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Altered food web structure
The document discusses the alterations in food web structure caused by the expansion of roach populations, leading to significant changes in the diets of native fish like pike and arctic charr. Notably, there is an increase in the efficiency of the food web due to a shift in carbon routing from pelagic to littoral zones. The study is supported by extensive stable isotope analyses spanning 27 years.
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Altered food web structure
- 1. Altered food webstructure 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. Food web structure Carnivores Perch Changesin 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. SIA samples • For stableisotope analyses: • 980 individual fish • 250 zooplankton samples • 140 macroinvertebrate samples • Spanning 27 years (1985-2011)
- 4. Archives & isotopes -12 A -14 Acidifiedscale 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. Hypotheses • Increase in roachcaused: 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. Recap from IJW • Dietchanges 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. 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. SI-derived metrics Layman etal 2007 a & b
- 9. SI-derived metrics Grey &Jackson 2012
- 10. Diet shifts inisotope 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. Diet shifts inisotope 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 (‰)
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- 16. Carbon routing topike 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. Food chain length 9.5 Foodchain 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. Summary • Distinct shifts inniche 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
Editor's Notes
- #4 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.
- #6 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.
- #7 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.
- #8 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.
- #11 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.
- #12 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.
- #13 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.
- #14 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.
- #15 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.
- #16 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.
- #17 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.
- #18 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.
- #19 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.