Seaweeds for the sustainable blue economy development: A study from the south east coast of Bangladesh.

Bangladesh is a maritime country with an area of 118000 km2 which supports a large number of commercially important species. Currently seaweeds are considered as important component of blue economy development in Bangladesh and farming is practiced at small scale level (Hypnea spp, Caulerpha reacemosa, Gelidium sp. are cultured). For the expansion of the seaweed farming in Bangladesh, a complete understanding of social and economic status of current farmers is important. However, information on socio-economic status of seaweed industry in Bangladesh is very limited. Therefore, this study aimed to understand existing culture methods and their cost, marketing channel and problems with seaweed farming in south east coast of Bangladesh. We used questionnaire survey and focus group discussions to collect data from seaweed farmers, researchers, local community and entrepreneurs. The study found that farmers are currently practicing long-line and horizontal net methods for the seaweed farming in the south east coastal region. The study also found that these culture methods are economically profitable. Seaweeds are currently sold locally and a proper value chain for seaweed marketing is still missing. Existing seaweed farmers are facing the problems related to insufficient credits for starting seaweed farming, lack of proper guidelines for farming and processing of harvested seaweed. This study suggests that for industrial level expansion of seaweed production in Bangladesh a proper value chain, development of seaweed derived products, farm monitoring systems, smooth seed supply and information hubs are required.

1980s-2010s: The world's largest mangrove ecosystem is becoming homogeneous.

Knowledge gaps in spatiotemporal changes in mangrove diversity and composition have obstructed mangrove conservation programs across the tropics, but particularly in the Sundarbans (10,017 km2), the world's largest remaining natural mangrove ecosystem. Using mangrove tree data collected from Earth's largest permanent sample plot network at four historical time points (1986, 1994, 1999 and 2014), this study establishes spatially explicit baseline biodiversity information for the Sundarbans. We determined the spatial and temporal differences in alpha, beta, and gamma diversity in three ecological zones (hypo-, meso-, and hypersaline) and also uncovered changes in the mangroves' overall geographic range and abundances therein. Spatially, the hyposaline mangrove communities were the most diverse and heterogeneous in species composition while the hypersaline communities were the least diverse and most homogeneous at all historical time points. Since 1986, we detect an increasing trend of compositional homogeneity (between-site similarity in species composition) and a significant spatial contraction of distinct and diverse areas over the entire ecosystem. Temporally, the western and southern hypersaline communities have undergone radical shifts in species composition due to population increase and range expansion of the native invasive species Ceriops decandra and local extinction or range contraction of specialists including the globally endangered Heritiera fomes. The surviving biodiversity hotspots are distributed outside the legislated protected area network. In addition to suggesting the immediate coverage of these hotspots under protected area management, our novel biodiversity insights and spatial maps can form the basis for spatial conservation planning, biodiversity monitoring and protection initiatives for the Sundarbans.