Barrel Sponge

Photo: Albert Kok · CC BY-SA

Barrel sponges of extraordinary size grow from Flagstaff Wall's face at depths between 20 and 45 metres, some reaching 1.5 metres in diameter and representing decades of filter-feeding growth in the nutrient-rich upwelling water around the island. These are ecosystem engineers that filter vast quantities of seawater, cycling dissolved organic matter into particulate form that feeds the benthic communities around them. Their chambers host resident clingfish, shrimp, and small gobies that are perfectly camouflaged against the sponge's internal walls.