Elephant ear sponge

Photo: Dan Schofield · CC BY

Elephant ear sponges form enormous, flat, purple-brown vase structures up to 1.5 metres across that drape the gun turrets and railings of the Tibbetts in dramatic swooping sheets. As filter feeders they process thousands of litres of water daily, removing bacteria and particulate organic matter, and harbour communities of brittle stars, shrimp, and blennies within their rough-textured outer surfaces. Their vivid colouration comes from symbiotic cyanobacteria and chemical defence compounds that make them unpalatable to most reef herbivores.