On the 23rd October 2015, JNCC, in partnership with the Centre for
Environment, Fisheries and Aquaculture Science (Cefas), began a 14 day survey
of Croker
Carbonate Slabs Site of Community Importance aboard the
Research Vessel (RV) Cefas Endeavour. Croker Carbonate Slabs is one of the 20
offshore candidate Special Areas of Conservation (cSAC) in UK offshore waters.
The area is located in the Irish Sea, approximately 30km west of
Anglesey.
Map showing the distribution of Annex I habitat
“Submarine structures made by leaking gases” within the cSAC/SCI boundary. View
and download spatial data for this MPA on the JNCC UK MPA
interactive mapper © JNCC, 2015.
The site is
designated for Submarine structures made by leaking gases, specifically
methane-derived authigenic carbonate (MDAC). These carbonate blocks and slabs
form when methane rising from deep below the seabed is consumed by microbes in
the seabed sediment. The microbes create the carbonate, which acts as a
cement, gluing sediment particles together to form a type of rock. The seabed
habitats created by these MDAC structures support a diverse range of marine
species that are absent from the surrounding seabed, which is characterised by
coarse sediment. Large carbonate blocks support a diverse range of soft
corals, erect filter feeders, sponges, tube worms and anemones, whereas the
flatter, pavement-like MDAC structures are colonised with scour-resistant
animals such as hydroids and bryozoans.
During the survey, we will focus on gathering evidence
to contribute to the development of a monitoring time-series for Croker
Carbonate Slabs SCI from which the rate and direction of change in the
condition of ‘submarine structures made by leaking gases’ can be
inferred in the long term.
The survey aims to improve our knowledge of the
distribution and spatial extent of MDAC, map the finer spatial extent of MDAC
and gather further information on biological communities, including
characterising the wider sediment areas found within the site.
By Alice
Cornthwaite
