Mangrove community structure of surabaya east coast

Mangrove has an important ecological and economical role for the environment of Surabaya east coast. However its presence now has threatened by various factors such as land conversion, pollution and the existence of many buildings of housing and industrial. The purpose of this research was to identify the diversity, dominance, and zoning of mangrove community in Surabaya east coast area. Data were obtained by using belt transect method, perpendicular from coastline. Parallel five plots were design to identify and analyze mangrove plant community with 10x10 m² squares for trees, 5x5 meters² squares for bushes, and 2x2 meters² squares for seedlings. In each plot was identified the species, measured stem diameter, and calculated the number of mangrove individuals. The analysis of vegetation was conducted by the Mueller and Dumbois formulas to obtain the value of diversity, frequency, dominancy, and plant importance values of mangrove community. Shannon's dominance index and dominance index were used to get the diversity index. The results showed that seven species and four families were found that composed mangrove vegetation on this area, such as: Avicennia (Avicennia marina and A. alba), Sonneratiaceae (Sonneratia alba), Rhizophoraceae (Rhizophora stylosa, R. apiculata and R. mucronata), and Meliaceae (Xylocarpus molucensis). The highest importance value index was found in A. marina (235.68%). Mangrove diversity in this area is low (1.1) and was dominated by A. marina. Mangrove zonation from the sea line to the mainland in sequence: A. marina, S. alba dan A. alba (in front line), R. stylosa dan R. mucronata (in middle line), X. molucensis dan R. apiculata (in terrestrial). The low diversity and distribution patterns were suspected to be affected by relatively similar physical and chemical conditions in the sampling area and are overshadowed by the growth and development of mangroves plants in the area.