Corraline Rock pools - Isles of Scilly

Rock Pooling Destination: Porth Seal, Isles of Scilly, UK. April 2012

The rock pools at Porth Seal vary with those in the upper shore characterised 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, osmundea, grazing molluscs and barnacles.

Below are photographs of some of the organisms in these pools:

Biotope classification: LR.FLR.Rkp.G Green seaweeds (Enteromorpha spp. and Cladophora spp). in shallow upper shore rockpools.

Common prawn (Palaemon sp) seeks cover under Ulva spp

Sea hare (Aplysia punctata) grazes on the green seaweeds 

Biotope classification: LR.FLR.Rkp.Cor Corallina officinalis, coralline crusts and brown seaweeds in shallow eulittoral rockpools. Coralline dominated rock pool with the alien brown seaweed Sargassum muticum, above the pools is a mosaic of fucoids, osmundea, grazing molluscs and barnacles.

Gibbula cineraria on encrusting coralline.

 

Feeding tentacles of polychaetes

Biotope classification: LR.FLR.Rkp.Cor.Bif Bifurcaria bifurcata in shallow eulittoral rockpools. Bifurcaria bifurcate  and sargassum muticum dominate the surface of the rock pool

Ceramium sp

Beadlet anemone (Actinia equina)

Snake locks anemone (Anemonia viridis)

Green sea slug (Elysia viridis)

 Other examples of corraline pools in Cornwall:

Corallina officinalis

What you can see …..an introduction to the major habitats

The environmental conditions and substratum upon and within which marine organisms live varies; each variant has a certain collection of species associated with it and thus represents a specific habitat.

Habitats are broad scale descriptions which can often be further defined to the biotope level. There are a variety of habitats/biotopes that can be encountered whilst rock pooling around the UK. Descriptions of these can be found within the JNCC marine habitat classification for Britain and Ireland V4.5 www.jncc.gov.uk/MarineHabitatClassification.

For rock pooling the principal division for broad habitat types is between Littoral rock and Littoral sediments; the substratum type and environmental conditions are then further subdivided with the addition of species list to classify the different habitats/biotopes.

Littoral Rock

Littoral Sediment

What you can see... an introduction to the major groups

There is a huge variety of marine organisms that live around the UK coasts. Below is a introduction to the major groups you may see whilst rock pooling.....



Marine Algae (Red-Rhodophyta, Green- Chlorophyta, Brown- phaeophyta)

Seagrass (Angiospermophyta)



Sponges (Porifera)



Sea squirts (Ascidiacea)



Bryozoans (Bryozoa)



Actinaria (Including Anemones (above), Corals, Hydrzoa & Jellyfish)



Annelid worms (Annelida)



Crustaceans (including Decopods, Amphipods, Isopods & Cirripedia)



Crustaceans (Decopods)



Crustaceans (Amphipods)



Crustaceans (Isopods)



Crustaceans (Cirripedia)



Sea spiders (Pycnogonida)



Molluscs (Including Gastropoda (above), Polyplacophora, Bivalvia & Opistobranchia)



Molluscs (Polyplacophora)



Molluscs (Bivalvia)





Molluscs (Opistobranchia)





Echinoderms ( Including Echinoidea (above), Asteroidea, Ophiuroidea & Holothurioidea)

Echinoderms (Asteroidea)



Echinoderms (Ophiuroidea)



Fish (Pisces)

Fish (Pisces)



Lichens (Ascomycota)



 

  

  

Looking amongst the strandline ....

The strandline is comprised of material deposited by the waves as the tide rises and falls. The strandline extent and composition can vary spatially and temporally. Look amongst the strandline and you will find a mix of living marine organisms and their remains.

Examples of strandlines . . . . .


Whelk egg masses, Bryozoa and Hydrozoa

 Hydrozoa, Bryozoa and sparse Rhodophtya

Rhodophtya, Hydrozoa and Bryozoa

Limpets and wrack

Cuttlefish and wrack

Looking amongst the rocks....

Rocks and boulders provide a hard substrate upon which marine organisms can colonise and grow, additionally when the tide is out they act as refugees by providing shade and shelter.

Common limpets (Pattella vulgata) congregate in the shade of boulder overhangs

Look beneath boulder overhangs, in crevices and on the undersides of small boulders to observe the under-boulder communities comprised of fishes, molluscs, crustaceans, cnidarians, sponges, bryozoans and polychaetes worms.

Under-boulder community

Green shore crab (Carcinus maenas) found under a boulder

Blenny (Lipophyrys pholis) found under a boulder

Looking amongst the algae......

There are a variety of organisms that you can see whilst rock pooling. Marine algae are the most obvious; look among and under the fronds to reveal the understory communities comprised of molluscs, crustaceans, cnidarians, sponges, bryozoans and polychaetes worms.

Flat periwinkle (Littorina sp) amongst Fucoid fronds.

Kelp, are marine algae which develop holdfasts inorder to attach to rock. Inspect the holdfasts of washed up kelp and you will discover organisms living within the holdfast.

Blue rayed limpet (Patella pellucida), Wart Barnacle (Verruca stroemia) 
and bivalves of the family Anomiidae.

Where to look...

Marine life can be observed from all UK coasts but the best places to start looking for marine organisms are where there are rock pools.

Why rock pools?

Rock and other hard surfaces provide a place where marine organisms can settle and live, whilst pools can act as temporary refuges whilst the tide is out.  As more organisms colonise the hard substrates and rock pools they themselves modify the environment enabling more marine organisms to be supported.