sc&mussel polyculture wa2006-217
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Suitability of the sea cucumberStichopus mollis
for marine polyculture
Matthew SlaterDr. Guy Carton
Leigh Marine Laboratory
University of Auckland
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Introduction
Mussel farming in New Zealand and farm effects
Deposit-feeding sea cucumbers in polyculture
Stichopus mollis
Experimental approach
Resulting sea cucumber growth
Resulting sediment remediation Conclusion
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Mussel farming in New Zealand
NZ Green-lipped mussel largest seafood export
Japanese longline method
> 4500 Ha of NZ coastal waters
Up to 35000 Ha in future
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The effect of mussel farms
Filter-feeders capable of filtering 300 l. ind. d-1
Faeces
Pseudofaeces
Shells and mussels
Localised inputs to the benthos
Elevated organic matter accumulation
Increased oxygen demand
Changes in sediment community
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The effect of mussel farms
Approx 150 mussels.m2 entire farm
Waste = ca. 230mg.mussel.d-1
Approx 35g mussel waste.m2.d-1
> 125 t mussel waste.hectare.y-1
Source: Dr. Neil Hartstein, University of Auckland 2004
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Mitigating mussel farm effects
How can farming effects be reduced or reversed?
Rotational farming
Removing the farms
Removing / processing the inputs
How can the inputs to the sediments be used in a
productive way?
Could a deposit-feeder cultured under mussel
farms consume the inputs and produce a secondaryproduct?
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Sea cucumbers in polyculture
Show potential to be grown in enriched areas
Grown in pond aquaculture
Potential ecological benefits of growing sea
cucumbers under mussel farms
Process high organic matter sediments
May lower nutrient load in sediment
and improve sediment chemistry
Accelerated remediation of sediments
Deposit-feeding sea cucumbers, i.e. Stichopus mollis, feed on enriched
sediments and are a desirable secondary crop
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The unknowns
What is the suitability of sea cucumbers for
polyculture with mussel farms?
- What is their growth rate / survivorship in a
polyculture situation?
- Do they improve / alter sediments affected
by mussel inputs?
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Research approach
1: Field trials of polyculture - determine growthand survivorship ofS. mollis under mussel farms
2 : Feeding and sediment quality - determine theeffects ofS. mollis feeding on the health of
sediments impacted by mussel farms
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Field trials under farms
Trials of polyculture in association with mussel farms
Monitoring specimens caged at three different densities
under farm and at control sites in the same area
Cages ca. 0.8 m2 (0.9 x 0.9 x 0.25; l x w x h)
Growth - weight change
Survivorship
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-25
-15
-5
5
15
25
2.5 5 15Density (.m2)
%w
eightchange
Mussel farm Control
Field trials under farms
Change in average weight at varying densities - 4 months
N=6 N=12 N=36
Two-way ANOVA: Between sites p < 0.02 / between densities p < 0.01 / site x density p = 0.8
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Field trials under farms
Change in average weight (cumulative) at varying densities time series
-15
-10
-5
0
5
10
15
20
25
May
Jun
Jul
Aug
Sep
Oct
Month
%Weightchange
15 / m2 5 / m2 2.5 / m2
ANOVA Farm density, p < 0.01 / Tukeys test, D2.5-D15 p < 0.05; D5-D15 p < 0.01
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Feeding and sediment quality
Mussel farm sedimentation simulation
Physical differences
Chemical differences?
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Feeding and sediment quality
Mussel farm sedimentation simulation
Sediment analyses:
Total organic carbon (TOC)Increases with biodeposition, i.e. Dahlbck
and Gunnarsson, Sweden.
Chlorophyll aIncreases as a result of remnant
phytoplankton chlorophyll inputs, i.e. Mirto
et al., Italy / Grant et al., Canada.
PhaeopigmentIncreases with deposition of remnant
digested phytopigments, i.e. Christensen et
al., New Zealand.
T 8a
C 8a
T 8b
C 8b
T 8c
C 8c
T 8d
WC
WC
T 1a
T 1b
C 1a
T 1c
C 1b
T 1d
C 1c
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Feeding and sediment quality
1
1.1
1.2
1.3
1.4
1.5
1.6
0 2 4 6 8
Experimental period (wks)
TOC(%s
eddrywt)
Total Organic Carbon Sea Cucumber tanks vs. Control tanks 1-8 wks
Control - Sea cucumber
ANCOVA Control vs. Sea cucumber p < 0.05
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Feeding and sediment quality
Chlorophyll a Sea Cucumber tanks vs. Control tanks 1-8 wks
0.0
2.0
4.0
6.0
8.0
10.0
12.0
0 2 4 6 8
Experimental period (wks)
Chlorophylla(g/g
seddrywt)
Control - Sea cucumber
One-way ANOVA Control vs. Sea cucumber at 8 weeks p < 0.05
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Summary of results
Sea cucumber growth is excellent under mussel
farms at higher than natural densities (5x)
Sea cucumbers reduce benthic impacts by
feeding on affected sediments
TOC and remnant chlorophyll a reduced
What are the underlying mechanisms?
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Proposed mechanisms
Growth mussel waste is an excellent reliable food source
Total organic carbon Suppression of bacterial production through
digestion and assimilation of bacterial carbon Assimilation of detrital carbon from mussel waste
Bioturbation
Solubilisation of organic matter to the water column
from sea cucumber faeces
Phytopigments Assimilation of remnant phytopigments from mussel
waste
Bioturbation
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Sea cucumbers in polyculture
Farms average 35g wet weight musselwaste.m2.d-1
S. mollis consumes approx 7g wet weight
sediment.sea cucumber.day
5 sea cucumbers.m-2 for an average farm, but
needs to be aligned with farm impact
Re-processing of majority of farm waste andReduction of nutrient inputs
Variable solution biomass focus or
remediation focus
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Conclusion
S. mollis is an excellent candidate species for
polyculture with mussels
S. mollis reduces benthic impacts by feeding
on affected sediments
Practicable polyculture system with economic
and environmental benefits
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Thanks and questions...
Thanks to:
Rich Ford
Mary Sewell
George Potae
Kim RadickCharles Christian Bedford
Javier Atalah
Claire Honeywill
Brian Dobson
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Feeding and sediment quality
Chl a / Phaeopigment Sea Cucumber tanks vs. Control tanks 1-8 wks
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8
Experimental period (wks)
Chla/Phaeo
ratio
One-way ANOVA Control vs. Sea cucumber at 8 weeks p < 0.05
Control - Sea cucumber
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Field trials under farms
Photo IDs
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Weight variation
0
50
100
150
10.01.05
12.01.05
13.01.05
17.01.05
07.02.05
09.02.05
11.0
2.2005
Weighing event
Anima
lweight(g)
Spec. 1 Spec. 2 Spec. 3
Specimen weight variation - repeat weighing random times
SD=6.1
SD=4.2
SD=1.2
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Control vs. farmSpecimen weights at varying densities 2 months
Site*Density; LS Means
Current effect: F(2, 97)=.51195, p=.60093
Type III decomposition
Vertical bars denote 0.95 confidence intervals
Site
F
Site
C2 4 12
Density
-20
-15
-10
-5
0
5
10
15
Weightch
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Feeding and sediment quality
Comparing sediment quality indicators in samples from
faeces and sediments pre- and post-grazing
Chlorophyll a and
Phaeopigment
Total organic matter
Organic Carbon and
Nitrogen C/N ratio
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