Sri Lanka is gifted with about 15,670 ha of mangrove habitats which are scattered along the coastal zone of the island. However, most of the studies on mangroves are confined to the western, northwestern and southern parts of the country. Although it is been neglected, Eastern province shares 28% of the mangrove cover of the country. Thus, the main objective of the current study was to determine the distribution, abundance and diversity of true mangrove species in Pottuvil, Heda oya, Ragamwela, Panama, and Okanda mangroves in the Eastern province of Sri Lanka. Mangrove vegetation was sampled using belt transects of 5 m in width laid perpendicular to the shoreline and across the water-land gradient. True mangrove species in each transect was identified and counted. Height and DBH (Diameter at Breast Height) were recorded. Relative density, relative frequency, relative dominance and the IVI (Importance value index) of the species in each mangrove ecosystem were calculated. Shannon diversity index (H'), Shannon Evenness (E') and Simpson index was used to compare the diversity between sites. Nine true mangrove species were recorded in Panama lagoon and the least number of species (3) were recorded from Ragamwela creek. Highest Shannon diversity value (H' = 1.7) was obtained for the Panama mangrove which was followed by the Heda Oya Estuary mangrove (H' = 1.1). Lowest Simpson index was recorded in Panama lagoon (0.22). Nearly half of the true mangrove species (11) that have been recorded from Sri Lanka occurs in the five study sites. They belongs to seven families and eight genera. More research is needed to understand the ecological aspects of theses mangroves as these systems have not been studied for the last thirty years. It is recommended that immediate action should be taken by the government to prevent distractive anthropogenic activities in these mangrove ecosystems.

Considering the environmental and specific socioeconomic significance of the critically endangered mangrove Lumnitzera littorea, this study was conducted aiming the conservation of the species. The specific objectives were to define the diversity of the other mangrove species in association with the existing L. littorea plant population in the Madu Ganga wetland, Sri Lanka, to study its seed germination and identify the barriers for seed germination. The existing population of L. littorea is an aged population with low regeneration potential. Most of the seeds collected at the dispersal maturity were empty. A micro moth belonging to Family Gelechiidae was identified as the embryo predator. Although GA3 (Gibberellic acid) treatment and dry storage reduced the germination time, none of the seed treatments significantly improved the seed germination of L. littorea. Low seed germination observed was due to absence of embryo in mature seeds as a result of insect predation and physiological dormancy of seeds. Optimum GA3 concentration, duration of dry storage and potting medium with suitable salt concentration for seedlings should be optimized in future research.