Classificação Marinha da Grã-Bretagne e da Irlanda

Classificação Marinha da Grã-Bretagne e da Irlanda

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A expressão classificação científica ou classificação biológica designa o modo como os biólogos  agrupam e categorizam as espécies  de seres vivos , extintas e actuais. A classificação científica moderna tem as suas raízes no sistema de Carl von Linée  (ou Carolus Linnaeus), que agrupou as espécies de acordo com as características morfológicas por elas partilhadas. Estes agrupamentos foram subsequentemente alterados múltiplas vezes para melhorar a consistência entre a classificação e o princípio darwiniano  da ascendência comum .

Uma classificação  dos habitats europeus encontra-se no projecto EUNIS - European Nature Information System . Veja ( Eunis - habitats  ).

Uma classificação dos habitats marinhos encontra-se na classificação dos habitas marinhos da Grande-Bretagne e da Irlândia . Esta classificação é compátivel e integrada na classificação EUNIS.

Os habitats do litoral (zona das marés)  são facilmente acessíveis ao visitante da praia, especialmente em dias de marés grandes. Porém, nos achados da praia encontram-se também espécies de outras zonas benticas como do sublitoral (zona subtidal) .

"The marine habitat classification for Britain and Ireland provides a tool to aid the management and conservation of marine habitats. It is one of the most comprehensive marine benthic classification systems currently in use, and has been developed through the analysis of empirical data sets, the review of other classifications and scientific literature, and in collaboration with a wide range of marine scientists and conservation managers. It is fully compatible with and contributes to the European EUNIS habitat classification system."

Habitat categories and codes - Categorias de habitats e os códigos
L Littoral (intertidal) L Litoral (Zona das marés)	LR Littoral rock  LR Rocha litoral	LR1 Exposed rocky shores  LR1 Costas rochosas expostas
		LR2 Moderately exposed rocky shores  LR2 Costas rochosas semi-expostas
		LR3 Sheltered rocky shores  LR3 Costas rochosas protegidas
		LR4 Mixed substrata shores  LR4 Costas com substratos mistos
		LR5 Sea caves  LR5 Grutas marinhas
	LS Littoral sediment  LS Sedimento litoral	LS1 Shingle and gravel shores  LS1 Costas com cascalho e seixo
		LS2 Sand shores  LS2 Costas arenosas
		LS3 Muddy sand shores  LS3 Costas com lama (silte/argila) e areia
		LS4 Mud shores  LS4 Costas com lama (silte/argila)
		LS5 Mixed sediment shores  LS5 Costas com sedimentos mistos

 

Esta secção da zona litoral ou zona das marés ("intertidal")  é definida como a área entre o limite superior da zona supralitoral (zona não coberta de água, mas sujeita à aspersão por gotículas de água provenientes das vagas em zonas rochosas e da borda de água ("strandline") nas costas com sedimento) e a zona do MLWS (Mean Low Water Spring = Baixa-mar média de sizígia*).

Alguns habitats, embora influenciados pelas tidas no limite superior da zona litoral, foram colocados na secção da costa  da classificação em vez da zona litoral ou zona das marés ("intertidal"):

• Entre estes encontram-se os sapais (salt marshes (CM1-2)), as falésias (sea cliffs (CS1-3)), as lagunas (Lagoas), lagos salgados (CW1) e rios tidais (CW2).
• Note também que construções costais do intertidal são tratados separadamente  sob ?paredes (sea walls), ?pontões (piers) e ?barras (jetties) (CC1).

A borda do sublitoral  ("sublittoral fringe"), zona costeira entre zona do MLWS (Baixa-mar média de sizígia) e baixa-mar extrema de sizígia, não está incluida nesta definição da zona litoral .

O termo " exposição " é usado em relação ao ambiente marinho e refere-se às acções das ondas e das tidas, e não ao ar. Em vez disso, os termos emersão (exposto ao ar) e submersão (submerso com água) são usados.

*As grandes marés causadas pelo alinhamento do sol, Terra e lua são chamadas de marés de sizígia (spring tides).

Distribuição de organismos marinhos

em função de exposição (horizontal) e zona intertidal (vertical).

Reproduced from Ballantine, W.J. (1961) Field Studies 1.

Porphyra  (SL)

Chthalamus  (ML)

Pelvetia  (MLs)

Fucus spiralis  (MLs)

        Balanus balanoides  (ML)

        Ascophyllum  (ML)

        Fucus vesicolosus  (ML)

        Gigartina  (MLi)

         Himanthalia  (MLi)

        Fucus serratus  (MLi)

        Alaria  (IL)

        Laminaria digitata  (IL)

        Laminaria saccharina  (IL)

Os habitats do litoral, da zona das marés, são subdivididos em duas secções na base do tipo do substrato: rocha litoral  (substrados duros e consolidados, colonialisados sobretudo por epibiota) e sedimento litoral  (materiais não-consolidados e colonialisado sobretudo por "Infauna*").

*Infauna é fauna que vive no substrato do sedimento.

Rocha inclui rocha maciça e acumulações de material rochoso estável  (veja Tabela 2).

Sedimento inclui acumulações móveis arredondados de seixo e pedregulhos, areias e lodos.

Costa marítima com substratos mistos de rocha e sedimento são incluidos na secção de substratos sólidos com rocha (LR4)

Depósitos intertidais de turfa são tratados como substratos sólidos com rocha

Substratos artificiais são tratados na secção da costa terrestre (CC1). Note que estes substratos geralmente contêm as mesmas comunidades marinhas como substratos naturais.

Islas de lodo ou areia e canais de estuários que estão expostos ao ar durante a maré baixa, não são tratados separadamente, mas devem ser categorizados na base do tipo de substrato na secção do litoral (zona das marés).

Canais de estuários que mantêm água (doce ou salobra) na maré baixa devm ser incluidas na secção do litoral.

Caniço em estuários deve ser categorisados como caniços e pauis (FS1).

Tabela 2: Intervais de tamanhos de partículas de rocha solta e sedimento

Particle Type	Size range - diameter (mm)
Boulder (?bloco)	>256
Cobble (?calhau)	64-256
Pebble (?Seixo - Pedregulho - Cascalho)	16-64
Gravel (?Seixo - Pedregulho - Cascalho)	4-16
Coarse sand (?Areia grossa)	1-4
Medium sand (?Areia media)	0.25-1
Fine sand (?Areia fina)	0.063-0.25
Mud (silt/clay fraction) (?Lodo)	<0.063

 

Littoral Rock

Littoral rock includes rocky habitats of the littoral, or intertidal zone that extends from the upper limit of the supralittoral, or spray zone, to the MLWS tide mark.

The extreme lower shore, or sublittoral fringe is excluded.

Rock includes bedrock, stable accumulations of loose and mainly angular rock (ranging in size from boulders to pebbles), and intertidal peats.

Shores with mixed substrata of rock and sediment are included in the littoral rock section. Accumulations of rounded and mobile rocky material, or shingle, should be considered under  shingle and gravel shores - LS1 .

Rocky shores are subdivided into three main categories on the basis of wave exposure since the degree of wave action on a shore determines, to a large extent, what animal and plant communities are present. It also determines the width of the supralittoral zone because, on the most exposed shores, the effects of sea spray and wave splash can be far-reaching.

Low rocky cliffs (<5 m in height), overhangs, rocky headlands and rock pools should be included in this section if they are subject to regular wetting by wave splash or sea spray, and if the cover of terrestrial vascular plant communities does not exceed 50%. 

Sea caves - LR5  are treated as a separate habitat, and 

rocky sea cliffs - CS1  (>5 m in height and sea stacks and islets - CS2  are included in the coastland section.

Areas of built stone and other artificial structures in the littoral zone should be considered under  sea walls, piers and jetties - CC1.

Most rocky shores exhibit distinct zonation patterns that relate to the length of time a particular area is emersed, or exposed by the tide.

• Rocks of the extreme upper shore, including the supralittoral or spray zone, are typically dominated by lichens. Grey lichens ( Ramalina spp. 1 ) usually occur above yellow lichens ( Xanthoria spp. 2 ) at the top of the littoral zone. A distinctive band of the black lichen ( Verrucaria maura 3 ), occurs below these at the bottom of the lichen zone. The width of the lichen zone varies with the degree of exposure, as does the height; both are greatest on the most exposed shores.

1        Ramalina spp.

2         Xanthoria spp.

3         Verrucaria maura

• On sheltered shores the lichen zone is usually greatly reduced.
• The more exposed rocky shores may support patchy cover of terrestrial vascular plant communities in the spray zone. Typical components of the vegetation include Thrift ( Armeria maritima 1 ), Sea Aster ( Aster tripolium 2 ) and the salt-tolerant grass, Red Fescue ( Festuca rubra 3 ). On sheltered shores, the transition to terrestrial habitats is usually abrupt. Cover of terrestrial vascular plants should not exceed 50% for inclusion in any of the littoral rock categories.

1          Armeria maritima  - existe em Portugal. Em Quiaios encontra-se a espécie endémica: Armeria welwitschii

2           Aster tripolium  - existe em Portugal em zonas estuarinas

3      Festuca rubra   - existe no Norte de Portugal

All rocky shores may feature rock pools  that remain water-filled at low tide. Rock pools support a wide variety of communities depending on their size, depth and position on the shore.

Supralitoral - Those on the upper shore are subject to variable or reduced salinity (mainly rainwater influence) and wide temperature fluctuations, and are typically dominated by ephemeral green seaweeds  ( Enteromorpha 1  and Cladophora spp. 2 ).

1        Enteromorpha

2        Cladophora spp.

?Enteromorpha

Mediolitoral - Rock pools of the mid-shore are characterised by encrusting coralline algae  and the red seaweed , Corallina officinalis 1 .

1        Corallina officinalis

Corallina sp.

Corallina ?elongata

Infralitoral - Seaweeds such as fucoids  and kelps  may occur in deeper rock pools on the lower shore.

Fucus vesiculosus

Fucus serratus

Wracks - ?Fucus

Kelp - ?Laminaria sp.

Links with Annex I:  Littoral rock categories may contain examples of the annexed habitat, 'reefs (1170)'.

Exposed rocky shores LR1

Lapas ( Patella spp. ), mexilhões ( Mytilus ?galloprovincialis )

e cracas ( ?Balanus spp. ) na zona litoral.

This category includes extremely exposed to exposed bedrock and boulder shores of the open coast. The effects of sea spray and wave splash are usually far-reaching and the lichen zone, described above, may be up to 30-40 m wide on the most exposed shores.

At the upper extreme, these shores may support some patchy cover of terrestrial vegetation with Thrift ( Armeria maritima ) 1 , Sea Aster ( Aster tripolium ) 2  and Red Fescue ( Festuca rubra ) 3 .

1         Armeria maritima  - existe em Portugal. Em Quiaios encontra-se a espécie endémica: Armeria welwitschii

2           Aster tripolium  - existe em Portugal em zonas estuarinas

3     Festuca rubra   - existe no Norte de Portugal

Snails such as Littorina saxatilis 1  and Melaraphe   neritoides 2  are common in the supralittoral zone.

1        Littorina saxatilis  - existe em Portugal

2        Melaraphe   neritoides - existe em Portugal

Below this, exposed rocky shores are typically dominated by communities of Common Mussel ( Mytilus edulis 1 ) and barnacles ( Semibalanus balanoides 2 , Chthamalus spp . 3 ). Limpets ( Patella spp. 4 ) are common throughout.

1       Mytilus edulis  - (na costa atlântica de Portugal Mytilus galloprovincialis )

2       Semibalanus balanoides

3           Chthamalus spp .

4       Patella spp.

Robust algae that can tolerate the physical stresses of wave wash are often abundant on the mid- and lower shore. These include red seaweeds such as Corallina officinalis 1  and Mastocarpus stellatus 2 , and the brown seaweed, Thongweed ( Himanthalia elongata 3 ).

1        Mastocarpus stellatus

2         Mastocarpus stellatus

3         Himanthalia elongata

Red seaweeds can form dense turfs that are resilient to wave wash; coralline crusts are also common.

Moderately exposed rocky shores LR2

This category includes moderately exposed shores of bedrock, boulders and stable cobbles. The lichen zone is generally less extensive than on exposed rocky shores - LR1 and, within this, there may also be some limited cover of terrestrial vascular plants.

Moderately exposed rocky shores are dominated by communities of barnacles and fucoids on the mid- and upper shore, or by fucoids and red seaweeds on the lower shore. Cover of fucoids is typically incomplete and is less continuous than on sheltered rocky shores - LR3 .

Fucoids occur in distinct horizontal bands;

• the upper shore is characterised by Channel Wrack ( Pelvetia canaliculata 1 ) and Spiral Wrack ( Fucus spiralis 2 ),

1            Pelvetia canaliculata

2         Fucus spiralis

• the mid-shore by Bladder Wrack ( Fucus vesiculosus 1 ), and the lower shore by Serrated Wrack ( Fucus serratus 2 ).

1        Fucus vesiculosus

2         Fucus serratus

Red seaweeds (including Mastocarpus stellatus 1 , Chondrus crispus 2 , Palmaria palmata 3  and Corallina officinalis 4 ) may form dense turfs of single species, or mixtures of species.

1        Mastocarpus stellatus

2         Chondrus crispus

3         Palmaria palmata

4         Corallina officinalis

The variety of other associated species depends on the influence of microtopography, salinity (inputs of freshwater) and sand scour. Communities of Common Mussel ( Mytilus edulis 1 ), limpets ( Patella spp. 2 ), snails ( Littorina littorea 3 , L. obtusata 4 , Nucella lapillus 5 ), amphipod crustaceans and crabs are common; ephemeral green and red seaweeds ( Enteromorpha 6 , Ulva 7  and Porphyra spp. 8 ) may also be present. The sedentary polychaete worm, Sabellaria alveolata 9 , may form honeycomb reefs if there is a plentiful supply of sediment.

1        Mytilus edulis ou M. galloprovincialis

2         Patella spp.

3         Littorina littorea

4         Littorina obtusata

5        Nucella lapillus

6        Enteromorpha spp.

7        Ulva spp.

8        Porphyra spp.

9        Sabelaria alveolata

The presence of boulders and cobbles on the shore increases microhabitat diversity which, in turn, may give rise to greater species richness.

Gastropode - ?Littorina neritoides

Gibbula sp.

Sabellaria alveolata

Sabellaria alveolata

Sheltered rocky shores LR3

This category includes sheltered to extremely sheltered rocky shores of bedrock, and stable accumulations of boulders, cobbles and pebbles.

At the upper extreme, the lichen zone is usually compressed to a narrow band as the influence of sea spray and wave action is greatly reduced in sheltered locations. The transition to terrestrial habitats above this is usually abrupt and distinct.

Sheltered rocky shores are characterised by very dense growth of fucoids (wracks).

Different species form distinct zones, typically with Channel Wrack ( Pelvetia canaliculata 1 ) above Spiral Wrack ( Fucus spiralis 2 ) on the upper shore,

1        Pelvetia canaliculata

2         Fucus spiralis

Knotted Wrack ( Ascophyllum nodosum 1 ) and/or Bladder Wrack ( Fucus vesiculosus 2 ) on the mid-shore, and

1        Ascophyllum nodosum

2         Fucus vesiculosus

Serrated Wrack ( Fucus serratus 1 ) on the lower shore.

1        Fucus serratus

On the mid-shore, Knotted Wrack ( Ascophyllum nodosum 1 ) increases in abundance with increasing shelter, and may support a dense underturf of red seaweeds such as Corallina officinalis 2 , Mastocarpus stellatus 3  and Chondrus crispus 4 . Snails ( Littorina saxatilis 5 , Littorina littorea 6 , Melarhaphe neritoides 7 ), barnacles and limpets may be present in low numbers under the dense seaweed canopy.

1        Ascophyllum nodosum

2         Corallina officinalis

3         Mastocarpus stellatus

4         Chondrus crispus

5         Littorina saxatilis

6         Littorina littorea

7         Melarhaphe neritoides

In situations where salinity is reduced through inputs of freshwater, Horned Wrack ( Fucus ceranoides 1 ), and ephemeral green seaweeds ( Cladophora spp. 2 ) may be common.

1        Fucus ceranoides

2         Cladophora spp.

Mixed substrata shores LR4

This category should be used in situations where the shore comprises a mixture of rock and sediment, and where the sediment may include gravel, sand or mud. Mixed substrata shores occur in moderately exposed to sheltered locations and may support fucoid communities that are similar in composition to those of sheltered rocky coasts, but usually with less dense canopy cover, and with a reduced variety of epifaunal species. Barnacles or dense aggregations of Common Periwinkle ( Littorina littorea 1 ) or Common Mussel ( Mytilus edulis 2 ) may also be present. In summer months, blankets of ephemeral green and red seaweeds ( Enteromorpha 3 , Ulva 4  and Porphyra spp. 5 ) can dominate these shores. Horned Wrack ( Fucus ceranoides 6 ) occurs in upper estuarine conditions and at stream outlets.

1        Littorina littorea

2        Mytilus edulis ou M. galloprovincialis

3        Enteromorpha spp.

4        Ulva

5        Porphyra spp.

6        Fucus ceranoides

Sea caves LR5

This category includes sea caves of the littoral zone only. Fully submerged caves are not distinguished in this classification (See sublittoral rock section) and non-marine caves - EU1 are treated as a separate habitat. Caves are defined as natural recesses in rock that have a complete ceiling. Narrow gullies, ravines or fissures in coastal rock that lack complete ceilings are excluded, as are sea arches; these should be considered under the appropriate littoral rock category, or as  rocky sea cliffs - CS1 . The colonising communities are determined by the position of the sea cave on the shore with regard to tidal fluctuations, and the degree of exposure to wave action. Reduced desiccation and increased shade inside the cave allow certain species to proliferate including, in particular, bryozoans, sponges, ascidians, barnacles, calcareous tubeworms and shade-tolerant red seaweeds.

Links with Annex I: Corresponds loosely to the annexed habitat, 'submerged or partially submerged sea caves (8330)'.

Littoral Sediment

This section covers habitats of the seashore in the littoral, or intertidal zone where the substratum comprises mainly unconsolidated material: shingle (mobile cobbles and pebbles), gravel, sand or mud, or mixtures of sediments of different grades. Habitats are classified according to sediment type since this determines the water-holding properties of the substratum and reflects, to some extent, the conditions of wave exposure. Both factors are important in influencing species distributions. Note, however, that making distinctions between the various different sediment categories, particularly the finer sands and muds, can be difficult in practice.

The littoral zone is taken as the area between the uppermost limit of the strandline and the MLWS tide mark. It includes the supralittoral zone which is subject to wetting by sea spray and wave splash, and excludes the sublittoral fringe, or extreme lower shore.

• The strandline is a zone on the upper shore where organic debris from the sea (mainly decaying seaweed) is deposited by the falling tide. Strandlines, at their upper limit, may support open communities of terrestrial vascular plants. Note that all other coastal or intertidal habitats that are characterised by terrestrial vascular plants should be considered elsewhere in the classification.

• Littoral sediment does not include   salt marshes (CM1-2) , sand dune systems ( CD1-6 ), shingle and gravel banks - CB1 , or sedimentary sea cliffs - CS3.  Estuarine sediments of the littoral zone that are emersed at low tide are included in this section.  Note that  tidal rivers - CW2, lagoons and saline lakes - CW1, and reed and large sedge swamps - FS1  are categorised as separate habitats. Any estuarine channels that remain occupied by water at low tide should be considered on the basis of substratum type under sublittoral sediments.

Shingle and gravel shores LS1

Shingle Shore, Co. Galway (J. Fossitt)

This category includes exposed or moderately exposed shores with accumulations of loose, coarse but usually rounded and mobile rocky material. Sediments comprise mainly shingle and gravel, where particle sizes are generally larger than coarse sand and smaller than boulders (mostly 4-256 mm in diameter). Shell fragments may also be common. Coastal accumulations of dead maerl, so-called 'coral beaches', are included in this category. The strandline at the upper limit of the shore may be characterised by open communities of terrestrial vascular plants including Annual Sea-blite ( Suaeda maritima ), oraches ( Atriplex spp.), Sea Sandwort ( Honkenya peploides ), Sea Beet ( Beta vulgaris ) and Sea Mayweed ( Tripleurospermum maritimum ). Two rare perennial plants, Sea-kale ( Crambe maritima ) and Oysterplant ( Mertensia maritima ), are associated with shingle shores. Note that elevated ridges and banks of shingle and gravel are treated as a separate habitat in the coastland section (See shingle and gravel banks - CB1 ). Coarse, mobile sediments typically support little marine life other than opportunist amphipod and isopod crustaceans and oligochaete worms. Ephemeral green seaweeds ( Enteromorpha spp.) may also be present in summer months.

Links with Annex I: This category may contain examples of the annexed habitat, 'annual vegetation of drift lines (1210)'.

Sand shores LS2

This category includes exposed to sheltered shores of coarse, medium or fine-grained sand, usually with a very small proportion of gravel and mud (<10%). Most of the sediment particles should range from 0.063-4 mm in diameter for inclusion in this category but scattered shells or stones may occur on the surface. Bedrock and loose rock may also be exposed in places. Intertidal sandflats and strandlines are considered as part of the sand shore, but note that any ridges and mounds of sand should be considered under embryonic dunes - CD1 . Strandlines may support open communities of annual terrestrial vascular plants such as oraches ( Atriplex spp.), Sea Rocket ( Cakile maritima ), Saltwort ( Salsola kali ) and Annual Sea-blite ( Suaeda maritima ). There may also be some sparse cover of Sand Couch ( Elymus juncea ), Lyme-grass ( Leymus arenarius ), Sea Sandwort ( Honkenya peploides ) and Sea-holly ( Eryngium maritimum ). Lines of decaying seaweed are characterised by communities of beach fleas and sand hoppers. Mobile sand of the upper shore is typically impoverished of animal and plant life. The lower shore is characterised by amphipod ( Pontocrates spp., Bathyporeia spp., Haustorius arenarius ) and isopod ( Eurydice pulchra ) crustaceans, with some polychaete worms ( Scolelepis squamata, Nephtys cirrosa, Lanice conchilega ) and bivalve molluscs ( Angulus tenuis ). Eelgrasses ( Zostera spp.) may colonise sand along the lower seashore.

Sea-holly - Eryngium maritimum  (L. Lysaght)

Links with Annex I:  Sand shores may contain examples of the annexed habitats, 'mudflats and sandflats not covered by sea water at low tide (1140)' and 'annual vegetation of drift lines (1210)'.

Muddy sand shores LS3

This category includes shores where most of the sand is medium or fine ( <1 mm in diameter ) and where muds ( the silt/clay fraction ) make up 10-30% of the sediment. Muddy sand usually occurs as gently sloping flats in sheltered areas and these remain water-saturated throughout the tidal cycle. Characteristic components of the fauna include communities of lugworms ( Arenicola marina ) and bivalve molluscs ( particularly Macoma balthica and Cerastoderma edule ). Mudflats may also support beds of eelgrasses ( Zostera spp.), vascular plants that stabilise sediments and provide a colonising surface for other marine species. Muddy sand shores frequently occur at the seaward edge of salt marshes and may support open or discontinuous stands of cord-grasses ( Spartina spp.) and glassworts ( Salicornia spp.). Dense stands of any of these plants should be considered under lower salt marsh - CM1. At low tide, any channels that remain occupied by water, including estuarine channels with freshwater, should be considered under sublittoral sediments.

Links with Annex I:  This category may contain examples of the annexed habitat, 'mudflats and sandflats not covered by sea water at low tide (1140)'.

Mud shores LS4

Mud shores are formed primarily of very fine sediment and usually occur along the most sheltered sections of coastline. The silt/clay fraction of the sediment (particle sizes of <0.063 mm in diameter) should be at least 30%. Small amounts of coarser material, mainly gravel and pebbles, may also be present. This category includes some sandy muds (with 20-70% sand and 30-80% silt/clay), in addition to soft mud shores (>80% silt/clay) that are typically found in the upper reaches of estuaries. They are subject to variable, reduced or low salinity conditions. Mud shores are often characterised by elevated mudflats that are dissected by networks of shallow channels associated with flooding and drainage. They support communities of polychaete worms ( Hediste diversicolor, Nephtys hombergii, Pygospio elegans ), bivalve molluscs ( Macoma balthica, Scrobicularia plana, Cerastoderma edule, Mya arenaria ), mud snails ( Hydrobia spp.) and amphipod crustaceans ( Corophium spp.). Oligochaete worms are also characteristic if there is a significant freshwater influence. Mud shores may support open or discontinuous stands of glassworts ( Salicornia spp.), and this may indicate the pioneer formation of salt marsh. Cord-grasses ( Spartina spp.) may also be present. Dense stands of either of these two plants should be considered under lower salt marsh - CM1  in the coastland section.

Links with Annex I:  Mud shores may contain examples of the annexed habitat, 'mudflats and sandflats not covered by sea water at low tide (1140)'.

Mixed sediment shores LS5

This category should be used for sheltered shores that comprise poorly sorted mixtures of sediments of different grades, including pebbles, gravel, sand and mud. Larger stones and cobbles may be present and these often support some cover of fucoids (particularly Fucus spp.) or ephemeral green seaweeds ( Cladophora spp.). Depending on substratum type, mixed sediment shores may support communities of polychaete worms ( Hediste diversicolor, Scoloplos armiger, Pygospio elegans ), bivalve molluscs ( Cerastoderma edule, Mytilus edulis, Mya arenaria, Macoma balthica ), oligochaete worms, amphipod crustaceans and mud snails ( Hydrobia spp.).