Life Between Rock and Sea

On the very edge of the land, washed and abandoned in turn by the tides, is a world teeming with life. It’s a place of strange and alien beauty, life-and-death struggles, and strange alliances. Come with me now to the tidepools in the fourth of my week-long series about the West Coast of Vancouver Island!

I’ve been illustrating this world for some years now, for a series of books by author Gloria Snively. We did a colouring book about tidepools some time ago (still available from Kingfisher Press) and continued with a couple of storybooks that are due to come out soon (and you can pre-order them!). You can see some of those illustrations here, which is a perfect lead-in to this post — because it’s about the critters that populated my drawings and paintings for these projects.

When I first started working with Gloria, I started viewing my trips to the beaches as research — I was learning as I went about the life of the coast, and to be able to see it close up and point my camera at it was my idea of heaven. These days I rarely get a photo of a subject I haven’t already got, but I keep taking pictures anyway, eagerly downloading them when I get home so I can pore over them in minute detail, looking for things my eyes might have missed at the time in these complex environments. Many of these photos are from my recent trip, but I’ve filled in for the sake of the storytelling with some from past trips.

Incinerator rock tidepool.JPG

Tidepools can wildly vary as habitats; tiny pools left high above the tide, like the one above at Incinerator Rock, or lush and spacious and washed more generously by the tides, being farther down on the beach, as the one below (photographed a few years ago at Half Moon Bay). There are tidepools at Botanical Beach, near Port Renfrew, which are ten foot deep potholes, like permanent little cities full of an incredible variety of sea life. The higher and smaller they are, the more vulnerable they are to dilution by rainwater, which is harmful to many salt-water organisms. And all of them are vulnerable to spills of man-made pollution, even the sunscreen on people’s hands or feet.

Surf grass tidepool.JPG

You have to learn to be still to see things in tidepools. What may look like a boring patch of still water full of beach detritus at first glance will slowly unfold its wonders to the patient watcher. First you’ll see random motion — maybe a tiny sculpin swishing its tail, or a shell containing a hermit crab bobbing along. The deeper you look the more you’ll see.

Here are some of the things you might encounter:

Anthopleura elegantissima.JPG

It’s not a flower, it’s an animal — it’s Anthopleura elegantissima  —isn’t that a lovely name? On of its many common names is the pink-tipped green anemone — this particular one isn’t that green, but some have more of the algae symbiont that allow them to take on that colour. They’re also called the clonal anemone, because they form clone colonies by splitting, though they can also reproduce sexually. But woe betide the clone that runs up against a neighbouring clone — they will wage war for territory with special stinging tentacles!

Anthopleura elegantissima 2.jpg

Elegantissima isn’t so elegant when the water recedes — it, like other sea anemones, becomes a rather unappealing brown donut covered in seashell bits — the remains of its previous dinners.

Green Anemones 2.jpg

Often sharing space in larger tidepools with Elegantissima is the Green Surf Anemone, or Giant Green Anemone (Anthropleura xanthogrammica — I’m not going to give you all the Latin names, but had this one handy). Same situation applies here with the algae symbiont.

goose barnacles.JPG

In rocky places, usually where there is good motion of the water, live intertidal goose barnacles. These guys have a long stalked neck, and really cool feathery feet (cirri) which they stick out to waft food into their “mouths”. I found the ones above on Incinerator Rock; there weren’t as many of them this year as I’ve seen in previous years. There were a lot of people clambering over the rocks, heedless of the damage they were doing to the poor barnacles, and I suspect this may be part of the reason.

Goose Barnacles on Mussel.JPG

Here’s a photo I took a few years ago of some luckless goose barnacles that had made their home on a large mussel shell, which shows their necks. When the mussel died, or was swept away from its anchors, the barnacles had to go along for the ride, and they ended up on the beach; a dry and sunny fate awaited them, and possibly being a snack for a seagull.

pelagic gooseneck barnacles.jpg

Another kind of goose barnacle, more rarely seen, is the pelagic goose barnacle. It attaches itself to such nautical things as ships, piers, and pilings, as well as seaweed (in this case, a bull kelp), and in one case, a crocodile. This unfortunate little colony was washed up a couple of years ago onto Long Beach. To get an idea of their size, the bull kelp to which they are attached was around 6-7 cm (2.5 in).

While we’re on the subject of barnacles, how about those familiar little volcano shaped ones?


Barnacles are so common on the rocky shores that I started calling them “beach furniture” — whenever I did a tidepool picture, it had to have barnacles in it, because there is a type for every depth of water. From the Small Acorn Barnacle living in the high spray zones to the Crenate Barnacle living as deep as 180 metres (600 ft), they’re ubiquitous! Their cone-shaped shells range in size from less than a centimetre (Small Acorn Barnacle) to 15 cm (6 in) across (Giant Acorn Barnacle)! They might look like some relation of molluscs, but they are actually crustaceans, which start out as free swimming larvae.  When it’s ready to graduate from plankton-hood, the young barnacle glues itself (its head, actually) to its chosen location of a hard surface, and builds a shell around itself, then, like the gooseneck barnacles, gathers food to itself with its feet.

In the photo above, you can see some empty barnacle shells, and some living ones with the trapdoor shut to keep in moisture while awaiting the tide’s return, with its bounty of microscopic food. There are also some pretty, tiny purple snails — you might miss them if you don’t look closely — those are Checkered Periwinkles, which live in the splash zone, venturing into tidepools for food. They can actually drown if underwater for too long!

Turban shells.JPG

Another pretty purple snail is the Black Turban, its shell a favourite prize when empty for hermit crabs. The tops are almost always eroded like this, exposing shiny mother-of-pearl underneath. Don’t they look lovely with that olive-green rockweed?

Mussel colony.jpg

I came upon this lush scene in the rocks at the Wickaninnish end of the beach — but it’s a common sight everywhere. Mussel beds are a haven for smaller creatures and seaweed; the mussels’ strong anchor (byssus) strands (you can see them here, looking like fine threads) allow them to cling to each other as well as the rocks. Several different kinds of barnacles can be seen here making the most of a nice, stable penthouse perch on a mussel condo.

Mussel condo.jpg

But sometimes… your real estate washes away.

Ochre Stars.JPG

And of course, there’s that darling (and terror, if you happen to be a mussel) of the west coast tidepool, the Ochre Sea Star — which paradoxically is just as often purple as ochre. In the last few years, they and other sea stars on the coast have been suffering from a wasting disease. I saw many afflicted with it two years ago (this photo was taken in 2011, when they were healthy and plentiful), and it was horrible to witness. This year, in areas that had once been teeming with them, I found just one, tucked so far under a ledge I couldn’t get a good photo. But word is that the populations are recovering, though the huge Sunflower Stars are lagging behind. In the meantime, the mussels have been having a heyday. Look out mussels, the overlords are back!

So there’s a taste of the tidepool — and I’ve barely scratched the surface of what one might find in the pools and washed up on the beach. Stay tuned for more!

Tomorrow: All Washed Up — on the Sand

My go-to reference for identifying species I wasn’t sure of for this article was Marine Life of the Pacific Northwest — I recommend it highly! — and check out the links to Wikipedia, the Monterey Aquarium, and iNaturalist that I’ve provided to learn more about these fascinating critters.

2 responses to “Life Between Rock and Sea

  1. Pingback: An Aquarium Photo Safari | Karen Gillmore Art·

  2. Pingback: The Wild Pacific Trail | Karen Gillmore Art·

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