Seashells from Swansea Bay

This assortment of  shells was found on  the sandy muddy shore of Swansea Bay. They include Common Cockles, Common Mussels, Saddle Oysters, Tellins, Common Winkles, Dog Whelks, Common Whelks, Sting Winkles, Necklace Shells, and Limpets, along with some pieces of beach glass and a common whelk shell entirely covered by the chalky tubes of the marine worm Pomatoceros triqueter.

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Ferrous fissures

The sea and salty air have corroded the iron revetment panels on this seaside pier to create a wide range of  colours, patterns and textures. The metal has begun to rupture in places to form deep cracks or fissures which make these particular views look like ancient geological strata.

For more images of naturally occurring designs on the surface of corroding metals, click here for the Metal Patterns category in Jessica’s Nature Blog. 

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Pebbles with white lines on Charmouth beach

Just some pictures today showing a few examples of the many pebbles and cobble-sized stones on the beach at Charmouth in Dorset which have abstract graphic designs and patterns on them – conferred by thin white lines. The stone is a blue-grey coloured limestone and the white lines are probably crystals of calcite. 

For the top picture, I gathered up a selection of the pebbles as I walked along and then arranged them on the beach to photograph. For the other images, I photographed the seemingly decorated stones where they lay on the seashore. I think that most visitors to this locality are focussed on fossil hunting and probably don’t notice these remarkable marked stones – each one looking hand-painted but in reality a small natural work of art. 

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Seaweeds on rocks at Eype

The major part of the beach at Eype is made up from small size shingle and pebble with scattered large boulders that have rolled across the beach from landslips along the cliffs. However, if you walk westwards along the seashore, the number of boulders increases until the far point is entirely rocky shore from the base of the cliff down into the sea. It is on these rocks and boulders between the extremes of tide that the seaweeds grow.

Strangely, not all of the rocks in the intertidal zone are colonised by algae. Seaweed seems to have definite attachment preferences. The large flat rocky surfaces are the most likely habitat to be occupied – as are large boulders that are constantly splashed and frequently submerged at lower levels of the shore. The seaweeds of different types that cover the flat-topped rocks make interesting patchworks of diverse colour and varying textures.

The most common seaweed is the olive-green Toothed Wrack, Fucus serratus, which is actually a member of the brown seaweed group or Phaeophyceae. Bright splashes of colour are provided by shapeless masses of soft green seaweed, probably Gut Weed Enteromorpha intestinalis, which belongs to the Chlorophyceae group. Pepper Dulse, Laurencia pinnatifida, is easily recognised by its wonderful golden hue, although it is actually a red seaweed belonging to the Rhodophyceae. Soft filamentous red seaweeds that are difficult to individually identify are responsible for extensive areas of pink or purple-brown colour; these provide a counterpoint and contrast to the other types of basically green to yellow algae.

If you would like to see more photographs and information about the seaweeds commonly found along the Jurassic Coast in Dorset, England, or the Gower seashores in South Wales, click here for earlier posts from Jessica’s Nature Blog in the SEAWEED Category.   

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Empty Turban Top shells from Weymouth

I love the colours, patterns and sculpted look of Turban Top Shells – Gibbula magus (Linnaeus). I found loads of them on Weymouth Beach recently. I was surprised to find them there because usually I find only Slipper Limpets. The Turban Tops were all sorts of sizes and conditions. Some were intact with beautiful red zig zag stripey patterns. Others were worn, broken and faded. Many were covered in a strange organic-looking textured reddish-brown coating. 

At the top of the sandy shore there were low-lying mounds concealing an old strandline of accumulated detritus that included large quantities of well-rotted seaweed. Winter waves had been eroding these deposits away and releasing the buried Turban Tops. The whole process was being speeded up by numerous pairs of large black crows that were systematically searching the beach for food. The bird pairs had divided up the territory and were leaving no piece of debris unturned in their patch.

There are earlier posts about these shells and the animals that occupy them. Click here for more information about Turban Top Shells in Jessica’s Nature Blog.

 

© Jessica Winder and Jessica’s Nature Blog, 2010. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Fossil oysters with ammonite impressions

This fossil is one of my most interesting beach-combing finds. The two valves of the oyster shell were still in position together. The shells had washed out of the clay and were just lying on the flint pebbles at the base of the low cliff at Ringstead Bay in Dorset. The species is probably Liostrea (Deltoideum) delta and dates from over 135 million years ago in the Upper Jurassic period.

The shells of recent oysters such as Ostrea edulis Linnaeus exhibit a great deal of variation. The same appears to be true for this type of fossil oyster shell. Some of the variability results from the way that the shell shape reflects the contours of the hard substrate or object on which the larva orginally settled. The young oyster is always attached by the left valve [see the earlier post Natural objects on which Flat Oysters settle].

The oyster will remain on and continue to grow with the left valve attached to the substrate. It is the left valve that usually has objects attached to it and mimics the shape of  the cultch or settlement substrate. It seems as if the fossil oyster illustrated here attached itself to an empty ammonite shell. 

The left valve is often lowermost and the oyster cannot change position when the settlement substrate is a permanently fixed rock. On the other hand, if the oyster larva settles on a loose object, like a shell or stone, then stormy waters can potentially tip it over and turn the oyster upside down. This could have happened with this fossil oyster and would account for ammonite impressions  on both the right and the left valves.

The two impressions are made in different ways. The one on the left valve shows the concave inner surface of the ammonite (a negative of the shape) with some fossilised shell remants adhering. This indicates that the shell may still have been attached when the oyster flipped over. On the right oyster valve the impression is a positive ‘cast’ made from a mould in the underlying clay that had been previously occupied by an ammonite shell – possibly even the actual one attached to the left valve. This specimen therefore provides an intriguing insight into the conditions prevailing in the seabed palaeo-environment in which the oysters lived and died.

For more information in Jessica’s Nature Blog about this subject see:

Fossil oysters from Ringstead 

More about fossil oysters from Ringstead Bay

Oyster Variations 

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Slipper Limpet shells on Weymouth Beach

Weymouth is famous for its fantastic clean sandy beach. However, patches of fine shingle with gravel-sized pebbles and stones do occur here and there. It was on shingle like this that I found masses of empty Slipper Limpet shells – Crepidula fornicata (Linnaeus) – last weekend.

This type of gastropod mollusc shell seems to be the single species most likely to be found on Weymouth beach at any time of year. They get the name from their strange shape which looks a bit like a shoe or slipper. They breed very successfully in our coastal waters although they are an introduced species to the British Isles. Their presence  can affect populations of our native filter-feeding mollusc species like mussels and oysters. When Slipper Limpets settle in vast numbers on other living shellfish, the huge amount of waste matter they generate can coat and suffocate the other animals beneath them, and foul hard substrates so that larvae cannot settle there. 

I have talked about Slipper Limpets in previous postings – so click here if you want to see more pictures and information about Slipper Limpets on Jessica’s Nature Blog.

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Patterns made by grazing limpets

The humble limpet is often found attached and motionless on seashore rocks at low tide. However, when the tide comes in, the limpet relaxes its grip on the rock, raises the conical shell, and glides forth on its muscular foot to search of food. It has been known for limpets to take bites out of seaweed but most of the time they simply graze on the barely perceptible algal film that coats the rocks.

If you’ve ever seen the underside of a living limpet, you will have noticed that it has a distinct head part with a mouth. Normally hidden from view inside the mouth is a long ribbon-like or tongue-like structure called the radula. Many rows of sharp ‘teeth’ are arranged along the length of the radula and the limpet uses these to scrape the microscopic algae from the surfaces around it. The limpet works in a very methodical and efficient way while it is grazing – moving slowly forward and scraping strips systematically from side to side. This process leads to the formation of patterns on the rocks that you can see at low tide. Some of these patterns are illustrated in here.

During the period that it is venturing forth underwater, the limpet completes a roughly circular route so that it ends up exactly where it started. This habit, of returning to the same home base after each trip, frequently results in the wearing away or dissolving of the stone at that point into a neat shallow circular depression. 

For more articles and photographs about limpets in Jessica’s Nature Blog click Limpets.  

 

 © Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

Dead & decomposing jellyfish

Dead jellyfish that wash ashore and end up on the strandline  seem to slowly melt into the sand and disappear. Even during life there are not many animals that feed on them except turtles. In death they don’t seem to be very appetising either; though sometimes birds may peck and crabs may claw at the remains.

I thought for a long time that the thousands of sand hoppers – Talitrus saltator (Montagu) – frequenting the strandlines were tucking in to the jellyfish feast as well as all the other detritus. However, as far as I can find out from books and the web, these small amphipod crustaceans are vegetarian and only eat seaweed and other vegetable remains.

This leaves a puzzle because, if you look closely at the photographs of dead jellyfish (mostly Rhizostoma octopus L.) in this post, you will see that that almost all of them are surrounded by hundreds of small holes in the sand. These holes lead to the burrows where nocturnal seashore creatures like the sand hoppers hide during the daytime. Maybe their presence can be explained by the fact  that these amphipods need a humidity of 90% minimum at all times to survive. The deliquescing jellyfish leaks moisture into the sand beneath and around it – providing an excellent microclimate for hopper habitation.

For more information from Jessica’s Nature Blog about this and other types of jellyfish found on Gower beaches click Jellyfish.

 

 © Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved

A spikey cockle at Weymouth

I found this spikey-shelled cockle on the beach at Weymouth. The tide was out and had left a series of shallow sandy ripples. Bait diggers had created some deep holes and I think that was how the cockle came to be lying on the surface in a ripple valley. It was sucking in water and periodically squirting it out.

I am not sure of its identity. It looks a lot like the Spiny Cockles (Acanthocardia aculeata) I find on Gower beaches but its overall appearance, size, and the sharpness of the spines make me think it is either a Prickly (Acanthocardia echinata) or a Rough Cockle (Acanthocardia tuberculata). Because it was alive and I returned it to the sediments, I could not examine the teeth in the hinge area or the inside of the shell, which would have provided vital clues. I’ll have to look out for empty Acanthocardia shells on the beach when I next visit Weymouth.

Click here for more pictures and information about Spiny Cockles in Jessica’s Nature Blog.

 

© Jessica Winder and Jessica’s Nature Blog, 2009. Unauthorised use and/or duplication of this material, including both text and photographs, without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Jessica Winder and Jessica’s Nature Blog with appropriate and specific direction to the original content.

 Photographs in this blog are copyright property of Jessica Winder with all rights reserved