Zeegrasrestoraties in Nederland •Herintroductie in Waddenzee 1987-2006 •Mitigatie in Oosterschelde 2007-2014 •Plannen in Waddenzee 2011-2015
Dick de Jong, Victor de Jonge, Fred Schmitz, Karin Hermus, Lucien Hanssen, Arthur Bos, Tjisse van der Heide, Tjeerd Bouma, Wim Giesen, Wouter Suykerbuyk, Laura Govers, Paul Erftemeijer, Luca van Duren
Marieke van Katwijk Radboud University Nijmegen Biobouwersdag 15 april 2011
Seagrass zonation in tidal systems NW Europe
Desiccation
Water dynamics Desiccation
Zostera marina
Light
Zostera marina
Zostera noltii
intertidal
subtidal Harmsen 1936 Van Katwijk et al. 1998 van Katwijk et al. 2000
Zostera marina
Projects
Zostera marina Zostera noltii
• Wadden Sea (1987-2006) Zostera marina (+ Z. noltii) • Eastern Scheldt (2007-2013) Zostera noltii • Wadden Sea (2011-2015): Zostera marina
1987 – 2006 Wadden Sea
Seagrass Ecology Light Nutrients Salinity Tidal depth Hydrodynamics Sediment type Various interactive effects … Donor suitability Plant morphology -Field experiments Outdoor mesocosms Laboratory Flume
Restoration projects Environment
Review: van Katwijk et al. 2009
restore natural values find suitable sites -habitat requirements -habitat characteristics
50 KM
Ecological findings Z. marina • • • • • •
Ammonium toxicity (water layer) High salinity: high nutrients unfavorable (multistress) Negative effect of hydrodynamics Importance of suitability donor population Macroalgal suffocation reduces seed production Ecosystem engineering
Bos & van Katwijk 2007, Bos et al. 2007, Van der Heide et al. 2007, 2008, 2009, 2010a, b van Katwijk et al. 1997, 1998,1999, 2000, 2009, 2010a, b van Katwijk & Hermus 2000, van Katwijk & Wijgergangs 2004
1987 – 2006 Wadden Sea
Seagrass Ecology Light Nutrients Salinity Tidal depth Hydrodynamics Donor population Sediment type Morphology Various interactive effects … Field experiments Outdoor mesocosms Laboratory Flume
Positive feedbacks Ecosystem engineering
Environment Ecosystem engineering
Other organisms
Review: van Katwijk et al. 2009
50 KM
Biobouwers 5 cases 1. Sediment modification 2. Self-facilitation water clarity 3. Self-facilitation hydrodynamics 4. Facilitation hydrodyn.: mussel beds 5. Bioturbation
July: 6 wk after transplantation
Sediment modification by intertidal, annual Zostera marina Transplantation experiment
August: 11 wk
Bos et al. ECSS 2007 van Katwijk et al. ECSS 2010
Comparing more situations: high plant density: muddification low plant density September: 14 wk + very sheltered: sandification
October: 21 wk
locally increased turbulence
- accretion - fines > muddification
reduced water dynamics
self-facilitation: water clarity
1930s: loss of 15000 ha Zostera marina (subtidal)
Zostera marina tera noltii
Zostera marina
10 km
self-facilitation: water clarity
1930s: loss of 15000 ha Zostera marina (subtidal) RESTORATION??? shoot density Simple growth model
+ water clarity
-
Monod equations, seagrass literature
waves+currents
Geomorphological + hydrodynamic formulas (van der Heide et al. 2007 Ecosystems)
self-facilitation: water clarity
1930s: loss of 15000 ha Zostera marina (subtidal) RESTORATION??? van der Heide et al. 2007: first study to show possible alternative stable states in seagrass systems state 1: seagrass, water is clear state 2: no seagrass, water is turbid
Zostera marina self-facilitation: hydrodynamics
Zostera marina Zostera marina Zostera noltii
50 KM
Zostera marina self-facilitation: hydrodynamics
Two densities 30 cm
50 cm
Photo: Bos
Exposed: high density ++ Sheltered: density no effect
Donor population
Transplantation
Bos & van Katwijk MEPS 2007
50 KM
Zostera marina facilitation by mussel beds: hydrodynamics
Transplant behind mussel beds Photo: Bos
Mussel bed increases seagrass survival rate
Donor population
Transplantation
Bos & van Katwijk MEPS 2007
50 KM
Flume experiments (self-) facilitation related to hydrodynamics confirmed
Bouma et al. subm.
Back to the field
seagrass
mussels
Water dynamics
Maybe….
Salt marsh Z. noltii
Z. Marina flexible
Z. Marina robust
Mussel bed
1990 1932
Wadden Sea restoration results
Zostera noltii: succesful > 13 years Zmarina 8 yr max (macroalgae)
Zostera marina: never transplanted: strong feedbacks related to turbidity
50 KM Review: van Katwijk et al. 2009
Restoration results Sheltered:
Relatively exposed:
Excellent survival 1st year Seed production minimum
Very good survival 1st year Excellent seed production
NO RECRUITMENT IN THE NEXT YEAR sheltered site
exposed site
van Katwijk et al. 2010b
Restoration results Sheltered year-to-year: Excellent survival 1st year Seed production Recruitment next year
only when low macroalgae
macroalgal cover RelativelyHigh exposed: Low macroalgal cover 1st year Very good survival HighExcellent macroalgal seed cover production No recruitment next year
Scouring?
Bad year Good year
Bos & van Katwijk 2007 van Katwijk et al. 2009
Eastern Scheldt Seagrass mitigation
Wadden Sea Restoration 50 KM
EU-regulations 50 KM
Seagrass mitigation Eastern Scheldt 2006-2013
Radboud University Nijmegen, The Netherlands
EU habitat directive: mitigate Approach:
Rijkswaterstaat Netherlands Institute of Ecology
Large scale: save all seagrass (z.noltii) TRANSPLANTATION Scientific: • •
Projectbureau Zeeweringen:
325 km dike reinforcement
ensure optimal survival knowledge development
Site-selection: • • •
Seagrass history present Cause of disappearance ‘known’ and removed (temporary changes after construction works) Locally reduce negative effect of bioturbating lugworms for a good start
Bioturbation
Photo: Wim Giesen
Anti-lugworm measures 1. Shell layer 2. Nets
Locations and setup transplantations 2007-2008 DM Exposed 2007 Shell/ Control
DM Exposed 2008 Shell/ Control
KKZ Sheltered 2007
KKZ Sheltered 2008
Donor 2007, 2008 (Viane)
Shell/NET Control
Shell/ Control
KKN Intermed. 2008
RH Intermed. 2008
Shell/ Control
Shell/ Control
KKN 16 +8 plots 2008
Dortsman N. DM 12 plots 2007 16 plots 2008
KKZ 24 plots 2007 16 plots 2008
15 m 10 m Plot Roelshoek (RH) 16 plots 2008 Zeegraspatch 1.5 m
1.5 m
2010: KKN 2011: RH 2012: Viane
Transplantation
prepare
Mitigation location
remove seagrass at donor location
apply shells
transport
lugworm treatment has visual effect on relief
place seagrass
5000 4500 Transplantations 2007 & 2008 in Aug/Sep 2009 4000
Shoots per patch
# scheuten/patch
3500 3000 2500 2000 1500 1000 500 0 O DN07
S
O
S
DN08
O
S
KN08
N
O KZ07
S
O KZ08
S
O
S
RH08
Propagation Roelshoek
Dijk
Some first results ...
Plannen zeegrasaanplant Waddenzee 2011-2015 • • • • •
Rijkswaterstaat Waddenvereniging Deltares Radboud Universiteit NIOO/Z Yerseke
• Methode: zaadstengels in zakken aan boeien (Buoy deployed seeding, Pickerell et al. 2005)
Plannen zeegrasaanplant Waddenzee 2011-2015 • Grotere schaal ivm positieve terugkoppelingen • Methode BuD: zaadstengels in zakken aan boeien • Zaadstengels (die anders grotendeels weg zouden spoelen, 80-90%) worden verzameld in Sylt • Uitgeplant op 3 plekken in Waddenzee met maximaal kans op succes: – historie van zeegras, – hoge score op zeegraskansenkaart, – redelijk succes bij eerdere aanplanten ondanks kleinere schaal (Balgzand) – bergingskom met minder waterexport zodat minder zaadstengelverlies (Oostelijke WZ, wrschl Schier en Groningse kust)
Plannen zeegrasaanplant Waddenzee 2011-2015 • Twee maal aanplanten (2011 en 2012) • Drie jaar monitoren (2012-2014) – zeegrasopkomst in augustus (en kenmerken) – meest bepalende factoren (zodat resultaten verklaard kunnen worden) uit expert judgement en literatuur
Plannen zeegrasaanplant Waddenzee 2011-2015 Bepalende factor voor succes, lokaal (op hoofdlijnen is de locatie bepaald door historie van zeegras en zeegraskansenkaart <- hydrodynamiek, droogvalduur, saliniteit, nutrienten):
sedimentdynamiek - ervaring Oosterschelde, o.a. bioturbatie - proeven in de Waddenzee (vK & Hermus 2000), zelfde resultaat in VS (Fonseca ea) - verspreidingskaarten Waddenzee (Kohlus & Reise 2008)
