Description of biotope or habitat type

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Ascidiella aspersa on circalittoral artificial substrata

Physical habitat description

Salinity	Full (30-35 ppt), Variable (18-35 ppt)
Wave exposure	Sheltered, Very sheltered, Extremely sheltered
Tidal streams	Moderately strong (1-3 kn), Very weak (negligible)
Substratum	Artificial, other
Zone	Circalittoral
Depth Band	5-10 m, 10-20 m, 20-30 m
Other Features

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 CR.FCR.FouFa.Aasp <I>Ascidiella aspersa</I> on circalittoral artificial substrata

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'
Predicted extent of the level 3 (for sublittoral rock & deep sea) or 4 (for sublittoral sediment) habitat

Point data based on records in the UK Marine Recorder Snapshot. Predicted habitat extent is from UKSeaMap.

Description

Sheltered artificial substrata (such as discarded fishing nets or scrap metal on muddy sediment plains), sometimes subject to variable salinity, with high numbers of the ascidian Ascidiella aspersa which is capable of rapidly colonising hard substrata. Other species that are quickly able to take advantage of such substrata include the dahlia anemone Urticina felina and the plumose anemone Metridium senile. The edible crab Cancer pagurus, the velvet swimming crab Necora puber and the shore crab Carcinus maenas may occasionally be found hiding under the discarded nets, lobster pots or anchor chains.

Situation

As a fouling community, this biotope may be found throughout the circalittoral zone in coastal waters. It may be more prevalent around harbours, moorings, and fishing grounds where suitable substratum is available. In situations where wave exposure or tidal stream increase, biotopes dominated by bryozoans and/or robust hydroids (EcCr) may arise.

Temporal variation

A gradual development of more long-lived species is expected, where the artificial substrata are of a more permanent nature (e.g. wooden or concrete pier pilings).

Characterising species

Taxon	Relative importance of taxon for defining this community (%)	Typical abundance - SACFOR scale	% of core records where taxon was recorded
Ascidiella aspersa	58	Frequent	81-100%
Metridium senile	19	Occasional	61-80%
Necora puber	6	Occasional	41-60%
Carcinus maenas	3	Occasional	41-60%
Cancer pagurus	2	Rare	41-60%
Urticina felina	2	Rare	41-60%