Type of fouling organism: Anemone

Sea anemones along with sea pens and most corals belong to the class Anthozoa. There are no medusa forms and polyps have vertical divisions or mesenteries. There is a central mouth which is surrounded by tentacles with nematocysts which are used to entangle and capture prey. Typically, sea anemone polyps have six to twelve mesenteries with a varying number of tentacles.

Metridium senile is an anemone with a diverse range of forms. The large base is wider than the column, which is smooth and often irregular. It has numerous tentacles at the top of the column, which when expanded form a ‘plume’. May reach 300 mm in height. The tentacles are long and slender and rarely exceed 200 in number. The colour varies but most commonly ranges from white orange to dark green/brown and grey, with the occasional appearance of red or yellow varieties.

Environment and Habitat

- Found attached to any suitable hard substratum.
- Subtidal species, found on the lower shore to ca. 100 m.
- Filter feeds on zooplankton.
- Growth is rapid.
- High intolerance of loss of substratum and change in emergence regime.
- Intermediate intolerance of desiccation, physical disturbance and abrasion, increases in water flow rate and increases in turbidity.
- Low intolerance smothering, increases in suspended sediments, displacement, decrease in water flow rate and increases in wave exposure.

Reproduction

- Reproductive type: Separate sexes, fission.
- Reproductive frequency: Unknown.
- Development type: Lecithotrophic.
- Age at Maturity: Unknown.
- Larval duration: 1 - 6 months.
- Dispersal potential: > 10 km.
- Gamete production: August to September.
- Lifespan: Long lived 10+ years.

Communities

- Gregarious.
- Temporary attachment. - Colonises areas aggressively.

Equipment

- Found on other biofouling organisms.
- Stock species particularly shellfish.
- Fishnets, cages, pontoons, shellfish trays, tanks, pipes.

Effects and Impacts

- Problematic for stock species as can compete for space and resources.
- Can obstruct the opening of bivalve shells and nets.
- Can reduce the value of shellfish.
- Increases the weight of equipment.
- Increases labour and production costs as a result of cleaning and removal of biofouling.

Control/ Strategies and Management

Nets
- Onshore Net washing
- Coatings (Copper sulphate, fouling release coatings e.g. silicon)
- Mechanical cleaning of infrastructure (Disk cleaners)
- Air drying nets
Trays
- Manual cleaning (scrubbing and/or brushing)
- Low power washing
- High power washing
- Jet washing
- Air drying
- Lowering trays below photic zone during major spatfalls
- Biological Control (Sea urchins and periwinkles)
- Coatings (Copper sulphate, fouling release coatings e.g. silicon)
Shellfish
- Manual Cleaning
- Mechanical Cleaning
- Hot water 55oC for 5 seconds (Stock mortalities of ca 5% with this method)
- Dipping (Freshwater or chemical solution)
- Lowering lines below photic zone during major spatfalls
- Biological control (Sea urchins and periwinkles)
- Coatings (Copper sulphate, spiky coatings, fouling release coatings e.g. silicon)

Principles of Management

C Combat Settlement
P Protect Equipment and Stock
R Remove Biofouling

Distribution

- Range encompasses from Scandinavia down to the Bay of Biscay in the north east Atlantic. Not known in the western Mediterranean but may have been introduced into the Adriatic, where it has been observed.

References

Hiscock, K. & Wilson, E., 2007. Metridium senile. Plumose anemone. Marine Life Information Network: Biology and Sensitivity Key Information Sub-programme [on-line]. Plymouth: Marine Biological Association of the United Kingdom. [cited 19/06/2007]. Available from:

Janet Moore (2001) An Introduction to the Invertebrates. Cambridge University Press

Hayward P, Nelson-Smith T & Shields C (1996) Seashore of Britain and Northern Europe. HarperCollins Pubs.