Wrack enhancement of post-hurricane vegetation and geomorphological recovery in a coastal dune

Abstract

Coastal ecosystems such as sand dunes, mangrove forests, and salt marshes provide natural storm protection for vulnerable shorelines. At the same time, storms erode and redistribute biological materials among coastal systems via wrack. Yet how such cross-ecosystem subsidies affect post-storm recovery is not well understood. Here, we report an experimental investigation into the effect of storm wrack on eco-geomorphological recovery of a coastal embryo dune in north-eastern Florida, USA, following hurricane Irma. We contrasted replicated 100-m2 wrack-removal and unmanipulated (control) plots, measuring vegetation and geomorphological responses over 21 months. Relative to controls, grass cover was reduced 4-fold where diverse storm wrack, including seagrass rhizomes, seaweed, and wood, was removed. Wrack removal was also associated with a reduction in mean elevation, which persisted until the end of the experiment when removal plots had a 14% lower mean elevation than control plots. These results suggest that subsides of wrack re-distributed from other ecosystem types (e.g. seagrasses, macroalgae, uplands): i) enhances the growth of certain dune-building grasses; and ii) boosts the geomorphological recovery of coastal dunes. Our study also indicates that the practice of post-storm beach cleaning to remove wrack–a practice widespread outside of protected areas–may undermine the resilience of coastal dunes and their services.

Foredune‐forming grass and plant diversity show contrasting responses along the southeastern United States coast after hurricane disturbance

“…In foredune systems, dune‐building grasses and forbs are integral to the dune's capacity to resist erosion (Bryant et al., 2019; Feagin et al., 2019; De Battisti & Griffin, 2020) while playing a key role in dune formation and growth (Hesp, 2002; Houser et al., 2015, 2018). Site‐specific studies highlight that vegetation starts to regrow within a few months of major disturbances (Joyce et al., 2022; Miller et al., 2010), approaching full, geomorphic recovery within three to five years after major hurricanes (Miller et al., 2010; Houser, 2013; Houser et al., 2015). These and other local/site‐specific studies also indicate that vegetation composition, anthropogenic disturbance, changes in nutrient retention and sediment grain size and availability can all influence recovery following disturbance (Brantley et al., 2014; Hesp, 2002; Maun, 2009).…”