Altered food web structure
Jonathan Grey1, Peter Smyntek1 & Ian Winfield2
1

Aquatic Ecology Group, School of Biological &...
Food web structure
Carnivores

Perch
Changes in
Pike diet

Planktivores

Increase in
roach
Reduction in
zooplankton

Zoopl...
SIA samples
•

For stable isotope analyses:
•

980 individual fish

•

250 zooplankton samples

•

140 macroinvertebrate s...
Archives & isotopes
-12

A

-14

Acidified scale δ13C (‰)

-16
-18
-20
-22
-24
-26

y = 0.99x + 0.64; r2 = 0.92; P<0.0001
...
Hypotheses
•

Increase in roach caused: a change in pike diet through provision of
extra / alternative prey; and a shift i...
Recap from IJW

•

Diet changes alongside roach increase:
•
•

Arctic charr decreases in macroinvertebrates and Daphnia,
i...
SI mixing models
11
10
9

δ15N (‰)

8
7
6
5
4
3
-32

-30

-28

-26
13

δ C (‰)

-24

-22

1.0

Predatory zooplankton

Macr...
SI-derived metrics

Layman et al 2007 a & b
SI-derived metrics

Grey & Jackson 2012
Diet shifts in isotope space
Pre-Roach
Expansion
(1986 – 87)

Post-Roach
Expansion
(2007 & 2009)
Pike
Charr
Perch
Zoopl.
M...
Diet shifts in isotope space
Early Roach
Period
(1993 – 95)

Recent Roach
Period
(2007 & 2009)
Pike
Charr
Perch
Zoopl.
Mac...
Samples for SIA
Pike GCA
Pike GCA
Pike diet
Carbon routing to pike

1.0

Pelagic carbon (%)

0.8

N Basin
S Basin
y = -0.011x + 22.569

0.6

0.4

0.2

0.0
1980

1990
...
Food chain length

9.5

Food chain length (‰)

9.0

Zooplankton baseline
Macroinvertebrate baseline

8.5
8.0
7.5
7.0
6.5
6...
Summary
•

Distinct shifts in niche space of native fish following roach expansion

•

Changes to pike diet: reduction in ...
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Altered food web structure

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Windermere Science Project stakeholder meeting presentations.
Grey on how invasive roach have caused changes to the dietary niche of native fish species, thereby altering the structure and functioning of the lake food web. Data derived from gut content and stable isotope analysis of contemporary & archived samples

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  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • The second reason is historical. The Freshwater Biological Association (or then The Freshwater Biological Association of the British Empire) was founded in 1929, located at Wray Castle from 1931 and, from 1950 onwards, at The Ferry House- both labs on the shores of Windermere.
  • Altered food web structure

    1. 1. Altered food web structure Jonathan Grey1, Peter Smyntek1 & Ian Winfield2 1 Aquatic Ecology Group, School of Biological & Chemical Sciences, Queen Mary University of London, UK 2 Lake Ecosystems Group, Centre for Ecology & Hydrology, Lancaster, UK
    2. 2. Food web structure Carnivores Perch Changes in Pike diet Planktivores Increase in roach Reduction in zooplankton Zooplankton Increase in Phytoplankton phytoplankton Increased internal Pload Chemistry Climate change Reduction in Arctic charr Warmer water Prolonged stratification Reduction in oxygen at depth Physics
    3. 3. SIA samples • For stable isotope analyses: • 980 individual fish • 250 zooplankton samples • 140 macroinvertebrate samples • Spanning 27 years (1985-2011)
    4. 4. Archives & isotopes -12 A -14 Acidified scale δ13C (‰) -16 -18 -20 -22 -24 -26 y = 0.99x + 0.64; r2 = 0.92; P<0.0001 -28 -30 -30 -28 -26 -24 -22 -20 -18 -16 -14 -12 Defatted muscle δ13C (‰) eg Grey et al 2009
    5. 5. Hypotheses • Increase in roach caused: a change in pike diet through provision of extra / alternative prey; and a shift in niche space for native equivalents • Shift in routing of carbon through food web to top predator (pike) from predominantly pelagic to littoral • Increased efficiency of food web via reduced trophic linkage
    6. 6. Recap from IJW • Diet changes alongside roach increase: • • Arctic charr decreases in macroinvertebrates and Daphnia, increase in zooplanktivores • • Perch decreases in macroinvertebrates and Daphnia, increase in zooplanktivores Roach remarkably stable and dominated by macroinvertebrates and predatory zooplankton Roach impact upon perch and Arctic charr, forcing greater food niche overlap between these native species
    7. 7. SI mixing models 11 10 9 δ15N (‰) 8 7 6 5 4 3 -32 -30 -28 -26 13 δ C (‰) -24 -22 1.0 Predatory zooplankton Macroinverts Daphnia Chironomids 0.8 0.6 0.4 0.2 0.0 1982 1987 Predatory zooplankton 1.0 0.8 1992 1997 Macroinverts 2002 Daphnia 2007 2012 Chironomids
    8. 8. SI-derived metrics Layman et al 2007 a & b
    9. 9. SI-derived metrics Grey & Jackson 2012
    10. 10. Diet shifts in isotope space Pre-Roach Expansion (1986 – 87) Post-Roach Expansion (2007 & 2009) Pike Charr Perch Zoopl. Macroinv. Roach Pike Charr Perch Zoopl. Macroinv. δ 15N (‰) δ 13C (‰) δ 13C (‰)
    11. 11. Diet shifts in isotope space Early Roach Period (1993 – 95) Recent Roach Period (2007 & 2009) Pike Charr Perch Zoopl. Macroinv. Roach Pike Charr Perch Zoopl. Macroinv. Roach δ 15N (‰) δ 13C (‰) δ 13C (‰)
    12. 12. Samples for SIA
    13. 13. Pike GCA
    14. 14. Pike GCA
    15. 15. Pike diet
    16. 16. Carbon routing to pike 1.0 Pelagic carbon (%) 0.8 N Basin S Basin y = -0.011x + 22.569 0.6 0.4 0.2 0.0 1980 1990 2000 Year 2010
    17. 17. Food chain length 9.5 Food chain length (‰) 9.0 Zooplankton baseline Macroinvertebrate baseline 8.5 8.0 7.5 7.0 6.5 6.0 5.5 1980 1990 2000 Year 2010
    18. 18. Summary • Distinct shifts in niche space of native fish following roach expansion • Changes to pike diet: reduction in charr; increase in perch + addition of roach • Significant shift (SB) in routing of carbon from pelagic to littoral • Increase in overall food chain length post roach expansion; slight but significant increase in efficiency if routed via littoral http://www.windermere-science.org.uk/home @WinSci

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