Three red seaweeds from Studland Bay in spring

Splashes of red colour against the more neutral hues on the seashore always catch the eye and lift the spirit. I love the variety of shade and shape in the red algae, Rhodophyceae, but I find red seaweeds are not always easy to identify.

As the number of red seaweeds on the beaches increases with the advent of summer, I am making another attempt to separate out the different sorts and put some tentative identifications on them. If I have got some of the names wrong, please do let me know – or just enjoy the wonderful variety that we are so lucky to find along our British shores and especially on the Jurassic Coast here in Dorset.

The top picture shows a cluster of living Slipper Limpets at Studland Bay. Attached to the shells is a weed that looks a lot like Gelidium latifolium(Greville) Bornet and Thuret – what a name! The main stem and branches are flat and ribbon-like. These have much smaller branchlets around the edges. It grows upto 8 cm high. There is a similar species called Calliblepharis ciliata(Hudson) Kutzing [Eyelash Weed] but this is a lot bigger – 10 – 25 cm long.

While some red seaweeds have flat fronds or blades, others are made up of long branching thread-like filaments. The overall size, the way the weed branches, and the degree of firmness of the weed are all used in identification. If the weed has fairly stiff stems and branches, then it will keep its shape better when washed ashore – and this makes it easier to find out what it is.

An example shown below is possibly Griffithsia flosculosa(Ellis) Batters which is described as being “delicate but rigid, often quite dense tuft of dichotomously branching filaments 75-200 mm high, with tiny spherical reproductive bodies on short stalks all over the plant” . However, it is also a lot like the Ceramium species – I just thought from the photograph that the branches did not show the regular dichotomy typical of that Genus.

In the last photograph, shown below, the red seaweed is definitely a lot softer and, exposed to the air on the water’s edge, it just looks like a gelatinous blob! The filamentous branches are much finer and more numerous. You would really need to examine a piece floating in water under a microscope to be sure what it is … but it could be  something like Cystoclonium purpureum (Hudson) Batters.