Fronds of Corallina officinalis grow in tufts that develop from a flat coralline base. They are segmented to provide flexibility in seawater. The fronds are also oppositely branched. This seaweed is a dull purple but its colour can vary depending on the conditions. It can appear red, yellow or white when bleached in bright light. Individuals are usually 1 to12 cm tall.

Lookalikes
The name Corallina officinalis has been used for specimens that look very similar and are found in other parts of the world, but these may not be the same species.

Corallina officinalis is a calcified red seaweed, a coralline alga commonly found in rock pools on seashores around the world. Corallina officinalis belongs to a large group of calcified seaweeds with more than 564 species that are found on seashores and in seas around the world.Corallina officinalis is a jointed or geniculate coralline alga. Other species of coralline algae are crustose species and look like someone has painted the rocks with pink or mauve paint.Other species of coralline algae can form deposits known as maerl beds. These are extremely important habitats for other organisms. Maerl is also commercially exploitable as a source of lime and trace minerals in the agricultural, horticultural and medical industries.

Reproduction
Life histories in red seaweeds are complex, and different reproductive structures have their own terminology. In Corallina officinalis male and female reproductive structures are found on separate plants. These structures develop in conceptacles - tiny flask-shaped structures just visible to the naked eye. After fertilisation, diploid spores are released which grow into a phase called the tetrasporophyte. These plants look just like the male and female ones but they develop conceptacles which contain tetrasporangia. Each tetrasporangium contains four spores. When mature, meiosis occurs in the tetrasporangium and haploid tetraspores are released. These grow into male and female plants.

 Corallina officinalis consists of calcareous, branching, segmented fronds, usually erect, up to 12 cm high but often much shorter. Fronds rise from a calcareous crustose, disk shaped, holdfast about 70 mm in diameter. Fronds consist of a jointed chain of calcareous segments, each becoming wedge shaped higher up the frond. Branches are opposite, resulting in a feather-like appearance. Colour varied, purple, red, pink or yellowish with white knuckles and white extremities. Paler in brightly lit sites. Different colours normally represent light induced stress and degradation of pigments (bleaching). Reproductive organs are urn shaped, usually borne at the tips of the fronds but occasionally laterally on segments. Distinguished from the similar Corallina elongata by the structure of its reproductive bodies which bear horns or antennae and from Jania rubens which branches dichotomously.Also known as 'Cunach Tra' or 'An Fheamainn Choirealach' in Ireland. Growth form can be variable, for example: 

• stunted specimens occur in high shore pools
 
• much branched forms in the lower littoral
 
• thick elongate forms in sublittoral

In Norway fronds 1-2 cm long recorded in lower littoral in contrast to 10-17 cm long fronds in pools. This variability has resulted in numerous species descriptions that are probably synonymous with Corallina officinalis (Irvine & Chamberlain 1994).

Thallus calcareous, articulated, branching from a crustose base to a hight of about 12 cms. Branches pinnate or irregular. Corallina elongata and Haliptilon squamatum.

Argentina, Atlantic, Azores Exclusive Economic Zone, Canada, Cap Gris Nez, Dutch Exclusive Economic Zone, European waters (ERMS scope), Gulf of Maine, Indian Ocean, Irish Exclusive economic Zone, Israeli part of the Mediterranean Sea - Eastern Basin, Mediterranean Sea, North West Atlantic, Oostende, Pacific Ocean, Pointe du Nid de Corbet, Pointe du Riden, South Africa, South Africa (country), Swedish Exclusive Economic Zone, United Kingdom, United Kingdom Exclusive Economic Zone, USA, Wimereux, Zeebrugge

Long Island Sound to Strait of Belle Isle

Distribution
The distribution of Corallina officinalis is not yet fully known. We know it occurs in the North Atlantic.

Habitat
Corallina officinalis can be found in rock pools in the middle and lower shore often forming a distinct zone just below the rim of rock pools. The seaweed also lives on rocks on the lower shore and in shallow water. This species also provides a home for little sea creatures and often has other seaweeds growing on it.

All around the British Isles. Europe: Azores, Portugal, Spain, Netherlands, Baltic Sea, Norway, Faroes and Iceland. Greenland. Atlantic coasts of North America from Labrador south to Connecticut and Maryland. Further afield: Arctic Sea, Canary Islands and South Africa.

Red colour results from the dominance of the pigments phycoerythrin and phycocyanin; this masks the other pigments, chlorophyll a (no chlorophyll b), beta-caratene and a number of unique xanthophylls.

tide pools to 20 m

Known from rocky shores.

Depth range based on 420 specimens in 2 taxa.
Water temperature and chemistry ranges based on 58 samples.

Environmental ranges
  Depth range (m): 0 - 155.46
  Temperature range (°C): 11.244 - 24.821
  Nitrate (umol/L): 1.216 - 7.121
  Salinity (PPS): 35.035 - 36.667
  Oxygen (ml/l): 4.848 - 6.339
  Phosphate (umol/l): 0.191 - 0.452
  Silicate (umol/l): 2.311 - 5.808

Graphical representation

Depth range (m): 0 - 155.46

Temperature range (°C): 11.244 - 24.821

Nitrate (umol/L): 1.216 - 7.121

Salinity (PPS): 35.035 - 36.667

Oxygen (ml/l): 4.848 - 6.339

Phosphate (umol/l): 0.191 - 0.452

Silicate (umol/l): 2.311 - 5.808
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

 Typically forms a turf in pools and wet gullies from the mid tidal level to the sublittoral fringe. A characteristic algae of rock pools on the middle to lower shore. Occurs as scattered clumps in the sublittoral down to 18 m although it has been recorded down to 29 m in continental Europe. It often flourishes in exposed conditions. Occasionally found on mollusc shells or macroalgae such as Furcellaria.

Abundant and dominant in some rock pools of the littoral and in the sublittoral to at least 18 m. Epilithic.

Plant / epiphyte
creeping colony of Walkeria uva grows on Corallina officinalis

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 65
Species With Barcodes: 1

Corallina officinalis is a common species and does not appear to be threatened. However, we do not know how it and its other calcified relatives will respond to ocean acidification. Maerl is already recognised for its conservation importance and is a UK BAP (Biodiversity Action Plan) habitat.