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1 DTU Aqua, Technical University of Denmark
BlueReef
Rebuilding of Marine Cavernous Boulder Reefs in Kattegat
Claus Stenberg1, Karsten Dahl2, Else Marie Stamphøj3, Josianne
Støttrup1, Per Dolmer1
and Anni Dalgas3
1National Institute of Aquatic Resources2The National Environmental Research Institute3The Danish Forest and Nature Agency
3 DTU Aqua, Technical University of Denmark
What
is a Cavernous
Boulder Reef?
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Background
•
On a national level cavernous boulder reefs in shallow waters have been an extensively exploited habitat targeted for their high concentration of easy to excavate large boulders suitable for construction of harbour jetties and sea defences.
•
A cautious estimate indicates a reduction
from more than
34 km2
to only 5 ha left untouched.
•
Læsø
Trindel
in Kattegat is an example of a destroyed boulder reef
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Why
are
boulder
reefs
important? •
Offshore cavernous boulder reefs in shallow waters have a high biodiversity and is now a rare and yet biological important subtype of the natural habitat 1170 Reef at a national and European level.
•
The conservation status at Læsø
Trindel
is unfavourable. –
Unstable conditions:–
Physical changes–
Changes in algae community
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Læsø
Trindel -
a unstable
boulder
reef
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Læsø
Trindel Before
-
After
Year
1831 Year
1978
Depth
4 feet
~1.2 mDepth
3.8 m
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•
Objectives–
The project objective
is to restore and maintain a favourable
conservation status of the offshore reef habitat at Læsø Trindel.
–
Fulfilment
of DK’s obligations according
to the Habitats directive.
•
Project frame–
The project budget is Euro 4.8 million (DKK 35 million).
–
Started1/8 2006 and will finish in the spring of 2012. –
Partners:
•
Danish Forest
and Nature Agency, •
National Environmental
Research Institute
•
National Institute
for Aquatic
Resources
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Project Project activitiesactivities
Geological survey
Hydrograpical
survey
Biological surveyReconstruction
Public awareness
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MapMap of the of the projectproject areaareaLæsø
Trindel, existing
reef
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BlueReefBlueReef Design Design
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BiologicalBiological MonotoringMonotoringTo document
the effects
of restoring
the offshore
”1170 reef
habitat”, physical
and biological structure
and function:
•
Detailed
flora and fauna surveilliance; suction
sampling, gillnet, traps
(estimate
species diversity, abundance, biomass, length
distribution, etc.).
•
Trophic
links and ecosystem
dynamics
The individual
elements in the monitoring programme
are
linked
and important
for
assessing
conservation
status of the restored reef.
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Pump
"Waterflow"
Suction aggregate
Suctionpipe
Samplingframe
Filterboxor
filternet
Rope
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ResultsResults of of BiologicalBiological MonitoringMonitoring
B V-M All areas
No
of ta
xono
mic
aly
dist
inct
spe
cies
ore
spe
cies
gro
ups
0
50
100
150
200
250 Sessile faunaMotile faunaMacrophytes Fish Total number of
macroalgae, fish, sessile and motile fauna species identified
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Macroalgae
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Fauna organism as function of macroalgal
biomasses
Algal biomasses (g ash free dry weight/m2)
0 20 40 60 80 100 120 140 160 180
Tota
l fau
na b
iom
ass
(g a
sh fr
ee d
ryw
eigh
t/m2 )
0
5
10
15
20
25
30
35B
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Fish fauna
Multi-meshed gillnet
Area
A 6-10 m B 2-6 m C 6-10 m
CP
UE
N (n
umbe
rs/s
tatio
n)
0
100
200
300
400
500
600
Area
A 6-10 m B 2-6 m C 6-10 m
CP
UE
bio
mas
s (k
g/st
atio
n)
0
1
2
3
4
5
6
7Cancer_pagurus Carcinus_maenas Centrolabrus_exoletus Ctenolabris_rupestris Cyclopterus_lumpus Gadus_morhua Icelus_bicoris Labrus_bergylta Labrus_bimaculatus Limanda_limanda Microstomus_kitt Myoxocephalus_scorpius Pleuronectes_platessa Psetta_maxima Solea_solea Spinachia_spinachia Symphodus_melops Trachinus_draco Zoaces_viviparus Hyperoplus_lanceolatus Mullus_surmuletus Pollachius_virens Scophthalmus_rhombus Zeugopterus_punctatus Lycodes_vahli Merlangius_merlangus Pholis_gunnellus Pollachius_pollachius
Numbers Biomass
Most fish in numbers and biomass in the shallow
corkwing
wrasse
rock cook
ballan
wrasse
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Fish
fauna -
acoustic
telemetry tracking
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Fish
fauna -
acoustic
telemetry tracking
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The ”new”
reefJuly
2008
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The ”new”
reef
ScanningHoffmann AS
August 2008
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The ”new”
reefAugust 2008
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The ”new”
reef
•
Video file
August 2009
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Direct and indirect spinoffs from Blue Reef
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Direct and indirect spinoffs from Blue Reef
•
Restoration and stabilisation
of the reef
at Læsø
Trindel. •
Knowledges
on
how
to restore
the rare cavernous
boulder
reefs
in shallow
waters.•
Knowledge
on
the effects
on
nature and the interaction
between
the”
new nature”
and fish
populations.•
A stepping
stone
within
the
marine Natura 2000 network•
Sanctuary
for donor populations.
•
Focus
on
marine nature, marine restoration and management.
•
New opportunities
for tourismand outdoor
life.