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Marine Habitat Classification


Description of biotope or habitat type

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   Foraminiferans and Thyasira sp. in deep circalittoral fine mud


Habitat (physical) description

Salinity Full (30-35 ppt)
Wave exposure
Tidal streams Very weak (negligible)
Substratum Soft mud
Zone Circalittoral
Depth Band 50-100 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 SS.SMu.OMu.ForThy Foraminiferans and <I>Thyasira</I> sp. in deep circalittoral fine mud

  • 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

In deep water and soft muds of Boreal and Arctic areas, a community dominated by foraminiferans and the bivalve Thyasira sp. (e.g. T. croulinensis and T. pygmaea) may occur (Thorson 1957; Knitzer et al. 1992). Foraminiferans such as Saccammina, Psammosphaera, Haplophragmoides, Crithionina and Astorhiza 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, Oliver & Rees 1995). It is likely that a community dominated by Astorhiza in fine sands in the Irish Sea may be another distinct biotope (E.I.S. Rees pers. comm. 2002). Polychaetes, e.g. Paraonis gracilis, Myriochele 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, Oliver & Rees 1995). The benthos in these offshore areas has been shown to be principally Foraminifera and similar, rich communities may exist in Scottish sealochs (McIntyre 1961). Communities from yet deeper (northern) waters at the extremes of the North Sea may be reminiscent, although dissimilar to 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'.

Situation

This community typically occurs in water deeper than 100 m in the northern North Sea (Knitzer et al. 1992) and have been referred to as 'Foraminifera communities' by other workers (e.g. Stephen 1923; Thorson 1957; McIntyre 1961).

Temporal variation

No temporal data available.

Characterising Species

Taxon
Foraminifera
Exogone verugera
Nephtys
Aricidea catherinae
Minuspio cirrifera
Thyasira
Thyasira flexuosa
Amphiura

Similar biotopes

SS.SMu.CFiMu.BlyrAchi
In shallower water a Brissopsis-dominated community (BlyrAchi) may develop

SS.SMu.CSaMu.ThyNten
ThyNten is similar to this biotope in terms of high numbers of Thyasira spp. but lacks the foraminiferan component and is generally found at shallower depths.

Biotope history

Classification Habitat code
97.06 COS.ForThy

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