I am familiar with the commonly occurring horizontal stripes of rocky shore zonation where organisms are distributed between the tide levels according to their tolerance of exposure to air – but I wonder what influences the distribution and arrangement of different species of seashore creatures to result in the irregular patchwork pattern as found on the intertidal rocks at Fall Bay in Gower. The sloping flat surfaces of the limestone strata can be covered with a complete encrusting layer of mussels, limpets, and barnacles, organised by colour, shape, and size to make a patterned carpet.
Nearing the end of my walk now from Hill End to Spaniard Rocks and back again. The damp sand for hours exposed to air revealed in the oblique light intricate traceries of trails where small invertebrates had travelled around unseen on the surface to hunt for food. The tide had turned and was fast washing the shore clean again. First the light particles of wood and coal dust floated away and gradually all the other organic debris and flotsam were removed in order of weight. Just a few items left to go. Incredibly, a soggy soft pink toy starfish found itself marooned with a real starfish. I photographed it exactly as I found it. The red mooring buoy seen high and dry earlier in the day was now licked by the waves, along with paired prickly cockle shells, living whelks, a dead dogfish, and a wellington boot.
The sun was bright and the sea was dark blue and scintillating. Rows of sand ripples reflected the blue sky like a natural abstract painting. Such a view of the sea and sand in Rhossili Bay is one of the most uplifting I know.
I reluctantly left the water’s edge to negotiate the makeshift bridge across Diles Lake once more. This time I photographed the unattractive brown periphyton attached to the underwater rocks as well as the beautiful sunlit surface ripple patterns of the flow. While it was time for me to leave, others were just arriving with surf boards, impatient to immerse in the iridescent sea – now that must be some high on such an afternoon. I can’t wait to go back.
Following the line of the limestone cliffs towards Kitchen Corner as the tide receded, the tide pools and beach were littered with dozens of living Rayed Trough Shells (Mactra stultorum Linnaeus) as they popped up to the surface of the sand. I don’t quite know why they chose to do this but it afforded an opportunity to see the living animal as opposed to the dead ones and empty shells that wash up more frequently on Rhossili Beach.
Two pale fleshy tubes joined together were extended between the two hinged shell valves. One inhalent siphon for sucking water with suspended nutrients inwards, and one exhalent siphon for dispelling de-oxygenated water with bodily waste products. I was afraid that these bivalved molluscs would die while gaping and exposed to the air, so I picked up a few and put them in the water of the pools but they were not very lively and did not re-bury themselves. I was surprised that no-one else seemed to notice them. Even the dog that I saw appeared more interested in splashing in the pools than snacking on the free harvest.
At low tide many thousands of common winkles or periwinkles (Littorina littorea Linnaeus) seek shelter from dessication and predation by clustering together in the few hiding places available on the beach. At Whiteford Sands these niches include the overhung bases of larger stones, crevices in ancient timbers from the rapidly emerging submerged forest, and nooks and crannies in the recently exposed ancient peat. Alternating layers of peat and clay, overlain by rocks from glacial till, provide algae-covered surfaces on which gastropods can feed, and islands of low tide refuge in the vast expanses of sand on this sea shore.
I thought I would share these photographs with you. People usually like pretty photo-shopped pictures and these are a bit gross, not very attractive….. but interesting none the less. They look like snot but they are not. Most of these glistening gelatinous masses, the ones with the patterns (whether they are green, yellow or white) are Ascidians from the family Styelidae called Star Sea Squirts (I think two species are represented: Botryllus schlosseri and Botrylloides. leachii). I found them along with other sea squirt species which I am unable to identify on a quayside lobster pot. This marine invertebrate species is a primitive chordate and therefore related to us Homo sapiens.
It is sheer delight from the moment I walk out the door of the one-up one-down cottage known as The Slope. In May, the house martins fly right past carrying food to the youngsters in the coal shed; while the clematis and honeysuckle flowers on the fence provide a safe nesting site for blackbirds. A few yards more and the still pond at Mewslade View is home to beautiful blue iris. The field is covered in lush grass with blossoming plantains; this is the field that is mowed for the Caravan Club visitors to park. Beyond, a flock of sheep clear Nitten’s Field for a re-seeding of wild flowers that will supply food for migrating birds. This year there will be extra red poppy flowers planted to commemorate the centenary of World War I.
The boundary between the private land of Nitten’s Field and Mewslade valley is marked by a stile made of driftwood. From this point you can see right down into the steep-sided dry valley that leads to the sea and Mewslade Bay. The shape of the valley is partly due to it lying along a geological fault line, and partly due to quarrying activities in times gone past. Once the stile is negotiated, you are on public footpaths that lead in various directions. – the coastal path that follows the cliff tops in both directions along the southern shore of the Gower peninsula; back up the valley to the village of Middleton; or down the slope to the bottom of the valley and the beach. The scree-covering on the lower slopes is the result of peri-glacial activity. Access to the shore is via a narrow rocky fault gully but only at low tide as the sea comes right up the gully at many high tides.
If you arrive too early to get on the beach because of the tide, you can walk around the valley sides finding wild flowers and exploring the small caves high up the slopes. From a high vantage point looking east, you can see the dipping rock strata beneath Thurba Head. Looking in the other direction towards Fall Bay, Tears Point, and Worms Head, the high-tide waves lap the jagged dark rocks that project into the sea – Carboniferous limestone with numerous pits created by bio-erosion into a karstic landscape.
The ripping and tearing of the rocks along the fault-line has created some very interesting geology at the gully, with many rock types embedded in white crystalline calcite. This fault breccia can be seen in the solid rock of the gully and in large boulders on the ground. The force of the pounding sea has worked away over the years to carve out interesting tunnels, arches, caves, and blow holes around the entrance to the bay.
As the tide begins to recede, you can see small seashore creatures that cling to the rocks – invertebrates like limpets, barnacles and small periwinkles taking advantage of every nook and cranny.
When at last the tide ebbs, you can get onto the beach. This shore has seen dramatic changes in preceding months. By May this lovely family-friendly sandy beach was recovering nicely after seriously strong seas whipped all the sand away in the first few months of the year. At that time there was nothing but a jagged rocky platform, with a revelation of strata and fossils that most people had not seen before in their lifetime. It wasn’t an altogether unique event for Mewslade – it has been recorded before – but it was a rare circumstance. Mewslade was not alone in suffering this albeit temporary fate. Beaches along many British coasts were severely eroded. Many, like Mewslade, have recovered but some have been changed for ever.
Where the sand has not quite reached its former levels, a white band of crystalline calcite remains exposed at the base of one of the bio-eroded limestone cliffs. Across the shore, numerous rocks with fantastical sculptural shapes are scattered – their forms resembling the peaks and troughs of whipped meringue or cake frosting. Some of these rocks contain fossil corals, bivalves, and marine snails.
I can’t wait to discover more about this fascinating place on my next visit.
COPYRIGHT JESSICA WINDER 2014
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Whilst in Oregon a few years back I explored the seashores along the North West Pacific Coast, and found fascinating and varied forms of seashore creatures. I also visited the Oregon State University Hatfield Marine Science Center which is an excellent place to find out all about the region’s marine wildlife. It also provides a wonderful opportunity to get up close and personal to many inter-tidal creatures by providing a Touch Tank or simulated tide pool. It was fantastic to be able to photograph at close quarters many varieties of sea anemone which I had only been able to spot with difficulty in tide pools and surge gullies on the rocky shores themselves.
Here are some images of the large and colourful sea anemones (with other marine invertebrates) representative of the types that could be encountered locally in the wild.
COPYRIGHT JESSICA WINDER 2013
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The Goose Barnacles on the North West Pacific Coast of America are different from the ones we see usually see in the UK. They are a sessile species, Pollicipes polymerus, and they are attached to rocks low on the shore. They are related to a similar species that grows in warmer European waters. This compares with pelagic species like, for example, Lepas anatifera, which settles on floating objects that are washed around in the sea at the mercy of tides and currents. There were huge numbers of Pollicipes on the beach at Yachats in Oregon when I visited a few years ago.
There is something rather prehistoric about the way these barnacles look. They have a tough black leathery stalk or peduncle about 2 cm long that contains the gonads and an adhesive gland for sticking them securely to the rock. They do need to hold very fast because the waves are enormous and relentless in the pounding they give the shore. The ‘head’ end, also with black flesh, contains all the other organs and the appendages that it uses to filter food particles from the water. This capitulum is protected by a series of separated white calcareous plates which are exceedingly robust and thick – often showing microscopic damage cause by an endo-lithic lichen.
The barnacles mostly live close together in large mounds or dense carpets on the rocks. They are often associated with colonies of the big California Mussel (Mytilus californianus) with the beds of which they either alternate or intermix. They occur most frequently on the lower shore, especially where the impact of the waves is greatest. They are found on vertical surfaces as well as horizontal; framing tide pools; under overhangs; and in steep-sided narrow surge gullies.
Pollicipes feeds by spreading its cirri (appendages) rather like a net so that the water passes through them. They catch small crustaceans and plankton. When sufficient particles have become trapped on the cirri, they withdraw them into the capitulum and the food is transferred to the mouth parts. The cirri do not face the oncoming waves but are arranged so that they can take advantage of the water running off the rock rather than the water hitting the rock. All of the animals in a particular group or colony will characteristically face in the same direction to maximise use of the run-off water – and this may differ from the next cluster a short distance away.
You can compare and contrast this American species of goose barnacles with ones that I have seen in the UK by clicking here for:
COPYRIGHT JESSICA WINDER 2013
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Just a gallery of photographs of living Common Goose Barnacles (Lepas anatifera Linnaeus) that were washed ashore in huge numbers attached to an old flotsam fishing crate. It was fascinating to watch how they opened their shells and rhythmically waved and grasped their fringed appendages, (cirripedes) in an automatic but futile gesture designed to capture food particles from the water. These pictures show various stages in the process of extending and withdrawing the cirripedes. I wrote about these seashore creatures a while ago and you can find more information about them by clicking here for Goose Barnacles on Rhossili Beach.
COPYRIGHT JESSICA WINDER 2013
All Rights Reserved
The jagged rocks along the spine of the Worms Head Causeway, exposed for longer periods of time at low tide, are mostly covered with mussels, barnacles, and winkles with little in the way of algae except in the tide pools. At the wetter edges of the Causeway, spending less time out of water, the boulders are covered with seaweed – and kelp beds lurk underwater just off-shore.
It is under this seaweed that you can find many interesting seashore creatures either attached to the rocks or simply sheltering in the damp places amongst the weed. Brightly coloured sponges can be discovered here – and one of the most common is the vivid yellow, orange or green Breadcrumb Sponge – Halichondria panicea (Pallas).
A great variety of red, green and brown seaweeds live alongside the sponges. As well as the common brown fucoids like Toothed and Bladder Wrack, Green and Purple Laver grow, and interesting small red algae like Pepper Dulse and Lomentaria. Sea squirts, anemones, and tube worms abound. The mud and mucous tubes occupied by marine polychaete worms can be found around the sponges if you look carefully (see the adjacent thumbnail image); and the dark mud tube entrances of the worms that have built actually into the sponge can be seen scattered among the in-halent and ex-halent pores.
In later postings I will be publishing pictures of some of the richly coloured sea anemones and glistening gelatinous sea squirts that also I recorded in this particular location.