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The ability of mangrove trees to reproduce and disperse in highly dynamic tidal environments is reflected in the contemporary genetic diversity and structure of their populations. Resilience and establishment may occur through either local recruitment (propagule pool model) or over longer distances with mixed origins (migrant pool model), thereby affecting the connectivity between natural populations. Anthropogenic activities such as encroachment and fragmentation or from mitigating reforestation could cause strategy switches and thus the connectivity and genetic structure of populations. In this study, we considered Avicennia officinalis, a dominant component of the Sundarban mangrove forest in Bangladesh to estimate dispersal dynamics over various distances within estuaries. A total of 423 individuals of A. officinalis, distributed over thirteen sites in the Sundarbans were sampled at both large and fine-scaled spatial level, the latter for comparison of natural and dense with fragmented sites. Up to 62 alleles showed a comparable level of allele diversity and gene diversities at both juvenile and adult life stages, assuming overall high levels of outcrossing. Significant inbreeding levels and high kinship values were solely observed at a reforested A. officinalis site. Genetic variables revealed high levels of connectivity between sites at close vicinity, with only a weak structure over larger geographic distances, between natural core Sundarban and coastal edge populations. Kinship coefficients were mostly low though significant up to several kilometers along estuarine branches, thereby suggesting propagule dispersal beyond each site. A fine-scaled analysis of kinship levels estimated for fragmented and natural forest plots along both sides of a river revealed that fragmentation induced higher kinship levels over 25–50 m distance, whereas dense natural populations were composed of less related individuals at shortest distances. A. officinalis populations might stay resilient through a mixture of unrelated propagules, clearly adhering a migrant pool model in natural sites and propagule pool model in fragmented sites. A poor gene diversity of planted trees might jeopardize the sustainability of mangrove plantation practices. Furthermore, high levels of diversity and connectivity indicated that the core Sundarban populations are a relevant source of germplasm in afforestation programmes.

In a mangrove environment, several groups of organisms are symbiotically associated with pneumatophores (aerial roots). But whether these organisms are exclusively found in this habitat (uniqueness) or accidentally settled here from water or sedimentary habitat, is not clearly understood. This hampers our understanding of their functional ecology. Hence the present study aimed to characterise the epibiotic microalga and meiofauna from the pneumatophores of mangrove Avicennia officinalis . To determine the habitat influence, these communities were also compared with those found in water and sedimentary habitat. Four estuarine mangrove sites represented by brackish water (salinity varying from 5 to 12) and located at different spatial scales (5–50 km distance) were chosen to determine whether these communities are consistent or vary with sites. Overall, the microalgal community was found to vary both among the habitats as well as sites. In the pneumatophore habitat, several tychoplanktons such as Coscinodiscus, Thalassionema , Cyclotella, Fragilariopsis, and Biddulphia were observed instead of benthic ones. These diatoms are planktonic genera and might have settled on pneumatophores from the water column. The observed variability in the microalgal composition among the sites is possibly due to predatory interactions or the dominance of particular species of macroalga that govern the diatom community. On the other hand, among the meiofaunal community, diptera, halacarida, tanaidacea, and foraminifera were mainly found in the pneumatophore habitat than in the sediment. Because pneumatophores either provide refugee to meiofauna against predators or are saturated with oxygen that meiofauna can utilize for respiration. Pneumatophores were also found to harbour several rare (abundance

Mangrove forest are used widely for meeting fuelwood needs of local communities in the tropics. However, the implications of fuelwood extraction on mangrove ecology has received very little attention. In this study, we investigated the impact of such small-scale fuelwood harvesting practices on mangrove forest structure, composition, regeneration, and biomass and carbon stocks in a protected area on the east coast of India. We sampled vegetation plots in areas where harvesting was practised and where no harvesting was observed. We found that species composition differed across forest categories with Exoecaria aggalocha and Heriteria fomes dominating non-harvested forest types and Sonneratia apetela, Sonneratia caseolaris, Avicennia officinalis along with mangrove associates comprising a large proportion of harvested mangrove forests. Similarly, tree, sapling and seedling densities, basal area, and biomass and carbon stocks were also found to vary across forest categories, with overall lower values observed in harvested areas. Lastly, total aboveground (11%) and belowground (18%) biomass and carbon stocks were also lower in harvested forests than non-harvested forests. However, large DBH size-class trees were found in harvested areas implying selective cutting practices that conserved old-growth trees and contributed to larger mean carbon pools. As harvesting is selective, mainly for cooking fuel demands, integrated management plans are required to accommodate local cultural and economic needs of the communities in this region.

For sustainable management of mangrove ecosystems, there is a pressing need to increase our knowledge of fish and invertebrates associated with this system. This study sampled microhabitats (89–258 ...

Production, elemental composition andin situdecomposition of litter ofRhizophora apiculata,R. mucronata,Sonneratia albaandAvicenna officinaliswere studied in a mangrove ecosystem fringing Madovi–Zuari Estuaries on the Central West Coast of India. Litter yield ranged from 10.2 tonnes ha-1year-1inA. officinalisthrough 11.8 (R. apiculataandR. mucronata) to 17 tonnes ha-1year-1inS. alba. Seasonally maximum litter fall was in pre- and post-monsoon monthe, with the lowest production in the monsoon. Modelling of litter fall as a function of Julian day and six environmental parameters showed that the observed changes can be explained in terms of dry/wet season and wind speed, with a 1000. Total decomposition (98–100% loss in dry weight and C, and >90% loss in N and P) of yellow leaves was within 15 weeks in the twoRhizosporaspp. andS. alba, and within 8 weeks inA. officinalis. In all four species, mass changes during decomposition obeyed first-order kinetics. Comparison of C, N and P fluxes from the decomposing mangrove litter with phytoplankton, bacterial and secondary production in the estuarine waters showed that mangrove production is important mainly for the C budget of the Estuaries and in sustaining the microbial food chain and nutrient regeneration, rather than the particulate food chain directly.