Orange Encrusting Sponge

Photo: Matthieu Gauvain · CC BY-NC

Vivid orange mats coat the cave walls wherever direct light fades, thriving in the dim photic zone that excludes algae but suits filter feeders. These chemically defended sponges release toxins that deter most grazers, allowing them to claim large surface areas in low-competition cave environments. They serve as habitat structure for tiny invertebrates and provide colour contrast that makes the cave walls visually dramatic.