Assessment of environmental status of coastal mangrove area using macrobenthic assemblages: a study case at Tapak Mangrove area, Semarang, Central Java

Macrobenthic structure can be used as a bioindicator in determining the level of disturbance in water ecosystem through their composition, presence or absence spatially and temporally as apart of ecological management. Tapak is a coastal area of Semarang City, Central Java, Indonesia that has potency as an ecotourism area for integrated aquaculture at mangrove area. On the other hand, industrial activity around Tapak coastal area may lead to a degradation of the ecological function of that area. This study aims to assess environmental status at Tapak Mangrove Area through the macrobenthic structure in space and time. Purposive random sampling method was applied, consisting five sampling stations with 3 replicates between March to May 2018. Sediment samples were taken by using Ekman grab and were analyzed through the stages of fixation, rinsing, sieving, preservation, sorting, identification, and enumeration. The biotic parameters observed were the macrobenthic community structure, including species composition, abundance, and diversity, evenness, and dominance indices. Physico-chemical parameters of the water and sediment were measured every month. The Early Warning System (EWS-3SWJ) software was used to assess the level of environmental disturbance at each station. The total of 15 species of macrobenthic assemblages were found. The most common species were Telescopium telescopium, Cerithidea cingulata, and Metapenaeus sp.. The diversity of macrobenthos was considered low at all sampling stations (H' = 0,56 – 1,52), with marked variability in dominant taxa (D = 0,21 – 0,71). Further analysis using the EWS-3SWJ showed that the environmental status of the Tapak Mangrove Area is categorized as slightly disturbed areas.