Croker Carbonate Slabs

Site overview: This area in the mid-Irish Sea, approximately 30km west of Anglesey, is really important as it is as area where submarine structures are made by leaking gases! The seabed surface is made up of large areas of exposed methane-derived authigenic carbonate (MDAC). As a result lots of animals call this area home, and live here as opposed to the surrounding area. Methane is released from the seabed and reacts with water, creating carbonate blocks and pavement style slabs. These areas support a large number of soft corals, sponges, tube worms and anemones.
At risk:  ! This site is still under consultation which means it is not designated as a Marine Protected Area. It needs to both be designated, and then managed correctly, to ensure that it remains a safe place for the sea creatures which call it home.

Designation Status
Last Updated
6 June 2017
MPA Type
Site of Community Importance
MPA Purpose
Sites which have been adopted by the EC, but not yet formally designated by governments of Member States are known as Sites of Community Importance (SCIs)


53° 28' 21" North,
5° 14' 17" West

Surface Area

65.94 km2
(25.46 mi.2 )


35.10 km
(21.81 mi.)

Iconic features protected by this site


  • Submarine structures made by leaking gases
  • Submarine structures made by leaking gases (Annex I habitat)