Sonneratia ovate Backer (Lythraceae): status and distribution of a Near Threatened mangrove species in tsunami impacted mangrove habitats of Nicobar Islands, India

Abstract

The world’s most productive ecosystem, the mangrove forest, is under immense pressure due to natural and human induced disturbances. The Indian Ocean tsunami on 26 December 2004 had an adverse effect on these habitats by breaking and uprooting the mangrove trees. The mangrove vegetation and the coastal forest of Nicobar Islands, India, were severally damaged by the force of the tsunami and the loss of habitat due to the sudden rise in sea level. We studied the re-colonization of mangroves species that began after the tsunami over 19 Islands and 25 locations present in the Nicobar group. Sonneratia ovata (Lythraceae), a Near Threatened landward mangrove species, is reported for the first time from India. A total of 43 individuals of S. ovata was recorded from two sites, namely, Oh Hi Poh and Dhili Kadi, on Katchall Island. All the individuals of mangrove species ≥ 1cm girth at breast height were counted from both sites. The relative density for Bruguiera gymnorhiza (77%) and Sonneratia caseolaris (77%) are high at Oh Hi Poh and Dhili Kadi, respectively. Global distribution, occurrence in India, threats and conservation of S. ovata are discussed in detail. The influence of the tsunami in the dispersal of S. ovata from the nearest known sources Thailand, Malaysia or Indonesia is not very clear. Hence, molecular based study is required for the confirmation of the possible seed source location.