Norfolk's Unique Reef
An exploration of Europe's longest chalk reef, just off the North Norfolk coast
Photographed by Dawn Watson and Rob Spray
Protecting Norfolk's Wildlife for the Future
North Norfolk's Amazing Chalk Reef
Few visitors notice the beautiful chalk reef that lies so close to the North Norfolk shore. The sliver of this
rich marine habitat which can be seen exposed at low tide gives just a subtle clue to its amazing history
and biodiversity. This chalk is the product of millions of years of geological construction which has
turned unimaginable numbers of plankton fragments into a sheet of limestone rock up to 460m thick. It
stretches across Britain from Yorkshire in the north, to Kent in the south and to the white horse hill
carvings of Wiltshire in the west.
The production of this rock started around 100
million years ago, in the Cretaceous period
when the Earth was a very different place. An
atmosphere rich in oxygen fostered some
spectacular species, such as dragonflies with
wingspans of over a metre! Volcanic carbon
dioxide had created a greenhouse effect.
There were no ice caps and what was to
become Britain was covered by a tropical sea.
This warm water was home to a massive
population of minute, floating football-shaped
algae. This phytoplankton harvested carbon
from the atmosphere and shed it as tiny plates (called coccoliths). These built up over millions of years
into a thick layer of chalk. Not only did this create our reef but the huge amount of carbon this captured
and locked away resulted in the comfortable climate we have now. Our unsustainable exploitation of
fossil fuels is now undoing the plankton's good work, threatening hotter and more unstable weather.
Little Cuttlefish – Sepiola atlantica – 50mm/2 inches long
Mature little cuttlefish
are only the size of a
bumblebee but they will
still face up to divers staging a threat display
- before jetting away
leaving a decoy blob of
swirling black ink.
Surprisingly these
clever, complicated
animals are molluscs,
related to snails. They
are an advanced subclass along with the
squid and octopus.
Members of this class
are known as the
cephalopods, meaning
'head feet'. It is easy to
see why; with versatile
tentacles placed around
their beaked mouths.
Looking closely at the picture you'll see the coloured dots (chromatophores) that allow them to vary their
colour and pattern. The dots change in size; spread to fill areas or contract to disappear completely.
What is a reef?
Most people think of tropical coral when they hear
the word 'reef' but rocky reefs can be just as exciting.
Sailors use reef to describe any obstruction but there
is no single, simple definition and so it can mean
practically any raised area of solid seabed.
Norfolk's
chalk reef
is an area
of rock
distinct from its surrounding seabed which forms a fantastic,
biodiverse habitat. It isn't uniform, in fact it is very varied
allowing it to provide a foundation for a complex ecosystem.
It's like an underwater town or city with a busy centre,
sprawling suburbs and surrounded by a wide open space that
buffers it from other habitats.
A varied terrain supports a wider range of species than one
which is bland. Every different niche has its own residents.
Animals, like people, prefer different types of homes and the
chalk provides housing for many hundreds of species.
We have only just started to appreciate how varied the life of
the reef is. There are animals on our reef which have not
been seen anywhere else in the world.
Dahlia Anemone – Urticina felina – 150mm/6 inches across
Many anemones are dainty but the dahlia is big and colourful
just like its floral namesake. It is tougher than most and can
live down on the seafloor. It often looks as though it is planted
in sand but always secures itself to a stable hard object
beneath the surface with its big sticky foot or basal disc.
The horseman anemone looks very
similar but it is simple to tell them apart.
The dahlia has a sticky stalk which picks
up stones when it retracts for extra
protection while it is closed (above).
An anemone is a single polyp, related to
corals where hundreds of polyps live
together in a communal structure.
Anemones as a whole are also named
after the garden flower, which just goes to show how firmly our thinking is planted on dry land.
Cley – Clay ridges and the start of the chalk reef
Cley marks the start of the chalk reef. It
emerges from under a thick layer of clay
which was carried in by glacial ice flows
and deposited during subsequent melts.
During glacial periods (ice ages) far more
of the world's water was frozen and sea
levels were very much lower. Britain was
linked to Europe by an area now known as
Doggerland. When the last ice age ended
around 10,000 years ago melt water from
retreating ice started to form the North
Sea. We were finally separated from the
continent about 6,000 years ago.
The clay is reef-like with ridges
running east-west which are more
than a metre high. The hard clay
hosts static anemones and
sponges as well as burrowing
crustaceans and boring molluscs.
Clay is a good habitat, but the
harder surface of the chalk is more stable and allows even more
animals to establish themselves as it extends to the east.
Plumose Anemone – Metridium senile – up to 30cm
The tallest anemone in UK waters, plumose
anemones can grow to 30cm/12 inches tall.
However even a large example can collapse
down to almost nothing if it chooses. Anemones
are simple animals which draw in water to
inflate themselves – to reach out high into the
strongest currents to feed on passing particles.
The duster like plume of 200-300 tentacles are
a trap for food particles and small animals.
They appear to be sticky as they contain thousands
of stinging cells which fire tiny tethered harpoons
into anything that touches them.
Plumose anemones prefer to feed in the fast
moving water high above the seabed so they
appear on tall outcrops of chalk and also cover
many shipwrecks. They compete for this position
with the dead man's finger soft coral, which also
comes in white and orange like the plumose.
Salthouse – A secret seascape
Salthouse beach doesn't offer any clue at all to the
areas of chalk which are so close to shore. The steep
gravel beach continues underwater down to a craggy
area which we have only just started to explore. The
water here deepens more quickly than at other sites –
but much depends on the movement of sand and
gravel underwater during winter storms.
Dives at exposed beaches like Salthouse have to be
planned carefully as fierce currents can run along the
coast. Divers use tide tables to predict the best and
safest times to make detailed surveys.
Within 50m of the shore crumbling chalk channels
lead to an area of seabed strewn with large shards
of rock. These provide overhangs beloved by small
crabs and young lobsters as well as a top edge
which catches the current for hungry filter and
suspension feeders which thrive here.
Further from the shore the rock fragments are
generally somewhat smaller. Hard flint and soft
chalk boulders cover the bedrock to produce a low
lying, tide swept seascape which is encrusted with
robust static animals.
Small Spider Crabs – 50-100mm/2-4 inches across
Lobsters and edible crabs are the most famous Norfolk crustaceans but there are lots of others. Among
the most interesting are our small spider crabs which have a real flair for fashion.
Much bigger spiny
spider crabs live on
the south coast but
they aren't nearly as
stylish as the species
we have locally. There
are numerous small
spider crabs on the
reef which adorn
themselves with plant
and animal material to
act as camouflage.
They are often called decorator crabs, for very obvious
reasons. Many species can only really be identified from a
clean, empty shell so they are usually simply separated
into two main groups when spotted on wildlife surveys.
Long legged spider crabs (Macropodia): tasselled with red
or brown seaweed to blend in with algae (Above)
Sponge spider crabs (Inachus): usually covered in living
pink and yellow sponges – like a novelty sumo suit! (Left)
Weybourne – Wreckage and wilderness
Many divers think the reef starts here, although few really know
where. Some motor to explore sandy areas not realising that
there is channelled chalk close to shore, straight off the beach.
These channels could have been cut by melt water running off
higher ground after the ice age but their rounded surfaces may
also be due to abrasion by the sand which surrounds these
inshore chalk features – and harbours little cuttlefish.
The very steep gravel
beach gives many
walkers and swimmers
the impression of great
depth, but the seabed
levels out within 50m.
Rumour of a much
deeper channel in the
chalk here persist but it
simply isn't evident at present. It may be filled by sediment,
perhaps hidden by the sand gathered around the wreck of the
Rosalie which was torpedoed and grounded here in 1914.
There was military activity here during both World Wars and
unspent ammunition can still be found lying on the seabed. Chalk
features increase in height going east from Weybourne, due to a
huge overlying slab of chalk stretching to West Runton.
Sea Toad – Hyas araneus – 150mm/6 inches across
Small spider crabs are talented decorators but the complete master of disguise is the sea toad or
greater spider crab. This stocky spider crab may not have film star looks but it knows how to blend in.
By enthusiastically covering themselves in the animals and plants found nearby – mostly sponge and
seaweed in the pictures - they disappear into their surroundings. Decorator crabs transfer their
camouflage when they moult - to grow all crabs have to shed their old, rigid shells and expand a new
soft one underneath. Many 'crabs' found on the beach are old, empty shells rather than dead animals.
Sheringham – The heart of the reef
The most rugged chalk starts north of Sheringham Park and runs east beyond Beeston Regis to West
Runton. The heart of the reef, with the most dramatic features, is off the centre of Sheringham itself.
The chalk is sometimes described as 'gullies', low
grooves in the stone. 'Gullies' gives just a hint as to
the impressive features a little further out. Low
channels deepen as they run out north from slight
depressions into 3m deep valleys. These are cut by
the rising and falling tides down into a huge slab of
chalk which has been thrust up on top of the main
body of the reef by ancient glacial action.
Chalk is
relatively
soft and
continues
to be
eroded by
tides, currents and humans while it provides a home to
myriad animals. Some of the valleys end between arches or
tunnels inhabited by animals which are unusual in the east
such as leopard spotted gobies and tompot blennies. They
provide features tall enough to attract sheltering shoals of
larger fish too – bib or pouting in the picture above.
Pictures of these features have helped make the North Norfolk reef better known. The North Sea is
rarely seen as an exciting wildlife haven but the chalk reef is an important habitat to be proud of.
Lesser Weever Fish – Echiichthys vipera – 14cm/6 inches long
These fish are seldom seen but have a fearsome reputation... it's not their fault, they are just trying to
stay out of sight. Like many marine animals they really don't want to waste energy chasing food. They
hide in the sand
to wait for their
prey and also to
avoid predators.
Unlike most fish,
they don't have
a swim bladder;
an adaptation to
this peculiar lifestyle.
If startled they
dart away low
over the sand
raising their
venomous
dorsal fin for
protection.
The chances of encountering a weever fish are very small but the effects can be agonising. Wearing
footwear and avoiding shallow sand around low tide will reduce your risk. It doesn't attack but has a
defence so effective that the name 'weever' comes from the French for viper. If stung, immediately
immerse in the hottest water you can stand, to break down the poison, and seek medical help.
Beeston Regis – Beneath the bump
The coast here is marked by 'Beeston Bump'
which at 63m is the highest point on the coast for
miles as well as being the home of the mythical
dog Black Shuck. Once past Sheringham the
inshore gullies and features in the chalk get
gradually smaller – but no less packed with life.
To survey over the full 30km/20 mile length of the reef
volunteers often dive in strong currents with a boat for
safety cover. Divers can cover up to 3km/2 miles in an
hour on a drift dive, towing a buoy to mark their position.
Seasearch and professional surveys have recorded
around 350 marine species on the reef but there are
hundreds more to be found. Surveys in 2011 found a
new species of sponge which is unique to Norfolk.
West Runton – Ancient river bed below fossil cliffs
The rockpools on the shore and the fossil rich cliffs behind offer a
tantalising introduction to what can be found here underwater.
Most of the reef gullies run parallel to each other out from the shore
but at West Runton some islands of rock have been isolated. These
are probably the result of melt water rivers cutting away the rock
around them after the ice age. These have exposed and often quite
efficiently removed a particularly soft lower layer of chalk.
A bus sized plateau has been undercut by caves and tunnels where
layers, which took thousands of years to build up, have eroded.
These overhangs and passages are a welcome refuge for fish and
many other animals from both the current and their predators.
In these well hidden
habitats there may be
rare or unexpected
creatures waiting to
be discovered.
Sea Bass – Dicentrarchus labrax – up to 1m/40 inches
Large shoals of bass are
fairly new to the region
and in summer they hunt
up and down the coast
for food.
Bass are slow to grow
and most bodies agree
that the minimum catch
size should be increased
to allow fish to breed
before they are caught.
Bass can live more than
30 years and females
don't mature until they
are more than 42cm (17
inches) long, which can
take up to 10 years.
Bass themselves are
very partial to sand eels
so the sandy areas
these prefer are a key
habitat for a sustainable
fishery. Small animals and simple seabeds often play a vital role in the food web which connects all species.
Without protection their loss can upset the balance and important commercial species can quickly disappear.
East Runton – Seaweed garden of Norfolk
From here the outer chalk plain starts to widen while the inshore chalk reverts to low polished channels
rather than rugged gullies. The channels are rather like those at Weybourne but shallower and stretch
over a much larger area. This pale, chalk plateau gives rise to an abundance of seaweed.
During the summer vibrant red and green foliage waves in the
moving water like colourful plants. Seaweeds share similarities but
are not true plants, they don't have the same internal structure.
The conditions are so good for seaweed that this site hosted more
species than any other surveyed in the county in 2011. Seaweed
is important as the foundation of a healthy ecosystem, just as
plants are on land, feeding the base of the food chain.
The offshore plain is
strewn with flints left
when the chalk
bedrock has been
eroded around them.
Flint is formed by
silica ooze which has
solidified under
pressure. Many of
the rocks are 'pot
stones' – doughnut
shaped formations
of stone also called
paramoudra flints. A geological mystery, they may have formed in prehistoric animal burrows.
Cromer – End of the pier show
Cromer's famous pier enables summer strollers to walk out
above the chalk – whether they know it or not! The legs of the
pier form an artificial reef that leads to the real thing - so
wildlife is always nearby. Beneath the pier many animals live
amongst the debris left by anglers, tourists, builders and
fishermen. The seabed has sadly become a bit of a tip, please
don't add to the mess and dispose of your litter carefully.
Foulness – Beyond the pier
Beyond the pier a
vast area of chalk
called Foulness
stretches out more
than 5km (3 miles)
from the beach.
This expanse of
bedrock forms a plain with banks and ridges 1-2m high. The
remains of the lost village of Shipden are spread across the
reef here. Small-spotted catsharks (often called dogfish)
rest here while shoaling fish swirl around the natural and
manmade reef features over a carpet of red seaweeds.
Seaweeds need light to flourish and red species are dominant further out. They are adapted to the
reduced spectrum of sunlight at this depth. Green varieties grow best in the brightness of the shallows.
Mermaid's Glove Sponge – Haliclona oculata – 30cm
The tallest sponge in the east grows more than a
foot high and is sometimes mistaken for fan coral or
the stagshorn sponge which grows on other coasts.
Despite this mermaid's glove is actually a quite
distinctive animal. Whether you are lucky enough to
see it living underwater or simply find it washed up
on the beach it is quite simple to identify.
The 'gloves' are porous and predictably spongy but
the key ID feature is the rows of larger holes along
each finger. Sponges pass water in through the very
small holes in their bodies and out through the larger
ones. The little pores act as sieves which prevent
them becoming clogged with particles that are too
big for them to digest.
Sponges are some of the very simplest animals;
without the nervous, digestive and circulatory
systems we have. They are reinforced with a
substance known as spongin which also gives them
their common name. It forms a sort of fibrous
skeleton and most sponges also have a framework
of tiny glassy spicules too. Spicule means 'spike',
because many of them are needle shaped.
Overstrand to Sidestrand - Sand worn seabed
Overstrand is another village where those looking out to sea will have little idea of the exciting marine
habitat so close by. The chalk here appears as fingers emerging from the sand as it slopes down.
This was another site where
the amazing little cuttlefish
were recorded and also one
where large numbers of
weever fish hunt, especially
at night. The soft sand
around the chalk suits both
of these ambush hunters.
(left) Cuttlefish blow sand
away to bury themselves.
(right) You can only really
appreciate just how small
they are beside a human
interloper – can you spot it!
If they aren't hunting all that
can be seen of them is their
eyes, which they colour
match to the sand they
spread over themselves
with their tentacles.
Skeleton Shrimps – Caprella spp. – 20mm/0.75 inches
Reef wildlife comes in many sizes, but if you are
small reaching the best food can be a real challenge
so you have to be resourceful. One species plays
host to another and as rough surfaces are ideal for
these tiny crustacean diners they often cover the tall
mermaid's glove sponges on the east coast.
Skeleton shrimps have claws rather like those of a
praying mantis and you can also see pregnant
females in both of the pictures if you look closely.
Trimingham – Chalk slips under clay, the end of the reef?
At low tide bright, white chalk shows here at the water's
edge. The sand here is very fine and the chalk is very soft so
it is hard for all but the toughest animals to gain a foothold
on the reef which starts just beyond the end of the groynes.
This is a geological transition point, with the chalk slipping
back under hard clay as it runs to the east. The very mobile
sand moves with the tides polishing, surrounding and often
covering the hard seabed. It is difficult to say where the reef
ends as winter storms can reveal or conceal more chalk.
The clay to the east is an important habitat in its own right.
Animals like mussels can form extensive beds on their own
but flourish on a more stable seabed too. Such animal-built
(biogenic) reefs are rich ecosystems and very important to
the food chains that we and many other animals depend on.
Delicate seabeds such as these are easily damaged and
important geological formations can never be truly restored.
The Marine Conservation Zone process aims to establish
some small haven areas which let us see how these habitats
would behave without human interference. Sadly this has
proved controversial - a huge mussel bed to the east was
destroyed by trawling after it was proposed as an MCZ.
Living Seas – Gaining protection for Norfolk’s chalk reef
Healthy seas rich in wildlife are a vital part of our own life-support system. Sadly the history of how we
have cared for the marine environment has often been one of damage and over-exploitation, just think
of the loss of North Sea herring, which formerly supported a thriving Norfolk herring industry.
Only a tiny proportion ( less than 0.01%) of our seas have any
significant protection at present. As a result we continue to see
damage and decline to marine ecosystems.
The Wildlife Trusts and others are supporting the setting up of
Marine Conservation Zones (MCZs) which are a new type of
protected area intended to ensure our seas are managed
sustainably. A network of 127 potential MCZs has been
proposed following the passing of the Marine and Coastal
Access Act in 2009.
Norfolk's chalk reef, because of its special habitats and diverse
wildlife, has been recommended to gain MCZ protection for its
future. Our reef has survived because trawling stopped more
than 100 years ago to protect the crab and lobster fishing and
this ban was secured as a byelaw in 1962. The current level of
crab and lobster potting is considered ‘low impact’ and is
unlikely to be affected by MCZ designation.
There is widespread support for the reef to become an MCZ but still we need your help to make this happen.
For ways to support the campaign visit www.northseawildlife.org.uk
Where to find out more
If you have been surprised and excited by the marine wildlife in this guide there are many ways to take
your interest further. These websites will help start your search:
Norfolk Wildlife Trust holds regular coastal events and whether you are a
diver or beachcomber the Trust is always keen to hear of interesting finds
and sightings around our coast. The Trust's website is a great place to
find out more and hear about the activities you can take part in.
www.norfolkwildlifetrust.org.uk
Twelve Wildlife Trusts have teamed up to help North Sea wildlife. Their
aim is to ensure that an ecologically coherent network of Marine
Conservation Zones is established in UK waters. Visit their website or
Facebook page to learn more about the project, the latest marine news
and how to help the wildlife of the North Sea.
www.northseawildlife.org.uk
www.facebook.com/northseawildlife
Qualified divers are privileged to be able to visit the reef and
Seasearch, a project run by Marine Conservation Society
volunteers, helps them to survey and record the habitat and its
residents. Divers can find out more and everyone can enjoy more
photos from the reef here: www.seasearcheast.org.uk
Copyright 2012 Rob Spray, Dawn Watson and Norfolk Wildlife Trust
Protecting Norfolk’s Wildlife for the Future