Diversity and community structure of seagrass ecosystem at Menjangan Island, West Bali National Park

Abstract

Menjangan Island, an uninhabited island located within The West Bali National Park (TNBB), is a prominent marine tourism destination site in northwest Bali which features rich coastal biogenic ecosystems. This study assessed the status of seagrass beds in the northwest of Menjangan Island, as part of a student-led research expedition by HIMITEKA-IPB University. Five sampling sites were observed during August 7-11, 2023, and modified Seagrass Watch method was applied to record seagrass species, abundance, diversity, dominance, and associated biota. Four seagrass species were identified, with Cymodocea rotundata as the most abundant, followed by Thalassia hemprichii and Halophila ovalis, while Halodule pinifolia was absent in Site 2. Seagrass percent cover was considered poor with a range between 17.89% and 27.09%. Seagrass density was prominent for Cymodoceaceae (NCr= 173.58-319.39 ind/m2, NHp= 0-164 ind/m2), while two Hydrocharitacean species had lower density (NTh= 42-112 ind/m2, NHo= 37-131 ind/m2). Diverse seagrass associated biota were observed and recorded during rapid assessment, for example macroalgae, vertebrates (finfish, eel), and invertebrates (clams, sea cucumbers, worms), indicating resilient seagrass communities exist in the offshore environment of the West Bali National Park.