Neil C. Capin, Brian L. Pototan, Aileen Grace D. Delima, and Annabelle U. Novero* Department of Biological Sciences and Environmental Studies College of Science and Mathematics, University of the Philippines Mindanao Mintal, Tugbok District, Davao City 8022 Philippines Distribution and Abundance of Seagrasses in the Southwest Coast of Davao Oriental, Philippines Keywords: Cymodocea rotundata, Davao Oriental, diversity, seagrass cover, seagrass management, Thalassia hemprichii Seagrasses are an important coastal resource that serves as homes and breeding grounds of fishes and other marine organisms and are useful indicators for the detection of changes in the coastal environment since they are vulnerable to bio-physical stressors. This study assessed the seagrass resources in terms of composition, percent cover, community similarity, and diversity in four municipalities (Banaybanay, Governor Generoso, Lupon, and San Isidro) situated in the southwest coast of Davao Oriental province facing Davao Gulf. Thirty-six (36) transects, each with ten quadrats arranged in an alternate manner, were laid perpendicular to shore yielding a total of 360 plots. A total of eight seagrass species were observed: Cymodocea rotundata, Enhalus acoroides, Halodule pinifolia, Halophila minor, Halophila ovalis, Halophila spinulosa, Syringodium isoetifolium, and Thalassia hemprichii. Governor Generoso (33.77%) and San Isidro (26.01%) were classified to have fair seagrass bed conditions while Banaybanay (24.31%) and Lupon with the lowest coverage (15.90%) had poor status. T. hemprichii dominated the seagrass community in Banaybanay and Governor Generoso while C. rotundata were dominant in Lupon and San Isidro. The two most abundant species, T. hemprichii (41%) and C. rotundata (34.48%), had fair coverage comprising 75% of the entire seagrass while the remaining 25% cover was shared by Enhalus acoroides (19%) and other five species with very poor cover (0.30–2.43%). Diversity analysis using percent cover data revealed low diversity with overall Shannon index, H’= 1.2955, evenness J = 0.6657, and Simpson’s index of diversity, D = 0.3577. Dice community of coefficient grouped Banaybanay, Governor Generoso, and San Isidro together, indicating high similarities while separating Lupon, which had the poorest seagrass condition in terms of coverage. The status of seagrass diversity on the southwest coast of Davao Oriental calls for immediate attention and effective strategies to alleviate poor conditions and protect the seagrass beds. *Corresponding Author: aunovero@up.edu.ph INTRODUCTION Seagrasses are flowering plants that usually grow best in high-reducing sediments of shallow tropical and subtropical locations in coastal communities, serving as an ecotone between a mangrove forest and coral reefs as well as a home of many marine organisms (Fortes 2013). Seagrasses serve as breeding and nursery grounds for fishes and other marine organisms (Noel et al. 2012; Jumawan et al. 2015). They are also an important food source for sea cows (“dugong”) and sea turtles (Alcala 383 Philippine Journal of Science 150 (S1): 383-394, Special Issue on Biodiversity ISSN 0031 - 7683 Date Received: 20 Aug 2020