The rock ledges below the new sea wall at Church Cliffs in Lyme Regis, Dorset, are the upper strata of the Blue Lias limestone. The natural limestone ledges and the smooth artificial substrate of the concrete sea wall, provide a home for numerous seashore creatures like limpets, winkles, and top shells as well as many commonly attached red, green and brown seaweeds, and encrusting calcareous algae (pink Lithamnion). The brown substance sticking to a lot of limpet shells is also an encrusting seaweed (probably Brown Limpet Paint Ralfsia verrucosa).
Multitudes of small holes penetrating the rocks are the often-occupied burrows of small marine polychaete worms like the Polydora species. Occasional drifts of sandy ripples coating the stone are punctured by largish round holes where bivalved burrowing piddocks living in the rocks below have squirted jets of water from their exhalent siphons and cleared the sand away.
It is interesting to see that the seashore life is equally at home on the old concrete footings from the defunct breakwaters as it is on the limestone.
The shore beneath the new sea wall in Lyme Regis looks very different now the old breakwaters or groynes have been removed. You can still see the linear concrete footings of the old wood and iron structures but most of the pebbles and cobbles that used to accumulate between the walls are now absent (at least for the moment). A bare rock pavement is revealed, comprising a series of steps representing the strata and colonised by seaweeds. Rippled sand sometimes deposits in the valleys between the rock ledges.
The topography of the shore near Cape Tribulation varies. At one point it is semi-vegetated with salt-tolerant shrubs. Here the substrate holds water for longer at low tide and the root systems of the plants trap finer sediments and nutrients that are washed down the beach from the nearby forest.
The different composition and consistency of the beach sediments in this place has given rise to a variation on the theme of sand ball patterns made by feeding crabs. The crabs may be the same species or a related species to Scopimera inflata which created the scatters and radiating patterns of drying-out pellets further along the beach (see the previous post). In this location, however, the enriched sand was relatively wet, which meant that the pellets coalesced into discrete linear masses that made very interesting designs on the surface of the beach.
On many sandy beaches along the Queensland coast of eastern Australia there are millions of small sandy balls. Each one is just a few millimetres across. They can form extensive mats or patterns as they cover the shore at low tide. There were many decorating the sand at Cape Tribulation when I visited in 2011. Closer inspection reveals small holes in the sand, usually at the centre of radiating lines of balls. These balls are the result of the feeding activities of small sandy coloured crabs that are themselves rarely seen. The holes are their burrows. They are the “Sand Bubbler” crabs belonging to the genus Scopimera, often S. inflata. The balls are created as the crab feeds on the organic matter attached to the sand grains on the surface around its burrow, and rolls up the cleaned grains into balls before moving on to the next spot.
The patterns vary according to the moisture level of the sand and its organic content, as well as the species concerned, I would imagine. I’ll post some more pictures later showing an interesting variation on the sand ball patterns from the other end of Cape Tribulation beach.
I love to take short video clips. I have many of them and they can be viewed with perfect clarity on my desktop computer screen. They even look good when they are first uploaded to posts on my blog and viewed from the admin side in the Media folder. However, once they are actually inserted into the post, they become too pixelated to view. This is very disappointing. I have contacted WordPress on a couple of occasions and it does not seem to be anything to do with their software. I have even tried posting them on You Tube and the same thing happens. I have concluded that it is something to do with my latest camera. I have experimented with conversions to other file formats without success. I think it is something to do with the specific way this particular camera captures videos – I mostly use the zoom to get fine detail. This is confirmed by the fact that the short clip shown here of a spoonbill and accompanying egret, taken with an earlier camera in Cairns 2011 seems OK.
After the beach boulders and scattered rusty metal debris, there is sequence of flat rock platforms exposed by the retreating water. They are riddled with holes made by the boring bivalves known as piddocks, some burrows just have empty shells in them but others are still occupied by the living molluscs that squirt water a foot or more into the air at frequent intervals. A velvet swimming crab mooches around the edges of the platforms, and sand tube and mud tube dwelling worms abound on all the surfaces.
I discovered an interesting stretch of shoreline when I visited Lyme Regis yesterday. The cliff location is known as The Spittles and it is situated immediately east of the new sea wall. The tide was going out but not as far as in March 2010. Enough to disclose an array of boulders with scattered fossils, broken coloured glass, and rusting metal. The man-made junk resulted from a major landslide in 2008 when the contents of an old town rubbish tip (which had been in existence from 1920 to 1973) cascaded shore-wards with the rocks and mud. The junk continues to wear out of the cliff face to the present time.
There are some interesting items to be found. The rusting metal components, often with remnants of paint, provide intriguing contrasts with the natural environment in which they are lodged. There is a striking similarity between the metal colours and textures and those of the dead and dying autumnal colours of seaweed. As the water receded, it left intricate patterns in the sand around the rocks and even in fine sediments of smoother rock surfaces.