Trembling sea mat
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
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
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,
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.
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.
is a UK BAP Priority Species (BAP species are now Species of Principal Importance/Priority
- 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
- Nationally rare marine animal.
Life Information Network
World Register of Marine Species
JNCC - UK BAP Priority
Species and Habitats