The Red Beard Sponge (Clathria prolifera = Microciona p. in older literature) starts growing as a an encrusting sponge on hard surfaces in marine and estuarine environments. In the lower intertidal, it develops sprawling lobes, and in the in the subtidal, it develops intricately branching bush-like colonies up to more than 200 mm, orange-brown to bright red. It grows on rocks, pilings, shellfish, shipwrecks, and boat and ship hulls. It tolerates salinities down to 15 PSU. Clathria prolifera is native from Prince Edward Island to Texas on the East Coast. It was introduced to San Francisco before 1950, where it is widespread. It was found in Willapa Bay Washington in 1967. and Humboldt Bay, California, in 2000. This sponge is conspicuous for its size and color, and provides habitat for many other invertebrates. It was probably introduced with transplanted Eastern Oysters, or in hull fouling.