Transcript Reefs out of Plymouth (`Prawle Point to

Reefs out of Plymouth (‘Prawle Point to Plymouth
& Eddystone’): Special features and conservation
needs.
Keith Hiscock
July 2009
(Presentation first given
April 2009, adjusted
to support the
announcement of a
draft Reef Special
Area of Conservation)
This presentation is available from www.ukmpas.org/presentations.html
Reefs out of Plymouth – special features
and conservation needs
• Context: 110 years of surveys, recent surveys and new
‘offshore’ SACs.
• Grand Tour – different and ‘Important’ landscapes, habitats,
communities and species.
• All is not well – existing damage to biodiversity, threats to
habitats and species, and conservation needs.
• Words of comfort.
• Improving information resources.
There is a long history of study of areas out of Plymouth early work at the Marine Biological Association was directed,
in part, at documenting the marine life present near Plymouth,
although reef habitats were often sampled by accident.
From: Allen 1899. ‘On the fauna and bottom deposits near the
thirty- fathom line from the Eddystone Grounds to Start Point.’
Those studies continued through the 20th century (gaps for
wars and until 1988, when government research policy
withdrew funding from long-term studies.)
Southward & Holme
Kitching
Forster
The Plymouth Marine Fauna is a valuable source of
information about the species recorded out of Plymouth and,
although last published in 1957, is available on-line:
www.mba.ac.uk/pmf
Surveys using diving:
in the 1980’s and 1990’s commissioned by the nature conservation agencies,
undertaken by Devon Wildlife Trust and, more recently the Seasearch programme.
Locations (square spots)in the vicinity of Plymouth that have been sampled since
the 1980’s in surveys commissioned by the nature conservation agencies and
undertaken by Devon Wildlife Trust and by Seasearch.
Habitat sample points from www.searchmesh.net
Surveys over the past 100+ years have demonstrated the
richness and special
features of the
submerged reefs
out of Plymouth
Hand Deeps
Recent survey areas to identify possible Special Areas of
Conservation (EU Habitats Directive)
Outcome: Prawle Point to Plymouth & Eddystone draft SAC
Using existing information: MESH and NBN
MESH maps seabed types and
the location of spot survey sites
which can be interrogated to list
biotopes but does not allow
access to survey data (which can
be accessed from
www.searchnbn.net).
There are large
areas of seabed with
no spot survey data
www.searchmesh.net
Results of video tows during Haskoning surveys
Video images are just about sufficient to
identify large species and biotopes present
Video surveys underway
Drop-down video - getting better
(some images from later in the survey)
But, you still
need to look
with your own
eyes to find
hidden nuggets
Understanding the character and special features of reefs out of
Plymouth benefits from a long history of study, surveys
undertaken in situ and ‘local knowledge’ of marine biologists.
The Grand Tour
• Hatt Rock & Hand Deeps
• Eddystone
• Drop-off (submerged
cliff-line)
• West Rutts
• East Rutts
• Mew Stone
• Fairy Land
• Hilsea Point Rock
• Stoke Point
• Chicken Rock
Offshore reefs
Hatt Rock
The top of Hatt Rock at about 25m below chart datum. Characteristic features
include a kelp park with sea fans mixed-in, common hydroids Gymnangium
montagui, only occasionally seen elsewhere, and common nationally scarce brown
algae, Carpomitra costata.
Diving through the year enables observation of breeding seasons and changes
through the year – here, the reproductive bodies on Gymnangium are seen in
December
Another remarkable feature of Hatt Rock and (to a lesser
extent) Hand Deeps, is the high abundance and large size of
the volcano sponge Haliclona viscosa
A series of buttresses extend out from the plateau looking like
a granite tor, but the rock is mica-schist.
Cliffs are universally dominated by jewel anemones, Corynactis
viridis
‘Headlands’ at Hatt Rock are characterised by plumose
anemones, Metridium senile
Deep upward facing sandy rocks at Hatt Rock are characterised
by parchment tube worms, most likely Chaetopterus variopedatus
Sea fans, Eunicella verrucosa are common and often have
the rare sea fan anemone Amphianthus dohrnii, attached
An ovulid (false cowerie) mollusc found on sea fans at Hatt Rock and believed to be
a species new to science – very similar to Simnia patula, common on soft corals
The species most often seen on sea fans is the sea fan sea slug Tritonia
nilsohdneri – the slug above, eggs below.
A chance find? The octopus Elodne cirrhosa
Hatt Rock is the only location on reefs out of Plymouth where
the cushion star Porania pulvillus has been reported in normal
diving depths
Hand Deeps - in a bloom of
coccolithophore algae
The top of Hand Deeps is at about 8-12m below chart datum
with a kelp, Laminaria hyperborea, forest and, on shallow
vertical surfaces, Sagartia elegans sea anemones, typical of
wave-exposed shallow reefs.
Spectacular underwater landscapes
Rocks below about 25m are
dominated by jewel anemones
with common dead man’s fingers
and a small variety of other
species. Plumose anemones occur
at the ‘headlands’.
Jewel anemones, Corynactis viridis
At about 40m, there is a boulder tumble, often with ling and
conger present, with a reduced abundance of jewel anemones
and extensive encrusting Bryozoa.
Typical cliff scene at Hand Deeps
Back towards the top
of the reef
In the shallows, there is a high abundance of wrasse especially
rock cooks, Centrolabrus exoletus
On the shallowest part of the reef, at 8m below chart datum,
there is a mixture of dense kelp, foliose algae, encrusting
sponges, hydroids and elegant anemones, Sagartia elegans.
And rarely seen species sometime turn-up on the offshore reefs.
This crawfish was put back
and two others seen on the
same dive were left in place
Eddystone
Shallow reef tops where the annual kelp, Saccorhiza
polyschides is prevalent
Steep rock slopes – sea fans
etc. (natural light)
Flash illuminates the foreground
Eddystone reefs are typically coated with shell sand
(‘Eddystone gravel’)
Sea fans, Eunicella verrucosa, are especially common on
offshore reefs
Eddystone, NW reef
Dead man’s fingers, Alcyonium digitatum, are a soft coral
common everywhere: here with a bloody Henry starfish, Henricea
sp.
Red sea fingers, Alcyonium glomeratum, are less common than
dead man’s fingers: here with a seven-armed starfish Luidea
ciliaris
Male cuckoo wrasse, Labrus mixtus, the most colourful British
fish, common at the Eddystone
Back towards the top
of the reef and
Sagartia elegans
dominate the vertical
(shaded) surfaces
The sublittoral fringe at the Eddystone is dominated by
coralline algae and by the kelp Alaria esculenta – a northern
species no longer found on the mainland coast.
Inshore reefs
Drop-Off (submerged cliff-line at c. 30m
depth and 2 nm south of the Breakwater)
And, sometimes, they can’t decide
Amongst the forest of pink sea fans, Eunicella verrucosa, some may be white – a colour
morph that increases in proportion south of Britain and on the west coast of Ireland.
A significant
location for rare
and scarce
species: football
sea squirt, sunset
corals, red sea
fingers
Sunset cup coral Leptopsammia pruvoti: recent research into the corals dna has shown
that individuals are clones of each other – signs of a genetically isolated population.
Football seasquirts are not ‘at their
best’ in midwinter when they lose
their zooids, which start to grow
again in about February.
Late 2008 and early 2009 saw a large
settlement of this scarce species
Football sea squirt, Diazona violacea
Mashed potato sponge, Thymosia guernei, a scarce species frequently seen at the
Drop Off
Axinella damicornis, a scarce sponge that is common at the Drop Off
Parazoanthus axinellae colonising Axinella damicornis
Another scarce and highly distinctive sponge: Axinella infundibuliformis
A scarce and highly distinctive hydroid: Polyplumaria flabellata
And plenty of ‘marine life’ for recreational divers
Conger, Conger conger
Lobster, Homarus gammarus
West Rutts
The sort of landscape and species that characterise the reefs out of Plymouth
East Rutts
Limestone rock that is peculiar for reefs out of
Plymouth
East Rutts reefs are rich in species and with features associated with the soft
nature of the rock including piddock borings that in turn provide a refuge for other
species. The abundance of the foliose bryozoan Chartella papyracea is unusual.
Mew Stone
Ross, Pentapora foliacea fascialis, a fragile bryozoan
Pink sea fingers, Parerythropodium hibernicum – occasionally found under overhangs
Peppercorn anemones, Isozoanthus sulcatus – often seen on Mewstone Ledges
Fairy Land including Hilsea Point
Cold water kelp, Laminaria
hyperborea, occurs abundantly
Increasing amounts warm water
golden kelp, Laminaria ochroleuca, in
shallow areas in recent years
Populations of the scarce solitary coral Balanophyllia regia
occur in shallow gullies
Occasional large populations of the scarce brown alga
Carpomitra costata
Shallow inshore areas along the coast are host to large
populations of wrasse – here a male corkwing guards its nest
of seaweeds
Spectacular landscapes
Hilsea Point Rock
Hilsea Point Rock has rich sponge communities and several
rare or scarce species present
26 May 2007
29 March 2009: same place, same stuff
The distinctive encrusting sponge Hexadella racroitrai has
recently been discovered on the Hilsea Point reefs – the first
record for England
The sponge Endectyon delaubenfelsi – rarely seen on open
coast reefs and more common in Plymouth Sound but a rarely
recorded species
File shells, Limaria hians, build
‘nests’ under boulders but are
rarely seen
Black sea cucumbers, Holothuria
forskali, are very common and are
sometimes seen spawning
Sea urchins, Echinus esculentus, are ‘everywhere’ and are
important grazers, potentially clearing space for new settlement.
On all of the reefs, a wide range of fish species
Cuckoo wrasse, Labrus mixtus
Small spotted catshark (aka dogfish), Scyliorhinus canalicula,
are frequently seen
John dory, Zeus faber
Tompot blenny, Parablennius gattorugine
The leopard spotted goby, Thorogobius ephippiatus, lives in
muddy fissures and when first found on Plymouth reefs in the
1950’s was thought to be a new species.
More frequent reports of warm-water species in recent years
Trigger fish, Balistes carolinensis
Stoke Point sponge gardens
The sandy low-lying reefs off Stoke Point provide a favoured habitat for a wide range
of branching and cushion sponges.
Some of the sponges are nationally
rare or scarce species
Nationally rare Adreus fascicularis
Reef communities clear of sediment at Stoke Point – note
the dog cockle shells bottom left
Inside the shells, the rare hemichordate
Rhabdopleura compacta
Away from the coast: Chicken Rock*
* Unnamed feature – the 30m contour, with imagination, is the shape of a chicken
Chicken Rock has similar communities to other reefs offshore of
the coast. The widely distributed and often abundant orange
sea squirt Stolonica socialis is conspicuous
The occasional candidate for the cooking pot
The distinctive hydroid Gymnangium montagui is often seen on
reefs that are offshore of the coast whilst antenna hydroids,
Nemertesia antennina, appear to be more common on reefs
towards Bigbury Bay
All is not well – existing damage to
biodiversity, threats to habitats and species,
and conservation needs
Dredging: the spoil has to be disposed of ……
Rame Head
disposal
ground
Image: Pete Messenger
Reef habitats are most conspicuously impacted
Dredge spoil disposal cannot be undertaken in protected areas
Image: Pete Messenger
In 2001-2003, many pink sea fans Eunicella verrucosa were
diseased and dead skeletons became covered in fouling species
Work at the University of Plymouth has identified the vibrio
bacteria responsible for the sea fan deaths, and, it might be a
natural, if unwelcome, event.
From the Plymouth Marine Fauna:
No sign of necrotic tissue on sea fans since about 2004. Whilst
possibly a natural event, better understanding of any human
contribution (e.g. increased nutrient levels) is needed.
Just a bit too close to a reef that couldn’t be ‘skipped-over’
(scallop dredge against the Drop-off)
Mobile fishing gear is well-established as the greatest threat to
biodiversity on seabed habitats especially where reef species are
impacted. Reef habitats need to be protected from mobile gear.
Static fishing gear can entangle reef wildlife
And, lost gear continues to fish including
entangling reef species
There should be no netting on reef habitats
Hatt Rock
No-one wants to lose their gear, and staying well clear of reef
habitats helps protect foraging areas for reef species and the reef
Habitat removal (& seabed homogonization)
Mobile fishing gear should be kept clear of reef habitats
Outside the fishmarket in Plymouth
‘Littering’ – from metal wrecks …..
To metal cans
Enforce the message “Overboard is over”
(and don’t have more wars!)
Persier
Removal of top predators – impacts?
Traps for crustaceans are relatively benign but removal of top
predators will affect ‘naturalness’ – some areas of mpa’s should
be Highly Protected to ensure they are as close as possible to
natural, providing reference points and areas for recreation.
All is not lost! Some of the locations
described as a result of early use of
SCUBA equipment have been re-visited
The rocky
subtidal
communities at
Hilsea Point
Rock are very
similar to those
described over
50 years ago
(Hiscock,
2005, JMBA
85, 10091010)
Improving information – multibeam sonar is a great start
Sables fines
per IFREMER
Multibeam sonar image of reefs off Rame Head
courtesy of Cefas.
The same area (boxed on the map) is registered
as ‘fine sand’ on www.searchmesh.org.
Video survey gives an overall picture of habitats
and biology
But, to survey reef habitats for biodiversity, nothing beats getting
down there!
In situ surveys of reef habitats by professional scientists
continue to be needed.
The Prawle Point to Plymouth & Eddystone area
has fabulous, important and sensitive marine life
Look after it!
Stoke Point
See the proposals for new SACs on:
www.naturalengland.org.uk/ourwork/marine/sacconsultation
Find out more about marine life and report your observations on:
www.marlin.ac.uk
Help to survey our subtidal areas, see www.seasearch.org.uk
For information on dive sites, see www.plymouthdivers.org.uk
Presentation available from www.ukmpas.org/presentations
The views expressed in this presentation are those of Keith Hiscock
Unless otherwise indicated, all images are taken by and are copyright Keith Hiscock