The Influence of a Red Algae-Grazing Abalone (Haliotis asinina) on the Density of Agarolytic Bacteria

Abstract

The influence of a red algae-grazing abalone, Haliotis asinina from Bolinao Pangasinan, on the density of agarolytic bacteria in seawater was studied. Three treatments were used in the experiment: treatment-I contained the abalone and algae; treatment-1I contained red algae only, and treatment-III with abalone only. The samples from the seawater were spread plated on a nutrient agar medium and were cultivated for 2 weeks. The agarolytic bacteria isolated from the water samples degraded agar and appeared as yellow-orange colonies with depressions. These motile, gram-negative bacteria appeared as long rods, ferment either lactose or sucrose, and are facultatively anaerobic. Results showed that the number of colony-forming units of agarolytic bacteria is significantly higher after 24 hours, and has a high abundance in its fecal pellets. In the second treatment with algae only, the number of colony-forming units of agarolytic bacteria is significantly lower. Thus, the presence of an abalone, Haliotis asinina, increases the density of agarolytic bacteria in water.