Natural England - Deep-sea sponge aggregations

Deep-sea sponge aggregations

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.

Deep-sea sponge aggregations © JNCC

Deep-sea sponge aggregations -
© JNCC

Sponge communities can support about 50 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.

Brief description of 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

UKBAP Priority Habitat

OSPAR List of Threatened and/or Declining Species and Habitats (Region V – Wider Atlantic)

Habitats Directive Annex I: Reefs

Further information sources

Case Reports for the OSPAR List of threatened and/or declining species and habitatsexternal link (PDF, 8.4 MB) (OSPAR)

UKBAP Priority Species and Habitatsexternal link (UKBAP)

Interesting fact

Giant sponges may be 50cm or more in diameter, but take several decades to reach full size.