Response of mangrove plant species to a saline gradient: Implications for ecological restoration

ABSTRACT Mangroves are salt tolerant plants that occur in tropical and sub-tropical sheltered coasts. Saltwater intrusions into terrestrial landscapes often occur due to either anthropogenic reasons or natural calamities such as tsunamis. We investigated the potential of using mangrove species for rehabilitation of high saline environments by revealing the capacities of species to remove salt from sediment. We established the salt retention capacity of common mangrove species in Sri Lanka i.e., Rhizophora apiculata, Rhizophora mucronata, Ceriops tagal, and Avicennia marina through ex-situ and in-situ measurements of NaCl content in plant tissue and soil samples, by titrating with 0.01 N AgNO3. The results revealed A. marina to be the most efficient in retaining salt within plant tissues while C. tagal is superior to R. mucronata but inferior to A. marina in performing this function. These findings were further confirmed by measuring salt uptake rates of hydroponically grown seedlings of the same species. Although R. mucronata is the most popular species used for restoration, A. marina appears the most suitable mangrove species not only for coastal mangrove restoration but also for rehabilitating salinity affected landscapes.