Marine Rock

Marine Rock -

Current Status

Kent holds a higher proportion of the national resource of littoral and sublittoral chalk than any other county, with approx 35% of UK coastal chalk (418 ha). Extensive chalk wave-cut platforms (known as reefs) are found at Thanet, between Kingsdown and Dover and to a lesser extent between Dover and Folkestone. Thanet supports the second most extensive chalk sea cave formations in the UK, with a smaller number of caves between Kingsdown and Dover. The Thanet coast is composed of Upper Chalk, a particularly soft form, with characteristic species including rockboring animals which give a ‘honeycombed’ appearance to the Thanet reefs. Between Kingsdown and Folkestone, Upper, Middle and Lower Chalk (each type containing a characteristic range of fossils) are all represented in the cliffs and reefs.

The sub-littoral (sub-tidal) areas are not well known, apart from at Thanet where they are designated as a Special Area of Conservation (SAC). However, diving surveys of the sub-tidal chalk reef around Dover, by Kent Seasearch, have revealed areas of chalk gullies up to 2m deep and other chalk features, supporting sponges, crustaceans, anemones & seaweeds.


• Coastal defence & development works: 56% coastal chalk in Kent has been modified by coastal defence and other works – a higher proportion than in any other county. At Thanet this rises to 74%. Such works have resulted in loss of upper shore micro-habitats & splash zone communities. • Water quality: Changes in water quality may result in changes in composition of chalk reef communities. • Human disturbance: Activities on the foreshore can affect chalk reefs, including collection of shellfish, installation of buoys or fixed nets and seaweed removal. Disturbance from recreational activities, in particular dog walking, can have a significant effect on turnstones and other wintering birds. • Non-native species: The seaweed Sargassum muticum (Jap weed) is found extensively on Kent's chalk reefs and is known to affect their species composition. Undaria pinnatifida (Wakame) has also been discovered recently at Ramsgate although its effects on chalk communities are not known. • Oil spills/incidents at sea: Vulnerability to oil spills, other pollution or physical damage to the reefs from accidents at sea. due to close proximity to busy shipping lanes. • Sea level rise: In the longer term, existing chalk reefs will be submerged by combined effects of sea level rise and post-glacial adjustment (isostatic rebound). Fixed sea defences will prevent new reefs from forming on the landward side of the existing, leading to permanent loss of some reef communities.

Current Action

Formations of the reef-building ross worm (Sabellaria spinulosa) tubes have been recorded at several sublittoral sites around Kent


  1. Maintain the extent of all littoral and sublittoral chalk i.e maintain 359 ha of littoral & sub-littoral chalk by 2010 and 378ha by 2026

  2. Aim to secure a notable decrease in detrimental effects of human activities on littoral and sub-littoral chalk habitats

Relevant Habitat Action Plans

The relevant UK Habitat Action Plans:

This should be read in conjunction with the following two Kent Habitat Action Plans:

  • Maritime Cliff & Slope
  • Marine