Today's photograph and write-up are courtesy of BPotD work-study student Bryant DeRoy. He writes:
This photo was taken on the western side of Catalina Island in California. The predominant species here is Egregia menziesii (aka feather boa), a member of the Alariaceae. Its common name refers to the rather obvious resemblance of this species' rachis to that of a scarf. Egregia menziesii is common up and down the western coast of North America, as far north as Alaska and as far south as Baja California. It is an intertidal/subtidal species that thrives in rocky shoreline environments, sometimes growing to depths of 20m (65ft).
Watching this species get thrashed around in the surf, and knowing that it can survive long (often hot and dry) periods out of water really makes one appreciate the hardiness of this macroalgae. There is an excellent article by the Monterey Bay Aquarium Research Institute that describes just how strong Egregia menziesii is and how the curling action seen in the image above may actually reduce wave stress on the holdfast (or base). For more detailed information on the mechanics of intertidal algae, see the 2002 paper by Mark Denny and Brian Gaylord: The Mechanics of Wave-swept Algae in The Journal of Experimental Biology (205:1355-1362).
If this name sounds familiar, it might be because Egregia menziesii has previously been featured on BPotD. For more information on this species, as well as some detailed images of its morphology as seen from dry land, visit the earlier BPotD post.