Biodiversity & Conservation

Foraminiferans and Thyasira sp. in deep circalittoral soft mud


Foraminiferans and <i>Thyasira</i> sp. in deep circalittoral soft mud
Distribution map

COS.COS.ForThy recorded (dark blue bullet) and expected (light blue bullet) distribution in Britain and Ireland (see below)

  • UK_BAP

Text page icon Habitat description

Map icon Distribution of biotope in Britain and Ireland Recorded from a few isolated sites in the northern North Sea, the Celtic Deep and Scottish lochs on the Atlantic coast.
National importance Not available

Text page icon Description of biotope

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

In deep water and soft muds of Boreal and Arctic areas, a community dominated by foraminiferans and the bivalve Thyasira sp. may occur (Thorson, 1957; Kunitzer et al., 1992). This community typically occurs in water deeper than 100 m in the northern North Sea (Kunitzer et al., 1992) and have been referred to as 'Foraminifera communities' by other workers (e.g. Stephen, 1923; Thorson, 1957; McIntyre, 1961). Foraminiferans such as Saccammina sp., Psammosphaera sp., Crithionina sp. and Astorhiza sp. are important components of this community with dead tests numbering thousands per m² (see Stephen, 1923; McIntyre, 1961) and sometimes visible from benthic photography (Mackie et al., 1995). It is likely that a community dominated by Astorhiza in the Irish Sea is another distinct biotope (E.I.S. Rees pers comm., 1997). Polychaetes, e.g. Paraonis gracilis, Myriochee heeri, Spiophanes kroyeri, Tharyx sp., Lumbrineris tetraura, are also important components of this biotope. These communities appear to have no equivalent on the continental plateau further south (Glemarec, 1973) but are known from the edge of the Celtic Deep in the Irish Sea (Mackie et al., 1995). The benthos in these offshore areas has been shown to be principally Foraminifera and similar, rich communities may exist in Scottish sea lochs (McIntyre, 1961). Shallower water may give rise to Brissopsis lyrifera dominated communities (CMU.BriAchi). Communities from yet deeper (northern) waters at the extremes of the North Sea may be reminiscent, although dissimilar to COS.ForThy (see Pearson et al., 1996) reflecting a higher proportion of silt/clay. A fully Arctic version of this biotope has also been described (Thorson, 1934, 1957) although it should be noted that Jones (1950) considered this Boreal foraminiferan community to be part of a 'Boreal Deep Mud Association'. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Additional information icon Additional information

None entered

This review can be cited as follows:

Riley, K. 2002. Foraminiferans and Thyasira sp. in deep circalittoral soft mud. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 30/11/2015]. Available from: <>