Repeated hurricane disturbance has minimal impact on shallow coastal infaunal communities

Disturbances are important drivers of seafloor community structure and diversity, especially in sediment infaunal communities with limited mobility. Shallow coastal sediment communities contribute to global nutrient cycling and carbon storage but also experience large-scale disturbances, including storms. Tropical cyclones and other extreme storms can dramatically restructure shallow sedimentary fabrics and disrupt infauna through resuspension and sediment transport and deposition. However, whether persisting storm-induced physical changes to sedimentary habitats affect post-storm infaunal community development is poorly studied or understood. Here we assess the relationship between relatively immediate (10 days) and more gradual (6 weeks to 8 months) changes to surficial sediment properties (grain size distribution, porosity, organic content) and infaunal community structure in Alabama, USA, coastal sediments following two consecutive tropical cyclone impacts in the fall of 2020: Hurricane Sally, where the storm's inner core passed directly over the study sites, and Hurricane Zeta, where the storm passed to the west of the sites. We hypothesized that infaunal communities at sites exhibiting drastic and persistent post-storm sedimentary changes (i.e., thick sand deposition over mud) would have greater losses of abundance and diversity and larger differences between pre- and post-storm community structure compared to communities at less physically restructured sites. However, almost all sites did not experience significant post-hurricane reductions in infaunal abundance or diversity or changes to community composition corresponding with the degree of sedimentary change. The lack of storm effects on infauna likely resulted from a combination of pre-Sally disturbances, seasonal recruitment, and opportunistic taxa adapted to dynamic coastal sediments. Our results indicate that infauna in frequently disturbed areas such as nearshore sediments adjacent to estuarine outflow may be resistant to physical habitat disturbance but also emphasize the importance of seasonal dynamics and disturbance history in shaping infaunal communities. These relationships will be especially important to understand as storm intensity is predicted to increase with climate change.