gammarus pulex watercress farming · •human health benefits. watercress (nasturtium officianale...
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Gammarus pulex&
Watercress Farming
Chalk Stream Headwaters Forum Oct 09
Melanie Dixon & Pete Shaw
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Gammarus pulex (L.)
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Bourne Rivulet – Gammaridae
Data courtesy of Environment Agency
1
10
100
1000
10000
'89
'90
'91
'92
'93
'94
'95
'96
'97
'98
'99
'00
'01
'02
'03
'04
'05
'06
'07
'08
'09
Nu
mb
er
0.2km (east branch) 0.2km 2km
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• PEITC
• Produced by crucifers e.g. watercress, broccoli, cabbage, rocket, kale.
• Plant defence against herbivores.
• Human health benefits.
Watercress (Nasturtium officianale (R.Br.))
Isothiocyanates
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Gammarus pulexreproduction
• Exposed Gammarus pulex breeding pairs to PEITC solution or watercress wash water.
• Measured separation of pairs within a 2 hour period.
G. pulex precopular pairs
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Response during 2h exposure
Pairsseparated
%
PEITC (1µl/l)
Wash water
Control
0
20
40
60
80
100
0 15 30 45 60 75 90 105 120Time (mins)
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After Exposure
• Were pairs able to re-form after return to clean water?
• Transient effect?
Watercress in flower
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Pairs re-forming after 24h in clean water
0
10
20
30
40
50
60
70
80
Washwater PEITC Control
Mea
n %
pairs re-formed after 24h
pairs at exposure end
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Management to improve water quality
• E.g. settlement tank, parabolic screens, chlorine wash ceased.
• De-silted East channel, de-culverted discharge.
• Redirected factory wash water through watercress beds.
Parabolic screen above outfall
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Survival in factory effluent
• Cages upstream & downstream of watercress bed.
• Factory wash water supplied bed.
• Borehole water supplied bed (control).
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Gammarus pulex - Acute effect
0
5
10
15
20
25
Borehole
supply
(control)
Below
control
bed
Wash
water
supply
Below
wash
water bed
Mea
n %
Im
mo
bil
isa
tio
n
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Re-direction of factory effluent
• ‘Treatment’ of wash water by passing though watercress beds before discharge is a positive measure
• Recent biological surveys indicate invertebrate populations recovering
Watercress farm outfall (Spring 08)
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Bourne Rivulet – Gammaridae
Data courtesy of Environment Agency
1
10
100
1000
10000
'89
'90
'91
'92
'93
'94
'95
'96
'97
'98
'99
'00
'01
'02
'03
'04
'05
'06
'07
'08
'09
Nu
mb
er
0.2km (east branch) 0.2km 2km
![Page 14: Gammarus pulex Watercress Farming · •Human health benefits. Watercress (Nasturtium officianale (R.Br.)) Isothiocyanates. Gammarus pulex reproduction •Exposed Gammarus pulex breeding](https://reader034.vdocuments.mx/reader034/viewer/2022042921/5f6ac50f2b50593af9244cfe/html5/thumbnails/14.jpg)
We gratefully acknowledge the support of the Vitacress Conservation Trust and use of facilities at the Environment Agency Biological Effects Laboratory.
Vitacress Salads Ltd, Hampshire, UK