Ten Wonders of Falmouth’s Rocky Shoreline
- Olivia
- Oct 1
- 7 min read
Rocky shores are a marine wonderland. Existing in the ‘intertidal zone’, they are in turn submerged and exposed by the ebbing tide, and are as diverse and surprising as the ocean itself. As the name suggests, rocky shore environments are made up primarily of solid rock, often giving rise to rock pools, crevices and platforms – all of which can be occupied by a whole host of fascinating creatures. From the flamboyant to the fantastical, the organisms that inhabit the rocky shore provide an incredible opportunity to experience the wonders of marine life while remaining on dry(ish) land.
Falmouth hosts a range of rocky shore environments, perhaps most accessible via its popular beaches; Gyllyngvase, Swanpool, and Castle beaches all include rocky shore components. The diverse range of organisms that occupy these environments make them a perfect living classroom for all ages. However, this abundance of creatures can also make it difficult to identify individual species when starting out – so here’s ten wonders of Falmouth’s rocky shore for you to look out for the next time you’re by the seaside.
10. Beadlet Anemone
Is it a plant? Is it a food? Amazingly, anemones are actually animals – and they can be voracious predators. Known to any keen rockpooler, the beadlet anemone is as interesting as it is ubiquitous. Resembling deep crimson blobs of jelly when closed, they reveal their characteristic red tentacles when submerged. These appendages are beautiful but deadly, containing stinging cells known as nematocysts. These are used like tiny harpoons, ensnaring their prey of small fish, crustaceans, and molluscs as they pass by. They can also be territorial. Their stinging cells are particularly concentrated in a ring of bright blue dots known as acrorhagi ringing their base, which come in useful when defending their chosen patch of the rocky shore from enemy anemones. Despite this somewhat aggressive nature, beadlets are nevertheless attentive parents, able to contain over one hundred embryos which are expelled once they have developed enough to attach themselves to the surrounding rock. Look for these anemones in the middle and lower areas of the rocky shore, where they lie in wait for high tide!
9. Common Limpet
One of three limpet species found along UK coastlines, the common limpet can be identified by its slightly larger size. Limpet anatomy consists of a soft ‘visceral mass’ contained within a conical shell. The shell adheres tightly to the hard surfaces of the rocky shore using a muscular foot. Much like beadlet anemones, common limpets only truly come to life at high tide, when they use their foot to slide along using a snail-like movement pattern. This foraging is necessary, as they feed on algae that grows across the rocky shore, using a tongue known as a radula. Fascinatingly, common limpets show site fidelity, returning to the same location to rest after feeding. This site becomes worn down with a limpet-shaped groove, touching known as a ‘home scar’.
8. Green-leaf Worm
Although they may appear extra-terrestrial, you need only to head to your local coastline to catch a glimpse of these otherworldly worms. They are identifiable by their bright green colouration, which may darken with age. Their long body is divided into around 150 segments, which they use to manoeuvre using a distinctive undulating motion. They are a member of the class Polychaeta, marine worms defined by having flat, limb-like ‘parapodia’ protruding from each body segment. They seek shelter during low tide, meaning that you can find them in areas of the shore with plentiful crevices and depressions. They play a vital role in this environment as scavengers, as well as being an important food source for various marine predators! Breeding during the warmer months, their egg masses can also be identified – they are most often attached to algae or wrack, and also appear greenish in colour.
7. Flat Periwinkle
Ask somebody to picture a sea snail, and it’s likely that they’ll imagine something like a flat periwinkle. Mundane at first glance, periwinkles resemble terrestrial snails, with a slime-coated soft body encased in a spiral shell. However, they have a number of uniquely intriguing characteristics – not least of which is their colour variation. Flat periwinkles come in a remarkable range of hues, from olive green to neon orange. They are also able to derive oxygen both on land and in the marine environment, making them particularly suited to the demands of rocky shore life. Although they are hardy in this way, they are most commonly found in the mid- and lower rocky shore, where they forage for seaweed at both low and high tide. They are most usually found taking refuge in bundles of bladder wrack, where they use camouflage to evade crabs and other predators.
6. Montagu’s Blenny
In the UK, the Montagu’s blenny is found only in the southwest – making these small fish a true Cornish wonder. Apart from their British range, they are also found in northern Africa and the mediterranean. They have an elongated body with a notched dorsal fin that extends the entire length of the fish. During low tide, they retreat into rock pools, where they may be seen lying along the bottom with eyes facing upwards. Their rounded pectoral fins are used not only while swimming, but also as forelimbs, allowing them to crawl along the benthic environment. In this way, they are able to meet their dietary needs – an omnivorous diet consisting of both marine invertebrates and encrusting algae. The species has complex breeding rituals, during which males rhythmically rotate their heads in order to impress a female. Males also take an active parental role, remaining with the eggs once laid to protect them.
5. Hermit Crab
Hermit crabs can be found across the UK, revealing themselves to those patient enough to look out for a shell with legs! In fact, hermit crabs are decapod crustaceans, having ten appendages that they use to move. Unlike other crustaceans, hermit crabs are soft-bodied, meaning that they must utilise shells produced by other marine organisms for protection. This also means that their shell does not grow with them, and they are forced to try larger shells on for size as they age. These shells are most typically produced by sea snails such as periwinkles, but they may also choose other marine debris, such as pieces of driftwood. Recently, a disturbing trend has emerged of hermit crabs utilising human rubbish as shells. Using digital data, scientists gathered evidence from 386 crabs that were found to have ‘artificial shells’ – a sobering reminder of the threat of plastic pollution.
4. Cushion Star
Instantly recognisable, sea star species such as the cushion star are icons of the rocky shore, and it only takes a glance at their unusual biology to see why. Sea stars have ‘pentaradial symmetry’, meaning that they could be split evenly into five sections from a central point. They move their characteristic five limbs using a ‘water-vascular system’, pumping seawater to their various sucker-like tube feet to cling onto hard surfaces. Cushion stars are identifiable by their stockier body and shorter limbs – but don’t be fooled by their adorable appearance. They prey on anything they can catch, and are able to evert their stomachs, beginning the digestion process externally before ingesting their victim for a more thorough dissection. They can be found across the range of the rocky shore, as well as clinging onto sheer harbour walls at high tide.
3. Bladder Wrack
Carpeting the lengths of Cornish shores with its thick, veined tendrils, bladder wrack is one wonder that is unlikely to require much searching to appreciate. Bladder wrack is a species of seaweed that ranges from deep brown to dark green in colour. It can be identified by its eponymous ‘bladders’ - bubble-like protrusions filled with air. These are useful in keeping the seaweed buoyant and upright when floating, maximising its sunlight and oxygen exposure. It is often confused with spiral wrack, but is found lower on the shoreline and is also distinguished by its straight pattern of growth. Despite its commonality on UK shores, the species is under threat. Research shows that, as ocean acidity rises, the size of bladder wrack also increases, but at a grave cost. The larger forms of the seaweed are more porous, making them more vulnerable to desiccation and less able to provide a habitat for the species that rely on them.
2. Dog Whelk
Like periwinkles, dog whelks are a species of sea snail – but they vary wildly in both appearance and temperament. Dog whelks are much larger, reaching 6cm compared to the maximum periwinkle size of 1.5cm. Their most prominent feature is their spiral shell, a whorl ending in a sharp, upward-facing point. Additionally, unlike seaweed-munching periwinkles, dog whelks feed on other animals, most frequently mussels and acorn barnacles. They have a radula that is hardened with chitin, enabling them to bore holes in the shells of their prey. Digestive enzymes are then secreted into the hole, dissolving their prey into a nutritious ‘soup’. Dog whelks are most commonly found in the middle of the intertidal zone, though are likely to be prominent throughout in less exposed areas.
1. Shore Crab
Whether encountered during childhood crabbing sessions or during a dedicated rockpooling excursion, shore crabs are perhaps the most easily recognisable inhabitant of the rocky shore. Their appearance is classically crablike, with a hard carapace, forward-facing eyes, and two large pincers used for grabbing food and defence against other crabs. Typically green in colour, individual crabs may also exhibit a red colour morph. Female crabs can be easily distinguished from males by their abdomen, visible on the underside of the crab. Females have a broad, rounded abdomen, while that of males is longer and more slender. They are an extremely hardy species, able to tolerate a wide range of salinities and levels of exposure, meaning that they are found on almost all shore types. This omnipresence means that they are one of the easiest species to find, as well as being one of the most interesting to observe.
Did you know that your rock shore adventures can also contribute to marine conservation? Shoresearch is the Wildlife Trust’s citizen science programme, asking volunteers to record their sightings of marine creatures on the rocky shore, including those around Cornwall. You can learn more about Shoresearch here. Be sure to also tag @falmouthmarineconservation in your shore pictures so we can see your finds!
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