Sanctuary Integrated Monitoring Network
SIMoN Tools

Species Database

Acanthancora cyanocrypta - Cobalt sponge

Cobalt sponge image

Geographic range:

British Columbia, Canada to northern Mexico

Key features:

Deep blue color is unique in central California.


bay (rocky shore), exposed rocky shore, kelp forest, protected rocky shore

Primary common name:

Cobalt sponge

Synonymous name(s):

Hymenamphiastra cyanocrypta

General grouping:


ITIS code:


Geographic Range

Range Description:

BC to northern Mexico, but originally thought to range in central and southern California, from Pacific Grove to Point Loma.

Intertidal Height

Lowest intertidal height:

meters OR -2 feet

Highest intertidal height:

meters OR 0 feet

Intertidal height notes:

Low intertidal and persistent tide pools, usually covering the bottom of overhangs and in crevices.

Subtidal Depth Range

Minimum depth:

0 meters OR 0 feet

Maximum depth:

37 meters OR feet

Subtidal depth notes:

Occurs on rocky reefs in the shallow subtidal.


bay (rocky shore), exposed rocky shore, kelp forest, protected rocky shore

Habitat notes:

Grows on rocks, usually in high flow areas but protected from scour.


Relative abundance:


Species Description

General description:

Thin sheet with a deep blue color. Relatively uniform, mostly smooth although occasionally with slight ridges and folds. Excurrent openings (osculae) are infrequent and irregularly spaced. Incurrent pores not obvious.

Distinctive features:

Bright blue color distinguishes this from all other sponges.


Thin sheets have no distinct growth form, and rise only 1-2 mm above the surface.

Natural History

General natural history:

The cobalt sponge is a readily recognized and commonly observed subtidally in central California. Commonly seen in kelp forests covering crevices and vertical surfaces on a rocky reef, this sheet-like sponge is a deep blue color. It is often overgrown by other species, just as it can overgrow sessile inverts, such as tube worms and barnacles.

The deep blue coloring is due to a symbiotic cyanobacterium. Also known as blue-green algae, cyanobacteria can photosynthesize and provide nutrients as by-products, just as the sponge serves as a protective shelter for the cyanobacteria.


It is not known what, if anything, feeds on this sponge.


The cobalt sponge is a filter feeder, and as such consumes detritus and very small plankton.

Feeding behavior

Omnivore, Sessile suspension feeder

Feeding behavior notes:

In addition to the energy derived from the symbionts, the sponge is an active filter feeder, and cells generate internal currents that pull water into the sponge via thousands of tiny incurrent pores. Other cells filter the water and eventually the water is expelled via a larger osculum, which is usually visible to the naked eye.

January - December


We do not know of any seasonal behavior.
  • Big Sur Nearshore Characterization (BSNC)

    Led by MBNMS staff, research divers qualitatively characterize subtidal (<20 m deep) algae, invertebrates, and fishes along the Big Sur coast, from Point Lobos to Cambria. These data are used to complement quantitative data collected by PISCO and fill in knowledge gaps. [View Project]

Click on an image below to view a larger version in the SIMoN Photo Library. You will also be able to view important information on each photo such as photographer, date, caption and more.
Lamb, A. and B. P. Hanby. 2005. Marine life of the Pacific Northwest. Harbour Publishing. 398 p.
Morris, R.H., D.P Abbott, and E.C. Haderlie. 1980. Intertidal Invertebrates of California. Stanford University Press, Stanford, California. 690 p.