Geographic variation in mangrove flooding and accessibility for fishes and nektonic crustaceans

Intertidal habitats are only available to most nekton when inundated by tides. We assessed the variability of access to mangrove habitats for aquatic organisms over 3500 km of Australia's east coast. After determining the elevation of the lower mangrove edge across 19 locations, we used 6 years of historic hourly tide gauge readings to estimate wetland edge flooding frequency, duration, and depth at each location. Although mangrove edges broadly tracked mean sea level along the east coast, deviations in edge elevation corresponded to substantial geographic variation in flooding dynamics. Mangrove edges were flooded from as little as 20% of the time in central Queensland sites, to as much as 90% of the time during some seasons in northern New South Wales. Flooding frequency and depth were also highly variable, with some mangrove edges flooding and draining almost twice as frequently as others. Flooding depth profiles revealed dynamic patterns of flooding of mangrove habitat. The variability in flooding dynamics demonstrates that the availability of mangrove habitat to aquatic organisms varies significantly among locations. This variability in flooding patterns suggests the nature of mangrove use and the functional value of these habitats for fishes and nektonic crustaceans may differ substantially among regions.