Herbivory by Dugong dugon on seagrasses
1998
Uri, J.S. | Trono, G.C. Jr | Yaptinchay, A.S.P. | Trono, R. (Philippines Univ. Diliman, Diliman, Quezon City (Philippines). Marine Science Inst.)
The seagrass bed in Dimakya Island (Busuanga, Palawan [Philippines]) is a known feeding ground for the dugong (Dugong dugon). It supports a total seagrass biomass of about 5600 kg wet weight, of which 90% was produced by Halophila ovalis (R. Brown) Hooker f. The daily seagrass consumption per dugong is about 25 kg wet weight. Because of feeding trench has an average size of 2.3 sq m, a dugong has to feed off some 22 trenches daily assuming that all seagrass in the trenches are consumed. An ungrazed biomass of about 343 g wet weight per trench was observed, however, and therefore only about 71% of the seagrasses in the trench was actually lost to grazing. Hence, the daily consumption of 25 kg wet weight would require a dugong to feed off 8 more trenches (for a total of 30 trenches per dugong per day). This apparently large (seagrass) consumption by the dugong does not pose any threat to any seagrass bed, however, since dugongs are known to use several feeding areas at a time. Certainly, this points to a close coupling between the feeding behavior of the dugong and seagrass growth dynamics and distribution. Moreover, an estimated horizontal rhizome growth of 2.5 cm at the apex per week for H. ovalis suggests a recovery rate of one week per trench. The results of further study on this topic will be used in the formulation of management scheme directed to protect the dugong and its feeding habitat
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