Usually mangroves don't possess much understories. In the Sundarban Mangrove Forests of Bangladesh, you will find some uderstory depending on the position from the rivers/canals/creeks. Near the water bodies, you will find Acrostricum, Nypa, Phragmitis etc. whereas if you go more inside, sometimes it may happen that you will not find any understory at all!!! May be some seedling will be present there.
Mangrove understory have a very defining role in the ecosystem. They are very sensitive to any fluctuations in abiotic factors and hence plays a very important part in understanding the overall health of the ecosystem. Publications are available categorizing the species in a wet mangrove ecosystem but inventory of species is rarely provided. I am attaching an article which could be of value in this regard as it deals with effect of salinity raise in the ecosystem as an indicator of climate change and hence an inventory data have been provided of the species composition at Indian Sundarbans.
Thanks,
Best wishes for your research endeavor.
Article Dynamics of mangrove diversity influenced by climate change ...
Mangroves are tropical formations between land and sea, I am studying the the mangroves of Godavari and krishna estuarine regions since 1985, but I didn,t find any understory plants in the mangrove ecosystems. while some estuarine algae such as Bostrychia, Caloglossa and Catenella are understory plants but these plants also exposed during the low tide. Mangroves are not small bushes or shurbs which are trees able to cope up with changing environmental condtions with help of prop roots, Pneumatopores and viviparous fruits. Halophytes are small herbs are shurbs but these plants are growing away from the creeks and canals. During the high tide period only water touch these plants.