Comparative trophic structure regulation across ecosystems Jonathan ShurinUBC Zoology

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Comparative trophic structure regulation across
ecosystems Jonathan Shurin UBC- Zoology
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Four pieces of received wisdom

• Aquatic biomass pyramids are inverted,
  terrestrial pyramids are regular
• Trophic cascades are stronger in water
• P limits freshwater productivity, N limits
  terrestrial and marine (sometimes Fe)
• Aquatic food webs are less complex than
  terrestrial

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Humans squeeze ecosystems from the top
Pauly et al. 1998 Science 279 860
Myers et al. 2007 Science 315 1846
Alroy 2001 Science 292 1893
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Human acceleration of geochemical cycles
and from the bottom

• C 13
• N 108
• P 400

Falkowski et al. 2000 Science 290 291
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Questions?

• How do resource and consumer control vary between
  ecosystems?
• Bottom-up control
• Trophic structure, productivity and plant
  chemistry
• Does nutrient limitation vary by system?
• Top-down control and variable trophic cascades
• What accounts for system differences?
• Aquatic-terrestrial?
• Marine-freshwater?

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Bottom-up controlTrophic structure comparison
working groupCo-organized with Helmut Hillebrand
and Daniel Gruner
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Productivity, plant quality and trophic pyramids-
two hypotheses

• Food chain length
• Hairston and Hairston 1993 Am Nat

• Producer quality
• Lindeman among others

land
water
Elser et al. 2000 Nature
Oksanen et al. 1981 Am Nat
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Trophic pyramids and productivityCebrian,
Shurin, Borer, Cardinale, Ngai and Smith., in prep
Food chain length
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Trophic pyramids and productivityCebrian,
Shurin, Borer, Cardinale, Ngai and Smith., in prep
Food chain length
Producer quality
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Trophic pyramids unrelated to productivityCebrian
, Shurin, Borer, Cardinale, Ngai and Smith., in
prep
Producer quality wins!
Food chain length
Producer quality
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but strongly related to plant chemistry
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but strongly related to plant chemistry
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Biomass pyramids in different currenciesAre
differences only because of lignin, cellulose et
al?
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Biomass pyramids in different currenciesAre
differences only because of lignin, cellulose et
al?
C
N
P
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Do limiting nutrients vary between
ecosystems?Elser, Bracken, Cleland, Gruner,
Harpole, Hillebrand, Ngai, Seabloom, Shurin,
Smith 2007. Ecology Letters
Phosphorus is much more important as a
limiting nutrient in aquatic systems (than
terrestrial -Wikipedia (Eutrophication)
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Do limiting nutrients vary between
ecosystems?Elser, Bracken, Cleland, Gruner,
Harpole, Hillebrand, Ngai, Seabloom, Shurin,
Smith 2007. Ecology Letters, in press

• Meta-analysis of 1,069 N and P field addition
  experiments
• 653 freshwater
• 243 marine
• 173 terrestrial

Phosphorus is much more important as a
limiting nutrient in aquatic systems (than
terrestrial -Wikipedia (Eutrophication)
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N and P are equally important in terrestrial and
freshwater ecosystems
N is more important in the ocean
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Comparing top-down control across ecosystemsAre
trophic cascades all wet? (Don Strong)

• Shurin et al. 2002 Ecology Letters 5 785
• Data from 102 experiments that
• manipulated primary predators
• measured herbivore, plant community biomass
• were done in six different ecosystems
• Plant and herbivore log ratios- ln(NP/NP-)

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herbaceous plants
streams
marine plankton benthos
Lake plankton benthos
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Weaker effects in marine plankton and on
land Shurin et al. Ecology Letters 2002 5785
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Herbivore effects are also stronger in
waterGruner et al., in press, Ecology Letters
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How are aquatic and terrestrial systems different?

• Size structure
• Shurin and Seabloom 2005 JAE 74 1029
• Consumer-resource stoichiometry
• Hall, Shurin, Diehl and Nisbet 2007 Oikos
  1161128
• Omnivory?
• Thompson, Hemberg, Starzomski and Shurin 2007
  Ecology 88 612

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Are terrestrial food webs more complex? Strong
1992, Lawton 1999
Carpenter and Kitchell 1993
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Are terrestrial food webs more complex? Strong
1992, Lawton 1999
Carpenter and Kitchell 1993
Martinez 1997
vs.
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Are food webs structurally different? Thompson,
Hemberg, Starzomski and Shurin. 2007. Ecology 88
612

• Use topological webs to calculate trophic
  position for all species
• Do species form discrete trophic levels?
• Does lumpiness vary by system?

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Kye Burn New Zealand
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Benguela Shelf, South Africa
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How to calculate trophic position?
TP 1
TP 2.25
TP 2
TP 1.5
TP 0
TP 1
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Broadstone Stream
Ythan Estuary
Skipwith Pond
Grassland
Maine Streams (2)
US NE Shelf
Chesapeake Bay
Duffin Creek
Coweeta Streams (2)
Coachella Valley
Broom food web
Little Rock Lake
Dung arthropod
El Verde rainforest
Benguela
St Martin Island
Carribean reef
St Marks
Taieri Streams (18)
Lerderberg River
Company Bay
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Lots of omnivory everywhere Oceans no more than
lakes
Ross Thompson, Martin Hemberg, Brian Starzomski
and Jonathan ShurinEcology 2007 88 612
Trophic position
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How are food webs different?

• Longer food chains in the ocean, shorter in
  streams
• No more omnivory on land than lakes
• How comparable are topological food webs?
• dont include abundance or importance of links

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Weaker effects in marine plankton than
lakes Shurin et al. Ecology Letters 5785
n22
n9
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Some recent evidence for marine trophic
cascadesFrank et al. 2005 Science 308 1621
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Are lake and ocean plankton different in food web
architecture? Stibor et al. 2004 Ecology Letters
7321
productive oceans
unproductive oceans
lakes
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A better way to measure trophic positionwith
Blake Matthews, Russ Markel and Stefan Dick

• Stable nitrogen isotopes

Higher order consumers are more enriched in
15N Going from 15N to trophic position requires
that we know the 15N signature at the base
14N
14N
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A typical lake food web
trophic position
body size
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A typical marine food web
trophic position
body size
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d15N increases with size in both lake and marine
zooplankton
Size Plt0.0001 System
Plt0.0001 Sizesystem P0.32
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Why do larger habitats have longer food chains?
Vander Zanden et al. 1999 Am. Nat. 154 406
Post et al. 2000 Nature 405 1047
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Two possible explanations
Species-area effects
Perimeter-area effects
T.P. 2.5
T.P. 3.28
2.5
2.33
2
2
2
2
1
1
1
1
1
1
0
0
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Probably not species-area
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Benthic food webs are less size structured
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Benthic food webs are less size structured
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Pelagic slopes are bigger than benthic
Log (pelagic/benthic slope)
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Four pieces of received wisdom

• Aquatic biomass pyramids are inverted,
  terrestrial pyramids are regular
• Yes, related to plant chemistry not productivity
• Trophic cascades are stronger in water
• Yes, but more data are needed
• Lakes are P-limited, oceans and land N limited
• No way
• Aquatic food webs are less complex than
  terrestrial
• No way, but more data are needed

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Rockfish Conservation Areas in British Columbia
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Thanks

• Jim Elser
• Matt Bracken
• Elsa Cleland
• Dan Gruner
• Stan Harpole
• Helmut Hillebrand
• Jackie Ngai
• Eric Seabloom
• Jen Smith
• Scott Cooper
• Ben Halpern
• Bernardo Broitman
• Carol Blanchette

• Elizabeth Borer
• Kurt Anderson
• Spencer Hall
• Roger Nisbet
• Sebastian Diehl
• Ross Thompson
• Martin Hemberg
• Brian Starzomski
• Blake Matthews
• Russ Markel
• Stefan Dick
• Just Cebrian
• Brad Cardinale
• Melinda Smith