Hurricane-Mediated Shifts in a Subtropical Seagrass Associated Fish and Macroinvertebrate Community

Hurricanes are important ecological disturbances that maintain biodiversity. We investigated the short-term impacts of Hurricane Irma, a category 4 storm that passed through south Florida on September 10, 2017, on fish and macroinvertebrate communities of western and north-central Florida Bay, FL, USA. Spatiotemporal trends in physical water conditions (temperature, salinity, water depth, dissolved oxygen, chlorophyll a, and turbidity) as well as rainfall and coastal discharge were assessed to characterize hurricane-induced habitat changes. Dramatic but ephemeral changes in water depth and rainfall were observed. Longer lasting reductions of salinity regime and increases in turbidity and chlorophyll a were also observed. The prevailing hypersalinity (≥ 40 ppt) conditions, ongoing since March 2017, were abruptly ended by the storm. Hurricane Irma significantly altered fish and macroinvertebrate communities. Analysis of community spatiotemporal trends revealed spatially distinct temporal community shifts. Cluster analysis distinguished four groups among nine highly abundant species identified as exerting the most influence on pre- and post-hurricane total community differences. Reductions in relative abundance of two groups were coincident with Irma’s passage while a third group, comprised solely of pelagic, zooplanktivorous Anchoa mitchilli, exhibited rapid population growth that started 2 months after the passage of the storm. These faunal disruptions are reminiscent of a prior Florida Bay community shift that followed a similar sequence of consecutive disturbances: hypersalinity, seagrass die-off, and a category-5 hurricane. Recovery from this prior community shift cascade took many years.