EUNIS habitat classification 2012 amended 2019 > A - Marine habitats > A4 - Circalittoral rock and other hard substrata > A4.1 - Atlantic and Mediterranean high energy circalittoral rock > A4.13 - Mixed faunal turf communities on circalittoral rock > A4.138 - Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock

Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock

English name: Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock

Quick facts

EUNIS habitat type code A4.138
Bern Convention Included in a Resolution 4 habitat type at a higher level (A4)

Description (English)

This biotope is typically found on slightly sand-scoured, tide-swept, moderately exposed circalittoral bedrock and cobbles. It is commonly recorded from the shallower reaches of the circalittoral around depths from 5m to 15m BCD, as it occurs mostly in very turbid waters. From afar, the physical characteristics are usually silted bedrock reefs and cobble, interspersed with patches of clean sand, causing a scour effect on the rock. Dense aggregations of the ascidian Molgula manhattensis form a silty mat on the rock and there is a sparse hydroid and bryozoan turf. A hydroid turf, composed of Nemertesia antennina, Halecium beanii, Hydrallmania falcata, Sertularella gaudichaudi, Tubularia indivisa and Alcyonium digitatum, in varying amounts, occurs at most sites on the tops of boulders and ridges. A bryozoan turf is also present, but not usually dense and includes Flustra foliacea, Alcyonidium diaphanum, Electra pilosa and the crust-forming bryozoan Conopeum reticulum. The polychaete Lanice conchilega thrives in the sandy patches which often occur between the rock ridges. The scour effect tends to reduce the diversity of sponges present with only Halichondria panicea occasionally present. Isolated clumps of the polychaete Sabellaria spinulosa may be present but they do not occur in dense aggregations as in the A4.2211 biotope. The anemones Urticina felina and Sagartia troglodytes may occur in cracks between cobbles or on stones buried in the sandy substratum. The anemone Sagartia elegans is more commonly found attached to crevices in the bedrock. Other species such as the hermit crab Pagurus bernhardus, the barnacle Balanus crenatus, the polychaete Sabella pavonia and Pomatoceros triqueter may all be present whilst the crab Pisidia longicornis may be found under cobbles and stones. Records of this biotope are distributed along the south coast of England and the north Wales coast as well as Pembrokeshire near the entrance to Milford Haven.
Situation: As this biotope is often recorded on soft rock (chalk), soft rock communities (A4.23 biotope complex) would be observed in close proximity with species of the genus Polydora and piddocks (Pholas spp. and Barnea spp). Moderately exposed kelp forests may be found within the shallow infralittoral zone.

Source: EUNIS habitat classification

Vegetation types

Relation to vegetation types (syntaxa)

Not available

Species mentioned in habitat description

Invertebrates Alcyonidium diaphanum
Invertebrates Alcyonium digitatum
Invertebrates Balanus crenatus
Invertebrates Conopeum reticulum
Invertebrates Electra pilosa
Invertebrates Flustra foliacea
Invertebrates Halichondria panicea
Invertebrates Hydrallmania falcata
Invertebrates Lanice conchilega
Invertebrates Molgula manhattensis
Invertebrates Nemertesia antennina
Invertebrates Pagurus bernhardus
Invertebrates Pisidia longicornis
Invertebrates Pomatoceros triqueter
Invertebrates Sabellaria spinulosa
Invertebrates Sagartia elegans
Invertebrates Sagartia troglodytes
Invertebrates Sertularella gaudichaudi
Invertebrates Tubularia indivisa
Invertebrates Urticina felina
Species scientific name English common name Species group
Alcyonidium diaphanum Invertebrates
Alcyonium digitatum Invertebrates
Balanus crenatus Invertebrates
Conopeum reticulum Invertebrates
Electra pilosa Invertebrates
Flustra foliacea Invertebrates
Halichondria panicea Invertebrates
Hydrallmania falcata Invertebrates
Lanice conchilega Invertebrates
Molgula manhattensis Invertebrates
Nemertesia antennina Invertebrates
Pagurus bernhardus Invertebrates
Pisidia longicornis Invertebrates
Pomatoceros triqueter Invertebrates
Sabellaria spinulosa Invertebrates
Sagartia elegans Invertebrates
Sagartia troglodytes Invertebrates
Sertularella gaudichaudi Invertebrates
Tubularia indivisa Invertebrates
Urticina felina Invertebrates

Other classifications

Classification Code Habitat type name Relationship type
Marine Habitat Classification Britain/Ireland 0405 CR.HCR.XFa.Mol <I>Molgula manhattensis</I> with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock source
CORINE Land Cover 5.2.3. Sea and ocean n/a
For relation to plant communities (syntaxa), see Vegetation types

History

Classification Code Habitat type name Relationship type
EUNIS Habitat Classification 200410 A4.138 Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock same
EUNIS Habitat Classification 200308 A3.672 Molgula manhattensis with a hydroid and bryozoan turf on tide-swept moderately wave-exposed circalittoral rock same
EUNIS Habitat Classification 200202 A3.672 Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock same
EUNIS Habitat Classification 199910 A3.672 Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock same
MNCR BioMar 97.06 (Britain & Ireland) MCR.As.MolPol Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock same
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