Chalk reef creatures

Kerry Williams
, 26 March 2025
Chalk reef creatures
Blue Mussels © Paul Naylor

By Kerry Williams

Communications Officer - Conservation

Sussex is home to a significant number of chalk reefs; a globally scarce habitat. Providing a rocky surface on the seabed for creatures to shelter and hold on to, these precious environments support high levels of biodiversity and thriving ecosystems. But who, amongst countless others, calls this vital habitat home?

Blue Mussel, Mytilus edulis

Capable of forming dense beds of many individuals which stabilise sediments in less rocky areas, the Blue or Common Mussel (pictured above) in turn provides habitat for other marine species. Mussels are a bivalve, meaning they have two sides of a shell which clamp together, and are a member of the eclectic mollusc family, so are related to Oysters, Snails, and even Octopuses. As Mussels are filter feeders, the species is an indicator of water pollution due to the potential for study of the pollutants which end up in their tissues.

Piddocks, Pholas dactylus / Barnea candida

Another bivalve mollusc, Piddocks bore into soft rock, like that of the chalk reef. They can spend their entire lives in their burrow, extending their tube-like siphons outward to feed. When the Piddock dies, they leave behind the ready-made crevice in the rock for other creatures to utilise. Although this can increase the complexity of the habitat and encourage diversity in the environment, reefs being ‘pitted’ like this can make these habitats all the more fragile. The long oval shells of Piddocks are notably wing-shaped, hence their common name of Angelwings, and to add to their ethereal vibe, they can glow in the dark.

Piddock © Nigel Phillips

Tompot Blenny, Parablennius gattorugine

Making use of the spaces Piddocks leave behind, the Tompot Blenny’s ideal habitat includes cracks and crevices. This makes them a regular reef fish species, and a highly territorial one at that. Adorned with distinctive tentacles on their heads, this charismatic species isn’t shy and has a penchant for investigating divers who might encroach on their nests. A subtidal species, Tompot Blennies reside in shallow water and close to the shore, below the low-tide mark. Their cousins, the Common Blenny, also known as Shanny, are more likely to be found in rock pools.

Tompot Blenny © Paul Naylor

Serrated Wrack, Fucus serratus

Serrated Wrack is a seaweed species, taking its name from the serrated edges of its fronds, another word for leaves. This species covers a vast majority of our chalk reefs around Brighton to Eastbourne. Creating a canopy on top of the bedrock, the Wrack traps moisture as the tide goes out, creating a safe place for other marine species to shelter. Seaweeds sit within the Algae family, of which chalk reefs can support a huge diversity.

Serrated Wrack © Ella Garrud

European Lobster, Homarus Gammarus

Another crevice dweller, Lobsters are another fan of a chalk reef habitat. Crabs and Lobster species have exoskeletons which they shed as they grow; a process known as moulting. Often these exoskeletons can be mistaken for dead Lobsters when found washed up on the beach; not unlike that of an abandoned snakeskin. Common Lobsters are a deep blue colour, with red antennae. A formidable nocturnal scavenger, their two distinctive pincers differ in size; a chunkier one as the grabber, and the smaller for tearing.

Lobster © Paul Parsons

Chalk reefs in Sussex are under threat from activities such as the dumping of dredged material at Beachy Head West Marine Conservation Zone (MCZ). Sussex Wildlife Trust is calling for this practice to stop. 

Find out more about the campaign to stop dumping of dredged spoil. 

To keep in touch with the latest updates, make sure you are signed up to Sussex Wildlife Trust's weekly newsletter.

Leave a comment

Comments

  • Malcolm White:

    Thanks for this description of some of the creatures that live amongst the crevices of the chalk reefs…..the idea of a chalk reef is new to me; are there maps of where the most significant are, how close to the shore and at what depths they lie? That would be very useful.

    Sussex Wildlife Trust: Thanks Malcolm - there's a map with approximate locations here. We'll check whether there is more specific information that can be shared.

    27 Mar 2025 13:08:00

  • Ros Hodges:

    Thank you for the information above, very interesting and a huge thank you for continuing to fight for this habitat.

    27 Mar 2025 14:40:00

  • Susan Gilbert:

    Thanks for this, really interesting. Piddocks are fascinating l sometimes find their broken shells on the beach at west st Leonard’s. Are there any recent studies of the Sovereign Shoals chalk reefs? Just wondering how much damage was done by the dismantling of the light tower.

    27 Mar 2025 14:58:00

  • H George:

    Thanks to other commenters, saw the maps – really interesting, have lived by East Sussex coast most of my life and had no idea we had reefs, althought I’ve often scrambled across them at low tide.

    27 Mar 2025 16:40:00

  • Christine Dafter:

    And thousands of people are sadly, never aware of just how amazing our offshore area is. Full of beautiful creatures.

    27 Mar 2025 17:19:00

  • Julia Dance:

    Please keep us posted on the marina sludge dumping and how to make our anger felt about anyone even thinking of doing this.

    27 Mar 2025 17:54:00

  • Jane Griffin:

    Thank you so much for sharing this amazing information. Can you tell me, do you go into schools and tell the kids about your work? If not, you really should. It’s the young ones who will shape a better future. They give me hope!
    The photographs are so clear and beautiful. Can you tell me what camera was used? Thank you x

    28 Mar 2025 04:49:00

  • Sussex Wildlife Trust:

    Hi Jane. Read more about Paul Naylor here  https://sussexwildlifetrust.or...

  • Mary Parker:

    Also, kelp is the most efficient up-taker of CO2 on the pllanet

    28 Mar 2025 08:56:00

  • Alan Walker:

    I prize our re-emerging reefs and kelp beds. It was good to look at what is dwelling there.

    28 Mar 2025 18:33:00

  • Zita Pilbeam:

    Thanks for the great information, is there anything on local sea slugs? I’ve always been curious about them but alas am too old to meet them in person now!

    29 Mar 2025 02:54:00

  • Sussex Wildlife Trust:

    Here's a recent blog about sea slugs that you might find interesting

  • Frank Riddle:

    We must take better care of our natural surroundings and habitats and stop dumping dredged material from our ports.

    29 Mar 2025 10:44:00

  • Carole Sutton:

    The dumping of dredged soil absolutely must stop

    30 Mar 2025 15:14:00

  • Frances Horton:

    I’m reading this from afar – New Zealand. Our Conservationists are beginning to get very concerned at the “rising temperatures of exposed mudflats in estuaries and large tidal beach areas. Apparently the increased heat from the sun is heating the substrate exposed at low tide and this kills a lot of biota. This in turn causes problems for marine and estuarine plants and animals as their food source is diminished. We also have in-shore rocky reefs, and they are beginning to feature algal blooms and seaweed loss.
    Hope that UK is faring better with climate change and that your special chalk reefs remain unaffected.
    Also best wishes with your protests against continued dumping of dredged matter onto the chalk reefs… how is this still even happening in 2025!

    31 Mar 2025 10:09:00

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