Urticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock

29-11-2002
Researched byDr Keith Hiscock Refereed byThis information is not refereed.
EUNIS CodeA4.213 EUNIS NameUrticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock

Summary

UK and Ireland classification

EUNIS 2008A4.213Urticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock
EUNIS 2006A4.213Urticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock
JNCC 2004CR.MCR.EcCr.UrtScrUrticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock
1997 BiotopeCR.MCR.ByH.UrtUrticina felina on sand-affected circalittoral rock

Description

Urticina felina frequently occurs on rocks at the sand-rock interface where scour levels are high and few other species seem to be able to colonise. This biotope is only occasionally recorded as a separate entity. More often the Urticina are included as part of whatever biotope occurs on the nearby hard substrata. These neighbouring biotopes vary considerably but often include other scour-tolerant species. Most data has been assigned to MCR.Urt.Urt and MCR.Urt.Cio. The biotope research presented below is based on MCR.Urt.Cio, the description of which follows.

Sand-covered low-lying rock with some scouring effect which has dense Urticina felina with Ciocalypta penicillus attached to the underlying rock. Polymastia spp., particularly Polymastia mamillaris and sometimes Polymastia agglutinans are also present. Has links with the ephemeral hydroid (MCR.Flu.SerHyd) and Pomatoceros and bryozoan crust biotopes (MCR.PomByC) and can occur adjacent to them. Not regularly recorded as a separate entity but is often recognizable in this habitat where rock and coarse sediment interface. (Information taken from the Marine Biotope Classification for Britain and Ireland, Version 97.06: Connor et al., 1997a, b).

Recorded distribution in Britain and Ireland

Recorded from a few locations in south-west Britain as far north as the Sarns in west Wales with isolated records on the west and east coast of Ireland. Probably more widely occurring than indicated.

Depth range

-

Additional information

The sub-biotope MCR.Urt.Cio is a conspicuous and easily recognized entity occurring widely in south west Britain.

Listed By

Further information sources

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Habitat review

Ecology

Ecological and functional relationships

The sub-biotopes of MCR.Urt are dominated by sessile, permanently fixed, suspension feeding invertebrates that are, therefore, dependant on water flow to provide: an adequate supply of food and nutrients; gaseous exchange; remove metabolic waste products; prevent accumulation of sediment, and disperse gametes or larvae. The majority of species found in this biotope are adapted to strong wave action, siltation and a degree of sediment scour. Little is known of ecological relationships in circalittoral faunal turf habitats (Hartnoll, 1998). Most species live independently except that they compete for space and for food. The following text indicates major feeding types.
  • Suspension feeders on bacteria, phytoplankton and organic particulates and detritus include sponges (Ciocalypta penicillus, Polymastia spp. and Cliona celata) and soft corals (Alcyonium digitatum), erect and encrusting bryozoans (e.g. Pentapora fascialis, Flustra foliacea, and Bugula spp.), brittlestars (e.g. Ophiothrix fragilis), barnacles (e.g. Balanus crenatus), caprellid amphipods, porcelain crabs (e.g. Pisidia longicornis), and polychaetes (e.g. Pomatoceros spp.). However, the water currents they generate are probably localized , so that they are still dependant on water flow to supply adequate food.
  • Passive carnivores of zooplankton and other small animals include, hydroids (e.g. Nemertesia antennina), soft corals (e.g. Alcyonium digitatum), while larger prey are taken by Urticina felina (Hartnoll, 1998).
  • Sea urchins (e.g. Echinus esculentus are generalist grazers, removing barnacles, ascidians, hydroids and bryozoans and potentially removing all epifauna, leaving only encrusting coralline algae and bedrock. Sea urchins were shown to have an important structuring effect on the community and epifaunal community succession (Sebens, 1985; 1986; Hartnoll, 1998).
  • Specialist predators of hydroids and bryozoans include the nudibranchs (e.g. Janolus cristatus, Doto spp. and Onchidoris spp.) and pycnogonids, (e.g. Achelia echinata), while the nudibranch Tritonia hombergi and the mesogastropod Simnia patula prey on Alcyonium digitatum.
  • Scavengers include polychaetes, small crustaceans such as amphipods, starfish and larger decapods such as hermit crabs (e.g. Pagurus bernhardus) and crabs (e.g. Cancer pagurus).
  • Mobile fish predators are likely to include gobies (e.g. Pomatoschistus spp.), butterfish (Pholis gunnellus), wrasse and eelpout (Zoarces viviparus) feeding mainly on small crustaceans, while species such as flounder (Platichthys flesus) are generalists feeding on ascidians, bryozoans, polychaetes and crustaceans (Sebens, 1985; Hartnoll, 1998)
Competition
Intra and interspecific competition occurs for food and space. Filter feeders reduce the concentration of suspended particulates and deplete food to other colonies/individuals downstream (intra and inter specific competition). Sebens (1985, 1986) demonstrated a successional hierarchy, in which larger, massive, thick growing species (e.g. large anemones, soft corals and colonial ascidians) grew over low lying, or encrusting growth forms such as halichondrine sponges, bryozoans, hydroids and encrusting corallines. The epifauna of vertical rock walls became dominated by large massive species, depending on the degree of predation, especially by sea urchins. However, encrusting bryozoans and encrusting corallines may survive overgrowth (Gordon, 1972; Sebens, 1985; Todd & Turner, 1988). In the sub-biotopes of MCR.Urt, the degree of sediment scour and siltation probably exerts a controlling factor on the succession (see temporal change below) and are dominated by species tolerant of sediment scour and high water flow.

Seasonal and longer term change

No information on seasonal or temporal change in MCR.Urt.Cio or related biotopes was found and the following information has been inferred from available studies of subtidal epifaunal communities (Sebens, 1985, 1986; Hartnoll, 1983, 1998).

Seasonal changes
Most of the species in the biotope and sub-biotopes are perennial but may show seasonal changes. For instance, some hydroids and bryozoans, may show annual phases of growth and dormancy or regression. For example, Flustra foliacea becomes dormant in winter, Bugula species die back in winter to dormant holdfasts, while the uprights of Nemertesia antennina die back after 4-5 month and exhibit three generations per year (spring, summer and winter). Hartnoll (1975) found that, in Alcyonium digitatum studied in the Isle of Man, from February through to July all colonies expand and feed regularly. However, from late July through to December the colonies remain contracted, during which time they do not feed and assume a shrunken appearance with a reddish or brownish colour. The change of colour is a result of the periods of inactivity as the surface of the colonies become covered with a layer of epibiota (diatoms and prostrate thalloid and filamentous algae initially, from which arises a forest of erect algae and hydroids). The amphipod Jassa falcata also builds its mucous and detritus tubes amongst the other epibiota, adding to and consolidating the covering (Hartnoll, 1975). Once the colonies recommence expansion in December the epibenthic film is sloughed off. The season of prolonged inactivity coincides with the final months of gonad maturation and the shedding of the epibenthic film immediately precedes the spawning of the gametes (see reproduction) (Hartnoll, 1975; 1977) (see MarLIN reviews; Hughes, 1977; Hayward & Ryland, 1998; Hartnoll, 1975, 1998).

Succession
Sebens (1985, 1986) described successional community states in the epifauna of vertical rock walls. Clear space was initially colonized by encrusting corallines, rapidly followed by bryozoans, hydroids, amphipods and tube worm mats, halichondrine sponges, small ascidians (e.g. Dendrodoa carnea and Molgula manhattensis), becoming dominated by the ascidian Aplidium spp., or Metridium senile or Alcyonium digitatum. High levels of sea urchin predation resulted in removal of the majority of the epifauna leaving encrusting coralline dominated rock. Reduced predation allowed the dominant epifaunal communities to develop, although periodic mortality (through predation or disease) of the dominant species resulted in mixed assemblages or a transition to another assemblage (Sebens, 1985, 1986). Sea urchin predation may play a significant role in freeing space for colonization in this community. Succession will be dependant on species tolerance to silt and sediment scour.

Community stability
Long term studies of fixed quadrats in epifaunal communities demonstrated that while seasonal and annual changes occurred, subtidal faunal turf communities were relatively stable, becoming more stable with increasing depth and substratum stability (i.e. bedrock and large boulders rather than small rocks) (Osman, 1977; Hartnoll, 1998). Many of the faunal turf are long-lived, e.g. 6 -12 years in Flustra foliacea, over 20 years in Alcyonium digitatum, 8-16 years in Echinus esculentus and probably many hydroids (Stebbing, 1971a; Gili & Hughes, 1995; Hartnoll, 1998).

Habitat structure and complexity

  • The bedrock is covered by a layer of encrusting corallines overgrown by dominant erect bryozoans and hydroids (e.g. Flustra foliacea, Bugula species and Nemertesia antennina) interspersed with cushion-like sponges (e.g. Ciocalypta penicillus, Polymastia spp., Cliona celata), dead men's fingers Alcyonium digitatum and dahlia anemones Urticina felina. The coralline-encrusted rock and the bases of sponges are often covered by sediment.
  • The faunal turf provides interstices and refuges for a variety of small organisms such as nemerteans, polychaetes, and amphipods, while the erect species provide substrata for caprellid amphipods, which use them as 'platforms' to suspension feed.
  • The erect bryozoans and hydroids support a variety of epizoics that use them as substratum and in some cases affect their growth rates. For example, Flustra foliacea supported 25 species of bryozoan, 5 hydroid species, some sessile polychaetes, barnacles, lamellibranchs and tunicates (Stebbing, 1971b). The bryozoans Bugula flabellata, Crisia spp. and Scrupocellaria spp. were major epizoics. Scrupocellaria spp. settled preferentially on the youngest, distal, portions of the frond, possibly to elevate their branches into faster flowing water (Stebbing, 1971b). Similarly, Alcyonidium parasiticum is epizoic on hydroid stems or the bryozoan Cellaria spp. and the sponge Esperiopsis fucorum may grow on the stem of Tubularia species or on the test of ascidians.
  • Mobile species include decapods crustaceans such as shrimp, crabs and lobsters, sea urchins, starfish and fish.
  • Gobies, shannies and butterfish probably utilize available rock ledges and crevices, while large species such as flounder and cod probably feed over a wide area.
  • Pockets of sediment that accumulate between boulders or in crevices (where present) may support benthic infaunal species such as Mya truncata and Sabella pavonina.
  • The biotope and sub-biotopes may show spatial variation in community complexity and exhibit a mosaic of different species patches (Hartnoll, 1998), due to colonization of areas recently cleared by predation, disease or physical disturbance in the process of re-colonization. The upper edges or boulders or rocky outcrops, most directly in water flow, tend to exhibit the most species rich and abundance faunal turfs, while species richness decreases with proximity to the sediment/ rock interface, which favours species such as the sponges Polymastia spp. or the anemone Urticina felina. Areas subject to increased scour or vertical surfaces tend to be dominated by tube worms such as Pomatoceros triqueter (Stebbing, 1971b, Eggleston, 1972b; Sebens, 1985, 1986; Connor et al., 1997a; Brazier et al., 1998; Hartnoll, 1998).
  • Periodic disturbance of the community due to physical disturbance by storms, extreme scour, or fluctuations in predation, especially by sea urchins, may encourage species richness by preventing dominance by a few species (Osman, 1977; Sebens, 1985, 1986; Hartnoll, 1998).

Productivity

Circalittoral faunal turf biotopes are primarily secondary producers. Food in the form of phytoplankton, zooplankton and organic particulates from the water column together with detritus and abraded macroalgal particulates from shallow water ecosystems are supplied by water currents and converted into faunal biomass. Their secondary production supplies higher trophic levels such as mobile predators (e.g. fish) and scavengers (e.g. starfish and crabs) and the wider ecosystem in the form of detritus (e.g. dead bodies and faeces). In addition, reproductive products (sperm, eggs, and larvae) also contribute to the zooplankton (Hartnoll, 1998). However, no estimates of faunal turf productivity were found.

Recruitment processes

Most of the species within MCR.Urt.Cio produce short-lived, larvae with relatively poor dispersal capacity, resulting in good local recruitment but poor long range dispersal. Although, the biotope occurs within moderately strong to strong water flow that could remove a large proportion of the reproductive output, most reproductive propagules are probably entrained within the reduced flows within the faunal turf or in turbulent eddies produced by flow over the uneven substratum, resulting in turbulent deposition of propagules locally. Many species are capable of asexual propagation and rapidly colonize space. For example:
  • Whilst very little is known about reproduction in the sponges that particularly characterise MCR.Urt.Cio, sponges may proliferate both asexually and sexually. A sponge can regenerate from a broken fragment, produce buds either internally or externally or release clusters of cells known as gemmules which develop into a new sponge. Most sponges are hermaphroditic but cross-fertilization normally occurs. There is a mass spawning of gametes through the osculum, which enter a neighbouring individual in the inhalant current. Fertilized eggs may be discharged into the sea where they develop into a planula larva. But in the majority of species development is viviparous, whereby the larva develops within the sponge and is then released. Larvae have a short planktonic life of a few hours to a few weeks, so that dispersal is probably limited and asexual reproduction probably results in clusters of individuals.
  • Hydroids are often the first organisms to colonize available space in settlement experiments (Gili & Hughes, 1995). Nemertesia antennina releases planulae on mucus threads, that increase potential dispersal to 5 -50m, depending on currents and turbulence (Hughes, 1977). Most species of hydroid in temperate waters grow rapidly and reproduce in spring and summer. Few species of hydroids have specific substrata requirements and many are generalists. Hydroids are also capable of asexual reproduction and many species produce dormant, resting stages, that are very resistant of environmental perturbation (Gili & Hughes, 1995). Hughes (1977) noted that only a small percentage of the population of Nemertesia antennina in Torbay developed from dormant, regressed hydrorhizae, the majority of the population developing from planulae as three successive generations. Rapid growth, budding and the formation of stolons allows hydroids to colonize space rapidly. Fragmentation may also provide another route for short distance dispersal.
  • The brooded, lecithotrophic coronate larvae of many bryozoans have a short pelagic life time of several hours to about 12 hours (Ryland, 1976). In temperate waters most bryozoans species tend to grow rapidly in spring and reproduce maximally in late summer, depending on temperature, day length and the availability of phytoplankton (Ryland, 1970).
  • Echinoderms are highly fecund, producing long-lived planktonic larvae with high dispersal potential but recruitment in echinoderms is poorly understood, often sporadic, variable between locations and dependant on environmental conditions such as temperature, water quality and food availability. Recruitment was reported to be sporadic in Echinus esculentus, e.g. Millport populations showed annual recruitment, whereas few recruits were found in Plymouth populations between 1980-1981 (Nichols, 1984). Bishop & Earll (1984) suggested that the population of Echinus esculentus at St Abbs had a high density and recruited regularly whereas the Skomer population was sparse, ageing and had probably not successfully recruited larvae in the previous 6 years. In Ophiothrix fragilis recruitment success is heavily dependent on environmental conditions including temperature and food availability. In years after mild winters Ophiothrix fragilis occurred in extremely high densities in the Oosterschelde estuary in Holland (Smaal, 1994). However, echinoderms such as Echinus esculentus, and Asterias rubens are mobile and widespread and are likely to recruit by migration from other areas.
  • Anthozoans, such as Alcyonium digitatum and Urticina felina are long lived with potentially highly dispersive pelagic larvae and are relatively widespread. They are not restricted to this biotope and would probably be able to recruit rapidly (refer to the Key Information reviews).
  • Mobile epifauna will probably recruit from the surrounding area as the community develops and food, niches and refuges become available, either by migration or from planktonic larvae. For example, Hatcher (1998) noted that the number of mobile epifaunal species steady increased over the year following deployment of settlement panels in Poole Harbour.

Time for community to reach maturity

No information was found on the development of MCR.Urt.Cio and the following has been inferred from studies of similar epifaunal communities (Sebens, 1985, 1986; Hartnoll, 1998).

The recolonization of epifauna on vertical rock walls was investigated by Sebens (1985, 1986). He reported that rapid colonizers such as encrusting corallines, encrusting bryozoans, amphipods and tubeworms recolonized within 1-4 months. Ascidians such as Dendrodoa carnea, Molgula manhattensis and Aplidium spp. achieved significant cover in less than a year, and, together with Halichondria panicea, reached pre-clearance levels of cover after 2 years. A few individuals of Alcyonium digitatum and Metridium senile colonized within 4 years (Sebens, 1986) and would probably take longer to reach pre-clearance levels.

Jensen et al. (1994) reported the colonization of an artificial reef in Poole Bay, England. They noted that erect bryozoans, including Bugula plumosa, began to appear within 6 months, reaching a peak in the following summer, 12 months after the reef was constructed. Similarly, ascidians colonized within a few months e.g. Aplidium spp. Sponges were slow to establish with only a few species present within 6-12 months but beginning to increase in number after 2 years, while anemones were very slow to colonize with only isolated specimens present after 2 years (Jensen et al., 1994.). In addition, Hatcher (1998) reported a diverse mobile epifauna after a years deployment of her settlement panels.

Hydroids are often initial colonizing organisms in settlement experiments and fouling communities (Standing, 1976; Brault & Bourget, 1985; Sebens, 1986; Jensen et al., 1994; Hatcher, 1998). In settlement experiments the hydroids Cordylophora caspia, Obelia dichotoma and Obelia longissima colonized artificial substrata within ca 1-3 months of deployment (Standing, 1976; Brault & Bourget, 1985: Sandrock et al., 1991). Once colonized the hydroids ability to grow rapidly and reproduce asexually is likely to allow them to occupy space and sexually reproduce quickly.

Flustra foliacea is the dominant species in this biotope. New colonies of Flustra foliacea take at least 1 year to develop erect growth and 1-2 years to reach maturity, grow slowly (Stebbing, 1971a; Eggleston, 1972a), and would probably several years to reach high abundance, depending on environmental conditions. Recruitment may be enhanced in areas subject to sediment abrasion, where less tolerant species are removed, making more substratum available for colonization, especially if larval release in spring coincides with the end of winter storms. The wreck of a small coaster (the M.V. Robert) off Lundy became dominated by erect bryozoans, including occasional Flustra foliacea, within 4 years of sinking, when it was first surveyed (Hiscock, 1981).

Overall, encrusting bryozoans, hydroids, and ascidians will probably develop a faunal turf within less than 2 years, and Flustra foliacea can evidently colonize and reach an abundance of occasional (1-5% cover) within 4 years. Slow growing species such as Flustra foliacea, Pentapora fascialis, and some sponges and anemones, will probably take many years to develop significant cover, so that this biotope may take between 5 -10 years to develop an stable community after disturbance, depending on local conditions.

Additional information

None

Preferences & Distribution

Recorded distribution in Britain and IrelandRecorded from a few locations in south-west Britain as far north as the Sarns in west Wales with isolated records on the west and east coast of Ireland. Probably more widely occurring than indicated.

Habitat preferences

Depth Range
Water clarity preferences
Limiting Nutrients
Salinity
Physiographic
Biological Zone
Substratum
Tidal
Wave
Other preferences

Additional Information

Rocky substratum biotopes covered or partly covered by sand occur at locations all around Britain and Ireland and share many characteristic species with MCR.Urt.Cio. However, the presence of the sponge Ciocalypta penicillus, a southern species, means that MCR.Urt.Cio is restricted to southern England, Wales and Ireland.

Species composition

Species found especially in this biotope

Rare or scarce species associated with this biotope

Additional information

Rocky substratum biotopes covered or partly covered by sand occur at locations all around Britain and Ireland and share many characteristic species with MCR.Urt.Cio. However, the presence of the sponge Ciocalypta penicillus, a southern species, means that this biotope is restricted to southern England, Wales and Ireland. It is believed that the sponge Adreus fascicularis is found only in this biotope.

Sensitivity reviewHow is sensitivity assessed?

Explanation

A range of species may be found on sand covered rocks depending most likely on degree of scour and geographical location. Ciocalypta penicillus, whilst characteristic of the biotope researched, has little information on its sensitivity and the conclusions of research rely mainly on widely distributed species such as the dahlia anemone Urticina felina, Nemertesia hydroids, dead men's fingers Alcyonium digitatum, bryozoans (Flustra foliacea and Pentapora fascialis) and keel worms Pomatoceros triqueter. Pentapora fascialis and Flustra foliacea provide a habitat for the species and are therefore described as 'Important structural'. Other species are important characterizing as the biotope might not be that biotope without them (or without Nemertesia antennina represented by Nemertesia ramosa).

Species indicative of sensitivity

Community ImportanceSpecies nameCommon Name
Important otherAlcyonium digitatumDead man's fingers
Important otherBalanus crenatusAn acorn barnacle
Important structuralFlustra foliaceaHornwrack
Important structuralPentapora fascialisRoss
Important otherPomatoceros triqueterKeel worm
Important characterizingUrticina felinaDahlia anemone

Physical Pressures

 IntoleranceRecoverabilitySensitivitySpecies RichnessEvidence/Confidence
High Moderate Moderate Major decline Moderate
Removal of the substratum will result in removal of all the sessile attached species, together with most of the slow mobile species (crustaceans, sea urchins and starfish) and an intolerance of high has been recorded. Recoverability will depend on recruitment from neighbouring communities and subsequent recovery of the original abundance of species, which may take many years, especially in slow growing sponges, Anthozoa and Flustra foliacea. Therefore, a recoverability of moderate has been recorded (see additional information below).
Intermediate High Low Minor decline Moderate
A4.213 is characteristic of areas subject to cover by coarse sediment. Holme & Wilson (1985) reported communities that were subject to periodic smothering by thin layers of sand, up to ca 5cm in the central English Channel. Flustra foliacea and hydroids such as Nemertesiaspp. and the anemone Urticina felina were noted in their sand scoured communities which may have included examples of A4.213. Smothering with a layer of sediment will prevent or reduce feeding and hence growth and reproduction.

Although the biotope will probably survive smothering at the benchmark level, the species richness of the biotope will probably decline due to the loss of more sensitive species due to clogging of their filtration apparatus, interrupted feeding and hence reduced growth, and potential short term anoxia under the sediment layer. Also, associated small species such as prosobranchs, amphipods and worms may be sensitive. Therefore, an intolerance of intermediate is suggested to reflect the reduced species richness. Recoverability is likely to be high (see additional information below) as the long-lived, slow growing species (Ciocalypta penicillus and Urticina felina) will most likely survive).

Low Very high Very Low No change Moderate
This biotope is characteristic of areas subject to sediment scour and therefore suspended sediment. While an increase in suspended sediment at the benchmark level for a month is likely to reduce the efficiency of filter feeding in some species (e.g. sponges, hydroids, soft corals and bryozoans), most species are likely to survive for a month. If there is an associated increase in siltation, it is likely to interfere with larval settlement if it coincided with the reproductive season. Therefore, an intolerance of low has been recorded.
Low Moderate Moderate Decline Very low
A4.213 is characteristic of areas subject to sediment scour and suspended sediment. Therefore, with decreasing suspended sediment levels, species richness is likely to increase. A decrease in suspended sediment may decrease food availability for the duration of the benchmark (one month) but otherwise not adversely affect the biotope in such a short period of time. Therefore, an intolerance of low has been recorded. Prolonged decreases in suspended sediment, and consequent reduced scour may allow other species to colonize the habitat and out-compete characterizing species, perhaps increasing dominance by ascidians, sponges or anemones, and their biotopes. In such a situation, the biotope would no longer be A4.213 and intolerance would be high.
Not relevant Not relevant Not relevant Not relevant Not relevant
Sponges, hydroids, and soft corals, are probably highly intolerant of desiccation. However, this biotope is circalittoral and unlikely to be exposed to the air and desiccation.
Not relevant Not relevant Not relevant Not relevant Not relevant
An increase or decrease in tidal emergence is unlikely to affect circalittoral habitats, except that the influence of wave action may be increased (see wave action below).
Not sensitive* Not relevant
An increase or decrease in tidal emergence is unlikely to affect circalittoral habitats, except that the influence of wave action may be increased (see wave action below).
High Moderate Moderate Minor decline Low
A4.213 is characterized by species that are tolerant of moderately strong to strong tidal streams and associated sediment scour. Increased water flow is likely to reduce predation by Asterias rubens and large sea urchins, e.g. Echinus esculentus was observed to be rolled along the substratum by currents of 2.6 knots or above (Comely & Ansell, 1988). But in severe scour, the community may become impoverished, consisting of Pomatoceros spp., encrusting bryozoans, encrusting coralline algae and Balanus crenatus, e.g. A5.141. The likely associated scour and displacement of some species in the biotope over the year (see benchmark), is likely to change the biotope to a different one. Therefore, an intolerance of high has been recorded. Recoverability is likely to be moderate (see additional information below).
High High Intermediate Rise Low
A4.213 is characterized by species that are tolerant of moderately strong to strong tidal streams and associated sediment scour. However, it is also typical of wave exposed situations. Although strong water movement is most likely required to prevent build-up of silty sediments that might smother the rocks on which the community occurs, wave action will continue to provide that water movement. Water movement is also important for suspension feeders such as hydroids, bryozoans, sponges, amphipods and ascidians to supply adequate food, remove metabolic waste products, prevent accumulation of sediment and disperse larvae or medusae. A decrease in water flow from e.g. moderately strong to very weak will only result in smothering of the community and/or decrease in supply of suspended food if wave action is low. During prolonged periods of calm weather, absence of strong tidal flow may allow siltation to occur and some damage to species may follow so that an intolerance of low has been suggested. Recoverability is likely to be rapid.
Tolerant* Not relevant Not sensitive* Rise Moderate
A4.213 is recorded from the southwest of Britain and Ireland suggesting that characteristic species at least include a significant warm water element. It therefore seems likely that increase in temperature in the short-term will not adversely affect the biotope and, in the long-term, might enable extension of distribution of the biotope and possibly increase in species richness. However, while not likely to be adversely affected by long term change, Urticina felina and Echinus esculentus are probably intolerant of short term increases in temperature at the benchmark level. Circalittoral habitats are probably protected from extreme changes in temperature by their depth in enclosed areas. Overall, the effects of increased temperature are likely to be favourable to the biotope.
Low Immediate Not relevant No change Moderate
The majority of the dominant or characterizing species in A4.213 are boreal in their distribution and occur to the north and to the south of the British Isles. However, some are south-western in distribution and the biotope is only recorded from southern locations. Although it is not expected that short-term decrease in temperature will adversely affect established individuals, low temperature may adversely influence growth and reproduction in many species of hydroids, bryozoans and ascidians and may reduce recruitment into the biotope (see species reviews). Therefore, an intolerance of low has been recorded but it is noted that a long-term decrease in temperature may result in loss of some characterizing species and the biotope may change to a different one.
Low Very high Very Low No change Moderate
An increase in turbidity is likely to result in a decrease in phytoplankton and macroalgal primary production, which may reduce food available to the suspension feeders within the community. As a result , growth rates and reproduction may be decreased, and some species may not be able to keep up with predation (e.g. see Gaulin et al., 1986). However, slow growing species such as the cushion sponges and Urticina felina typical of this community and can probably survive reductions in food availability for a year. Therefore, an intolerance of low has been recorded.
Tolerant Not sensitive* No change Moderate
A decrease in turbidity may increase phytoplankton and hence zooplankton productivity and potentially increase food availability. Increased light penetration may allow macroalgae to colonize deeper water. Macroalgae effectively compete for space and grow over and may smother fauna. Therefore, decreased turbidity may allow macroalgae to colonize the more shallow examples of this biotope, resulting in loss of a proportion of the biotope, although some members of the community are likely to survive even in the presence of macroalgae. The favourable effects of a potential increase in food supply are probably more important than overgrowth by macroalgae at shallow depths. Therefore a rank of not sensitive has been recorded.
Intermediate High Low Minor decline Low
A4.213 occurs in exposed or moderately wave exposed habitats.

The oscillatory flow generated by wave action is potentially more damaging than unidirectional flow but is attenuated with depth (Hiscock, 1983). Wave action is also important in causing mobilization of coarse sediments and subsequent scour. Whilst many of the species in the biotope are clearly tolerant of oscillatory water movement and scour, less flexible or weaker hydroids and bryozoans may be removed, e.g. Nemertesia ramosa. Increased wave action may decrease sea urchin and starfish predation, perhaps allowing larger, massive species (e.g. sponges and anemones) to increase in dominance. Therefore, it is likely that some species within the biotope, especially hydroids may be lost and an intolerance of intermediate has been recorded. Recoverability is likely to be high (see additional information below).

High High Intermediate Rise Low
A4.213 is found in situations of both strong wave action and strong tidal streams. However, occasional very strong wave action is probably most important in causing the scour conditions that seem to typify this biotope. A decrease in wave action may allow species not able to withstand scour, such as delicate hydroids, erect bryozoans, ascidians and encrusting sponges to increase in abundance. In the absence of strong wave action, sea urchin predation may also increase and hence encourage increased patchiness and species richness (Sebens, 1985; Hartnoll, 1998).

The sponges that typify the biotope are most likely long-lived and would not disappear in the short term. However, colonization by other species may alter the character of the biotope sufficiently that it is no longer A4.213 and therefore an intolerance of high is recorded. On return to previous conditions, and providing that important but potentially long-lived characterizing species such as the cushion sponges remain, recoverability is expected to be high.

Tolerant Not relevant Not relevant No change High
Sponges, hydroids and bryozoans are unlikely to be sensitive to noise or vibration at the benchmark level. Mobile fish species may be temporarily scared away from the areas but few if any adverse effects on the biotope are likely to result.
Tolerant Not relevant Not relevant No change High
Hydroid and bryozoan polyps or barnacle cirri may retract when shaded by potential predators, however the community is unlikely to be affected by visual presence. Mobile fish species may be temporarily scared away from the areas but few if any adverse effects on the biotope are likely to result.
Intermediate High Low Decline Moderate
The species that characterize this biotope are tolerant of sediment scour but may be damaged by the impact of a hard surface such as an anchor or dredge.
Erect epifaunal species are particularly vulnerable to physical disturbance. Hydroids and bryozoans are likely to be detached or damaged by bottom trawling or dredging (Holt et al., 1995) whilst the upper surfaces at least of cushion sponges may be ripped off. Veale et al. (2000) reported that the abundance, biomass and production of epifaunal assemblages decreased with increasing fishing effort. Colonies of ross (Pentapora fascialis) are likely to be particularly sensitive and will be broken by slight impact from a hard object. Hydroid and bryozoan matrices were reported to be greatly reduced in fished areas (Jennings & Kaiser, 1998 and references therein). Mobile gears also result in modification of the substratum, including removal of shell debris, cobbles and rocks, and the movement of boulders (Bullimore, 1985; Jennings & Kaiser, 1998). The removal of rocks or boulders to which species are attached results in substratum loss (see above). Species with fragile tests such as Echinus esculentus and the brittlestar Ophiocomina nigra and edible crabs Cancer pagurus were reported to suffer badly from the impact of a passing scallop dredge (Bradshaw et al., 2000). Scavengers such as Asterias rubens and Buccinum undatum were reported to be fairly robust to encounters with trawls (Kaiser & Spencer, 1995) and may benefit in the short term, feeding on species damaged or killed by passing dredges. However, Veale et al. (2000) did not detect any net benefit at the population level.

Overall, physical disturbance by an anchor or mobile fishing gear is likely to remove a proportion of all groups within the community and attract scavengers to the community in the short term. The characterizing species will be injured but not, in the main, lost. Therefore, an intolerance of intermediate has been recorded. Recoverability is likely to be high due to repair and regrowth of hydroids and bryozoans (e.g. Pentapora fascialis), and recruitment within the community from surviving colonies and individuals or parts of sponges and bryozoans left behind (see additional information below).
High Moderate Moderate Decline Moderate
Most permanently fixed, sessile species, such as bryozoans (e.g. Pentapora fascialis and Bugula species), the cushion sponges and hydroids (e.g. Nemertesia species) cannot reattach to the substratum if removed, and may be damaged or destroyed in the process. Hydroids and sponges may be able to grow from fragments, aiding recovery. Mobile species, such as amphipods, gastropods, small crustaceans, crabs and fish are likely to survive displacement. Anemones (e.g. Urticina felina) are strongly but not permanently attached and will probably reattach to suitable substrata. However, the dominant, sponges, bryozoans and hydroids are likely to be lost and, since the cushion sponges are likely to recruit slowly, an intolerance of high has been recorded. Recolonization by cushion sponges and by Urticina felina may be slow and a recoverability of moderate has been recorded (see additional information below).

Chemical Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
Intermediate High Low Decline Low
There is little information available on effects of chemicals on most of the main characterizing species in A4.213. In particular, no information was found on sponges. However, bryozoans are common members of the fouling community, and amongst those organisms most resistant to antifouling measures, such as copper containing anti-fouling paints (Soule & Soule, 1979; Holt et al., 1995). Nevertheless, Hoare & Hiscock (1974) suggested that Polyzoa (Bryozoa) were amongst the most sensitive species to acidified halogenated effluents in Amlwch Bay, Anglesey, reported that Flustra foliacea did not occur less than 165m from the effluent source and noted that Bugula flabellata did not occur within the bay. Urticina felina survived near to the acidified halogenated effluent discharge in a 'transition' zone where many other species were unable to survive, suggesting a tolerance to chemical contamination but did not survive closer to the effluent source (Hoare & Hiscock, 1974).

The species richness of hydroid communities decreases with increasing pollution (Boero, 1984; Gili & Hughes, 1995).

Alcyonium digitatum at a depth of 16m in the locality of Sennen Cove (Pedu-men-du, Cornwall) died resulting from the offshore spread and toxic effect of detergents e.g. BP 1002 sprayed along the shoreline to disperse oil from the Torrey Canyon tanker spill (Smith, 1968). Possible sub-lethal effects of exposure to synthetic chemicals, may result in a change in morphology, growth rate or disruption of reproductive cycle. Smith (1968) also noted that large numbers of dead Echinus esculentus were found between 5.5 and 14.5 m in the vicinity of Sennen, presumably due to a combination of wave exposure and heavy spraying of dispersants in that area (Smith, 1968). Smith (1968) also demonstrated that 0.5 -1ppm of the detergent BP1002 resulted in developmental abnormalities in echinopluteus larvae of Echinus esculentus.

Tri-butyl tin (TBT) has a marked effect on numerous marine organisms (Bryan & Gibbs, 1991). The encrusting bryozoan Schizoporella errata suffered 50% mortality when exposed for 63 days to 100ng/l TBT. Bryan & Gibbs (1991) reported that virtually no hydroids were present on hard bottom communities in TBT contaminated sites and suggested that some hydroids were intolerant of TBT levels between 100 and 500 ng/l. Copepod and mysid crustaceans were particularly intolerant of TBT while crabs were more resistant (Bryan & Gibbs, 1991), although recent evidence suggests some sublethal endocrine disruption in crabs. Rees et al. (2001) reported that the abundance of epifauna had increased in the Crouch estuary in the five years since TBT was banned from use on small vessels. Rees et al. (2001) suggested that TBT inhibited settlement in ascidian larvae. This report suggests that epifaunal species (including, bryozoan, hydroids and ascidians) may be at least inhibited by the presence of TBT.

Therefore, hydroids crustaceans, gastropods, and ascidians are probably intolerant of TBT contamination while bryozoans are probably intolerant of other chemical pollution and an intolerance of intermediate has been recorded, albeit at low confidence. Assuming that sponges (which are likely to be long-lived and slow to recruit) are not sensitive, a recoverability of high has been recorded (see additional information below).
Heavy metal contamination
No information Not relevant No information Not relevant Not relevant
No studies have been found which investigate the effects of heavy metals on the main characterizing species (Cushion sponges, Urticina felina especially) in A4.213. Various heavy metals have been show to have sublethal effects on growth in the few hydroids studied experimentally (Stebbing, 1981; Bryan, 1984; Ringelband, 2001). Bryozoans are common members of the fouling community and amongst those organisms most resistant to anti-fouling measures, such as copper containing anti-fouling paints.

Bryozoans were also shown to bioaccumulate heavy metals to a certain extent (Soule & Soule, 1979; Holt et al., 1995).

Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton and their tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999). Waters containing 25 µg / l Cu caused developmental disturbances in Echinus esculentus (Kinne, 1984) and heavy metals caused reproductive anomalies in the starfish Asterias rubens (Besten, et al., 1989, 1991). Sea urchin larvae have been used in toxicity testing and as a sensitive assay for water quality (reviewed by Dinnel et al. 1988), so that echinoderms are probably intolerant of heavy metal contamination. Gastropod molluscs have been reported to relatively tolerant of heavy metals while a wide range of sublethal and lethal effects have been observed in larval and adult crustaceans (Bryan, 1984).

Therefore, an intolerance of low has been recorded to represent the sublethal effects on dominant bryozoans and hydroids. Loss of predatory sea urchins, may result in an increased dominance by some species and a slight decrease in species richness. Overall, without information on the intolerance of the most abundant characterizing species, an assessment cannot be made.

Hydrocarbon contamination
Intermediate High Low Minor decline Very low
A4.213 is likely to be protected from the direct effects of oil spills by its circalittoral occurrence but may be exposed to emulsified oil treated with dispersants, especially in areas of turbulence, or exposed to water soluble fractions of oils, PAHs or oil adsorbed onto particulates. For example:
  • Species of the encrusting bryozoan Membranipora and the erect bryozoan Bugula were reported to be lost or excluded from areas subject to oil spills. (Mohammad, 1974; Soule & Soule, 1979). Houghton et al. (1996) also reported a reduction in the abundance of intertidal encrusting bryozoans (no species given) at oiled sites after the Exxon Valdez oil spill.
  • The water soluble fractions of Monterey crude oil and drilling muds were reported to cause polyp shedding and other sublethal effects in the athecate hydroid Tubularia crocea in laboratory tests (Michel & Case, 1984; Michel et al., 1986; Holt et al., 1995).
  • Suchanek (1993) reported that the anemones Anthopleura spp. and Actinia spp. survived in waters exposed to spills and chronic inputs of oils. Similarly, one month after the Torrey Canyon oil spill the dahlia anemone, Urticina felina, was found to be one of the most resistant animals on the shore, being commonly found alive in pools between the tide-marks which appeared to be devoid of all other animals (Smith, 1968).
  • Amphipods, especially ampeliscid amphipods, are regarded as especially sensitive to oil (Suchanek, 1993).
  • Smith (1968) reported dead colonies of Alcyonium digitatum at depth in the locality of Sennen Cove (Pedu-men-du, Cornwall) resulting from the combination of wave exposure and heavy spraying of dispersants along the shoreline to disperse oil from the Torrey Cannon tanker spill (see synthetic chemicals).
  • Crude oil from the Torrey Canyon and the detergent used to disperse it caused mass mortalities of echinoderms; Asterias rubens, Echinocardium cordatum, Psammechinus miliaris, Echinus esculentus, Marthasterias glacialis and Acrocnida brachiata (Smith, 1968). Echinus esculentus populations in the vicinity of an oil terminal in A Coruna Bay, Spain, showed developmental abnormalities in the skeleton. The tissues contained high levels of aliphatic hydrocarbons, naphthalenes, pesticides and heavy metals (Zn, Hg, Cd, Pb, and Cu) (Gomez & Miguez-Rodriguez 1999).
  • Halichondria panicea survived in areas affected by the Torrey Canyon oil spill, although few observations were made (Smith 1968).
If the physiology within different animals groups can be assumed to be similar, then bryozoans, amphipods, echinoderms and soft corals may be intolerant of hydrocarbon contamination, while hydroids may demonstrate sublethal effects and anemones and some species of sponge are relatively tolerant. Some members of the bryozoan turf and some members of the community may be lost or damaged as a result of acute hydrocarbon contamination, although a recognisable biotope may remain. Assessment of intolerance can only be made for a proportion of the community species and therefore a confidence of very low is indicated. Therefore, an intolerance of intermediate has been suggested, albeit at very low confidence. Recoverability is likely to be high (see additional information below).
Radionuclide contamination
No information Not relevant No information Not relevant Moderate
No information found.
Changes in nutrient levels
Low Very high Very Low No change Low
An increase in nutrient levels from e.g. sewage sludge, sewage effluent or riverine flooding, may result in an increase in inorganic and organic suspended particulates (see above), increased turbidity (see above) and increased phytoplankton productivity. Moderate nutrient enrichment may increase the food available to the community in the form of phytoplankton, zooplankton or organic particulates. However, eutrophication may result in increased algae and deoxygenation (see below). While the biotope is unlikely to be directly affected by algal blooms, the biotope may be adversely affected by toxins from toxic algae that accumulate in zooplankton, or smothered by dead 'bloom' algae and deoxygenation resulting form their subsequent decay (see below). Death of a bloom of the phytoplankton Gyrodinium aureolum in Mounts Bay, Penzance in 1978 produced a layer of brown slime on the sea bottom. This resulted in the death of invertebrates, including Echinus esculentus, Marthasterias glacialis, while sessile bryozoans, sponges and Alcyonium spp. appeared moribund, presumably due to anoxia caused by the decay of the dead dinoflagellates (Griffiths et al. 1979). This biotope occurs in areas subject to moderately strong to strong tidal streams, so that prolonged deoxygenation is unlikely to occur. However, an intolerance of low has been recorded to represent the potential toxic effects of the algae and the siltation caused by death of an algal bloom.
Not relevant Not relevant Not relevant Not relevant High
This biotope occurs in full salinity and is unlikely to encounter increases in salinity.
Intermediate Moderate Intermediate Decline Very low
Most of the species identified as indicative of intolerance are of 'intermediate' or 'low' intolerance to a reduction in salinity. However, some of the main characterizing species especially cushion sponges are not generally found in low salinity situations, perhaps because of wave shelter rather than salinity reduction. It is concluded that a decrease in salinity may result in mortality of some of the species in the biotope and an intolerance of intermediate has been recorded. Assuming that likely slow growing and low recruitment species such as the cushion sponges will be adversely affected, a recoverability of moderate is suggested.
Not relevant Not relevant Not relevant Not relevant Moderate
This biotope occurs in areas subject to moderately strong to strong tidal streams, so that deoxygenating conditions are unlikely to develop.

Biological Pressures

 IntoleranceRecoverabilitySensitivityRichnessEvidence/Confidence
No information Not relevant No information Not relevant High
No information has been found.
Not relevant Not relevant Not relevant Not relevant High
No non-native species currently known from Britain and Ireland are known to occur in A4.213 and so 'not relevant' is recorded. Intolerance in the future would depend on the nature of new non-native arrivals.
Not relevant Not relevant Not relevant Not relevant Not relevant
It is extremely unlikely that any of the species indicative of sensitivity would be targeted for extraction and we have no evidence for the indirect effects of extraction of other species on this biotope.
Not relevant Not relevant Not relevant Not relevant Not relevant

Additional information

Recoverability
Where local populations exist or remain after disturbance, recruitment is likely to be rapid for many species including regrowth from any remaining fragments of species such as Ciocalypta penicillus and Pentapora fascialis. Some others, such as Pomatoceros triqueter and Balanus crenatus are likely to settle rapidly after loss. In studies of subtidal epifaunal communities in New England, Sebens (1985, 1986) reported that cleared areas were colonized by erect hydroids, bryozoans, crustose red algae and tube worms within 1-4 months in spring, summer and autumn. Some species will take longer. For instance, Alcyonium sp. colonized within 4 years.

Flustra foliacea is slow growing, long-lived and new colonies take at least 1 year to develop erect growth and 1-2 years to reach maturity (Stebbing, 1971a; Eggleston, 1972a), depending on environmental conditions. Four years after sinking, the wreck of a small coaster, the M.V. Robert, off Lundy was found to be colonized by erect bryozoans and hydroids, including occasional small Pentapora fascialis (Hiscock, 1981). The wreck was several hundreds of metres from any significant hard substrata, and hence a considerable distance from potentially parent colonies (Hiscock, 1981 and pers. comm.). Pentapora fascialis is noted as having good reproductive and recolonization abilities, quite fast growth rates and gaining reproductive competency at an early stage (Cocito et al., 1998(b)).

However, no information has been found about the reproduction and recolonization potential of Ciocalypta penicillus and other cushion sponges (species of Polymastia) which may be slow. Also, recovery of Urticina felina is likely to be slow in populations where nearby individuals do not exist. The large size, slow growth rate and evidence from aquarium populations suggests that Urticina felina is long lived. Although it probably breeds each year there is no information regarding fecundity. Breeding probably does not occur until the anemone is at least 1.5 years old. Dispersal ability is considered to be poor in the similar Urticina eques (Solé-Cava et al., 1994). The larva is most likely benthic and, although unlikely to settle for many days after release (based on work on the similar Tealia crassicornis for north-west USA), is unlikely to travel far. Adults can detach from the substratum and relocate but locomotive ability is very limited. In view of the likelihood that two of the main characterizing species are unlikely to recover former abundance rapidly following catastrophic loss of the biotope, a recoverability of moderate is identified in those circumstances.

Importance review

Policy/Legislation

Habitats Directive Annex 1Reefs

Exploitation

None known.

Additional information

The biotope appears to require a degree of sand scour and occasional inundation by sand.

This biotope is host for the nationally rare branching sponge Adreus fascicularis.

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Citation

This review can be cited as:

Hiscock, K. 1970. Urticina felina and sand-tolerant fauna on sand-scoured or covered circalittoral rock. In Tyler-Walters H. and Hiscock K. (eds) Marine Life Information Network: Biology and Sensitivity Key Information Reviews, [on-line]. Plymouth: Marine Biological Association of the United Kingdom. Available from: http://www.marlin.ac.uk/habitat/detail/290

Last Updated: 01/01/1970