Sea-pen and burrowing megafauna communities

Areas of stable muddy seabed, where animals burrow below and sea pens protrude from the surface


Sea pen and burrowing megafauna communities © Sue Scott JNCC

On stable plains of fine mud, at depths typically from 15m to over 200m 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, such as the Norway lobster, mud shrimps and even a fish, called the Fries’ goby.

Below the seabed surface, the mud can be 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.

Populations of luminous, slender sea pens may be found protruding from the surface of the mud. The tall sea pen, rare in UK waters, can also occur within this habitat, 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 type of seascape.

Bottom trawling for Norway lobsters, more commonly known 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.

For the official habitat definition please see the documents listed below.


European distribution

Recorded from the north-eastern Irish Sea and in the deep offshore waters of the North Sea, as well as sheltered inshore environments such as sea lochs.


Conservation status/need

Sea pen and burrowing megafauna fact

OSPAR List of Threatened and/or Declining Species and Habitats (Region II – North Sea, Region III – Celtic Sea)  


Official habitat definition

Descriptions of habitats on the OSPAR list of threatened and/or declining species and habitats (OSPAR agreement 2008/07).


Further information

OSPAR Commission – Background Document for Seapen and Burrowing megafauna communities

JNCC biotope classification - Seapens and burrowing megafauna in circalittoral fine mud

JNCC EUNIS habitat correlations table

UK Marine SAC Project - Interactions between megafaunal burrowers

UK Marine SAC Project - Sea pens and burrowing megafauna

Marine Life Information Network - The tall sea pen - Funiculina quadrangularis

JNCC EUNIS habitat correlations table