2018 Hurricane Season Impacts to Dissolved Organic Matter and Microbial Communities in the Albemarle-Pamlico Estuarine System (APES) and Gulf Stream

Major hurricanes can considerably impact carbon, nutrient, and microbial cycling in coastal areas. The 2018 hurricane season resulted in elevated amounts of terrigenous carbon and microbes being flushed out through rivers and streams into the Albemarle-Pamlico Estuarine System (APES). Dissolved organic carbon (DOC) to total dissolved nitrogen (TDN) in filtered water and ratios of Be-7/Pb-210xs from the 2018 samples are suggestive of elevated amounts of terrigenous organic matter delivered to the Gulf Stream. This terrigenous signal decreased with increasing salinity. However, ratios of DOC:TDN, Be-7/Pb-210xs were substantially higher than what is typically observed in coastal waters. Overall, the microbial community showed a decrease in percent terrestrial taxa with increasing salinity, although a significant portion of the microbial community off shore were terrestrial-based taxa. Collectively, these results suggest runoff from the storms did lead to inputs of terrestrial organic matter and microbes. For example, a large proportion of terrestrial-based microbes (20-23% terrestrial bacteria) were found in the water column even at the edge of the continental shelf, compared to a maximum of 45% terrestrial bacteria at the most inland estuarine sites. Bacteria taxa capable of breaking down terrestrial woody plant material such as lignin were reported in the sediment of high salinity sites around Oregon Inlet (~30 ppt), at ~60% of the abundance found at the most inland sites. There was also evidence of terrestrial and lignin-degrading bacteria taxa that were active at sites near the inlet. Collectively, these results suggest terrestrial-based runoff from the 2018 storms affected DOC and microbial cycling in the NC coastal marine system and the Gulf Stream.