Rock Pooling: Rockpooling destination: Porth seal, St. Martins April 2014

The shore comprises bedrock and boulders with swathes of sand on the upper shore. Rock pools and channels occur throughout the central section of the bedrock supporting a variety of marine life.

The distribution of habitats across the bay is patchy. Lichens occur at the top of the shore below which fucoids form a mosaic with barnacles. Rockpools occur across the shore and increase with species diversity toward the low water mark.

The rock pools vary with those in the upper shore characterized by the green seaweeds Cladophora and Ulva spp; whilst mid shore pools are dominated by encrusting coralline algae and a variety of red and brown seaweeds; further down the shore brown seaweeds, such as Bifurcaria bifurcata and Himanthalia elongata, become more prolific within the coralline pools with red seaweeds occupying the understory. Above the pools is a mosaic of fucoids, osmoundea, grazing molluscs and barnacles.

Spring storms had washed seaweed up onto the shore where it formed successive strandlines and filled many of the higher shore pools. The presence of the decomposing seaweed in the pools caused the water to become de-oxygenation and stagnant. In comparison to April 2013 there was less washed up seaweed and sand in the rock pools.

The shore comes under the broad habitats (LS.Lsa) Littoral sand, LR.FLR.Rkp (Rockpools)and LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) with a number of sub variants of the latter.

Habitat classification:

^Substrate	^{LR (Littoral rock)}
^Habitat	^{LR.MLR (Moderate energy littoral rock)}				^{LR.FLR (Features of ilttoral rock)}
^{Biotope complex}	^{LR.MLR.BF (Barnacles and fucoids on moderately exposed shores)}				^{LR.FLR.Rkp (Rockpools)}				^{LR.FLR.Eph (Ephemeral green or red seaweed communities}
^Biotope	^{LR.MLR.BF.FspiB (Fucus spiralis on full salinity exposed to moderately exposed upper eulittoral rock)}	^{LR.MLR.BF.Fser (Fucus serratus on moderately exposed eulittoral rock)}	^{LR.LMR.BF (Pelvetia canaliculata and barnacles on moderately exposed shores)}	^{LR.MLR.BF.Rho (Rhodothamniella floridula on sand scoured lower eulittoral rock)}	^{LR.FLR.Rkp.Cor (Corallina officinalis, coralline crusts and brown seaweeds in shallow eulittoral rockpools)}		^{LR.FLR.Rckp.SwSed (Seaweeds in sediment- floored eulittoral rockpools).}	^{LR.FLR.Rkp.G (Green seaweeds (Entomorpha spp. and Cladophora spp.) in shallow upper shore rock pools)}	^{LR.FLR.Eph (Ephermeral green or red seaweeds (Fresh water or sand influenced)}	^{LR.FLR.Eph.EntPor (Porphyra purpurea and Entomorpha spp. on sand scoured mid to lower eulittoral rock)}
^{Sub Biotope}	^{LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock)}				^{LR.FLR.Rkp.Cor.Cor (Corallina officinalis and coralline crusts in shallow eulittoral rockpools)}	^{LR.FLR.Rkp.Cor.Bif (Bifurcaria bifurcate in shallow eulittoral rockpools)}

Below are images of organisms you may encounter whilst rock pooling in this habitat:

The bay comprises sandy patches in the upper shore with bedrock and boulders that shallowly descend to the low water mark with rockpools throughout. Habitat classification: LS.LSa (Littoral sand), LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) and LR.FLR.Rkp (Rockpools).

Channel wrack (Pelvetia canaliculata) and tar lichen (Verrucaria maura) occur at the top of the shore on the right hand side of the bay. Habitat classification: LR.LMR.BF (Pelvetia canaliculata and barnacles on moderately exposed shores) that occurs within the broader habitat LR.MLR.BF (Barnacles and fucoids on moderately exposed shores).

Spiral wrack (Fucus spiralis) occurs in patches on the upper shore rock. Fucus spiralis is characteristic of the habitat LR.MLR.BF.FspiB (Fucus spiralis on full salinity exposed to moderately exposed upper eulittoral rock) that occurs within the broader habitat LR.MLR.BF (Barnacles and fucoids on moderately exposed shores).

Spiral wrack (Fucus spiralis) in its reproductive phase with swollen receptacles at the end of its fronds.

Ulva spp (Previously Entomorpha spp)

Bare rock has a patchy distribution of barnacles with thick topshells (Osilinus lineatus), Limpets (Patella vulgata), beadlet anemones (Actinia equina) and the occasional mussel (Mytilus edulis) within rock crevices.

Barnacles, Limpets (Patella vulgata) and a thick topshell (Osilinus lineatus) occur on the bare patches of rock.

Thick topshells (Osilinus lineatus) aggregate together in a crevice as a behaviour response to reduce desiccation.

Barnacle density is relatively low.

Patches of fucoids and barnacle covered rock form a mosaic across the shore with occasional clumps of Ulva spp. LR.MLR.BF (Barnacles and fucoids on moderately exposed shores) and LR.FLR.Rkp (Rockpools).

Ephemeral green seaweeds dominate the pools of the upper shore. Habitat classification: LR.FLR.Rkp.G (Green seaweeds (Entermorpha spp. and Cladophora spp.) in shallow upper shore rock pools).

Lower down the shore serrated wrack (Fucus serratus) becomes the dominant fucoid, forming a mosaic with barnacles. Habitat classification: LR.MLR.BF.Fser (Fucus serratus on moderately exposed eulittoral rock) that occurs within the broader habitat LR.MLR.BF (Barnacles and fucoids on moderately exposed shores).

Above the rock pools of the lower shore Fucus serratus forms a mosaic with barnacles and an increasing number of red seaweeds including Osmoundea sp., Mastocarpus stellatus and Corallina officinalis. Habitat classification: LR.MLR.BF.Fser.R (Fucus serratus and red seaweeds on moderately exposed lower eulittoral rock) that occurs within the habitat LR.MLR.BF.Fser (Fucus serratus on moderately exposed eulittoral rock) that occurs within the broader habitat LR.MLR.BF (Barnacles and fucoids on moderately exposed shores).

Fucus serratus forms a mosaic with the red seaweeds Osmoundea sp., Mastocarpus stellatus and Corallina officinalis.

Fucus serratus forms a mosaic with red seaweeds including Osmoundea sp., Mastocarpus stellatus and Corallina officinalis. Thong weed (Himanthalia elongata) also occurs.

Mastocarpus stellatus

Osmoundea sp, Fucus serratus and common limpets (Patella vulgata)

A red seaweed grows on a limpet.

Lomentaria articulata

Limpets, including (Patella vulgata) with a covering of red algae, Dog whelk (Nucella lapillus) and Flat topshell (Gibbula umbilicus).

Limpets (Patella velgata)

As the low tide mark is approached thong weed (Himanthalia elongata) occurs and red seaweeds become more abundant.

Fucus serratus, Osmoundea sp, Mastocarpus stellatus, Ulva sp, Porphyra sp and filamentous greens.

Large rockpools stretch across the mid and lower shore. Within the rock pools is a variety of fauna and seaweed species. Habitat classification: LR. FLR. Rkp (Rock pools).

A shallow mid shore rock pool with coralline, red and green seaweeds. Habitat classification: LR.FLR.Rkp.Cor (Corallina officinalis, coralline crusts and brown seaweeds in shallow eulittoral rockpools).

Within in the rock pools corallinaceae crusts cover much of the exposed rock, upon which Corallina officinalis then grows.

Corallinaceae crusts, Grey topshells (Gibbula cineraria), limpets and encrusting fauna on a boulder in a rock pool.

Corallinaceae crust

A seaweed

A Red seaweed

A red seaweed

Japweed (Sargassum muticum) is an invasive species which can come to dominate pools and in doing so shade the other species and change the environmental conditions of intertidal rockpool.

Ephemeral green seaweeds

Seaweeds

Codium fragile

Gastroclonium ovatum, Corallina officinalis, Corallinaceae crusts, Ulva sp and filamentous greens.

Calliblepharis jubata

Lower down the shore the brown seaweed, Bifurcaria bifurcata comes to dominate the coralline pools. Bifurcaria bifurcata dominated coralline rockpool with Corallina officinalis, Corallinaceae crusts, Ulva sp, Sargassum muticum and Fucus serratus. Habitat classification: LR.FLR.Rkp.Cor.Bif (Bifurcaria bifurcata in shallow eulittoral rockpools).

Bifurcaria bifurcata dominated coralline rockpool with Corallina officinalis, Corallinaceae crusts, Ulva sp and Fucus serratus.

Bifurcaria bifurcata dominated coralline rockpool with Corallina officinalis, Corallinaceae crusts, Ulva sp, Sargassum muticum and Fucus serratus.

Bushy rainbow wrack (Cystoseira tamariscifolia), Corallina officinalis, Corallinaceae crusts, Ulva sp, Bifurcaria bifurcata and brown seaweeds.

Bifurcaria bifurcata

Bifurcaria bifurcata dominated coralline rockpool with Corallina officinalis, Corallinaceae crusts, Ulva sp, Fucus serratus and filamentous reds.

Beneath the shade of the Bifurcaria bifurcate, Mesophyllum lichenoides grows.

Gem anemone (Aulactinia verrucosa)

Anemones

Anemone

Beadlet anemone (Actinia equina)

Snakelocks anemone (Anemonia viridis)

Snakelocks anemone (Anemonia viridis)

Coarallinacea crust and Botryllus schlosseri.

Beneath the boulders is a rich under boulder community of cushion stars (Asterina gibbosa), Grey topshells (Gibbula cineraria), Seasquirts (Botryllus schlosseri), Beadlet anemone (Actinia equina), Sponge, Painted topshell (Calliostoma zizyphinum) and Spirorbid polychaetes. Above corallinacea crust, Corallina officinalis and Mastocarpus stellatus grows.