Intertidal Invertebrates of the Monterey Bay Area, California

Compiled & photographed by Gary McDonald, Long Marine Laboratory, University of California, Santa Cruz

Description: This sponge forms a thin encrustation, up to 1mm thick on rocks in the low intertidal, usually under ledges or on underside of rocks. The deep blue color easily distinguishes this sponge from other sponges in the intertidal.
Notes: The blue color is caused by a symbiotic blue-green alga; when the alga is absent, the sponge is light orange in color. Relatively uncommon in the intertidal in Monterey Bay area.