduced amounts of terrestrial organic matter large enough and dynamic enough for those storm-derived materials to enter from coastal NC soils into the Albemarle Pamlico Estuary System (APES) and ultimately into coastal areas of the northwestern Atlantic Ocean via the Ocracoke, Oregon, or Hatteras inlets. Because organic matter is "food" for heterotrophic bacteria, the project hypothesized that this terrestrial organic matter pulse from the storm would also cause a shift in aqueous coastal microbial communities compared to "normal" standing stock populations. To test these hypotheses, the research group collected rainfall from Hurricane Florence and undertook several post-Florence research cruises in the Fall of 2018, to collect surface water at stations along a transect in the APES, through Oregon Inlet, and across the continental shelf, heading towards the Gulf Stream. These stations were revisited in July of 2019, which represented a "non-storm" period. Bulk suspended matter abundance, salinity, terrestrial organic matter abundance and composition, and microbial community diversity were all determined in both sets of samples. In addition, some preserved samples from coastal North Carolina collected in 2016, were also analyzed for microbial populations representing a more distant "non-storm" period. This was one of the first studies to quantify both rainwater carbon abundance and composition during an Atlantic hurricane. The rainwater samples were scant in abundance but nonetheless demonstrated that Hurricane Florence rainwater carbon contained elevated amounts of a recently identified pool of carbon termed, "Exchangeable Dissolved Organic Carbon", with implications for heterotrophic microbial respiration. The results of this study suggest that in the fall 2018, immediately after the largest Atlantic hurricanes of the season, water in the APES were generally enriched in particulates, terrestrial organic matter (particulate and dissolved) and microbial populations that were derived from terrestrial areas. Indeed, the terrestrially derived heterotrophic microbes were found in some of the samples closest to the Gulf Stream in the 2018 samples. Impacts from these environmental disturbances toward microbial communities are important to understand in the context of warming global climates that predict increased frequency and intensity of future extreme storms. These microbial community disruptions likely affected regional ecosystem function due to shifts in carbon and nitrogen cycling, with data suggesting a reduced role for the region as a net sink of atmospheric CO2. These community disruptions also imply a geographic- or system-dependent effect, with our geographic region of study adding further context to similar studies on different regions. Sample analysis methods in this study are unique from similar studies in that we show hurricane-correlated disruptions to microbial communities at both total and active portions of the communities. We also highlight a disconnect across taxonomic domains (i.e., bacteria impacted but not archaea) which may have implications for domain-specific variation in resistance toward future climate-induced disturbance events. Finally, our results improve the link between taxonomy and function by showing hurricane-correlated impacts toward specific microbial functional genes that are important indicators of ecosystem health and stability. Collectively, these results suggest that during Atlantic hurricanes, atmosphere-land-sea boundaries collapse and become a continuum for rapid one-way exchange of materials and dynamic microbial metabolic processes. Student participation in the project included 5 graduate students (4 MS and 1 PhD) and three undergraduate students (geology and biology) at ECU and another undergraduate summer student from St. Mary’s College, MD. Their direct role as researchers in the project stoked all these students’ interest in continuing to pursue STEM careers for their future. One of the undergraduate students created an educational module targeted towards elementary school students on "Increased Suspended Sediment as a Result of Storms". Public outreach events discussing these climate change issues occurred at "What’s Up Bio", "Earth Day", and CSI Open Houses throughout the project timeline. Moreover, several oral platform or poster presentations on the project were disseminated at regional meetings and a national meeting. Lastly, one manuscript has been accepted and another one is in preparation for submission. Last Modified: 03/16/2022 Submitted by: Siddhartha Mitra