OCEAN LIFE Volume 3, Number 1, June 2019 E-ISSN: 2580-4529 Pages: 11-17 DOI: 10.13057/oceanlife/o030102 Assessment of the Holothuria atra (Echinodermata: Holothurians) habitat based on the antibacterial effectiveness approach at Karimunjawa, Central Java Province, Indonesia BAMBANG SULARDIONO ♥ , SUTRISNO ANGGORO, SITI RUDIYANTI, ARIF RAHMAN Department of Aquatic Resources, Faculty of Fisheries and Marine Sciences, Universitas Diponegoro. Jl. Prof. H. Soedarto, SH, Tembalang, Semarang 50275, Central Java, Indonesia. Tel.: +62-24-7474698, Fax.: +62-24-7474698,  email: bambangsulardiono@gmail.com Manuscript received: 5 May 2019. Revision accepted: 7 June 2019. Abstract. Sulardiono B, Anggoro S, Rudiyanti S, Rahman A. 2019. Assessment of the Holothuria atra (Echinodermata: Holothurians) habitat based on the antibacterial effectiveness approach at Karimunjawa, Central Java Province, Indonesia. Ocean Life 3: 11-17. Sea cucumber Holothuria atra lives in shallow marine benthic habitats and in its life cycle depends on the quality of its environment. Bacteria in the body of sea cucumbers come from the bioaccumulation of bacteria in the sediment that they exposed to through the process of absorption of sediments as a deposit feeder. To inhibit bacterial growth in the body, sea cucumbers release bioactive compounds as antibacterial. The purpose of the study is to determine the effectiveness of sea cucumber inhibition ability of sea cucumber H. atra as an antibacterial in the waters of Karimunjawa. A total of 15 individual sea cucumbers were taken from the waters of Menjangan Besar and 20 individuals from the Alang-alang waters, then cleaned and dissected to take the part of the body wall. The body wall samples obtained from each observation station was as much as 1 kg, which was then sliced into small pieces and preserved in 96% ethanol, and and the bioactive compound was extracted by maceration method. Antibacterial activity test was carried out by disc diffusion method on paper discs (10mm) and using the media of EMBA (Ethylene Methyl Blue Agar) (Merck) for E. coli bacteria and BPA (Baird Parker Agar) for S. aureus bacteria. The obtained antibacterial test results were based on the measurements of the formed clear zone diameter, so that it can be known the effectiveness status of the antibacterial sea cucumbers of each observation station. The results of the study show that the antibacterial effectiveness of sea cucumber H. atra in the Menjangan Besar waters is higher than in the Alang-alang waters. The increase of sea cucumber bioactive compounds in the waters of Menjangan Besar shows that the waters are suitable for the development zone of sea cucumber cultivation Keywords: Bacteria, bioactive compound, Holothuria atra, Karimunjawa INTRODUCTION Menjangan Besar waters are included in the Karimunjawa National Park, Central Java Province, Indonesia. Based on the decision of the General Directorate of Forest Protection and Nature Conservation, No. SK.79/IV/Set-3/2005, the Menjangan Besar waters are included in the tourism and cultivation development. The Menjangan Besar waters have coral reef ecosystems and their associations, and as a suitable habitat for the survival of sea cucumbers (Sulardiono et al. 2017). In addition, the Menjangan Besar Island area is a tourist destination with various activities, including floating hotels, fish cage and sea transportation supporting tourism activities. The increasing intensity of activities in the Menjangan Besar waters has caused an increase in domestic waste so that the aquatic environment becomes vulnerable to pollution. On the other hand, from 2013 to 2016, the waters of Menjangan Besar have experienced a decline in coral reef ecosystems as a habitat of 7.92 ha (Januardi et al. 2016). Furthermore, Sulardiono et al. (2018), informs that the status of the Menjangan Besar water is included in the oligotropic category. Based on this, it is thought to influence the pattern of dynamics of sea cucumber life in the habitat of coral reef ecosystems. Furthermore, Sulardiono et al. (2017) informs that the fertility status of the Menjangan Besar waters is oligotropic category, which means that the water fertility conditions are low to medium. Based on this, it is alleged that it will influence the pattern of the dynamics of sea cucumber life in the habitat of coral reef ecosystems in the waters of Menjangan Besar. Sea cucumber H. atra which is then termed H. atra is a type of sea cucumber (Echinodermata: Holothurians) that is able to cope with extreme shallow aquatic environments. H atra sea cucumber likes habitats with various types of substrates and can adapt to sand and fine sandy habitats to maintain heat by coating themselves with fine sand on their entire body (Azis 1995). Dissanayake and Stefansson (2012) state that H. atra sea cucumbers live predominantly in shallow seagrass beds with a depth of 10 m, and the more towards the deeper sea, the H. atra density decreases. Marine biota is a source of bioactive compounds having diverse functions in nature, including anti-bacterial activity (Farjami et al, 2015) and one type of marine biota containing bioactive compounds is H. atra sea cucumber (Lawrence et al. 2009). The same thing is said by Mayer et al., (2013) that marine biota (including sea cucumber) contains bioactive compounds which have a variety of functions, one of which is as an anti-bacterial. The study of bioactive compounds from sea cucumbers is usually widely