Yellow sponge

Aplysina aerophoba is a vivid yellow tube sponge that carpets the cave walls and overhangs at Neptune's Grotto, forming the visual backdrop that makes the site so photogenic. It is a filter feeder that processes large volumes of water to extract bacteria and dissolved organic matter, playing a key role in nutrient cycling. The sponge contains bioactive secondary metabolites (aplysinamisin group) that are under ongoing pharmaceutical research.