Polychaete worm reefs in the Mediterranean infralittoral zone
Quick facts
Red List habitat type | code MEDA5.61 |
---|---|
Threat status | |
Europe | Data Deficient |
EU | Data Deficient |
Relation to |
|
Source | European Red List habitat factsheet |
European Red List of habitats reports | |
European Red List of habitats (Excel table) |
Summary
Worm reefs are large bioconstructions built by polychaetes the most important of which in the Mediterranean are the sabellarids Sabellaria alveolata and S. spinulosa and the serpulids Hydroides dianthus and Ficopomatus enigmaticus. The development of such reefs is assured by the gregarious settlement of polychaete larvae, which occurs mainly on pre-existing reefs or their dead remains.
Sabellaria bioconstructions can be relatively unstable and undergo a natural cycle of development and decay, they can form relatively quickly and may take the form of sheets, hummocks and reefs as well as evolving from globular formations into reef platforms. Reefs may persist in an area for many years although individual clumps may regularly form and disintegrate. Sabellaria alveolata reefs in the Mediterranean are located between 1 to 7 m of depth where can reach 60 cm thick when they are well developed. In most sites, however, they tend to be very scattered and not particularly extensive
Most serpulids are considered to be 'secondary frame builders'. Ficopomatus enigmaticus, typically growing in coastal lagoons and brackish water lakes, can form large reefs. They can occur as a fringing reef along the rocky shoreline, forming a continuous layer that can reach up to 3 m thick, at a depth of about 1 m, or can develop as dense patch reefs growing from the bottom, with hemispherical forms called micro atolls (over 2 m height and 4 m in diameter) and with a distribution related to the depth (from 0.5 to 1.5 m).
This habitat provides a diversity of microhabitats increasing available substrate for numerous species; sheltering both hard and soft-bottom rare species which are potential colonizers of adjacent habitats; providing refuge for invertebrates including snails and crabs that may have an impact on native species communities and are attractive for some fish such as Sygnathus abasteri, Aphanius fasciatus and Knipowitschia panizzae
Indicators of quality
The status and dynamics of the reefs must be defined integrating the physical characteristics, taking into account the degree of fragmentation of reef features (mainly produced by species which are known to degrade, smother and break up areas of Sabellaria, e.g. the mussel Mytilus galloprovinciallis), and the prevalence of different structural characteristics within the reef formations. The health of the reefs can be determined with reference to the percentage of newly settled worms, those with crisp apertures, those with worn apertures and dead worms.
Threat status
Synthesis of Red List assessment
EU | |
Red List Category | Red List Criteria |
Data Deficient | - |
Europe | |
Red List Category | Red List Criteria |
Data Deficient | - |
Confidence in the assessment
Pressures and threats
- Biological resource use other than agriculture & forestry
- Marine and Freshwater Aquaculture
- Intensive fish farming, intensification
- Leisure fishing
- Bait digging / Collection
- Human intrusions and disturbances
- Other human intrusions and disturbances
- Trampling, overuse
- Shallow surface abrasion/ Mechanical damage to seabed surface
- Pollution
- Pollution to surface waters (limnic, terrestrial, marine & brackish)
- Pollution to surface waters by industrial plants
- Pollution to surface waters by storm overflows
- Other point source pollution to surface water
- Nutrient enrichment (N, P, organic matter)
- Marine water pollution
- Toxic chemical discharge from material dumped at sea
- Invasive, other problematic species and genes
- Invasive non-native species
- Climate change
- Changes in abiotic conditions
- Temperature changes (e.g. rise of temperature & extremes)
- pH-changes
- Water flow changes (limnic, tidal and oceanic)
- Wave exposure changes
- Sea-level changes
Habitat restoration potential
Sabellaria reefs are extremely dynamic too, they may persist in an area long time although individual clumps may regularly form and disintegrate. Usually, reefs show a cycle of development undergoing 4 different easily determined morphologies (reef compactness, tube orientation, percentage of tubes with 'sand crown', and presence/absence of epibionts on the reef surface) and defined as 'phases'. Each phase is the result of a constantly disturbed and precarious balance between physical factors (hydrodynamic forces, temperature, and local environmental conditions, such as seabed topography and water clarity), and biological factors (reproduction and recruitment mechanism of the pelagic larvae). Sabellaria alveolata can live up to 9 years, whilst S. spinulosa is a fast growing annual species so that degradation and recovery of the reefs that occurs as a response to external environmental pressure, can be different, even if in both species recruitment rates are high and recovery could be quite rapid, the speed of changes is different according to their different life cycle. As a consequence S. alveolata reefs seem to be more persistent and more abundant than S. spinulosa which, in most parts of its geographic range, is solitary or form small groups.
The limited understanding of the factors affecting recruitment success and of the source of larval supply preclude further predictions on the potential for recovery and the rate at which it might occur. Biogenic reefs can take many years to recover, and some may never recover. For example, Sabellaria spinulosa reefs have failed to recover in the Wadden Sea following their dramatic decline over recent decades. According to the life-cycle knowledge it can be hypothesised that the recover of S. alveolata may occur within at least 10 years if condition are maintained optimal, but that can last more time naturally.
Trends in extent |
|
Average current trend in quantity |
|
Unknown ![]() |
Unknown ![]() |
EU28 | EU28+ |
Trends in quality |
|
Average current trend in quality |
|
Unknown ![]() |
Unknown ![]() |
EU28 | EU28+ |
Conservation and management needs
List of conservation and management needs
- Measures related to marine habitats
- Other marine-related measures
- Measures related to spatial planning
- Establish protected areas/sites
- Measures related to hunting, taking and fishing and species management
- Regulation/Management of fishery in marine and brackish systems
- Measures related to special resouce use
- Regulating/Managing exploitation of natural resources on sea
Distribution
Geographic occurrence and trends
Seas | Present or presence uncertain | Current area of habitat (Km2) | Recent trend in quantity (last 50 years) | Recent trend in quality (last 50 years) |
---|---|---|---|---|
Adriatic Sea | Present | Unknown | Unknown | Unknown |
Aegian-Levantine Sea | ||||
Ionian Sea and the Central Mediterranean Sea | ||||
Western Mediterranean Sea |
Extent of Occurrence, Area of Occupancy and habitat area
Extent of Occurrence (EOO) (Km2) | Area of Occupancy (AOO) | Current estimated Total Area | Comment | |
---|---|---|---|---|
EU28 | 943,913 | >19 | Unknown | EOO and AOO have been calculated on the available data but this is known to be incomplete. |
EU28+ | >19 | Unknown | EOO and AOO have been calculated on the available data but this is known to be incomplete. |
EOO = the area (km2) of the envelope around all occurrences of a habitat (calculated by a minimum convex polygon).
Characteristic species
Species scientific name | English common name | Species group |
---|---|---|
Aphanius fasciatus | Mediterranean Toothcarp | Fishes |
Knipowitschia panizzae | Painzza's Goby | Fishes |
Apseudes latreillii | Invertebrates | |
Balanus eburneus | Invertebrates | |
Botryllus schlosseri | Invertebrates | |
Bowerbankia gracilis | Invertebrates | |
Conopeum seurati | Invertebrates | |
Ficopomatus enigmaticus | Invertebrates | |
Gammarus aequicauda | Invertebrates | |
Hydroides dianthus | Invertebrates | |
Lekanesphaera hookeri | Invertebrates | |
Leptochelia savignyi | Invertebrates | |
Neanthes succinea | Invertebrates | |
Nereis falsa | Invertebrates | |
Sabellaria alveolata | Invertebrates | |
Sphaeroma serratum | Invertebrates | |
Striarca lactea | Invertebrates |
Legal status
Relation to other habitat types mentioned in legal instruments
Legal text | Annex | Name in legal text | Code in legal text |
Habitat type relationship |
More information |
---|---|---|---|---|---|
Council Directive 92/43/EEC of 21 May 1992 on the conservation of natural habitats and of wild fauna and flora - consolidated version 01/01/2007 | Annex I: natural habitat types of community interest whose conservation requires the designation of special areas of conservation | Reefs | 1170 | Narrower | http://ec.europa.eu/environm...rective/index_en.htm |