Red Seaweeds

Red seaweeds have had a more diverse evolution than the green and the brown. Many species cannot stand desiccation and dominate the inter-tidal rock pools. Others tolerate desiccation, such as the purple laver which can often be seen stretched out like a dry black film over mussle beds on rocky beaches.

Red seaweeds such as Polysiphonia lanosa are epiphytes, these are plants that grow on other plants for physical support. In this case the epiphyte benefits from the host's buoyancy lifting it closer to the sunlight.

The red colour of the seaweeds is due to the larger amount of red phycoblin pigments overriding the green pigment chlorophyll.

The pigments that colour it red have a purpose, enabling the seaweeds to photosynthesis light from a specific part of the light spectrum. Within the group of phycoblins two pigments are of importance phycoerythrin and phycocyanin. Phycoerythrin absorbs green, yellow and red light while phycocyanin absorbs blue, green and yellow light. These parts of the spectrum are the type of light that penetrates the deepest in sea water. The red pigments absorb the light but chlorophyll is still required to process it. This method allows red seaweed to survive in low light conditions where green seaweeds could not.

The light intensity has an affect on the red pigments which is reflected in the colour of the seaweeds. With high light levels the pigment starts to break down, the seaweeds becoming pink or even bleached white. With low levels pigment production is stepped up producing really red plants.

        Purple Laver Porphyra umbilicalis

        Lithothamnia

        Coral Weed Corallina officinalis  

        Carragheen Chondrus crispus

        Red Epiphyte Polysiphonia lanosa

        Pepper Dulse Laurencia pinnatifida

        Ceramium

Coral Weed Corallina officinalis  

This is a red seaweed, found commonly in pools on rocky shores. In rock pools it can be the dominant seaweed and form a dense carpet. The colour varies with the light conditions. The more shaded the position the deeper the purple.

The name is derived from the calcareous deposits in its structure that gives it a hard and rigid texture.

Red Epiphyte Polysiphonia lanosa   

A small red feathery plant commonly found growing on Egg Wrack. It is an epiphyte, a plant that only grows on another plant for physical support.

In this case the epiphyte benefits from the wracks' buoyancy lifting it closer to the sunlight.

Lithothamnia

Calcium carbonate secreting algae found on exposed shores. They obtain calcium from seawater. They occur as linings to rock pools, often completely covering them, with the exception of small bare circles, the resting places of limpets.

The more shaded the position the more purple the colour. When out of water it is bleached by the sun and turns white.

Ceramium

A common red seaweed with over twenty species found on Cornish Shores.

Individual species are difficult to tell apart. The most common is ceramium rubrum. It is found growing on both seaweeds and rock surfaces.

The fine filaments grow dictomously, that is every time they subdivide into two equal branches.

If you look closely the filaments are cross banded with light and dark red bands.