Assessment of Seagrass Distribution in Dugong Grazing Areas of Pujada Bay, Mati City, Philippines

Abstract

The study was conducted to assist and map the distribution of seagrass in dugong grazing areas of Pujada Bay, Mati City, Davao Oriental, and determine the seagrass composition, percent cover, shoot density, and relative abundance within the dugong grazing areas of Pujada Bay. Conducted from December 2016 to January 2017, it also examined environmental parameters and identified anthropogenic threats. Data on management interventions were gathered from ICRMP secondary sources. Three dugong grazing sites were studied: Taganilao (Station 1), Pujada Island (Station 2), and Lawigan (Station 3). Using aerial surveys, manta tow, and transect quadrat methods, five seagrass species were identified: Thalassia hemprichii, Syringodium isoetifolium, Halophila ovalis, Cymodocea rotundata, and Enhalus acoroides. Of these, Halophila ovalis was the only confirmed food source for dugongs. Thalassia hemprichii had the highest shoot density (3,890/m²) and relative abundance (40.62%), followed by Syringodium isoetifolium (3,451/m²; 36.03%). Cymodocea rotundata and Halophila ovalis had lower densities and abundances at 1,798/m² (18.78%) and 429/m² (4.48%), respectively. Enhalus acoroides showed the lowest values, with 9/m² and 0.09%. Environmental factors such as pH, salinity, and water depth, along with human activities like siltation, destructive fishing, and land conversion, were found to negatively impact seagrass growth. These findings highlight the need for conservation strategies to protect seagrass meadows and dugong habitats in Pujada Bay.