Intriguing, isn't it? Pretty little tufts of narrow filaments at intervals along the branch.
Here's a slightly zoomed out view:
Meet Dasya binghamiae (formerly Pogonophorella californica — quite a name change!). Not only is this a fun seaweed, but this individual represents a new record for Sonoma County, and the northernmost record of this species in California!
Congratulations are due to Peter Connors for noticing a seaweed that looked "different." It was growing on the South Jetty (at the entrance to Bodega Harbor). Although it had been documented in Marin County — near the Estero de San Antonio in 1912 and in Tomales Bay in 1995 — it hadn't been observed in Sonoma County until 18 June 2015.
I am familiar with another species of Dasya from the East Coast, whose common name is Chenille Weed. I haven't seen a common name for Dasya binghamiae. How about Tufted Dasya?
Its former name, Pogonophorella, basically means "a bearer of beards," presumably for all of those little tufts. So I suppose another possible name could be Bearded Dasya. Which name do you like? Can you come up with something better?