Trembling sea mat

Victorella pavida


The inconspicuous trembling sea mat lives in brackish water (where salt and freshwater mix), and so is found in coastal lagoons and estuaries. 

Trembling sea mats may grow in various forms, from branching chains to dense clumps, and it often looks more like a plant than an animal.  During the summer, colonies of individual animals have the appearance and texture of brown velvet. 

Trembling sea mats can be found growing on any hard surface, from stones to concrete structures, but they have a particular preference for the submerged stems of coastal reeds.

This sea mat was first discovered in 1870 and was described from two sites in London – the Surrey Canal and Victoria Docks – to which it was probably transported on the hulls of ships. However, it has now disappeared from both of these sites, probably as a result of the docklands development.  It has since been rediscovered in the brackish water lagoon at Swanpool, Cornwall.

As the trembling sea mat is only found in one location in the UK, its continued survival is dependent upon the conservation of that lagoon. Coastal lagoons are threatened by silting, changes in the freshwater/seawater mix, pollution and coastal development.   Fortunately, the trembling sea mat’s home in Swanpool is designated as a Site of Special Scientific Interest and is a Local Nature Reserve.


European distribution

The trembling sea mat has only been recorded at one site in the UK (in Cornwall).  It has been recorded in Sweden, along Northern European coasts as far as Spain, and in the Baltic and Black Seas. It is common in the Mediterranean.


Conservation status/need

  • Trembling Sea Mat FactThis is a UK BAP Priority Species (BAP species are now Species of Principal Importance/Priority Species).
  • Species of principal importance for the purpose of conservation of biodiversity under the Natural Environment and Rural Communities Act 2006 in England.
  • Protected under Schedule 5 of the Wildlife and Countryside Act 1981.
  • Nationally rare marine animal.


Further information

European Environment Agency

Marine Life Information Network

World Register of Marine Species

JNCC - UK BAP Priority Species and Habitats