Last month, a team of MESH Project scientists
undertook a collaborative survey explored the deep underwater canyons at the edge of
the continental shelf, 320 km off Lands End directly between the UK, Ireland
and France. The cruise involved three MESH partners: the UK'S Joint Nature Conservation
Committee, the British Geological Survey and Ireland's Marine Institute.
They were hoping to find large areas of cold water coral reef, such
as those found further north off Ireland, Scotland and Norway. These coral reefs
are a rare habitat, easily damaged by seabed activities like bottom trawling for
fish, and in need of protection.
Starting at around 200m water depth, these canyons plummet to the abyssal
plain over 4,000m below, but almost nothing is known about what lives there, on
the seabed. The survey mapped the shape, topography and geology of three
canyons, which cover an area of 850km2 (more than 120,000 football pitches),
using a variety of seabed mapping techniques and instruments. A high
resolution deep water camera was lowered by winch to capture video and still
images of the seabed at depths of up to 1,000m.
Scientists found that the canyons were made up of fine muddy sands at their
tops, on the edge of the continental shelf, the home to delicate seapens,
anemones, sea cucumbers, and patches of featherstars. There was also
evidence of former coral mounds at the tops of the canyons, similar to those
found on the edge of the Irish continental shelf. Those coral mounds have
been proposed as Marine Protected Areas under the EU Habitats Directive, and
protecting them from fishing is currently under consideration by the EU.
The mounds found in UK waters during this survey contained only broken coral
rubble, where we would have expected to find living coral.
Further down the canyons the seabed was made up of layers of silty clay, with
steep outcrops of white chalk at depths of around 900m. These rocky
outcrops did support a few cold water corals and other species, but not as much
as could have been expected. One small area of coral reef was found, with
bright orange cold water corals, anemones, starfish and featherstars, and a few
fish. Several discarded fishing nets, plastic bags and boxes were
Charlotte Johnston, who leads JNCC's effort in recommending
offshore areas for conservation to the UK Government said: it was
fantastic to find out what is on the seabed in this area, and to find cold water
corals here in a different situation to those found in other parts of UK and
Irish waters, but also disappointing to find this much evidence of damage,
presumably by trawling, to former coral mounds