There is also a reef formed of siliceous Demospongiae species off of Axel Heiberg Island in the Arctic Ocean.

Four hexactinellid reefs were discovered in the Queen Charlotte Basin (QCB) in 1987-1988. Three more reefs were reported in the Georgia Basin (GB) in 2005. The QCB reefs are found 70-80 km from the coastline in water 165-240 m deep. These reefs cover over 700 km² of the ocean floor.

Sponge reefs require unique conditions,

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