Red seaweeds and kelps on tide-swept mobile Atlantic infralittoral cobbles and pebbles

Quick facts

EUNIS habitat type code MB32111
Relation to Resolution 4 habitat type (used for designation of Emerald sites)

Description (English)

Shallow mixed substrata of cobbles and pebbles swept by moderately strong tidal streams in exposed areas, and characterised by dense stands of red seaweeds. Tide-swept infralittoral cobbles and pebbles which may be highly mobile, create an environment that is difficult for many algae to survive in. Foliose and filamentous seaweeds with an encrusting phase in their life history, or those that are able to withstand rolling of the substratum and scouring, can form dense turfs of seaweed in the more settled summer months. Characteristic red seaweeds include Halarachnion ligulatum which is able to survive attached to the pebbles and cobbles. Ephemeral algae grow rapidly in periods of relative stability. Other characteristic red seaweeds include Plocamium cartilagineum, Hypoglossum hypoglossoides, Bonnemaisonia asparagoides and Brongniartella byssoides. Coralline encrusting algae cover many of the cobbles and pebbles; some areas of cobbles may be quite barren, dominated only by encrusting coralline algae and brittlestars. Of the brown seaweeds scattered Laminaria spp. and Desmarestia spp. may be present on more stable large boulders or bedrock outcrops. Chorda filum and Halidrys siliquosa may be present in low abundance but where these seaweeds occur in greater abundance (typically >Frequent) refer to MB1-233 and MB1-236 respectively. Although the faunal component of this biotope is usually relatively sparse it can include a wide variety of species. Turfs of hydroids (Nemertesia spp., Aglaophenia tubulifera) and bryozoans (Crisia spp. and Bugula spp.) are the major components but sponges and anemones may also occur. Brittlestars, sea-urchins, hydroids and solitary ascidians are more prominent in the Scottish examples of this biotope, which tend to occur in deeper water, due in part to clearer waters.
Situation: Although not common, this biotope is widely distributed from Sussex to the shallow areas of the Sarns in Cardigan Bay, the west coast of Scotland and the north-east coast of Ireland. Despite the wide distribution, the red seaweed composition remains remarkably constant. In areas such as the Sarns, in Wales, where mixed substrata continue into the shallows, dense swathes of MB1-233 can be found. More stable but highly scoured areas adjacent to MB1-274 can support the Halidrys biotope MB1-236. Where bedrock or large boulders occur above the mixed substrata of MB1-274 it may support a kelp forest or park (MB1-213 or MB1-21A). At many sites the mixed substrata supporting the dense seaweed turf gives way to sediment of varying composition.
Temporal variation: This biotope will take on a much more depauperate appearance during the winter months, once the ephemeral seaweeds have died back in late summer/autumn. Storms can mobilise the loose pebbles and cobbles, removing all but the most resilient of seaweeds and animals. By summer, under more stable conditions, new growth will flourish and dense stands of seaweeds dominate the seabed.

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 Halarachnion ligulatum
Algae Halidrys siliquosa
Algae Hypoglossum hypoglossoides
Algae Plocamium cartilagineum
Invertebrates Aglaophenia tubulifera
Species scientific name English common name Species group
Bonnemaisonia asparagoides Algae
Brongniartella byssoides Algae
Halarachnion ligulatum Algae
Halidrys siliquosa Algae
Hypoglossum hypoglossoides Algae
Plocamium cartilagineum Algae
Aglaophenia tubulifera Invertebrates

Other classifications

Classification Code Habitat type name Relationship type
EUNIS Habitat Classification 2007 (revised descriptions 2012) A5.5211 Red seaweeds and kelps on tide-swept mobile infralittoral cobbles and pebbles same
For relation to plant communities (syntaxa), see Vegetation types

History

Classification Code Habitat type name Relationship type Comment
EUNIS Habitat Classification 200410 A5.5211 Red seaweeds and kelps on tide-swept mobile infralittoral cobbles and pebbles same
EUNIS Habitat Classification 200308 A3.235 Ephemeral red seaweeds and kelps on tide-swept mobile infralittoral cobbles wider
EUNIS Habitat Classification 200202 A3.235 Ephemeral red seaweeds and kelps on tide-swept mobile infralittoral cobbles overlap
EUNIS Habitat Classification 199910 A3.235 Ephemeral red seaweeds and kelps on tide-swept mobile infralittoral cobbles overlap
MNCR BioMar 97.06 (Britain & Ireland) MIR.SedK.EphR Ephemeral red seaweeds and kelps on tide-swept mobile infralittoral cobbles overlap
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