Deep-sea sponge aggregations

Deep-sea sponge aggregations © JNCC

In some deep-sea areas, sponges may represent as much as 90% of the weight of living material within the community (excluding fish).  These aggregations are mainly made up of two types of sponge: the glass sponge and the giant sponge.  They occur offshore in water depths of between 250m and 1300m, where currents are moderate and temperatures do not exceed 10°C.  They are found on seabed types from silt and mud to boulders, and can occur in the rocky ridges formed as icebergs ploughed through the seabed at the end of the last ice age.

Sponge communities can support a range of species of other animals, but the types of animals found there tend to be different from those on the surrounding seabed.  Sponges have tiny spine-like ‘spicules’ within their tissues, which are made of silicon.  When the animals occur in large numbers, the spicules from dead sponges form dense mats on the seabed, which appear to prevent burrowing animals from setting up home.  Instead, it is animals that live on the surface of the seabed, such as brittlestars, which dominate.  They use the sponges as raised perches to help them collect passing food particles.

Deep-sea sponges are thought to be slow-growing, and sponge communities are likely to take many years to recover if damaged.  Physical disturbance to the seabed is the greatest threat, and it is probable that bottom trawling and increased amounts of sediment in the water may damage deep-sea sponge aggregations. They may also be sensitive to pollution.

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

 

European distribution

Deep-sea sponge aggregations are found in locations across the north-east Atlantic, including the Faroe Islands, Norway and the Porcupine Seabight to the south-west of Ireland.

 

Conservation status/need

Deep-sea sponge aggregation fact

 

Official definition

UK Biodiversity Action Plan; Priority Habitat Descriptions. BRIG (ed. Ant Maddock) 2008 (updated December 2011)

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 Deep-sea sponge aggregations

JNCC - UK BAP Priority Species and Habitats

JNCC EUNIS habitat correlations table