Notes on the distribution, ecology and open sea mariculture trials of the Philippine blue sponge, Xestospongia sp. (Porifera)

Abstract The Philippine blue sponge,  Xestospongia  sp., is a potential source of natural products for pharmaceutical use. However, knowledge on different aspects of its biology and ecology is still lacking, and improvement on biomass production through mariculture is still needed. In this study, we conducted ecological surveys and open sea mariculture trials of the Philippine blue sponge. The ecological surveys conducted were abundance and size–frequency surveys, as well as monitoring of wild blue sponge colonies. Mariculture trials were done by monitoring explant health and survival using different farming methods and consistent observation of various factors (i.e., predation, biofouling, maintenance effort, presence of disease). We also compared growth rates of explants and wild colonies. Colonies were highly abundant, and all size classes were wellrepresented in stations characterised by previous studies to have low water movement and high nutrient levels. These pieces of information were critical in selecting the sites for establishing mariculture setups. We additionally demonstrated the survival and growth of explants using artificial substrates made of polyvinyl chloride pipes. Several factors affecting sponge survival and health included predation, biofouling, habitat, and maintenance effort. We observed a higher growth rate of sponge explants compared with wild colonies. This study provides novel information on the ecology of the Philippine blue sponge and highlights the process of establishing an open sea mariculture setup for biomass production, which can potentially lead to increased production of biomedically important chemicals.