Biodiversity & Conservation

Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock



Image Keith Hiscock - Molgula manhattensis dominated seabed, middle channel with associated common starfish Asterias rubens. Image width ca 50 cm.
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Distribution map

CR.HCR.XFa.Mol recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • EC_Habitats

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland Recorded in south-west England and west Wales and off the coast of Kent in south-east England.
National importance Uncommon

Text page icon Description of biotope

For a full description of this biotope including characterizing species, distribution, survey information and references visit JNCC

This biotope occurs in the shallower reaches of the circalittoral (upper and lower) at depths of around 8 to 13 m with the main ascidian cover of Molgula manhattensis with some Polycarpa pomaria and a wide variety of other ascidians mixed in. Sponge species associated with this biotope include Tethya, Cliona, Stelligera rigida, Stelligera stuposa, Raspailia ramosa, Esperiopsis, Hemimycale and Dysidea. There are also several records with Axinella dissimilis and Axinella infundibuliformis. Nemertesia antennina occurs at most sites, also with Alcyonium digitatum and Actinothoe. Flustra is common in all these ascidian biotopes, but Chartella is only found in this one. Red algae associated with the upper circalittoral occur sporadically - more an artefact of the way in which the habitat records have been split. This biotope has some parallels with the erect sponge biotopes (e.g. MCR.ErSPbolSH), although it appears to be far siltier at most sites. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Additional information icon Additional information

The main characteristic of this biotope is the dominance of rock by ascidians. However, the associated species are ones that are found in a wide range of biotopes.

This review can be cited as follows:

Hiscock, K. 2002. Molgula manhattensis and Polycarpa spp. with erect sponges on tide-swept moderately exposed circalittoral rock. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 01/12/2015]. Available from: <>