BONOROWO WETLANDS P-ISSN: 2088-110X Volume 7, Number 2, December 2017 E-ISSN: 2088-2475 Pages: 65-73 DOI: 10.13057/bonorowo/w070202 An assessment of a tropical urban stream using benthic macroinvertebrates as a bio-indicator in Muara Angke, Jakarta, Indonesia CHRISTOPHER KELLY 1,♥ , TATANG MITRASETIA 2,♥♥ , JITO SUGARDJITO 3,♥♥♥ 1 Kings College. Strand, London WC2R 2LS, London, United Kingdom. ♥ email: chris.kellyy@gmail.com 2 Faculty of Biology, Universitas Nasional. Ps. Minggu, Jakarta Selatan 12520, Jakarta, Indonesia. ♥♥ email: tatang248@gmail.com 3 Centre for Sustainable Energy and Resources Management, Universitas Nasional. Ps. Minggu, Jakarta Selatan 12520, Jakarta, Indonesia. ♥ email: sugar@unas.ac.id Manuscript received: 31 August 2016. Revision accepted: 28 June 2017. Abstract. Kelly C, Mitrasetia T, Sugardjito J. 2017. An assessment of a tropical urban stream using benthic macroinvertebrates as a bio-indicator in Muara Angke, Jakarta, Indonesia. Bonorowo Wetlands 1: 65-73. A preliminary study was conducted on the populations, density and distributions of benthic macroinvertebrate species along the course of the Ciliwung/Angke River, Jakarta. The selected river section is highly urbanized and heavily polluted, and five study sites were selected along its course to assess the health of the river ecosystem. Benthic macroinvertebrates are used as a bio-indicator for evaluation of ecosystem health. Their different pollution sensitivities, wide distribution and relatively sedentary lives make them useful candidates for this role. The focal point of the study is the MuaraAngke mangrove forest and wetland, a small remnant wetland at the mouth of the river in Jakarta Metropolitan. A comparison is drawn between the different study sites to assess the health and potential utility of this unique habitat. Despite several intense pressures resulting from the highly urbanized surroundings, and the mangrove's position at the mouth of the river where pollution accumulation would be highest, the data collected from this site showed a macroinvertebrate population dominated by pollution -sensitive taxa, suggesting the mangrove itself continues to provide significant ecosystem services in water -purification. Keywords: Biological filter, urban wetland, ecosystems services, benthic macroinvertebrates INTRODUCTION At the margins of the land, mangrove habitat has long been recognized as a key component of nutrient transfer and species movement across large eco-regions. They have been identified as cornerstone ecosystems, supporting healthy functioning in other habitats through the food web (Mastaller 1997). It has been demonstrated in numerous simulation studies that coastal wetland plants are capable of absorbing excess phosphates, nitrates, and other organic materials, helping to prevent eutrophication of water courses and the asphyxiation of downstream biotic communities (Wong et al. 1997; Chu et al. 1998; Tilley et al. 2002). This is crucial for rivers receiving high levels of organic waste, particularly downstream from large scale agriculture operations which are known to use excessive nitrate and phosphate loading to increase yields. However, the nutrient load entering mangroves is often found to exceed wetland plant growth requirements, and other biological filtering mechanisms are also important factors (Ye et al. 2001). It is not only sedentary mangrove species which depend on coastal wetlands. Studies have demonstrated a huge number of fish species rely on mangroves to provide nursery habitat for their juveniles (Sasekumar et al. 1992), and many migratory birds visit these rich environments for food and shelter (Giesen et al. 2007). This makes coastal wetlands vital ecosystems in the regional context, and yet the application of this knowledge to coastal development in the Jakarta Metropolitan area is worryingly under- developed. In recent years extreme degradations in the marine and coastal habitats of the Jakarta bay have been observed, an ecologically and commercially significant area. Reductions in size and health of coastal wetlands have already begun to undermine a number of key processes outlined above, and precipitated the decline of numerous species which rely on the mangrove. Perhaps most critical for this study is the ongoing reduction in commercial marine stocks. Not only do a number of key fish, shrimp and mollusc species depend on mangrove habitat for at least one part of their life cycle (Burhanuddin 1993), they also depend on nutrients carried downstream from Java's fertile volcanic highlands passing through coastal wetlands (Ligtvoet et al. 1996). A robust coastal wetland has the potential to support several commercial operations for Indonesia's citizens but this potential remains unrealized (Supartono et al. 2016). This preliminary study investigates the influence of a unique urban wetland on regulating the water quality of a highly degraded urban stream, and terrestrial-marine interactions more generally in one of the world's largest coastal metropolitan areas. Diversity, abundance and community composition of benthic macroinvertebrates relative to wetland proximity was used as an indicator of overall ecosystem health and vigor in the Ciliwung-/Angke river. The ultimate purpose of this study is to appraise the immense value of one of Jakarta's remaining natural habitats in the hope of preserving its critical function in the