Hydrological suitability for mangrove species in restored mangroves in abandoned ponds

Mangrove restoration projects in Indonesia are widely conducted in abandoned aquaculture ponds, however the success of planting mangroves is limited as tidal flooding is often not considered. The hydrology of mangrove surrounding water is both complex and dynamic and creates tide-induced flow and mangrove vegetation interaction that influences hydrological suitability of mangrove species. In this study, we aimed to determine the hydrological suitability for specific mangrove species in mangrove restoration efforts in abandoned aquaculture ponds by measuring tidal inundation duration in mangrove waters. The study was undertaken in two restored mangroves sites in abandoned ponds in Perancak estuary, Bali and Lubuk Kertang, North Sumatra, which was combined with measurements of intact mangroves for comparison. Tidal flooding (inundation and current velocity) was recorded to obtain flooding period measurements (depth, duration and tidal velocity) in association with mangrove succession rates. We found that the variability of tidal flooding between study sites was found to determine dominant mangrove species, suggesting a mangrove species-specific tolerance to tidal flooding in establishing habitats. Among the species observed, Nypa fruticans was found to be the most resilient to prolonged tidal inundations. Rhizophora spp., Avicennia spp., Sonneratia alba, however, adapted to a wider range of inundation periods. The tidal inundation in restored mangrove ponds was characterized by low current velocities, which provides suitable conditions for mangrove recovery in restoration sites. This information on hydrological classification proves that the effectiveness of mangrove restoration projects can be improved by highlighting the necessity to account for localized tidal inundation regimes.