Author(s): Alamgir Kabir; Tanjina Hasnat
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Abstract: The structuring feature of coastal mangrove forests of Bangladesh is tree species adapted to growth in anoxic intertidal sediment saturated with seawater. Among their adaptations are special structures such as pneumatophores (e. g. Avicennia spp. ) and prop roots (e. g. Rhizophora spp. ) that supply the roots with oxygen from the air and provide physical support for growth insoft mud. Salt from the seawater is either excluded at the roots (e. g. Rhizophora spp. ) or excreted by glands on the leaves (e. g. Avicennia spp. ) The benthic fauna associated with coastal mangrove forests of Bangladesh is typically dominated by various burrowing decapods, such as sesarmid crabs and fiddler crabs. They are herbivores and have unexplored roles on coastal hydroecology and sustainability of mangrove forests in Bangladesh. Present study aimed to identify positive roles of crabs and fiddler crabs on coastal hydroecology and sustainability of mangrove forests surveying coastal plantations of greater Patuakhali district of Bangladesh. It was found that crabs retain, bury, macerate and ingest litter and microalgal mats in coastal newly accreted charlands of Patuakhali region covered with mangrove forest plantations and prevent loss of nutrients and promote decomposition processes. Most crabs inhabiting in coastal mangrove plantations of Patuakhali region actively dig and maintain burrows in the sediment. The burrows affect sediment topography and biogeochemistry by modifying particle size distribution, drainage, redox conditions and organic matter as well as nutrient availability. Mounds generated by the crab modified physical structures, transport conditions and substance chemistry, and by doing so changes the availability of resources and water for the associated microbial, fauna and plant communities. Mounds provided safe sites for regeneration for pioneer mangrove forest species that could not establish if tidally inundated. Burrowing activity of crabs in estuarine newly accreted charlands was found similar with earth warm activity in mainland agricultural soil. Financial analysis of human built mounds in coastal raised lands for planting mainland tree species by the Bangladesh Forest Department (BFD) showed that mound generation activity by the crab has also great monetary value in addition to ensuring sustainability of regeration of pioneer managrove forest species through maintaining hydro-ecological sustainability.
Year: 2018