AS I clamber out of the car for a day at the beach, it is – in typical British fashion – absolutely freezing. Most sensible people have stayed at home. But despite the conditions, I am in a joyous mood. I have come to West Runton, Norfolk, to do something I have loved ever since I was a child: go rock pooling.
Even better, I have persuaded one of the world’s foremost experts on seashells to come along with me. Author Helen Scales trained as a marine biologist and has written . There isn’t much about marine creatures she can’t tell you.
We pull on windcheaters and woolly hats. But as we stride towards the water, I worry that we won’t find anything interesting. How fascinating can life get on a cold and windy beach in England? As it turns out, I needn’t have been concerned. Rock pools are just as beguiling in real life as they are in our collective imagination, and I am about to encounter an incredible range of underappreciated species.
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What’s more, you can too. If you look closely and arm yourself with a little knowledge, there is an awful lot to appreciate about the lives in this little-understood habitat.
As we walk towards the beach, we pass a sign encouraging us to be “respectful rockpoolers”. Scales gives me a quick primer on what that means. Lift up rocks carefully and always put them back where they came from. Don’t pull animals like snails off rocks – you could hurt them. For extra points, do a quick beach clean, picking up any litter you see, before leaving.
To be a successful rock pooler, you want to investigate not just the water, but the damp nooks and crannies between rocks. “That’s when things start getting more interesting,” says Scales. “Under the rocks and among the seaweed.” I crouch down and begin looking.
Scales quickly finds our first animal. It looks like a tiny jelly sweet, the colour of a red-velvet cupcake, stuck to a dry rock. This beadlet anemone (Actinia equina) looks kind of small and forlorn to me, and I ask Scales if these animals are threatened. “No, they’re fine,” she says. “They’re pretty hardy, they’re not a species that we’re particularly worried about in terms of climate change.” In the next rock pool along, I see four more. In the water, they have a delicate fringe of tentacles and stinging cells they use to catch surprisingly large animals like crabs or fish. We watch them for a while. I put my little finger next to them in the cold water and feel one of the anemones gently suck at it.
While beadlet anemones are doing fine, climate change is having a big effect on intertidal environments. Heatwaves are one of the most striking problems. In July 2021, searing temperatures struck Canada and millions of shellfish were cooked in their shells at low tide as temperatures reached 49°C in some places. In addition, the gradual increase in average temperature is causing patterns of habitation to shift. In the Shetland Islands, north of mainland Scotland, the mix of species now includes many more warmer-water animals. These are the kinds of species that lived on the shores of mainland Scotland 40 years ago, says Scales.
Worms and thunderstones
I am beginning to get my eye in. In the next rock pool, I spot a strange structure that looks almost like a tiny, filamentous plant, the colour of sand. This is the work of the sand mason worm (Lanice conchilega), Scales explains, which sticks together sand and shell chippings into a tube that it lives in. The tubes are common, but you rarely see these worms, which live under the sand or mud, even though they can reach 30 centimetres in length and there can be thousands per square metre.
Next, we find our first shell – well, sort of. To me, it looks like a small, conical stone. When Victorian naturalists first found these, they called them thunderstones, thinking they were created by bolts of lightning. But Scales explains that it is a , the fossilised internal shell of a squid-like animal that went extinct about 65 million years ago. Belemnites are robust and fairly common on UK shores, often surviving while others get smashed by the waves. Fossil deposits sometimes have lots of them lined up in the same direction, which can tell us the direction of prevailing ancient currents. We can also analyse the chemical isotopes stored in their shells to reconstruct trends in temperature for the distant past.
Now we are really getting into it, sticking our arms into the pools and upturning rocks. We start to find a lot of molluscs. There are top shells, which are small and roughly symmetrical in shape, like a cone. There are common winkles (Littorina littorea). And there are dog whelks (Nucella lapillus), which seem to be doing exceptionally well here. “In the mollusc world, these are a top predator,” says Scales. They hunt other snails, secreting acid to weaken their shells and then using their tongue-like radula to punch through them. “They drill a hole and slurp out the insides.” We even find a crop of pink and bright-yellow dog whelk eggs under one rock.
Scales gives me a helpful rule of thumb to distinguish between all the shells. Look at the shape of the opening on their bottom. If it is more or less round, you have a herbivore (like a winkle or top shell). If it is shaped more like a comma, that is probably a predator. The little notch in the shell (the pointy end of the comma, if you like) is a space through which the predator sticks its “nose” – more properly known as its siphon – to “sniff” for prey.
Shells can also reveal the age of the animal that inhabits them. Molluscs, such as snails, have the same shell all their lives and build it by secreting calcium carbonate, which they take in from seawater. There are lines in the shells that can be read in a way that is akin to tree rings. By counting them, you can get a rough idea of how many years old the inhabitant was.
To do this properly, you cut a slice of the shell and examine it under a microscope. About a decade ago, Paul Butler, then at Bangor University in the UK, and his colleagues did this with a shell from a species of clam called the ocean quahog (Arctica islandica). They found that one clam, , had reached the ripe old age of 507, making it , excepting some colonial animals like corals.
The next thing we find is an animal I have never heard of. I turn over a rock and Scales points to what looks like a tiny, white flake about half the size of a fingernail. Peering closer, it looks much like a woodlouse. “I do like a nice chiton,” says Scales. “It’s super cute.”
Chitons are strange animals. The bodies of these molluscs are covered in a shell made of six articulated segments. If they are dislodged from a rock, they can curl up into a ball. They have also been shown to be capable of finding their way back to the same spot on the same rock at each low tide. They have “teeth” on their undersides made of a magnetic mineral called magnetite, which might be able to sense Earth’s magnetic field and perhaps help them navigate.
As if that wasn’t enough, scientists confirmed in 2015 that chitons have . These are made of aragonite, the same material as the rest of the shell, but here it is transparent. Studies have shown that they can focus light on a retina containing about 100 light-sensitive cells and so form simple images. “With eyes dotted all over their back, they have a good field of vision, even if the images are grainy,” says Scales.
We decide to make our way up the beach, further towards the high-tide line. We come across some bryozoans, a class of tiny animals, each only half a millimetre or so long, that cluster in colonies of all shapes and sizes. Here, colonies have formed branching structures that seem very much like seaweed. But looking closely at the surface, we find pinprick-like pores, where each individual animal, called a zooid, lives. If you want to work out if a find is seaweed or bryozoans, look for those holes.
I am listening to some skylarks when Scales takes a sharp intake of breath and says: “Ah, no! Wow!” A pause. “I’ve never seen that before – this is amazing.” I quickly walk over. She is crouching over the remains of a creature that looks like a giant seahorse or perhaps a strange species of snake. It is almost as long as my arm and incredibly beautiful. Its body is striped green and black, but it reflects daylight in all sorts of other colours, too. I have no idea what I am looking at, but Scales says it is a pipefish.
“It’s a big one,” she says. “I think it’s a greater pipefish.” Like seahorses, the males carry and care for the young. We think seahorses evolved from a pipefish ancestor about 45 million years ago. “Imagine this pipefish upright in the seagrass,” says Scales, “its head bent over so it could see in front of it and its tail curled round the grass so it could hold on.” Hey presto, you’ve got yourself a seahorse. Like seahorses, pipefish are quite poor swimmers because they only use a small dorsal fin for propulsion. This means they often live in the shallow waters that are easily affected by pollution, so they are threatened. It also means they are sometimes washed up onto the beach after storms.
By this point, I have lost all feeling in my fingers, but, boy, the cold has been worth it. As we are making our way off the beach, Scales talks about how we are bombarded with bad news and worries about the environment these days, what with the dual crises of climate change and biodiversity losses. It is right that we worry about those, she says, but it is also no bad thing to reconnect with nature. Having been astounded at the richness of life hiding out here among the rocks, I couldn’t agree more.
The shells that got away
Here are impressive shells that we didn’t find on the east coast of the UK, in Norfolk, but that you might be lucky enough to spot elsewhere.
Conch – the common name for a number of sea snails found in the tropics. They have elaborately shaped shells that rise to a cone at one end. In some communities, holes are made in conch shells to turn them into horns.
Painted top shell – there are many types of top shell to find in British waters and elsewhere. One attractive kind is the painted top shell, which can be found in south-west England, for instance. Its cream spirals are interlaced with a vivid light and dark-pink strand.
Geoduck – pronounced “gooey-duck”, this is a species of giant clam native to the North Pacific Ocean. The shells are around 15 centimetres long and look unremarkable. But because this species buries itself deep in the seabed, it has a huge, fleshy siphon, the organ through which it “breathes” water, that can be 1 metre long.
Gumboot chiton – found on the northern shores of the Pacific Ocean, this chiton can reach nearly 40 centimetres in length.
