small animals, organic particles
to 1 inch (2.5 cm)
hydroids, corals and jellyfishes; Phylum Cnidaria
British Columbia to Baja California
Corals in the cold waters along the coast of California don't build reefs like their tropical kin do. This coral does make its own outer skeleton: that cuplike limestone base underneath. A cup coral larva crawls on the rocky seafloor before settling. After cementing its limestone skeleton to a rock, the coral is set for life.
Rocky reefs are important homes for many kinds of fishes and invertebrates. But "rockhopper" trawls, used in commercial fishing, can leave reefs a tumbled wasteland, unable to recover for decades.
Reef-building corals form huge colonies, but cup corals live solitary lives, taking refuge in their individual "cups."