Note: This was originally October 7, 2013. I made minor edits August 13, 2017
In previous posts, Eelgrass in the Wrack and Turkish Towel, I’ve written about plants and marine algae that commonly wash up on sandy beaches even though they live elsewhere. Rockweed, Fucus, is another example. Rockweed normally lives attached to rocky intertidal substrates (they don’t call it rockweed for nothing) in habitats ranging from estuaries to the open coast. The photo above shows what a clump of rockweed looks like it looks like when it’s freshly deposited on the beach. If you care about such things, I think all the images here are Fucus distichus. You’ll sometimes see it treated as Fucus gardneri.
In sheltered settings , as in the above photo, rockweed can form a profuse carpet of summer growth, a condition it rarely achieves on the surf-swept rocks of the exposed outer shores.
Above, rockweed is shown submerged at high tide. Note the periwinkles, small snails, in the lower left-hand corner. Fucus is a favorite food of periwinkles, so they are frequently found together.
Above is an exposed clump of Fucus at low tide. The expanded branch tips are where the reproductive structures reside. These hollow expanded regions are responsible for rockweed’s other common names, bladderwrack and popping weed. If you want to learn more about Fucus gardneri, checkout the accounts in Seaweeds and Seagrasses Between the Capes and Seaweeds of Alaska.