Crustose coralline algae    


The thick red material resembling spilled paint that covers this rock surface as well as the calcium home's of tube worms is not a coral, but a member of the red algae group.  Red algae are a large and diverse group of usually soft bodied seaweed that are quite common in Puget Sound.  Crustose coralline algae range from the intertidal zone to deep water (around 100 ft) from Alaska to Mexico.


There are numerous species of crustose coralline algae, but they can usually only be told apart based on microscopic examination.  Their growth habit ranges from a wide spread, thick covering, like the one in the photograph, to small 1 to 4 inch patches.  In addition the surface may be smooth or include knobs and plates. The color can range from whitish pink to deep purple.  They are perennial, some living for a number of years.  The cell walls contain calcium carbonate which gives them a hard texture and protects the plant tissue from grazing animals.


There is a related group of coralline red algae that are erect and branching with articulations between the hard segments (articulated coralline algae). They have a similar range but occur in shallower water.