Rock
Pooling Destination: St. Martins, Isles of Scilly, UK. April 2012
On the southern side of
St. Martins stretches of rocky shore occur in the mid to lower shore, comprised of boulders and
cobbles lying on sand or, bed rock.
Fucoid seaweeds dominate the rocky shore habitat,
exhibiting zonation, whilst other organisms live and seek refuge amongst the
fucoid understory, in crevices, under boulders and within
rock pools.
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| Rocky shore dominated by fucoid seaweeds. Biotope classification: LR.LLR.F Fucoids on sheltered marine shores. |
The mosaic of boulders and cobbles on sand or,
bedrock provides a variety of micro habitats which in turn enables more
organisms to co-exist. For example, the organisms living on top of the boulder
will vary to those living underneath.
On the rocky shore of St. Martins the tops of the
boulders are colonised by limpets, barnacles and seaweeds. Whilst the
undersides have encrusting faunal layers of bryozoans, hydrozoans and sea
squirts, spirobid and serpulid polychaetes, topshells, whelks and sea slugs, cushion stars,
brittle stars and green sea urchins, beadlet anemones, blennies, pipefish and
the occasional eel, plus a variety of crabs and other small crustacean isopods
and amphipods. If you look closely you may even see the feeding tentacles of
cirratulid or terebelomorpha polycheates in the sediment beneath the boulder.
Flat periwinkles tend to
stay among the fucoid seaweeds, where you may also uncover many of the
organisms mentioned above; and in the rock pools additional fish such as long-spined
sea scorpion and stickle back, as well as prawns and gem anemones can be found.
Below are photographs of
some of the organisms encountered whilst rock pooling in this habitat:
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| Bladder wrack (Fucus vesiculosus) |
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| Serrated wrack (Fucus serratus) |
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| Egg wrack (Ascophyllum nodosum) and Polysiphonia spp |
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| Thick Topshell (Osilinus lineatus) beneath the fucoid understory |
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| Painted Topshell (Calliostoma zizyphinum) in crevices of fucoid understory. |
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| Under-boulder community - overturned boulder in the lower shore. |
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| Green sea urchin (Psammechinus miliaris) on underside of boulder. |
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| Yellow plumed sea slug (Berthella plumula) on underside of boulder. |
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| Male and female Dynamene bidentata on underside of boulder. |
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| Serpulid worm on underside of boulder. |
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| Worm pipefish (Nerophis lumbriciformis). |
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| Grey Topshell (Gibbula cineraria) and Brittle star (Ophuroidea) on underside of boulder. |
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| Three spot Cowrie (Trivia monacha) on underside of boulder - Notice bryozoans - appears like a white mesh over the rock. |
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| Beadlet anemone (Actinia equina) and Cushion Star (Asterina gibbosa) on underside of boulder. |
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| Aphrodititdae worm beneath boulder. |
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| Cushionstar (Asterina gibbosa) beneath boulder. |
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| Male and female amphipoda mate in shallows. |
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| Montagu's crab (Xantho hydrophilus) under a boulder. |
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| Rosy featherstar (Antedon bifida) underneath a boulder. |
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| Neridae worm underneath boulder. |
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| Gem anemone (Aulactinia verrucosa) in shallow rock pool. |
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| Worm Pipefish (Nerophis lumbriciformis) in shallow pool. |
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| Black brittlestar (Ophiocomina nigra) under boulder. |
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| Edible crab (Cancer pagurus) and limpets (Patella vulgata) under fucoids. |
