North-West Anglesey Reef
The aim of this study was to investigate an area identified as
containing potential Annex I bedrock, stony or biogenic reef.
To the north and north-west of Anglesey four areas were
identified by the British Geological Survey under a separate
contract as potentially containing bedrock or stony reef, covering
an area of approximately 140 km2. It was also
anticipated that areas of biogenic reef may be found within the
survey areas, due to historic records of Modiolus modiolus
in the vicinity.
In the summer of 2005, the opportunity arose for JNCC to
collaborate with partners of the INTERREG funded HABMAP project. Between 9th and 14th
August 2005, JNCC, in collaboration with the Countryside Council
for Wales and University College Cork, surveyed these four areas
from the RV Celtic Voyager. High resolution
multibeam bathymetry and backscatter data were
obtained for all four survey areas. Seventeen grab
samples were obtained in three of the four survey areas.
Twenty-nine video tows were obtained from all four
survey areas.
The results from the current study suggest that the seabed in
this study area was broadly characterised by complex topography and
mixed sediment mosaics, which were home to tide-swept
benthic communities.
Analysis of the infaunal communities sampled using a grab showed
that all samples belonged to the same circaliottoral coarse
sediment biotope,
SS.SCS.CCS.MedLumVen. A range of biological communities were
also determined from the video analysis. Some were typical of
boulder areas subjected to moderate tidal streams and were typified
by faunal crusts. In one of the survey areas, very high densities
of the brittlestar Ophiothrix fragilis,
along with lower numbers of Ophiocomina nigra, were
present, blanketing the underlying rocky substrate. Gravelly
substrates were also common throughout the survey areas, supporting
biological communities that did not easily match existing biotopes
within the Marine Habitat Classification for Britain and Ireland
(version 04.05).
Annex I reef was observed in patches throughout
the four study areas. Where Annex I reef was found, it was
comprised of boulders and cobbles. Along video tows, reef habitat
tended to alternate with more gravelly areas of non-reef habitat.
No biogenic reefs (formed by either Modiolus modiolus or
Sabellaria spinulsoa) were encountered through the survey,
although some juvenile Modiolus modiolus were recovered in
grab samples.
Although Annex I reef was found in a number of locations,
indicating that this could be an area of conservation interest,
further work is required to compare the results of the current
study with other known areas of reef within the Irish Sea, with
respect to the SAC site selection criteria.
Further Reading
- Blyth-Skyrme, V., Lindenbaum, C., Verling, E., Van Landeghem,
K., Robinson, K., Mackie, A., Darbyshire, T. 2008. Broad-scale
biotope mapping of potential reefs in the Irish Sea (north-west of
Anglesey). JNCC Report 423.
Project Partners
If you have any further questions about JNCC's offshore survey
work then please contact us.