Monday, 25 June 2012

Rocky Shore- Isles of Scilly

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.
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:

Bladder wrack (Fucus vesiculosus)

Serrated wrack (Fucus serratus)

Egg wrack (Ascophyllum nodosum) and Polysiphonia spp

Thick Topshell (Osilinus lineatus) beneath the fucoid understory

Painted Topshell (Calliostoma zizyphinum) in crevices of fucoid understory.

Under-boulder community - overturned boulder in the lower shore.

Green sea urchin (Psammechinus miliaris) on underside of boulder.

Yellow plumed sea slug (Berthella plumula) on underside of boulder.

Male and female Dynamene bidentata on underside of boulder.

Serpulid worm on underside of boulder.

Worm pipefish (Nerophis lumbriciformis).

Grey Topshell (Gibbula cineraria) and Brittle star (Ophuroidea) on underside of boulder.

Three spot Cowrie (Trivia monacha) on underside of boulder - Notice bryozoans - appears like a white mesh over the rock.

Beadlet anemone (Actinia equina) and Cushion Star (Asterina gibbosa) on underside of boulder.

Aphrodititdae worm beneath boulder.

Cushionstar (Asterina gibbosa) beneath boulder.
Male and female amphipoda mate in shallows.

Montagu's crab (Xantho hydrophilus) under a boulder.

Rosy featherstar (Antedon bifida) underneath a boulder.

Neridae worm underneath boulder.

Gem anemone (Aulactinia verrucosa) in shallow rock pool.

Worm Pipefish (Nerophis lumbriciformis) in shallow pool.

Black brittlestar (Ophiocomina nigra) under boulder.

Edible crab (Cancer pagurus) and limpets (Patella vulgata) under fucoids.

Monday, 18 June 2012

Rocky Shore

Rock and hard substrata can occur throughout the intertidal range and is dominated by different groups of characteristic organisms in the low, mid and upper shore; a distribution pattern known as intertidal zonation.

Channel Wrack (Pelvetia canaliculata) occurs within a defined tidal range on the rocky shore.

On this rocky shore in the Hebrides different seaweeds can be seen occurring within distinct vertical bands on the shore: Channel Wrack (Pelvetia canaliculata), below which Spiral Wrack (Fucus spiralis) occurs and lower down Egg Wrack (Ascophyllum nodosum).