Croker Carbonate Slabs SCI

Status: Designated


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. 

MPA Type

Site of Community Importance

Special Areas of Conservation (SACs) are strictly protected sites designated under European legislation. They contribute both to the UK MPA network and set up to protect habitat types and species considered to be most in need of conservation at a European level (excluding birds). Sites that have been adopted by the European Commission but not yet formally designated by the government of each country are referred to as Sites of Community Interest (SCIs).

Designation date

1 August 2012

Surface Area

65.93 km2 (25.46 mi.2)


35.26 km (21.91 mi.)

  • Submarine structures made by leaking gases

    Tell tale marks that show that gas is making its way up through the seafloor from deeper layers below.

Did you know?…

An area over 9 times the size of Wales is now in marine protected areas in the UK, but less than 1% is considered by MCS scientists to be well managed

Over 500,000 records of undersea species and habitats have been collected by volunteer Seasearch divers

To the shelf limits, Scotland has 61% of UK waters, of which 23% are now in existing or new ‘marine protected areas’