Focusing on the Details: Thatched Barnacles

Dropping down on a new reach of shore is disorienting enough that it takes a while to shake it off. It’s not unusual to arrive with questions about how and where to proceed. (Most of these, with a bit of planning, can be answered in advance). Once I’m on a new shore, all preparation seems to fly away, leaving me feeling a bit lost at first. And so it was when I dropped, for the first time, down upon this spine of intertidal rocks.

It’s no place for tide pools. But compared to the surrounding shifting sands, rocks are a haven, and intertidal life is plentiful. Much of marine biodiversity—and the intertidal varieties are no different—are compellingly alien, so despite any initial confusion, you almost can’t help but focus on the details after a little acclimation. Playing along with the orientation and acclimation themes, the image below features the higher intertidal zones and higher. In the lower left-hand corner is the upper boundary of the mussel bed. The bed is recognizable as a blackish band fanning out to the right. Large lighter-colored barnacles prevalent in its upper portion and just above are thatched barnacles. Above them, a scattering of smaller acorn barnacles. Higher, above the highest acorn barnacles, the seemingly unoccupied ground gets spray from the sea, the occasional splash, and only a rare dunking. (If you’re imagining along, sand, noticeable in the lower right-hand corner, surrounds the backside of the outcrop; it’s your footing from this vantage. The upper mussel bed is about chest high on a six-foot-tall person.)


Close up in the mussel bed, an alcove appears to have been a place of safety. The thatched barnacles, Semibalanus cariosus, within are large, and their shells are eroded, indicating old age, I imagine, by barnacle standards. There is intimacy here too. It’s a community crowded together. Within and around the barnacle patch are aggregating green anemones, Anthopleura elegantissima. They adorn their exterior surfaces with shell fragments. Looming behind, dark mussels, Mytilus californianus. And now that we’re down to details, I don’t mind mentioning the portion of a dogwinkle shell (you’ll notice the diagonal stripes) down at the bottom right-hand corner. That’s Nucella ostrina. (For fans of Nucella, there is another nestled within the barnacle patch.)

Focusing on the details