Sir

S. apetala was once germinated and reared in controlled environment with saline watering at the Tree Propagation Laboratory, Institute of Forestry and Environmental Sciences, University of Chittagong, Bangladesh. For years, seedling growth didn't increased to a significant rate or became stunted.

Regeneration problem of the species may be due to changed salinity regime in coastal areas, succession problem, increased sedimentation in mangrove benches. Research in this regard is needed.

You may use following paper where growth, density and natural regeneration of S. apetala at coastal plantations were assessed.

Article Growth density and regeneration of afforested mangroves at M...

Thanks Dr. Siddique. I have gone through your paper and to be honest was surprised to see the regeneration of S. apetala in Mirsorai area. 

Dear Sir

For further surprises please read following papers which show S. apetala found to be naturally regenerated in coastal shores of Bangladesh like in Sitakunda, Mirersarai and Hatia.

Latif MA, Del Castillo RA. 1990. Growth and yield of keora (Sonneratia apetala) in coastal Plantations of Bangladesh. Bangladesh J Forest Sci. 19:11–18.

Haque SMS, Hossain MK, Kabir MA. 2000. Performance of some common mangrove species in Sitakunda and Mirersarai Forest Ranges under Chittagong Coastal Afforestation Division. The Chittagong Univ J Sci. 24(2):1–10

Uddin MM, Hossain MK. 2013. Status of coastal plantations and its impact on soil PH, salinity and land stabilization at Nolchira range of Hatiya Island, Bangladesh. IOSR Journal of Agriculture and Veterinary Science (IOSR-JAVS). 3 (4):7–15

Siddiqi NA, Khan MAS. 1990. Growth performance of mangrove trees along the coastal belt of Bangladesh. Mangrove Ecosystem Occasional papers. No. 8 UNDP/UNESCO/RAS/86/120. Thomas Press, Delhi, pp. 5–14.

Thank you.

Mr. Siddiq

Here  is another paper that might help you.

http://www.academia.edu/1352268/Threats_to_the_Sundarbans_Mangrove_Wetland_Ecosystems_From_Transboundary_Water_Allocation_in_the_Ganges_Basin_A_Preliminary_Problem_Analysis

Good luck,