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Littoral rocks

Littoral rocks

Biotope description

Littoral rock includes habitats of bedrock, boulders and cobbles which occur in the intertidal zone (the area of the shore between high and low tides) and the splash zone. The upper limit is marked by the top of the lichen zone and the lower limit by the top of the laminarian kelp zone. There are many physical variables affecting rocky shore communities - wave exposure, salinity, temperature and the diurnal emersion and immersion of the shore. Wave exposure is most commonly used to characterise littoral rock, from 'extremely exposed' on the open coast to 'extremely sheltered' in enclosed inlets. Exposed shores tend to support faunal-dominated communities of barnacles and mussels and some robust seaweeds. Sheltered shores are most notable for their dense cover of fucoid seaweeds, with distinctive zones occurring down the shore. In between these extremes of wave exposure, on moderately exposed shores, mosaics of seaweeds and barnacles are more typical.

Situation

No situation data available.

Temporal variation

No temporal variation data available.

Similar biotopes

Not applicable or unknown.

Characterising Species

Characterising species data not applicable.

Example photographs of biotope

No characteristic photos currently available. If you are able to provide a photograph of this biotope please contact JNCC   email address: comment_[AT SYMBOL]_jncc_DOT_gov_DOT_uk  (replace _DOT_ with full stop/period and _[AT SYMBOL]_ with the usual @ symbol) .

Current status

Littoral rock habitats are widespread around the UK. The geology and waveexposure of the shore influence the form, which can be as varied as vertical rock, shoreplatforms, boulder shores, or rocky reefs surrounded by areas of sediment. These twofactors are also major influences on the associated marine communities. In generallittoral rock tends to be colonised by algae in wave-sheltered conditions, and by limpets,barnacles and mussels as wave-exposure increases. Relatively soft rock such as chalk andlimestone can support boring species whereas colonisation of basalt and granite is limitedto the rock surfaces. In all cases there is a distinct zonation of species down the shorewhich principally reflects the degree of immersion and emersion by the tide. Biogeographicdifferences are also apparent with the littoral rock areas of south-west England tendingto be richer in species than similar rocky habitats in the north and east.

The marine biotope classification for Britain and Ireland (Ver. 97.06)developed by JNCC's Marine Nature Conservation Review (MNCR) identifies a number ofdistinct littoral rock biotopes. These are grouped into categories depending on exposureto waves and currents, and position on the shore.

Very wave exposed shores, which tend to be found on northern and westerncoasts and on headlands, generally support a limited range of species. The littoral fringeis encrusted with the lichen Verrucaria maura , the red alga Porphyra   umbilicalis ,or by sparsely distributed barnacles. If there are pools present these are likely to becolonised by coralline crusts and the red alga Corallina   officinalis . Theeulittoral (mid shore) zone is usually dominated by mussels Mytilus   edulis and barnacles, while the lower shore may have a dense red algal turf. Deep pools in thiszone can contain fucoids and kelps. At the sublittoral fringe, where conditions can alsobe severe, a typical coloniser is the kelp Alaria   esculenta  amongst a denseband of small mussels.

Moderately wave exposed rocky shores are more common around the UK than thevery exposed shores described above, and they generally support a greater variety ofbiotopes. The upper littoral fringe is similar because of the presence of the lichen Verrucariamaura  but characteristic species of the lower littoral fringe are the channelledwrack Pelvetia   canaliculata , the spiral wrack Fucus   spiralis and the bladder wrack Fucus   vesiculosus . These are mixed with barnacles, redalgae and limpets. The lower shore is more likely to be dominated by the serrated wrack Fucusserratus  or thongweed Himanthalia   elongata  and by the kelp Laminariadigitata  at the sublittoral fringe.

Sheltered sites tend to have a denser covering of fucoids as well as the eggwrack Ascophyllum   nodosum  on the mid-shore and the kelps Saccorhiza   polyschides and  Laminaria saccharina  on the sublittoral fringe.

Unusual communities on moderately wave exposed rocky shores include thosedominated by the brown alga Fucus   ceranoides  in areas of low salinity and bythe unattached brown alga Ascophyllum   nodosum  ecad mackaii  inconditions of extreme shelter and reduced salinity. Chalk foreshores are relatively rare,forming only 0.6% of the British coastline. This percentage is nevertheless the largestexpanse of intertidal chalk in northern Europe. Chalk caves may be colonised by bands ofthe red alga Audouinella   floridula , the brown alga Pilinai   maritima and, on the roofs, the green alga Pseudendoclonium   submarinum . Filamentousgreen algae such as Ulothrix   flacca  occurs on open vertical chalk and, inthe lower eulittoral, Fucus   serratus  as well as piddocks that can bore intothe relatively soft rock.

Apart from wave exposure and position relative to the tide, the topographyof the shore has an important influence on the communities present. Boulders, gullies,pools, and overhangs provide a variety of micro-habitats as do areas of mixed substrate.On sand influenced rocky shores, the tubes of the honeycomb worm Sabellaria   alveolata can form reef-like hummocks or, on more exposed coasts, crusts on the rocks. These reefsare scarce in the UK, and restricted to areas of coast between the Solway and Cornwall.Other sand influenced shores may support beds of the mussel Mytilus   edulis .

Current factors affecting the habitat

Littoral rock habitats are generally robust with little currently affectingthis habitat type. The associated communities may however be vulnerable to damage frompollution. Nutrient enrichment from land-based sources or from sewage outfalls, as well aschemical discharges can alter the balance of species present on rocky shores. More diffusesources of pollution may also have an effect. In the 1980s, the build-up of tributyl tin(TBT), a component of antifouling paints, in inlets and bays popular with recreationalcraft and used by commercial vessels, led to a decline of dog whelk Nucella lapillus populationson the adjacent rocky shores. Littoral rock areas near major shipping lanes are also atsome risk from oil pollution although any effect will depend on conditions at the time ofany spill and subsequent clean-up operations.

Disturbance through collection of algae and animals such as peeler crabs,land claim, construction of barrages, trampling on areas such as S. alveolata  reefs, and coast protection works areother factors which can affect this habitat. The accidental introduction of non-nativespecies such as the vigorously growing alga Sargassum   muticum  or the slipperlimpet Crepidula   fornicata  may also alter the local balance of ecology onrocky shores.

Current action

Legal Status

Littoral rock habitat is present in UK sites that have national andinternational designations. Nationally important sites are found within SSSIs/ASSIs, NNRs,and Local Nature Reserves. The international significance of some SSSIs and ASSIs isreflected in their designation under the 1979 EC Birds Directive as Special ProtectionAreas (SPAs). Littoral rock habitats also occur in areas that have been selected ascandidate Special Areas of Conservation (SACs) under the EC Habitats Directive. The threehabitat types listed in Annex 1 of the directive which may include rock habitats are:'shallow marine inlets and bays', 'submerged or partly submerged sea caves' and 'reefs'.These account for 16 of the proposed marine SACs under consideration. Littoral rock isalso present in candidate SACs selected for other Annex I marine habitats. The additionalrecognition of the importance of some NNRs is reflected in their duel classification asinternational Biosphere Reserves (St. Kilda and Rum), and World Heritage Sites (theGiant's Causeway).

A number of landscape designations whose boundaries may extend to the lowwater mark include littoral rock habitats. Twenty Areas of Outstanding Natural Beauty(AONB), and five National Parks in England and Wales include coastal areas as do NationalScenic Areas in Scotland. The habitat is also present in areas of Heritage Coast which,although not a statutory designation, is recognised by local planning authorities inStructure Plans and Local Plans. Local authorities also work with landowners and theCountryside Commission (in England) or CCW to prepare management plans for the landwardcomponent of these sites.

Management, research and guidance

Several Planning Policy Guidance (PPG) documents are relevant tomanagement of this broad habitat type. PPG 20 (Coastal Planning) published by theDepartment of the Environment and the Welsh Office in 1992 sets the general context forpolicy, identifies planning policies for the coast and offers guidance on how they shouldbe reflected in development plans. In Wales this has since been superseded by TechnicalAdvice Note 13. National Planning Policy Guidance NPPG 13, issued by the Scottish Officein August 1997 gives similar guidance in relation to coastal planning in Scotland. Otherrelevant guidance is provided in PPG 9 (Nature Conservation) and Scottish Circular 6/1995(Habitats and Birds Directives). Documentation has been issued by MAFF/Welsh Office onbest practice procedures to be followed by flood defence operating authorities. This willensure that environmental issues are afforded due consideration when flood defence worksare being planned, designed and implemented.

Voluntary codes of conduct are another management tool. Codes have beenintroduced in voluntary marine conservation areas to minimise the impact of recreationaluse of such areas and to discourage collection of wildlife or habitat damage.Non-statutory documents such as coastal zone management plans, estuary management plans,coastal strategies and Local Environment Agency Plans may also provide advice onmanagement of activities which may have an impact on the habitat. An important mechanismfor management of such activities are bye-laws and a review of bye-law making powers atthe coast is currently being undertaken by Department of the Environment, Transport andRegions (DETR). There are also opportunities to influence the management of this habitatwhere it occurs in sites identified by NE as 'Sensitive Marine Areas' or identified by SNHas 'Marine Consultation Areas'.

Both broad scale mapping and specific research projects have focused onlittoral rock. General information is available in documents such as the 1991 NatureConservancy Council Estuaries Review and the regional reports on the Coasts and Seas ofthe United Kingdom, published by the JNCC. More detailed reports have been prepared aspart of the JNCC's Marine Nature Conservation Review and in other survey reports from thecountry conservation agencies. Monitoring work includes the long running rocky shoremonitoring programme around Shetland and more recent work on the rocky shores and otherhabitats in Milford Haven following the Sea   Empress  oil spill.

Conservation direction

Maintain the extent and quality of littoral rocky habitats in the UK, includingthe full diversity of communities.

Measures to be considered further include:

  • protecting sites of conservation importance from damage through contamination, physical disturbance or excessive use (eg maritime accidents, trampling and collection);
  • minimising the risk of the introduction of non-native species;
  • ensuring that EIAs for coastal developments, including developments above high water mark, examine potential effects on intertidal and nearshore areas;
  • ensuring a co-ordinated framework for management of protected areas which span the coastal zone;
  • developing and implementing strategies for the conservation and management of the wider marine environment at local, regional and national levels. For example, integrated coastal management plans, water quality objectives, pollution control and avoidance measures. Species recovery and habitat restoration programmes should be included.

Local implementation

The following LBAPs are working on Littoral rock:

Action for Wildlife - The Durham Biodiversity Plan

Ayrshire

East Lothian Biodiversity

Publication details

Originally published in: UK Biodiversity Group Tranche 2 Action Plans - Volume V: Maritime species and habitats (October 1999, Tranche 2, Vol V, p208)

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