Giant barrel sponge

Photo: Albert Kok · CC BY-SA

Often called the 'redwoods of the reef,' barrel sponges at Japanese Gardens reach over a metre in diameter and are estimated to be several hundred years old. They filter hundreds of litres of seawater per hour, cycling nutrients and supporting a microscopic community of bacteria, shrimp, and small fish within their chambers. Their orange-brown colouring comes from symbiotic cyanobacteria living in the sponge tissue.