Just a quick note, to the people who regularly follow Jessica’s Nature Blog, to say that I will not be able to post new material for a while because of urgent family reasons. I’ll resume as soon as I can.

Most seashells with a coiled shape are Gastropod molluscs – like the common winkles and whelks. However, the small, loosely-coiled seashell from Myall Beach at Cape Tribulation in Queensland, Australia, shown here belongs to the Cephalopod molluscs.  The most commonly-occurring Cephalopod molluscs at the present time are animals without external shells. Examples of these include the squid, and cuttlefish -  which have a reduced internal skeleton – like the familiar cuttlefish bones found so frequently on beaches. Octopuses are also Cephalods.

We know from the fossil record that, in the distant past, there were many cephalopods with external coiled shells; and these were called ammonites. There are several earlier posts in this blog about fossil ammonites. There is a similar loose coil shaped Cretaceous ammonite called Aegocrioceras quadratum (Crick) found in the UK. 

There are a still a few modern Cephalopod species which retain an ancestral-style external coiled shell such as the ones found as Ammonites. These include the Nautilus and and Paper Nautilus group of species. Less commonly known is the single species of the single genus belonging to the family Spirulidae – shown in the photographs here. This is the Common Spirula or Ram’s Horn (Spirula spirula L.). You can see through the fragile translucent shell to the internal septa or partitions that divide the shell up into the compartments that are so familiar from ammonite fossils. The octopus-like animal itself would have in life mainly occupied the outermost compartment, with its swimming tentacles protruding from the circular opening.

Apparently the shell of the Common Spirula is found on beaches all over the world but the living animal is rarely seen because it is a pelagic deep water form. This particular shell specimen has washed ashore with minute goose barnacles or stalked barnacles attached to it. The small balls of sand on the beach with the shell are made by the many burrowing Bubbler Crabs that inhabit this tropical shore.

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Previously I have talked about a small rock pool at Rhossili that had filled up  with  multi-coloured pieces of plastic probably arriving at this one small area of the beach from hundreds, even thousands, of miles away. Bright coloured fragments and pellets of plastic were also observable in the regurgitated remains spewed up by seabirds on the beach. That was back in the summer 2009. I have been keeping an eye on the pool to see what its fate might be.

By October 2009, high tides seemed to have mostly cleaned out the pool and it looked on the road to recovery.

By January 2010 the pool was contaminated again. However, a large proportion of the rubbish in the pool this time was organic. Vegetable remains included straw-like terrestrial plant stems, broken fronds of brown seaweeds, and the large air bladders of Egg Wrack.

For earlier postings related to the plastic pollution in this pool, click here Multi-coloured Rock Pool at Rhossili and More about the multi-coloured rock pool at Rhossili.

Revision of a post first published 19 January 2010

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Not so pretty now! Earlier I wrote about a multi-coloured rock pool at Rhossili that I had photographed on 26th June 2009. The pool was full of small pieces of brightly coloured plastic and other rubbish. This was highly unusual for this otherwise outstanding and beautiful location. A great deal of flotsam does accumulate on the sand here but I had never observed it migrating to the rock pools before. I commented that, despite its detrimental effect on the environment, it was visually quite attractive.

Several weeks later, on 6th August 2009, I noticed that regurgitated seabird pellets on the sand (near to the outcrop of rocks with the rubbish-filled pool) contained not only mussel shells from the rocks but also small pieces of coloured plastic (see Gulls’ gobbets on Rhossili seashore).

At the same time, the pretty pool was no longer pretty. More rubbish had accumulated and the water itself was stained deep red. The photographs in today’s blog show what it looked like then.

I will be visiting the place again soon. I hope that high tides and stormy seas will have scoured the pool clean. The rubbish, however, will be a continuing problem which washes ashore from hundreds of miles away.

I often see dead and decomposing seabirds on the shore. Most seem to have broken their neck while diving. From now on, I will look to see if the stomach contents remain in situ to determine the extent to which plastic rubbish is being ingested by the birds.

If you would like to read more about the way plastic rubbish is contaminating the environment and entering the food chain, have a look at Pharyngula. 

Revision of a post first published 20 October 2009

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Bark patterns and textures in the Plane tree. I am always looking for interesting patterns, colours, and textures wherever I go – particularly in all things natural. The Plane, usually the London Plane Platanus x hispanica (x acerfolia) is a very commonly occurring source for these features and is found in many streets and parks. I love the ever-changing appearance of the bark on Plane trees. They seem to be constantly shedding their bark. It is supposed to be a way of the trees getting rid of toxins – so Plane trees are perfectly adapted to urban environments where pollution levels are generally high.

The colour of a piece of bark depends on how new or how old it is – plus how wet or dehydrated it is. The newer basal lyers are more green or yellow, and the upper flaking pieces are browner. The lowermost layer of bark is superficially smooth but a close inspection reveals miniscule finger-like projections that are responsible for pushing away and detaching the layer above them. The upper layers of bark are rough and crusty.

The overall effect of the bark renewal process in Plane trees is a kaleidoscopic, multicoloured, and variably textured mosaic pattern.

Unfortunately, The London Plane in the UK is currently threatened by the Massaria fungus which has been found in as many as one of five mature trees in London’s royal parks, and one in twenty  in Islington North London. This fungus lives symbiotically in the trees where it normally helps the trees to ‘self-prune’ but now a gradual drying up of the soil in which the trees grow (drought stress) has led to an imbalance in the relationship between the fungus and the tree – so that it has now become pathogenic. The activity of the fungus causes large main branches to dry out, splinter, and fall, in as little as three months from infection, creating a major potential danger. At the moment there are plans for a radical pruning of affected trees. [Source: Tree fungus shakes reign of London plane by Howard Swains in The Sunday Times 09.10.11] 

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On the beach at Whiteford, near Llanmadoc in Gower, there is one place where many boulders and occasional water-logged timbers outcrop on the sands. The rocks could well have been deposited by an ice-sheet, while the wood may well be the remains of a forest that was submerged ten thousand years ago.

At low tide, hundreds of thousands of common winkles, Littorina littorea (Linnaeus), emerge from hiding places under stones and sand.  You can see trails in the sand showing how they travel to exposed hard surfaces on rocks and wood to feed. These surfaces may be covered with acorn barnacles but the winkles are vegetarians and are not interested in eating these. The winkles are after the thin encrusting film of microscopic green algae which coats every surface. Winkles have a sort of rough tongue called a toothed radula which they use to scrape this deposit off the surfaces.

Huge numbers of empty winkle shells can occur on the strandline at Whiteford. Many of the empty winkle shells found there, on the sandy spit beyond the point, have started life on the stones and boulders around the old Whiteford lighthouse. 

In common with these drifts of empty winkle shells on the strandline, the shells of these living specimens of gastropod mollusc are also thick and rough with a dull and worn surface. In close-up the shells also appear pitted; pitting can be caused by a lichen living in the matrix of the shell. 

In other locations in Britain – like the seashore along the Jurassic Coast in Dorset – the shells of the living common winkles are not dull and rough like the Whiteford shells: they look very different. You can see some photographs of these, for example, in the post called Holdfast habitat at Ringstead Bay.

Here is an ancient piece of wood projecting from the sand. At its base you can see the trails in the sand left by winkles as they move towards this hard surface. The winkles congregate at the base of the timber and climb upwards along the worn grooves to graze the algae.

Here is a close-up view of the winkles grazing on the eroded surface of a piece of old water-logged wood.

A scattering of  living winkles are also found feeding amongst the smaller, smoother, algae-coated stones.

On larger boulders the winkles are tightly clustered together and may entirely cover the surfaces. In the picture below you can see how dull and worn the shells are. Some of them have grains of sand sticking to them and a few even have barnacles attached.

Revision of a post first published 24 September 2009

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White chalk pebbles from the Jurassic Coast in a blue bowl – looking a bit like mint imperial sweets. They are smooth, rounded, slightly flattened, frequently ovoid, porous, and have a matt surface.

Chalk is one of several rocks from which white pebbles are made. Chalk is a Cretaceous rock and outcrops in many places along the seashores of the Jurassic Coast. The photographs show some arrangements of these chalk pebbles; and also illustrate how they look on the beach when naturally occurring. In the shore pictures, they are mixed with mostly grey flint and yellow chert pebbles against which the white pebbles contrast and stand out. The pebbles are shown at various magnifications and in both the wet and dry condition.

Pebbles of white chalk with grey flint and yellow chert on a Jurassic Coast seashore. 

Revision of a post first published 17 July 2009

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Tantalising glimpses of ammonite fossils, still deeply embedded in rock – rather than the complete, perfect, and separate specimens that you frequently see featured in books and displays – are the types most likely to be encountered by someone simply walking along and enjoying the beaches of the Jurassic Coast. Many characteristics of these ancient cephalopod mollusc shells are preserved and visible in these embedded fossils but the most evident one is the coiled, compartmented, and ornamented shell which invariably describes a natural spiral pattern.

Revision of a post first published 18 January 2010

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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.

Revision of a post first published 13 July 2009

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Lichens are a strange kind of organism that is partly algae and partly fungi. They exhibit a great deal of variability in shape and colour and are found in all sorts of places – from the splash-zone rocks of the seashore, to high altitude boulders, to living and dead trees and wood, and man-made objects of almost every conveivable material – provided the environment is right. They are supposed to favour clean, fresh air. Each species has a defined habitat preference.

Lichens can be smooth and glossy coatings; dry and scabby encrustations; leaf-like; finely-branched; or lacey. They can grow as individuals that slowly increase in area and/or height. They can grow in groups of the same species that remain separate or that eventually coalesce to form a patchwork of similar colours – perhaps with matching or contrasting dots of colour provided by the fruiting bodies. They can grow intermingled with a variety of other lichen types with different, contrasting, or co-ordinating colours and morphology.

Though difficult to name, they are frequently interesting to observe. The abstract patterns that they make on variable substrates are often attractive and also a source of artistic inspiration.

 Revision of a post first published November 2009

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