Thick mats of seaweed wash ashore on beaches along the Jurassic Coast. Dead seaweed is often automatically viewed as horrid, unsightly, and a nuisance – but if you pause and look, there is beauty in it. There are many types of seaweed to be discovered in the masses on this strandline. Their fronds intertwine in a kind of accidental natural weaving. Each species has its own characteristic shape, texture, and pattern. Their combined presence forms greater abstract designs of infinite variety, the individual fronds making strands or threads as in a tapestry. The puckered patterns of the crinkly Sugar Kelp stand out as the most decorative features of the assemblage. The colours change from deep olive brown to golden yellow and cream as the algae decompose. The textures range from leathery to satiny, from slimy to crispy depending on moisture content. Opaque and hardening on exposure to air; or translucent and soft when floating in shallow water rock pools.
Brightly coloured seaweeds were washing ashore at Studland Bay in Dorset on 21st May 2017. Isolated clumps of vivid red, green, and brown soft seaweeds, that looked attractive floating in the clear shallow water, or scattered individually on the yellow ribbed sand, soon accumulated into thick solid multi-coloured mats undulating on the water’s edge. When a mat of algae like this is pushed high with the rising tide, and left stranded on the upper beach, it decays rapidly to become what the human eye perceives as a rather smelly, ugly mess. For every other organism large or small on the beach, rotting seaweed is a marvellous bonanza of food and shelter, which also helps to stabilise the sandy beach for further colonisation by plants.
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.