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Marine Habitat Classification

Description of biotope or habitat type

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   Rhodochorton purpureum and Cladophora rupestris on upper to mid-shore cave walls

Physical habitat description

Salinity Full (30-35 ppt)
Wave exposure Moderately exposed, Sheltered
Tidal streams
Substratum Bedrock
Zone Eulittoral - mid, Eulittoral - upper, Littoral fringe, Supralittoral
Depth Band
Other Features Moist, dark caves; chalk

Download comparative physical and biological data. The comparative tables enable a rapid comparison of the species composition and principal physical characteristics between a given set of biotopes.

Distribution of habitat LR.FLR.CvOv.RpurCla <I>Rhodochorton purpureum</I> and <I>Cladophora rupestris</I> on upper to mid-shore cave walls

  • Records used to define the biotope (core records)
  • Other records assigned to this biotope, marked as 'certain'
  • Other records assigned to this biotope, marked as 'uncertain'

Point data based on records in the UK Marine Recorder Snapshot.


Vertical and steeply-sloping upper walls at the entrances and inner reaches of upper to mid-shore caves that are partially sheltered from direct wave action characterised by a turf of the 'velvety' red seaweed Rhodochorton purpureum. Patches of green filamentous seaweed Cladophora rupestris can be present. The fauna is generally limited to limpets Patella spp., the winkle Littorina saxatilis and the barnacle Semibalanus balanoides, while they usually occur in low abundance. Filamentous or crust forming brown seaweeds may occur mixed with A. purpurea, often becoming a zone in its own right (AudPil) above the AudCrup biotope. Other shade-tolerant red seaweed such as Catenella caespitosa and Lomentaria articulata may occur (but at lower abundance), and where freshwater seepage occurs, Ulva intestinalis can form patches. Some variation in the species composition of the individual caves must be expected depending on local conditions. A. purpurea can be the only seaweed present in caves on the Thanet coast in south-east England. This biotope is known to occur in hard rock caves in north-east England and chalk caves in south-east England. Received after deadline: A. purpurea has changed name to Rhodochorton purpurea.


In hard rock caves, this biotope is generally found on the upper walls above the ScrFa and FaCr biotopes and beneath the biotopes dominated by green and/or brown crusts (GCv; AudPil). In chalk caves, AudCrup may cover the lower and upper walls, while it is usually found below GCv and/or AudPil.

Temporal variation


Characterising species

Taxon Relative importance of taxon for defining this community (%) Typical abundance - SACFOR scale % of core records where taxon was recorded
Rhodochorton purpureum 49 Abundant 81-100%
Littorina saxatilis 17 Frequent 61-80%
Patella 11 Frequent 41-60%
Cladophora rupestris 9 Common 41-60%
Semibalanus balanoides 3 Frequent 41-60%

Similar biotopes or habitat types

The turf-forming red seaweed Audouinella spp. can be present though not at a high abundance. The red crust Hildenbrandia rubra is present.

Classification history of this biotope or habitat type

Classification version Code
2015 (15.03) LR.FLR.CvOv.AudCla
1996 (6.95) SUR.PilPse
1995 LRK.APP

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