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Sea pen and burrowing megafauna communities
Areas of stable muddy seabed, where animals burrow below and sea pens protrude from the surface.
Sea pens © JNCC/Sue Scott
On stable plains of fine mud on the seabed, at depths from 15m to 100m or more, areas of the seabed may be marked by prominent mounds and burrows. These are caused by the burrowing activities of animals below the surface - animals such as the Norway lobster, mud shrimps and even a fish, called the Fries’ goby.
Below the seabed surface, the mud is riddled with burrows, often interconnected, that offer shelter to a wide range of smaller animals. The mud is full of diverse marine life, such as shrimp-like animals, brittlestars, worms and bivalves (with their paired, hinged shells). Crabs, hermit crabs and starfish hunt and scavenge on the surface of the mud.
Most prominent, however, are the populations of luminous, slender sea pens protruding from the surface of the mud. The tall sea pen, rare in UK waters, also occurs here, and can grow to more than 2m in height. Another rare species is the burrowing fireworks anemone, which is scarce in the UK and appears to be restricted to this single type of seascape.
Bottom trawling for Norway lobsters (which are eaten as scampi or Dublin Bay prawns) is thought to cause severe physical disturbance to the seabed. Such disturbance results in a decline in the variety of animals found within this habitat, with large, slow growing species such as sea pens particularly at risk.
Brief description of European distribution
Recorded from the north-eastern Irish Sea and in the deep offshore waters of the North Sea.
Conservation status / need
OSPAR List of Threatened and/or Declining Species and Habitats (Region II – North Sea, Region III – Celtic Sea)
The deep water mud on which these communities are found is a UKBAP Priority Habitat and is listed in Annex I Habitats Directive: Large shallow inlets and bays
Further information sources
Seapens and burrowing megafauna in circalittoral fine mud
(JNCC)
Community ecology: interactions between species (UK Marine SACs Project)
Sea Pens and Burrowing Megafauna (UK Marine SACs Project)
Case reports for the OSPAR list of threatened and/or declining species and habitats (PDF 8.4Mb) (OSPAR)
The tall sea pen - Funiculina quadrangularis - General information (MarLIN)
Interesting fact
In this habitat, an association has been noticed between a species of brittlestar and the tall sea pen. The starfish uses its long, prehensile arms to cling to the sea pen, so keeping itself raised above the seabed.
