A Banded Wedge Shell at Rhossili

Donal vittatus (Da Costa)

The beautiful orange-yellow paired valves of a Banded Wedge Shell, Donax vittatus (Da Costa), lying like a butterfly on the beach at Rhossili Bay. It is one of the most common bivalved molluscs on this stretch of shore and there are lots of the empty shells of this type on the strand line. They exhibit a range of colours and sometimes the inside of the shell is tinted a wonderful purple.

Barrel-mouthed Jellyfish at Rhossili

Rhizostoma octopus Linnaeus

Barrel-mouthed Jellyfish washed ashore on Rhossili Bay at the base of cliffs near Kitchen Corner, 27th August 2017. One of several seen on the beach yesterday, each one looking different in size, colour, and arrangement of the organs. This one was pale blue and the domed umbrella surface had become turned inside out. The main shot was taken at ground level and into the sun to show how the light was shining right through the jelly. The inserted thumbnail image shows the same specimen viewed from above.

Composition of Black Sediments at Rhossili

Composition of black beach sediments viewed under the microscope

Natural patterns on a sandy beachImages of patterns on the beach caused by wave action winnowing out lighter black sediments from the heavier yellow sand grains have been shown in earlier posts. Here are three microphotographs of the black sediments from a small sample that I scooped up on the shore at the time. Sorry there is no scale because I haven’t fathomed out how to include one in the images yet.

Natural patterns in black detritus on the strandline at Rhossili beachHopefully these shots are clear enough to show that the numerous black particles are small fragments of waterlogged wood; shiny hard pieces of coal (coal dust); a few large pale seeds not yet identified; minute fragmented seashells such as mussels; and many white slender organic objects which I think are small fish rib bones but could be or include heart urchin spines. It was these bones that gave the dried sample in the petri dish an almost fibrous appearance. I am going to see if I can find someone from the world of archaeology who would be familiar with the analysis of this type of material – to see if I can get some more specific information about these black sediments from the beach at Rhossili in Gower.

Composition of black beach sediments viewed under the microscope

Composition of black beach sediments viewed under the microscope

Hill End to Spaniard Rocks & Back: Step-by-Step Part 8

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.

Hill End to Spaniard Rocks & Back: Step-by-Step Part 7

Walking back from Spaniard Rocks now, I took a route closer to the dunes where the character of the shore is quite different from the wet sand and strandlines between high and low tide levels. Here there are pebbles. Rhossili’s pebbles intrigue me. I love scrambling over the banks of stones at the very top of the beach. The colours are lovely pastel shades with pinks and blues and overall reminding me of sugared almonds. A total delight. Many rock types are represented. Some have interesting patterns.

I like the way that the numbers of beach stones seem to increase or decrease depending on how they are pushed around the shore between one visit and the next, and how the sand changes its level and distribution throughout the year and the transition from season to season. This time the wooden ribs and keel of the shipwrecked ketch Anne were only just visible above the sand and pebbles. I like the way that pebbles are arranged partly buried in the damp sand that quickly dries to a different hue and texture. The pebbles underlie the tall sand dunes of the Llangennith Burrows. The dunes have been scooped out by stormy seas and footsteps in many places to demonstrate that even wind-blown sand is stratified; and marram grass roots exposed to air show how deep they penetrate the soft fine sediments to bind them together and stabilise the dunes.

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.