Ecological Assessment of Thalassia hemprichii as a Food Source fbr Toxopneustes chlorocanthus in Paniquian Island, Puerto Galera, Oriental Mindoro

Abstract

Seagrass beds have served as nursery grounds and suitable habitats for many marine organisms. Specifically, the leaves have provided a good source of food and nutrition for marine organisms. Sea urchin herbivory on seagrasses had already been demonstrated to cause reductions in the biomass of seagrasses. This present study investigated the amount and rate of reduction in the biomass of Thalassia hemprichii in a grazing set-up, conducted over a period of one week in Paniquian Island, Puerto Galera, Oriental Mindoro. Comparisons of biomass reductions and grazing rates were made between two varying stocking set-ups of sea urchins. Single-grazer set-up (SGSU): 1 grazer/cage or 11 grazers/m2, and multiple-grazer set-up (MGSU): 2 grazers/cage or 22 grazers/m2, were established in cages, 0.3m x 0.3 m x 0.3 m dimensions. Also observed were the grazing behavior of the sea urchins and the influence that their behaviors have had on the amount and rate of seagrass biomass reduction. Results showed that at 0.05 level of significance, there was no significant difference between biomass reductions of Thalassia hemprichii, but that there was significant difference between grazing rates of Toxopneustes chlorocanthus. The averaged values from the three replicates, for each stocking set-up, showed higher biomass reduction and grazing rate values for SGSU than for MGSU. The study demonstrated that grazing behavior of the sea urchins, Toxopneustes chlorocanthus had influenced the grazing capacities of these organisms.