Sea Brush (South Sound Marine Life)

November 5, 2007 

Sea Brush (Odonthalia floccosa)

This red algae usually is found in rocky, low intertidal and shallow subtidal areas with moderate wave action or strong currents. It and several other similar species occur throughout the northeastern Pacific Ocean shoreline from Alaska to central California. They are characterized by a dark red color, brushy appearance and branchlets that are pointed, but are difficult to tell apart. They range in size from a few inches to 20 inches tall. The clump of sea brush in the photograph is about 12 inches high.

The plant is a perennial, living for more than four years. Usually the blades die back to basal branches in the fall from which the plant is regenerated in the spring.

Because of its proliferation of branches and branchlets, the sea brush offers shelter for a variety of animals and small plants. Lift the mass of seaweed at low tide and you will usually find several animals, including zooplankton, using the moisture held by the sea brush to survive. A 1998 study at the University of Washington showed that usually diatoms (colonial, single celled plants) attach to the branches in late summer as the plant stops its growth and reproduction. If the bloom occurs earlier, it can affect the health and reproductive success of the sea brush.

(Thanks to Tom Mumford, seaweed scientist with the state Department of Natural Resources, for confirmation of the identity of this species.)

David W. Jamison is a marine biologist and Boston Harbor resident.

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