BIODIVERSITAS ISSN: 1412-033X Volume 22, Number 1, January 2021 E-ISSN: 2085-4722 Pages: 247-252 DOI: 10.13057/biodiv/d220130 Mangrove associated macrobenthos community structure from an estuarine island MD. HABIBUR RAHMAN 1 , M. BELAL HOSSAIN 1 , AHASAN HABIB 1,2,3, , MD. ABU NOMAN 4 , SHUVAGATO MONDAL 1 1 Department of Fisheries and Marine Science, Noakhali Science and Technology University. Noakhali–3814, Bangladesh. Tel./fax.: +880-321-71484,  email: a.habib@umt.edu.my 2 Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu. 21030 Kuala Nerus, Terengganu, Malaysia 3 Aquatic Food Security Research Interest Group (RIG), Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu. 21030 Kuala Nerus, Terengganu, Malaysia 4 College of Marine Science and Technology, China University of Geosciences. 388 Lumo Rd, Hongshan, Wuhan, Hubei, China Manuscript received: 23 August 2020. Revision accepted: 22 December 2020. Abstract. Rahman MDH, Hossain MB, Habib A, Noman MDA, Mondal S. 2021. Mangrove associated macrobenthos community structure from an estuarine island. Biodiversitas 22: 247-252. Macroinvertebrate living on or around the mangroves has not been or less investigated in Bangladesh. This study was carried out to describe the density, distribution, and community structure of mangrove associated macrobenthos in Nijhum Dwip, central coast of Bangladesh. A total of 17 taxa were identified belonging to mainly Polychaetes (67.37%), Mysids (23.53%), Isopods (3.83%), Amphipods (0.58%), and Gastropods (0.29%). Polychaetes were dominant by contributing 67.37% of total macrobenthos. The number of benthic fauna ranged from 359 to 1617 inds./m 2 with a mean value of 1003.93± 400.3 inds./m 2 There was no significant difference observed (p > 0.05) in the abundance of macrofauna among the stations. The maximum Shannon-Wiener Index (H’) of species diversity was found at St2 (1.323) and the lowest at St4 (0.8) in the monsoon period possibly due to high rainfall and disturbance of benthic habitat. The Shannon-Wiener diversity values suggest the area was less polluted. The information from the present study can be used to measure the impacts of pollution to conserve biodiversity in sustainable manner. Keywords: Estuarine island, macrobenthos, mangrove ecosystem, Nijhum Dwip, Bangladesh INTRODUCTION The coastal vegetated wetlands such as mangroves, seagrass beds, and salt marshes account for <0.2% of the total ocean area and have been considered as most productive ecosystems in the world (Su et al. 2020). Mangrove ecosystems normally occur in sheltered locations along the coastline. In optimum condition mangrove ecosystem develops into a large productive forest (Loughland et al. 2020). In addition, mangroves play an important role worldwide serving as unique and vital ecosystems connecting the land and sea in tropical and subtropical coastal regions (Li et al. 2017). They provide shelter, food, breeding sites for marine organisms, and ecosystem services on which coastal people depend on their livelihood, and for their socioeconomic development (Lee et al. 2014; Chen et al. 2015). These ecosystems provide diverse ecological benefits including supporting high biodiversity and ecosystem service functions (Luo et al. 2010; Su et al. 2020). Due to their effects on biodiversity and productivity of macrofauna, estuarine and marine ecosystems also serve as nursery grounds for ecologically and economically important marine species (Bertelli and Unsworth 2014). However, the increased anthropogenic activities in the coastal regions also produced adverse effects on marine life and disturb the coastal environment particularly mangrove ecosystem (Farooq and Siddiqui 2020). Bangladesh coastline is also prone to various natural disasters such as cyclones, river erosion, salinity intrusion, floods, high population density, and poor socio-economic conditions. The Sundarbans is the biggest mangrove forest in Bangladesh, which is used as strengthen of coastal forest (Iftekhar and Takama 2008). Different mangrove communities support different macrobenthic faunal communities (Samidurai et al. 2011; Chen et al. 2015). The sediment differs among mangrove communities, which has great effects on diversity indices (richness, evenness) of macrobenthic fauna (Alfaro 2010; Chen et al. 2015; Leung 2015). In addition, variation in species diversity and population of benthic organisms reflects the environmental composition and condition in specific wetland (Leung and Cheung 2017). Research on community structure of macrobenthic fauna in mangrove areas might provide valuable information on management, restoration, and sustainable use (Chen et al. 2015). Thus, it follows the community structure of macrobenthos in an estuarine island and/or changes in a mangrove forest succession. Like other estuarine islands, the Nijhum Dwip island occupies large area of mangroves including mudflats, tidal creeks with high level of biodiversity (Asadujjaman et al. 2012). This island is under Hatiya Upazila and Noakhali District, Bangladesh. The island began to form in the 1950s, at present the total area of the island is 4,057 ha and the soil is mainly undeveloped with little development of Meghna alluvial deposits. The surface soil is primarily