Natural England - Ross worm reefs

Ross worm reefs

Ross worms (Sabellaria spinulosa) build tubes from sand and shell fragments. The worms are usually found individually, but in some shallow water areas they are found in colonies

Ross worm reefs © JNCC/Keith Hiscock

Ross worm reefs -
© JNCC/Keith Hiscock

The tubes of large numbers of the worms can form reefs, which at their largest can be about half a metre in height and cover an area of several hectares. Ross worms require a good supply of sand grains for tube-building, and so like murky water.

These worm-built reefs are important because they provide a habitat for a wide range of other seabed-dwelling animals. A greater variety of marine life is found association with ross worm reefs than on other similar areas of the seabed. Where they occur on the soft seabed, they are of particular significance for nature conservation. By providing a complex seascape with hard surfaces and nooks and crannies in an otherwise flat, featureless seabed, they provide a home for animals which would not normally be found there.

The greatest impact on this habitat is thought to be physical disturbance from fishing activities. Dredging for oysters and mussels, trawling for shrimp or finfish, net fishing and potting can all cause physical damage to these reef communities. While the reefs appear to recover well from minor damage, serious impacts from mobile fishing gear break the reefs down into small pieces.

Aggregate dredging often takes place in areas of mixed sediment where ross worm reefs may occur, but the effects of this on the reefs are being investigated. Ross worms appear to be very tolerant of pollution.

Brief description of European distribution

Given its few key requirements, and its tolerance of poor water quality, ross worms are common in the north-east Atlantic. Distinct reefs (as opposed to low crusts on the seabed) have been recorded from much of the British Isles (although few in Scottish waters) as well as off the coasts of France and Germany. They are absent from the Baltic Sea.

Conservation status / need

UKBAP Priority Habitat

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

Listed in Annex 1 of the Habitats Directive: Reefs, and as a feature of Sandbanks which are covered by seawater at all time; Large shallow bays and inlets; and Estuaries

Further information sources

Sabellaria spinulosa reefsexternal link (UKBAP)

Sabellaria spinulosaexternal link (UK Marine SACs Project) 

Case reports for the OSPAR list of threatened and/or declining species and habitatsexternal link (PDF 8.4Mb) (OSPAR)

Interesting fact 

We think the worms need something hard to attach to – rock, boulders, pebbles or shell fragments. On a soft seabed, these anchorage points might be sparse, but once a few worms have found them and a crust of tubes has begun to form, more worms can simply attach to the growing reef.