_:b1218241 . _:b1218241 "PLB:plb"^^ . _:b1218241 "Wikipedia:Sponge_reef"^^ . _:b1218241 "The marine sponge reef biome comprises marine reefs primarily built by marine sponges. The primary frame-building sponges are all members of the order Hexactinosa. They are found only in glacier-scoured troughs of low-angle continental shelf. The seafloor is stable and consists of rock, coarse gravel, and large boulders."^^ . _:b1218241 . _:b1218241 .