Black Tassel Seaweed
Scientific Name: Odonthalia floccosa
Category: other
Brief Description
A complex, branching red alga that often appears dark purple to black, commonly found in the intertidal zones of the Pacific Northwest.
Characteristics
Forms dense, bushy tufts of dark brownish-purple to black fronds. The branches are finely divided and cylindrical, often appearing feathery or tasseled. It can reach lengths of 10-40 cm.
Habitat
Attached to rocks in the mid-to-low intertidal zones and upper subtidal areas of wave-exposed or semi-exposed rocky shores.
When to Find It
Perennial; most visible and lush during the spring and summer months, though present year-round.
Conservation Status
Not Evaluated / Common
Ecological Role
Provides critical habitat and primary productivity for small marine invertebrates like amphipods, snails, and crabs. It serves as a nursery area for various tidepool organisms.
Easily Confused With
Polysiphonia species (usually smaller and more delicate) or Neorhodomela larix (Sea Brush), which has coarser, stouter branches arranged in a spiraled pattern around a central axis.
Observation Tips
Look for dense, dark clusters hanging from rocks during low tide on rocky Washington beaches. Be careful as the rocks can be very slippery; never turn your back on the ocean.
Interesting Facts
Despite its dark, almost black appearance when out of water, it belongs to the Rhodophyta (red algae) phylum. The dark pigments help the seaweed absorb light even when submerged in deeper or murky coastal waters.
User Notes
Washington state beach