EUNIS habitat classification 2017 > M - Marine benthic habitats > MB1 - Infralittoral rock > MB12 - Atlantic infralittoral rock > MB122 - Seaweed or faunal communities on Atlantic infralittoral rock > MB1221 - Foliose red seaweeds on exposed lower Atlantic infralittoral rock > MB12211 - Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock

Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock

Quick facts

EUNIS habitat type code MB12211
Relation to Resolution 4 habitat type (used for designation of Emerald sites)

Description (English)

A dense turf of foliose red seaweeds mixed with a dense turf of the foliose brown seaweeds Dictyota dichotoma and/or Dictyopteris membranacea on exposed and moderately exposed lower infralittoral rock, generally at or below the lower limit of the kelp zone. In some areas the lower infralittoral is subject to a moderate amount of scour from nearby sand. D. dichotoma is relatively tolerant of such scour and in such areas a zone forms with other sand-tolerant seaweeds. D. membranacea is confined to south-western coasts. Typically brown seaweeds dominate the seabed or are at least in equal abundance to the red seaweeds, some of which may also form dense stands such as Plocamium cartilagineum, Calliblepharis ciliata, Cryptopleura ramosa, Bonnemaisonia asparagoides, Heterosiphonia plumosa, Delesseria sanguinea and Brongniartella byssoides. The urchin Echinus esculentus can be found grazing the rock surface which can be covered in coralline algae. The anthozoans Caryophyllia smithii and Alcyonium digitatum are usually present in this biotope along with the tube-building worm Pomatoceros sp. which is more common in sand-scoured areas. The starfish Asterias rubens and Henricia sp. and sponge crusts including Cliona celata can also be found here. D. dichotoma also occurs in the kelp park, and records should only be assigned to this biotope where kelp such as Laminaria hyperborea is sparse or absent and a relatively high density of D. dichotoma and/or D. membranacea is present.
Situation: This biotope usually occurs at or below the lower limit of kelp L. hyperborea (units MB1-2152 or MB1-21A). In south-west England a zone of mixed kelp forest L. hyperborea and Laminaria ochroleuca may occur above the dense foliose algae (unit MB1-2153). Unit MB1-2211 marks the lower limit of the lower infralittoral zone.
Temporal variation: Like many of the red seaweeds found in this biotope the dominant brown seaweeds D. membranacea and D. dichotoma have annual fronds which tend to die back in the autumn and regenerate again in the spring. This produces a seasonal change in the density of the seaweed cover, which is substantially reduced over winter months and reaches its most dense between April and September.

Source: EUNIS habitat classification

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Species mentioned in habitat description

Algae Bonnemaisonia asparagoides
Algae Brongniartella byssoides
Algae Calliblepharis ciliata
Algae Cryptopleura ramosa
Algae Delesseria sanguinea
Algae Dictyota dichotoma
Algae Heterosiphonia plumosa
Algae Laminaria hyperborea
Algae Plocamium cartilagineum
Invertebrates Alcyonium digitatum
Invertebrates Asterias rubens
Invertebrates Caryophyllia smithii
Invertebrates Cliona celata
Invertebrates Echinus esculentus
Species scientific name English common name Species group
Bonnemaisonia asparagoides Algae
Brongniartella byssoides Algae
Calliblepharis ciliata Algae
Cryptopleura ramosa Algae
Delesseria sanguinea Algae
Dictyota dichotoma Algae
Heterosiphonia plumosa Algae
Laminaria hyperborea Algae
Plocamium cartilagineum Algae
Alcyonium digitatum Invertebrates
Asterias rubens Invertebrates
Caryophyllia smithii Invertebrates
Cliona celata Invertebrates
Echinus esculentus Invertebrates

Other classifications

History

Classification Code Habitat type name Relationship type Comment
EUNIS Habitat Classification 200410 A3.1161 Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock same
EUNIS Habitat Classification 200308 A3.1171 Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock same
EUNIS Habitat Classification 200202 A3.1171 Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock same
EUNIS Habitat Classification 199910 A3.1171 Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock same
MNCR BioMar 97.06 (Britain & Ireland) EIR.KFaR.FoR.Dic Foliose red seaweeds with dense Dictyota dichotoma and/or Dictyopteris membranacea on exposed lower infralittoral rock same
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