The Honeycomb worm
Each individual worm is only 3-4cm long but females may reach 10cms, each worm can add 12cm a year to its tube gathering sand and shell fragments but this is dependant on the availability of loose sand and water temperature. Bellow 5 Deg C the worms become inactive, they are more productive in warmer French coastal areas. Most worms live for 3-5 years but they are recorded at 7-9 years old. The larvae (summer) float around for anything from 6 weeks to 6 months until they chemically locate an existing reef (some start new ones) they settle on the rock and start to build. If there is limited space they build upwards and make the honeycomb reef, if they have the room they build flat on the rock.
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Worms are filter feeders and when submerged they extend tentacles and entrap passing particles, including more sand. They can hide deep in the sand tube and so have few predators, although crabs and blennies can feed on them. The colonies are found in the mid to low shore but do not extend far out to sea, perhaps this is due to the sand movements being greater in this surf region.
Colonies can dominate and exclude most other organisms from the rock, even seaweeds and mussels. Dense young colonies are typically poor in other species. As they age or become damaged other organisms move in, this can add greatly to the species that would be present on just the bare rock. One theory is that colonies are cyclic, however, little is known about the age of individual colonies. This is dependant on continuing supplies of water borne sand and the rock they are attached to remaining solid. Mussels are known to colonise over older areas and then become dominant, but if the loose sand available increases this can shift the dominance back towards the worms. This cyclic progression and possible age of colonies has not been fully proven and would make a great area for study.
Colonies can dominate and exclude most other organisms from the rock, even seaweeds and mussels. Dense young colonies are typically poor in other species. As they age or become damaged other organisms move in, this can add greatly to the species that would be present on just the bare rock. One theory is that colonies are cyclic, however, little is known about the age of individual colonies. This is dependant on continuing supplies of water borne sand and the rock they are attached to remaining solid. Mussels are known to colonise over older areas and then become dominant, but if the loose sand available increases this can shift the dominance back towards the worms. This cyclic progression and possible age of colonies has not been fully proven and would make a great area for study.
Humans have a major impact on the species and local developments such as the construction of sea defences, dredging or any change in currents or sand movements can decimate colonies.
Another species of worm, Ross’s worm (Sabellaria spinulosa), is found mainly in sublittoral areas (always underwater). These make reefs like the honeycomb but in the UK they are more likely to be individuals or thin sheets of multiple tubes. Where the reefs do occur they significantly increase the range and number of other organisms found. These worms are pollution tolerant but are damaged by bottom fishing methods.
References
http://www.ukmarinesac.org.uk/communities/biogenic-reefs/br4_1.htm
http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats-47-SabellariaSpinulosaReefs.pdf
http://jncc.defra.gov.uk/Docs/UKBAP_BAPHabitats-46-SabellariaAlveolataReefs.doc
Another species of worm, Ross’s worm (Sabellaria spinulosa), is found mainly in sublittoral areas (always underwater). These make reefs like the honeycomb but in the UK they are more likely to be individuals or thin sheets of multiple tubes. Where the reefs do occur they significantly increase the range and number of other organisms found. These worms are pollution tolerant but are damaged by bottom fishing methods.
References
http://www.ukmarinesac.org.uk/communities/biogenic-reefs/br4_1.htm
http://jncc.defra.gov.uk/pdf/UKBAP_BAPHabitats-47-SabellariaSpinulosaReefs.pdf
http://jncc.defra.gov.uk/Docs/UKBAP_BAPHabitats-46-SabellariaAlveolataReefs.doc