Isle of Wight sized reef found by seabed mappers
05 December 2011
A string of new discoveries by seabed habitat
mappers around the world seem to bear out the old adage - that
we know more about the surface of Mars than we do about the
Earth's seabed.
In UK waters, recent work by Cefas scientists has revealed an
extensive system of rocky ridges in the central English Channel.
Previously, the mapped area was thought to contain
little or no rock outcrops.
So the mappers were surprised to find a "reef" that
is about four times the size of the Isle of Wight. As
remarkable as that is, the reef is also important for another
reason: it supports a large variety of marine animals. The abundant
fauna includes sponges, bryozoans, anemones and sea-squirts.
Markus Diesing, of Cefas' Marine Habitats and Mapping
team said: "We used a combination of existing data and new
survey information, collected on our research vessel, the Cefas
Endeavour, to outline and characterise the area of
rock ridges.
"These extend over 1,100 square kilometres of seabed, some
30 kilometres south of the Isle of Wight. The reef rests at
depths between 40 and 100 metres below the surface, so it isn't
hazardous to shipping."
Multi-beam sonar shows a
complex of rock formations exposed at the seabed - with ridges
up to 4 metres high - generally running in an east-west
direction. Underwater video and seabed photographs reveal the
detailed physical nature of the seabed and show the range of
animals that live there.
Multi-beam sonar image showing some of the
rock ridges in the central English Channel and the path of an
ancient river that has cut through them. The scale shows water
depth in metres.
The feature, now known as the
Wight-Barfleur Reef (PDF), is currently under
consideration for protection under the European Union's
Habitats Directive as part of a European network of Marine
Protected Areas, known as Natura
2000.
This particular discovery has recently been published as a case
study in a major new book called
Seafloor Geomorphology as Benthic Habitat - GeoHab Atlas of
Seafloor Geomorphic Features and Benthic Habitats.
The atlas provides a synthesis of current knowledge in relation
to seabed geomorphology as benthic habitat and
presents a total of fifty-seven case studies from around the
world.
It seems there is still plenty to explore and discover here on
Earth.
Seabed fauna 
1. Sponges (Porifera) are collections
of cells that can be organised into a variety of shapes. They live
attached to rock and feed by filtering particles out of the water.
There are many encrusting forms in the UK, but the massive forms
such as the large white or grey "Elephant's Hide" sponge
(Pachymatisma johnstonia, not shown in this image) are
relatively uncommon.
2. Bryozoans (Ectoprocta) are colonies
of "zooids", small individuals about the size of a grain of sugar
that are not quite independent from each other. They live in a
matrix of individual chambers and different groups of zooids
perform different functions for the colony (e.g. feeding,
excretion, reproduction). The colonies live attached to rocks and
there are many forms in UK waters. The "Hornwrack" (Flustra
foliacea) was very common on the rock ridges.
3. Anemones (Actiniaria) are
individual soft-bodied animals with a central mouth surrounded by a
ring of tentacles armed with stinging cells. They usually live
attached to rocks with their tentacles spread wide waiting for prey
items to brush into them.
4. Sea-squirts (Ascidiacea) have
sac-like bodies with a primitive backbone and are typically about
the size of a grape. They live attached to rocks and can be
solitary, gregarious (living in groups) or colonial. They pump
seawater through their body cavity and filter out tiny particles of
food.