ABSTRACT:

Hurricane Helene made landfall as a Category 4 storm on September 26, 2024, bringing 12-16 inches of rainfall and a 9-feet storm surge to Florida’s Gulf Coast. During hurricanes, the combined effects of excessive rainfall, storm surge, and flooding can elevate groundwater recharge and discharge, increase saltwater intrusion, and mobilize contaminants from the vadose zone and aquifers. The overall objective of this project is to assess the immediate and long-term effects of hurricanes on the salinization and recharge-discharge processes, and how these processes affect nutrient geochemistry of Florida’s Gulf Coast aquifers. We will focus on Wakulla Spring-Apalachee Bay transect, the landfall site of Hurricane Helene, as well as a region where groundwater is central to natural ecosystems and human need, emphasizing the importance of investigating the impact of extreme events to aquifer systems. Our central hypothesis is that hurricane induces significant changes in coastal aquifer systems by increasing salinization, enhancing groundwater fluxes, and altering nutrient fluxes and speciation. To test this hypothesis, the following two specific objectives are proposed: (1) Evaluate the degree of aquifer salinization and how it affects nutrient speciation, and (2) Quantify groundwater discharge and nutrient fluxes. All research activities will be conducted post-hurricane and during baseflow conditions.

ABSTRACT:

Microbial communities in subterranean estuaries (STE) mediate biogeochemical reactions of coastal groundwater discharging into the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use alterations are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under different nitrate (NO3-) inputs, saline solutions, and incubation times. This is a supplementary data to manuscript "Microbial assemblages and functional predictions in organic-rich subterranean estuaries: impact of climate and land use changes" submitted to Journal of Geophysical Research: Biogeosciences.

ABSTRACT:

Microbial communities in subterranean estuaries (STE) mediate biogeochemical reactions of coastal groundwater discharging into the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use alterations are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under different nitrate (NO3-) inputs, saline solutions, and incubation times. This is a supplementary data to manuscript "Microbial assemblages and functional predictions in organic-rich subterranean estuaries: impact of climate and land use changes" submitted to Journal of Geophysical Research: Biogeosciences.

ABSTRACT:

Microbial communities in subterranean estuaries (STE) mediate biogeochemical reactions of coastal groundwater discharging to the oceans; however, studies on their response to abrupt environmental changes caused by climate and land use changes are still limited. In this study, we conducted a controlled laboratory study using combined geochemical and metagenomic approaches to investigate microbial structures and their metabolic pathways under different nitrate (NO3-) inputs, saline solution, and incubation times, which were used as proxies of land use, salinization of the shallow aquifer, and climate changes. We found a highly reducing habitat and amplification of genes related to denitrification, sulfate reduction, and methanogenesis processes. Core communities consisted of Clostridia, Bacilli, Alphaproteobacteria, Gammaproteobacteria, and Desulfobaccia were observed. The qualitative degradation of terrestrial, plant-derived organic matter (i.e., tannin and lignin) was predicted to not being affected by NO3- inputs or salinity because of it being implemented by core communities and the abundance of electron donor and acceptors. However, long-term incubation allowed sufficient time for microbes to degrade less labile DOM, promoted the re-release of buried solid phase organic matter into the active carbon cycle, and increased the relative abundance of biofilm or spore-forming taxa while decreasing that of rare taxa such as methanogenic archaea. The relative proportion of less prevalent taxa were also susceptible to seasonal and endmember variability. Our results illustrate the sensitivity of microbial assemblages to environmental change and their capacity to mediate C and N cycles in coastal areas, further affecting coastal water quality and ecosystem-scale biogeochemistry.