EUNIS habitat classification 2012 > A - Marine habitats > A1 - Littoral rock and other hard substrata > A1.4 - Features of littoral rock > A1.44 - Communities of littoral caves and overhangs

Communities of littoral caves and overhangs

English name: Communities of littoral caves and overhangs

Quick facts

EUNIS habitat type code A1.44
Bern Convention Resolution 4 habitat type (used for designation of Emerald sites)
Relation to Annex I habitat types (EU Habitats Directive)

Description (English)

Where caves and overhangs occur on rocky shores, the shaded nature of the habitat diminishes the amount of desiccation suffered by biota during periods of low tides which allows certain species to proliferate. In addition, the amount of scour, wave surge, sea spray and penetrating light determines the unique community assemblages found in upper, mid and lower shore caves and overhangs on the lower shore. Biotopes from the surrounding shore such as A1.111, A1.113 or any of the fucoid communities occasionally extend into cave entrances. A1.113 often extends some way into the cave. Other open shore biotopes may also be found within caves, such as the green seaweed Prasiola stipitata on cave roofs where birds roost (B3.112), and localised patches of green algae where freshwater seepage influences the rock (A1.451). Rockpools containing encrusting coralline algae (A1.411), fucoids and kelp (A1.412) and hydroids and littorinid molluscs may occur also on the floor of cave entrances. The cave biotope descriptions are largely based on data obtained from surveys of Berwickshire caves (ERT,2000), chalk caves from the Thanet coast (Tittley et al., 1998; Tittley & Spurrier 2001) and data from Wales (CCW Phase 1 data). In general, the biomass and diversity of algal species found in upper and mid-shore littoral caves decreases with increasing depth into the cave as the light levels diminish. Fucoids are usually only found at the entrances to caves, but red algae, and filamentous and encrusting green algae are able to penetrate to lower light intensities towards the back of the cave, and mats of the turf forming red seaweed Audouinella purpurea and/or patches of the green seaweed Cladophora rupestris may occur on the upper walls (A1.444). Brownish velvety growths of the brown algae Pilinia maritima occurring in mats with the red alga A. purpurea on cave walls and upper littoral levels of cliffs (A1.443) should not be confused with the green (A1.442) or golden brown algal stains often found above this zone on the ceilings of the caves (A1.443; A1.441). Below is a zone of Verrucaria mucosa and/or Hildenbrandia rubra on the inner and outer reaches (A1.445). Fauna usually only occur on the lower and mid walls of the caves and generally comprise barnacles, anemones and tube-forming polychaetes (A1.448; A1.449) depending on the level of boulder scour or wave surge. Where the floors of caves consist of mobile cobbles and small boulders, little algae and fauna occur due to the effects of scouring (A1.44A). Vertical or steeply sloping cave walls and overhangs on the mid and lower shore, subject to wave-surge but without scour, support a rich biota of sponges, hydroids, ascidians and shade-tolerant red algae (A1.447, A1.446 or A1.4461).
Situation: Caves and overhangs in the littoral zone in hard rock and limestone (including chalk).

Source:
EUNIS habitat classification
Interpretation Manual of the habitats targeted by Resolution No. 4

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Species mentioned in habitat description


List

Other classifications

Classification Code Habitat type name Relationship type
Marine Habitat Classification Britain/Ireland 0405 LR.FLR.CvOv Littoral caves and overhangs source
Barcelona Convention 199812 II.4.3. Mediolittoral caves same
HELCOM Baltic Sea Marine and Coastal Biotopes 1998 03.06.06 Coastal cliffs and caves: caves same
For relation to plant communities (syntaxa), see Vegetation types

History

Classification Code Habitat type name Relationship type
EUNIS Habitat Classification 200410 A1.44 Communities of littoral caves and overhangs same
EUNIS Habitat Classification 200308 A1.61 Communities of littoral caves and overhangs same
EUNIS Habitat Classification 200202 A1.61 Communities of littoral caves and overhangs same
EUNIS Habitat Classification 199910 A1.61 Communities of littoral caves and overhangs same
EUNIS Habitat Classification 199811 A1.61 Communities of littoral rock caves same
EUNIS Habitat Classification 199712 A9.11 Communities of littoral rock caves same
MNCR BioMar 97.06 (Britain & Ireland) LR.Ov Overhangs and caves same
MNCR BioMar 96.7 (Britain & Ireland) SUR.PilPse   narrower
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