Microplastic abundance in the water, seagrass, and sea hare Dolabella auricularia in Pramuka Island, Seribu Islands, Jakarta Bay, Indonesia

Abstract This research focused on the amount of abundance of microplastics in the sea hare Dolabella auricularia as well as the seagrass fields along the southern coast of Pramuka Island. Sampling of 8 individuals of Dolabella auricularia along with seagrass Cymodocea rotundata leafblades was done at the southern coast of Pramuka Island, after which the samples were preserved and brought to a laboratorium in Depok for microplastic analysis. The sea hares’ digestive tracts were extracted and dissolved in strong nitric acid. A 1 cm 2 portion of a seagrass leaf blade was cut for observation. Prepared samples were observed under a monocular microscope and further analysis was done. Microplastic fibers and film particles were found in highest abundance within the digestive tracts of each sample of Dolabella auricularia as well as on the seagrass surface where the sea hare obtains its algae from, with fragment particles found in much lower amounts. Overall, number of microplastics was found between 40.1 to 73.7 particles/g weight of sea hare digestive tract and the estimated amount of microplastic found at seagrass leafblade was 185 particles/cm 2 . Results provide evidence that microplastics in the ocean brought by water currents could adsorb on to algae through which it enters the food chain as it is consumed by marine biota.