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AARHUS
UNIVERSITET
VERSITET
KARSTEN DAHL SENIOR ADVISOR
AARHUS
UNIVERSITY
UNI
FLORA AND FAUNA ON RE-ESTABLISHED REEFS
- EXPERIENCE FROM THE BLUE
REEF PROJECT
By: Karsten Dahl, Steffen Lundsteen, Ole
Gorm Norden Andersen, Cordula Göke
and Berit Langkilde Møller
Setting the scene (1)
Ka
tte
ga
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est
Ka
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ast
Da
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elt S
ea
Gu
lf o
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iel
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e S
ou
nd
N-W
Ba
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(b
etw
ee
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ea
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kå
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)
Ark
on
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Ha
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Ba
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Bo
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olm
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sta
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lf o
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da
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Pro
pe
r W
- c
oa
sta
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rs
Ba
ltic
Pro
pe
r E
- c
oa
sta
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rs
Ba
ltic
Pro
pe
r N
W -
co
asta
l w
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Fin
ish
arc
hip
ela
go
- W
Åla
nd
an
d
Esto
nia
n a
rch
ipe
lago
E Å
ish
arc
h
So
uth
ern
Go
lf o
f B
otn
ia
Gu
lf o
f F
inla
nd
Gu
lf o
f R
iga
No
rth
ern
Go
lf o
f B
otn
ia
Num
be
r of id
entified s
pecie
s
0
50
100
150
200
250
300
350
Salin
ity
(psu)
0
5
10
15
20Red algal
Brown algal
Green algal
Salinity Effect of salinity
Example
Macrophyte data
from:
Nielsen et al, 1995
Setting the scene (2)
Substrat
Human impact:
• Boulder extraction
• Gravel extraction
• Fishery with
dredging gear
Depth
Light Human Impact:
• Phytoplankton produc-
tion (eutrophication)
• Re-suspension
• Changes in foodwebs
(Riemann et al, 2015 Estuaries and Coast vol 39 issue 1)
Læsø Trindel • Monitored the reef since 1991 as part of the
National monitoring program.
Conclusion: a reef in a poor condition
Investigations of benthic communities
at Læsø Trindel
• 2007 and 2012: Intensive quantitative
investigations of:
– species specific biomass of fauna and
macroalgae
– solitary fauna species numbers
Blu
e R
eef
pro
ject
New reef structures
Imported boulders cover:
27600 m2
Cover in depth intervals
1½-4½m: 7175 m2
4½-7½m: 11725 m2
7½-10m: 8500 m2
Quantitative investigations of
biodiversity
• Suction sampler (“underwater vacuum cleaner”):
– Gentle, not harming even fragile species
– Able to sample swimming
organism like crustaceans
living among the
macroalgae
– Quick
Pump
"Waterflow"
Suction aggregate
Suctionpipe
Samplingframe
Filterboxor
filternet
Rope
Benthic sampling • Frame sampling at the gravely/sandy seabed
Size: 1/6m2 – suction to 10cm
depth.
All samples in 2007 and a
few in 2012
• Frame sampling on large boulders
Size: (1/10m2)
Most samples in 2012
• Total sample area:
• 2007: 4,7m2
• 2012: 7,2m2
•
Assumptions: Estimations of biomass and
species number per m2 on the new reef
• Only algal and fauna on the top layer of boulders.
• Boulders are round and lay side by side with holes
in between.
• 1/6 of the boulder surface is in contact with other
boulders or the seabed.
• The top frame sample represent 1/6 and the side
frame sample 4/6 of the boulder surface.
Average biomass of taxonomic groups
2012
3m
2007
5-6
m
2012
5-6
m
2007
8-1
0m
2012
8-1
0m
Ash
fre
e d
ry w
eig
ht
in g
/m2
0
100
200
300
400
500
RHODOPHYTA
PHAEOPHYTA
CHLOROPHYTA
POLYCHAETA
GASTROPODA
ECHINODERMATA
CRUSTACEA
BRYOZOA
BIVALVIA
ANTHOZOA
Others
Av. biomasses of dominant species
2012 3m
2007 5-6m
2012 5-6m
2007 8-10m
2012 8-10m
As
h f
ree
dry
we
igh
t in
g/m
2
0
100
200
300
400Metridium senile
Electra pilosa
Asterias rubens
Desmarestia viridis
Desmarestia aculeata
Laminaria juvinil
Saccharina latissima
Laminaria dig/hyp
Chorda filum
Ectocarpus siliqulosus
Delesseria sanguinea
Polysiphonia stricta
Phyllophora pseudoc.
Others
Average number of solitary fauna
individuals/tax. group/m2
2012 3m
2007 5-6m
2012 5-6m
2007 8-10m
2012 8-10m
nu
mb
er
of
ind
ivid
ua
ls
0
5000
10000
15000
20000
25000
30000
35000
CRUSTACEA
GASTROPODA
BIVALVIA
ANTHOZOA
NEMATODA
POLYCHAETA
ECHINODERMATA
Others
Average number of most frequent
solitary fauna species/m2
2012 3m
2007 5-6m
2012 5-6m
2007 8-10m
2012 8-10m
No
of
ind
ivid
ua
ls
0
5000
10000
15000
20000
25000
30000
35000 Jassa falcata
Ischyrocerus anguipes
Parajassa pelagica
Caprella linearis/septentrionalis
Gammarellus homari
Monocorophium insidiosum
Metridium senile
Nematoda
Hiatella arctica
Mytilus edulis
Pusillina sarsii
Asterias rubens
Others
Summing up: what was achieved in 3 years
• What was lost in ash free dry weight?
– Fauna 220 kg
– Algal vegetation 1280 kg
– Total 1480 kg (< 3% infauna)
• What was gained – so far?
– Fauna 3075 kg
– Algal vegetation 7400 kg
– Total 10475 kg
Surplus of app: 6100 kg ash free algal biomass
and 2850 kg fauna biomass
State of the colonization process - year 2016
• Very scattered distribution of normally
community structuring species in northern
Kattegat:
– Chondrus crispus
– Phyllophora pseudoceranoides
– Coccotylus truncatus
– (Coralina officinalis)
– (Ahnfeltia plicata)
• Newcomer in 2016
– Dilsea carnosa
Observed development and expectation and
development for the years to come (1)
• More species
• A full developed
understory of
red algal species
• Increase in algal
biomass
(more and fully
grown kelp species
2009
20102011
20122013
20142015
2016
Co
ve
r (%
)
0
10
20
30
40
50Saccharina latissima
Laminaria dig/hyp
Observed development and expectation and
development for the years to come (1)
• Less fauna biomass?
– Likely some sea anemones will
loose the battle of space to
algal species
– The presence of bryozoans on
the algal vegetation has
increase with the increased
biomass of perannual algal
biomasses
2006 (before)
2008 2009 2011 2012 2015 2016
Thanks to
”The vacuum cleaner gang”:
Michael Bo Rasmussen, Jens Larsen,
Peter Stæhr og Jan Dangaard Nielsen
- Daniel K. Johansson for lab-assistance
- Statens Naturhistoriske Museum
- And to you for the attention
Dahl, K., Støttrup, J.G., Stenberg, C., Berggreen, U.C, Jensen, J.H.
2016. Best practice for restoration of stone reefs in Denmark (codes of
conduct). Aarhus University, DCE – Danish Centre for Environment and
Energy, 33 pp. Technical Report from DCE – Danish Centre for
Environment and Energy No. 91.
http://dce2.au.dk/pub/TR91.pdf
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