Hill End to Spaniard Rocks & Back: Step-by-Step Part 6

As my walk continued from Hill End northwards on Rhossili beach, the dark drift patterns and fine strandline debris covering the sand eventually faded away to be replaced by dry sand ripple and swash/backwash patterns before arriving at the extreme north-east corner of Rhossili beach. This is the place where much of the flotsam ends up. It is not that Gower visitors are careless with their trash. Most of this stuff comes from far afield – sometimes as far away as South America. It does get periodically cleared away but is difficult to manage because the rubbish arrives and leaves with each tide, and can get buried or revealed from one high water to the next. Bicycle wheels, brightly coloured plastic pieces, fishing net and ropes, toothbrushes, balloon stoppers, and flip flops are common items along with the driftwood. The pile of organic and plastic rubbish lies adjacent to Spaniard Rocks which connect the tidal island of Burry Holms to Llangennith Burrows.

The geology here is interesting but on this occasion I focussed on the seaweeds which attach to the rocks along the water-filled channel between Burry Holm and Spaniard Rocks. There are many types intermingled. They include amongst others the brown Fucoid algae such as Toothed Wrack (Fucus serratus) , Spiral or Flat Wrack (Fucus spiralis), and Egg or Knotted Wrack (Ascophyllum nodosum). Bladder Wrack or Pop Weed (Fucus vesiculosus) was also present but not in its typical form. The numerous small, paired, almost spherical air bladders typical of the species were few and far between on specimens in the area where I was looking – so that there is confusion in my mind as to the identity of some of the weed I have named as Spiral Wrack.

There were also some red algae of the thin bladed type that dry out between tides into blackened streaks on the rocks (of the kind to which the lavabread seaweed belongs). Another red alga was the Sand Binder seaweed (Rhodothamniella floridula) which forms small humps of fine filaments trapping sand grains on rocks low on the shore; it is often found beneath the taller stalked fucoids. Finely branching red Polysiphonia lanosa was epiphytically attached to the Egg Wrack.

Of special interest this visit was the fact that the seaweeds were getting ready to reproduce. The Spiral Wrack had swollen receptacles on the forked frond tips that were not fully ripened yet. However, the Egg Wrack was ready to go. It has separate males and females. The male receptacles are bright golden green studded with orange pustules (conceptacles) that release a colourful fluid containing the sperms. I had seen these and reported on them before. This time I also saw the female receptacles which were dull green and covered with minute darker almost black blisters (conceptacles) containing the eggs. It almost seems as if you can see the eggs when you zoom in on the picture – actually just the light bouncing off the ripe eggs within the pustule.

Spaniard Rocks Part 1

Natural geological abstract patterns of cracks, crevices, and ornamenting lichen encrustations, in the Carboniferous Limestone of Spaniard Rocks at the northern end of Rhossili Bay, on the Gower Peninsula, in South Wales.

Abstract patterns in rock

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Multi-coloured rock pool at Rhossili

Thousands of small multi-coloured pieces of flotsam plastic floating in a rock pool at Spaniard Rocks, Rhossili Bay, Gower, South Wales, UK (1) 

Thousands of small multi-coloured pieces of plastic flotsam floating in a rock pool at Spaniard Rocks, Rhossili Bay, Gower, South Wales. Even in the most beautiful of places, flotsam – particularly plastics – can be a problem. At Rhossili Bay, it is said that most of the plastic rubbish comes from as far away as South America as there is nothing but open water between these two places. Very little plastic rubbish is thought to have been generated by local visitors.

By some quirk of fate, small pieces of plastic seem to end up en masse at the extreme north end of the beach.  The way that  they have accumulated in small rock pools on Spaniard Rocks can be seen in these photographs.  However, even though this rubbish shouldn’t be here and it may affect the environment in a detrimental way, potentially damaging habitats for the native seashore animals and plants, there is still a beauty to be found in the juxtaposition of these brightly coloured pieces of floating flotsam against the pale neutral of the Carboniferous limestone; in much the same way that the bright splashes of orange-coloured lichen and yellow-flowered rock plants enliven the stone.

There is a related post to this article. See also Gulls’ gobbets on Rhossili seashore.

 Rock pool at Spaniard Rocks, Rhossili Bay, Gower, South Wales, showing multi-coloured plastic flotsam on the water surface (2) 

Revision of a post first published 13 July 2009

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Green Leaf Worms at Spaniard Rocks, Rhossili

Green Leaf Worm, Eulalia viridis (Linnaeus), on mussels and barnacles encrusting limestone cliffs at Spaniard Rocks, north end of Rhossili Bay, Gower, South Wales.UK (1)

Bright green worms on mussel beds? I have never even noticed them before but I guess they are common from the numbers I found and by accounts I have now read in text books. This is the Green Leaf Worm, Eulalia viridis (Linnaeus). It was photographed writhing around with many others on the mussels and barnacles that were encrusting the vertical faces at the base of the Carboniferous limestone cliffs on the north side of Spaniard Rocks at Rhossili Bay, Gower.

The Green Leaf Worm is one of thirty species of marine polychaete worm belonging to the Family Phyllodocidae in Britain. Although not visible in the photograph above, the worm has a row of paddle-like appendages along each side of its body. These are very lively carnivorous worms that secrete loads of mucus which, no doubt, helps them to wriggle around the rocks at low tide looking for food.

The bright orange patch in the photograph above is encrusting sponge. The light green colour on the rock and the barnacles is a coating of microscopic surface algae. The deep pink tufts are red algae. There was a lot of this seaweed attached to the rocks here, often in a distinct band.

You can see from the pictures below how there is rocky shore zonation of the organisms colonising the limestone surface on Spaniard Rocks.  

Green Leaf Worm habitat - Spaniard Rocks, Rhossili, Gower, encrusted with red seaweed, mussels and barnacles in April 2009 (2)

Home of the Green Leaf Worms - rocky shore zonation of Carboniferous limestone at Spaniard Rocks, Rhossili Bay, Gower - showing successive colonisation of the surface by various organisms at different heights above sea level (3)

Green Leaf Worm, Eulalia viridis (Linnaeus), on mussels and barnacles encrusting limestone cliffs at Spaniard Rocks, north end of Rhossili Bay, Gower, South Wales.UK (4)

Revision of a post first published 8 May 2009

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Egg, Bladder & Channelled Wrack at Rhossili

Ascophyllum nodosum: Egg or Knotted Wrack, Ascophyllum nodosum (Linnaeus) Le Jolis, on Spaniard Rocks, Rhossili Bay, Gower, showing yellowy pendant reproductive bodies looking like sultanas on short stalks (1) 

Looking like bunches of flattened yellow sultanas hanging down on stalks, the reproductive bodies of the Egg or Knotted Wrack, Ascophyllum nodosum ( Linnaeus) La Jolis, were a very noticeable feature of the weed in April. This picture was taken of the seaweed attached to the limestone of Spaniard Rocks, adjacent to the causeway separating the mainland from Burry Holms, on Rhossili Bay.

Egg Wrack with reproductive bodies: Frond of Egg or Knotted Wrack, Ascophyllum nodosum (Linnaeus) La Jolis, washed in by the tide at Rhossili Bay, Gower, South Wales - showing the large egg-shaped air bladders along the olive coloured stem and yellow reproductive bodies attached to the stem by short stalks (2) 

Here a detached frond of egg wrack has been washed up onto the sandy beach. You can clearly see the large egg-shaped air bladders spaced along the central olive-coloured frond which lacks a mid-rib.

It is interesting to note the way the Egg Wrack at Rhossili differs in its appearance from the same weed at Ringstead in the same month. The plant and fruiting bodies photographed in Rhossili are larger, more robust, and lacking the attached red seaweed – at least when growing on rocks by the causeway to Burry Holms. Although the Egg Wrack occupied the same approximate tidal position on the shore in both places, the main distinction between the two habitats is the greater exposure to wave action at Rhossili. It looks like the Rhossili Egg Wrack thrived where the sea was rough.

Common British seaweeds: Bladder Wrack or Popweed, Fucus vesiculosus Linnaeus, growing on Spaniard Rocks, Rhossili Bay, Gower, South Wales - showing small bean-sized air bladders along the fronds and swollen reproductive bodies at the tips (3) 

Bladder wrack or Popweed, Fucus vesiculosus Linnaeus, was growing on the limestone Spaniard Rocks right next to the Egg Wrack (there is a small bit of Ascophyllum gate-crashing top left corner of the picture above). You can tell the two seaweeds apart by the mid-rib to the frond and much smaller bean-sized air bladders positioned lower on the blade in Bladder Wrack, and the reproductive bodies are confined to the lighter coloured swollen tips. Bladder Wrack tends not to grow so large as Egg Wrack.

Olive green seaweed: Channelled Wrack, Pelvetia canaliculata (Linnaeus) Decaisne and Thuret, growing on Spaniard Rocks, Rhossili, Gower, South Wales (4) 

Channelled Wrack, Pelvetia canaliculata (Linnaeus) Decaisne and Thuret,  is a much smaller seaweed than the previous two described. It grows in short dense tufts upto 15 cm high attached to rocks just above high water level of neap tides. It is frequently seen dried up and blackened. Black Pygmy Lichen is often mistaken for very small tufts of Channel Wrack.

Pelvetia does not have a midrib or gas bladders; the edges of the fronds tend to curl inwards – creating the groove or channel from which it gets its name – but this is not a reliable feature for identification. The fruiting bodies are irregular shaped, swollen, forked ends to the fronds.

Egg, Bladder and Channelled Wrack are all brown seaweeds belonging to the Class Phaeophyceae.

You can find more information about these seaweeds on the marLIN  or British Isles Seaweed Images web sites.

Channelled Wrack, Pelvetia canaliculata (Linnaeus) Decaisne and Thuret, growing on Spaniard Rocks at Rhossili Bay, Gower, South Wales. 

Revision of a post first published 2 May 2009

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Sea-foam at Rhossili

Sea-foam picture close-up: Iridescent bubbles of sea-foam at Rhossili Bay, Gower, South Wales, UK (P1440223aBlog1)

When stormy seas and stronge surges are driven hard by forceful onshore winds, the surf is whipped into foam that flies from the wave crests; and waves crashing on the beach spread the foam onto the shore. The constant wind last October pushed a thin layer of white froth in ever-moving, ever-changing, transient scalloped patterns for hundreds of metres across the vast wet acres of Rhossil sand – until at last the iridescent bubbles of froth piled up in heaps on the higher parts of the seashore. At Spaniard Rocks there was dramatic textural contrast between the delicate and ephemeral sea foam and the hard smooth enduring limestone rocks which the foam decorated.

Seashore picture with seafoam: Sea-foam pushed by the wind up the sandy beach at Rhossili Bay, Gower, South Wales, UK (P1440242aBlog2)

Seashore seafoam picture: The vast reflecting expanse of low-tide seashore, with a thin film of surface water and seafoam pattern, at Rhossili Bay, Gower, South Wales, UK (P1440234aBlog3 )

Sea-foam natural pattern: Sea-foam pattern moving across the low-tide sand at Rhossili Bay, Gower, South Wales, UK (P1440233aBlog4)

Rocks with seafoam picture: Sea-foam on limestone at Spaniard Rocks at Rhossili Bay, Gower, South Wales, UK (P1440074aBlog5)

Seafoam on rocks: contrasting textures: Iridescent bubbles of sea-foam on pink limestone at Spaniard Rocks, Rhossili Bay, Gower, South Wales, UK (P1440056aBlog6) 

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Brittle Stars at Burry Holms

 

Brittle Stars are related to starfish but are generally smaller, much more active, and very prone to breaking their long,  thin, fragile arms. Like the starfishes and sea urchins their structure is based on a design of fives: with five arms, for example, and five toothed jaws around the mouth. This is termed pentamerous symmetry.

The animals have a small central disc – upto 30 mm across – that houses the body organs. The upper surface of the disc is covered with scales; the shape of the scales and the pattern they make differs from one species to another. In the specimen illustrated, which I think is Ophiura ophiura (Linnaeus), there are five rather pleasing heart-shaped configurations of scales at the base of each arm.

The slender arms are cased in scales and the segments articulate one with the other like in a suit of armour. Movement in the up and down directions is rather limited. Most movement is from side to side. By these horizontal movements, brittle stars can move very quickly and with great agility.

These Bruttle Stars were washed ashore en masse at Rhossili Bay. They were stranded with hundreds of other marine creatures in shallow pools and on the surface of wet sand left by the retreating tide on the causeway between the island of Burry Holms and Spaniard Rocks. The arms of some specimens were damaged with only stumps remaining. Others were intact. Some were half buried in sand. Others clustered in the shallow water pools. Isolated individuals high and dry on the wet sand wriggled vigorously until they gravitated to safer, wetter, positions. The six photographs at the bottom of this post show a rapid sequence of shots of the varied positions adopted by a Brittle Star as it manoeuvred itself to safer territory – it looked as if it was dancing.

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Otter Shells at Rhossili Bay

Undeniably phallic – the thick, non-retractlile, double fused siphons lie exposed to view as this Common Otter Shell Lutraria lutraria (Linnaeus) tries to rebury itself after stranding. If it doesn’t get underground quickly, the birds will eat it. This young specimen was photographed with many other larger and older specimens (like the one below) at low tide on the causeway between Burry Holms and Spaniard Rocks at the north end of Rhossili Bay.  

It is unusual to see the living molluscs because they live very deep down in the sediments. Some particular kind of turbulance in the sea must have dredged them up. The empty shells, however, are frequently found on the beach. The shells below were clustered on the causeway but many individual or paired shells were scattered along the entire length of the drift line – some having just been eaten by birds.

……….and this was one of many particularly decorative-looking otter shells with a filling of iridescent sea foam bubbles. [It’s funny how difficult it is to photograph bubbles without capturing your own reflection in every one!]

For more information about otter shells see the additional information pages.

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