Annex I Submarine structures made by leaking gases
Annex I submarine structures made by leaking gases are rocks,
pavements and pillars up to four metres high and composed of
carbonate cement. This cement is produced by microbial oxidation of
gases (mostly methane) that bubble up from below the seafloor. Like
reefs, they provide shelter for many species such as crabs, conger
eels and wolfish but they also support a unique community of
chemosynthetic organisms that are able to survive on the methane
and hydrogen sulphide gases. Such species include the gutless
nematode Astomonema southwardorum, which is thought to
have a symbiotic relationship with chemosynthetic bacteria and
known only to occur at Scanner Pockmark in the North Sea.
There are two main types of submarine structure known to occur
in the UK:
- Bubbling reefs; and
- Submarine structures associated with pockmarks.
There are several examples of pockmark associated submarine
structures in the North Sea and bubbling reef submarine structures
have been found in the Irish Sea. SACs will be selected, where
possible, to include examples of both types of submarine structure
and to protect the habitat throughout the full geographic range in
which it occurs. More information is available on how we are
selecting
where SACs should be located.
JNCC maintain a
map that shows the location of known
submarine structures made by leaking gases. It also shows areas
where gas seeps are known to occur and therefore where there may be
additional submarine stuctures that have not yet been found.
Through
offshore survey, JNCC is working to confirm the
presence of Annex I submarine structures in these areas and to
identify those sites which merit selection as SACs. For information
on the identification of SACs for submarine structures made by
leaking gases within 12 nautical miles of the coast, please contact
the relevant
country conservation agency.
Further reading
General: