COLLABORATIVE RESEARCH: RAPID 2017 Hurricane Irma: How do the effects of pulse disturbance vary with abiotic conditions, disturbance history, and proximity to a transition zone.

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Storm surge is often considered the greatest threat to life and property associated with a hurricane. Studies of the ecosystem effects of storm surge often focus on exposed coastal areas such as beaches. However, the upstream delivery of salt water can have long-lasting effects and can result in the decline of valuable freshwater tidal areas, which provide habitat to fish and wildlife, protect and improve water quality, and store floodwaters. This is especially important given the fact that these areas are already facing potential loss due to upstream salt water intrusion as a result of sea level rise. Hurricane Irma, which passed over the US on Sept. 11, 2017, caused the highest storm surge ever recorded on the central Georgia coast and resulted in salt water moving much further upstream than usual. The NSF-sponsored Georgia Coastal Ecosystems Long Term Ecological Research Project (GCE-LTER) has long-term experiments and monitoring programs that provide "before" data and a context for understanding the effects of this event. The investigators anticipate that the salt water delivered by the storm surge will affect multiple components of intertidal wetland ecosystems, including plants, animals, water chemistry, and soil surface elevation. The results of this research will be shared with coastal managers through the Georgia Coastal Research Council and the Georgia Coastal Hazards Community of Practice. The LTER researchers will also host K-12 teachers as part of the GCE Schoolyard Program and work with them to use this experience in the classroom.Understanding the effects of disturbances like Hurricane Irma is difficult because they are hard to manipulate experimentally and can act differently on different parts of the landscape. The investigators hypothesize that: 1) the effects of the storm surge will be greater in upstream as opposed to downstream areas, with the greatest effects and longest recovery times in tidal fresh sites; 2) areas that have had previous exposure to salt water will show greater effects based on their history; and 3) changes will be more likely in areas that are at the borders between different wetland habitats (i.e. the edge between salt marsh and brackish marsh plants). They will test these hypotheses by 1) augmenting sampling of the GCE-LTER wetland monitoring sites, which are distributed along and extend inland from the central Georgia Coast; 2) taking advantage of an ongoing GCE-LTER field experiment to determine how prior saline disturbance treatments affect responses to the hurricane storm surge; and 3) collecting aerial imagery that will allow them to look at landscape level shifts in vegetation type compared to pre-storm maps, and doing additional sampling in pre-established transitional plots. The LTER researchers speculate that rare but severe events like this storm are the major occasions that re-set the distribution of habitats in these valuable intertidal wetlands.