Identification of Tunicates-associated bacteria (Class: Ascidiacea) from Karimunjawa islands with plastic-degrading activity

The Karimunjawa Islands, one of Indonesia’s marine conservation areas, face ongoing challenges to their natural diversity due to marine debris, predominantly composed of plastic The aim of this research are: i) To identify candidate symbiotic microorganisms from ascidians collected from Geleang Island and Menjangan Besar Island that have the potential to degrade plastic. ii)To determine the percentage of plastic-degrading activity from ascidian-associated bacteria. ii) To identify the species of bacteria associated with ascidians that exhibit the highest percentage of plastic-degrading activity. This research employed a descriptive exploratory approach combined with laboratory experiments conducted over a 30-day period at a constant temperature of 27 °C, using sterile media+LDPE plastic without bacteria as a control variable. Molecular identification was performed targeting the 16S rRNA gene.This research conducted during July - November 2024. Purification using spread plate method and isolation using streak plate method. The results obtained that there were 39 bacterial isolates from 7 different Ascidian species. Low Density Polyethylene (LDPE) plastic degradation test by bacteria carried out using weight reduction method. Based on the results of the plastic degradation tests, five bacterial isolates demonstrated the highest plastic degradation activity. The bacterial isolate with the highest degradation rate was coded KJ11-10 (-4)/5 , achieving a degradation percentage of 71.19%. Molecular identification using the PCR method revealed that this isolate shares 99.37% similarity with the bacterial species Vibrio fortis .