As a marine ecologist and nature superfan, exploring natural beaches is one of my greatest joys. Experiencing natural beaches affords us the opportunity to not only think about connections and processes at different scales, but about the period of time over which beaches have been developing since the end of the last ice age. Yet, many Salish Sea beaches aren’t entirely natural anymore. While infrastructure does change shoreline ecosystems, it can provide a focused window into the complexities of making a home between the tides. One relatively common and accessible group of structures to explore on a low tide are pilings, the tall pieces of tree or metal or concrete that have long supported our desire to extend our lives and activities from our terrestrial constraints out over the water.

photo by John F. Williams

The sea life near the top of the piling high rise, where the water reaches highest, spend much of their time out of the water and have to be able to survive the physical pressures of being high and dry or blasted by sun, heat, cold, rain, or whatever the above world can throw at them. They may also have to be able to survive on infrequent meals. For instance, a plankton eater can only eat when covered in water, and animals at upper edges of the tide may only be under water briefly each day or even less than daily. Upshots of living near the top of the high rise are less competition for space and potentially less predation. Lots of marine predators, like sea stars, won’t have enough time to eat you when the water is in or simply won’t go higher than the floors on which they’re safe from exposure.

One photo shows plumose anemones hanging when the tide is out, the other shows plumose anemones when they are submerged.

Acorn (larger) and little brown barnacles. 

Barnacles are a prominent part of the piling community and a good example of the responses we’ve been exploring here. A tiny barnacle, with an oval opening and smaller than a pea, mixes with but generally lives higher than the others and is called the little brown barnacle. In the middle and lower floors, you find the well-known, marble-sized acorn barnacle, with its diamond-shaped opening. In the lower floors, you also find the thatched or haystack barnacle, our second largest, that can grow as big as a tennis ball.

Thatched or haystack barnacles. The second second largest species in the Salish Sea, after the giant barnacle, which is mostly found below the lowest tides. 

Acorn barnacles growing densely, stretching up instead of out. 

While usually situated a bit lower than the animals, the seaweeds can also occupy different floors of the piling apartment. Often red and green seaweeds will inhabit the middle floors, and the more sensitive brown kelps dwell near the lowest tides where they’re exposed to the elements less often. These patterns are similar to the tidal zones you can see stretched from top to bottom of a beach, but just concentrated in a small, vertical space on a piling. Some pilings have very few seaweeds or only small ones hanging out in cracks and crevices. Really small algae, called diatoms, occupy surfaces of pilings and may even be farmed by limpets that keep their little territories free of barnacles so they can scoot around and dine on diatoms.

So many interactions in such an observable space! Explore pilings next time you’re near a pier or on a dock at low tide, or in a place where pilings are the relics of some past structure. Fewer and farther between, glacial erratics provide a similar experience on a more natural substrate. Look slowly, closely, and curiously, imagining what interactions and pressures the sea life you observe may be adapted to and living under.  Whether you step back and look across all Salish Sea beaches, consider a single place, ponder a particular habitat, focus on a specific rock, or identify an individual organism, these complexities come into play at all scales. Take a moment or many and wonder at all this ecological connectedness. (Breathe deeply… exhale.)

Love it.

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Thanks so much for your interest and your support.