SC&Mussel PolyCulture WA2006-217

8/2/2019 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


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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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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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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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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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


Chlorophylla(g/g

seddrywt)


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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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


Chla/Phaeo

ratio

One-way ANOVA Control vs. Sea cucumber at 8 weeks p < 0.05



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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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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

SC&Mussel PolyCulture WA2006-217

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