maberly et al 2013 sil presentation
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Stephen Maberly, Alex Elliott, Peter Henrys, Ian
Jones, Stephen Thackeray & Ian Winfield
Lake Ecosystems Group
Centre for Ecology & Hydrology, Lancaster, UK
Echoes in the ecosystem: top-down & bottom-up responses of Windermere to
environmental perturbation
Jonathan Grey & Peter Smyntek
Queen Mary University of London, UK
Top-down & bottom-up multiple stressors
Maberly & Elliott (2012) Freshwater Biology 57, 233-243
Nutrients (& toxins)
Acid (& nutrients)
Climate change
Natural variability in weather
Bo
tto
m-u
p
Top
-do
wn
Windermere
Photos from
FBA Image
Archive
• England’s largest lake
• Two basins: deeper, less productive North
and shallower more productive South
• One of the most intensively studied lakes in
the world
• Long-term data and archives from early
1900s and regular sampling for range of
variables since 1945
• Freshwater Biology Special Issue Feb 2012
57 (2)
Windermere as a model system
Mean winter SRP (mg m-3
)
0
5
10
15
20
25
30
1950 1960 1970 1980 1990 2000 2010
Year
North Basin
South Basin
6
8
10
12
1950 1970 1990 2010Year
Mean surface temperature (oC)
North Basin
South Basin
Nutrient enrichment Warming Expansion of non-native species
0
1000
2000
3000
4000
5000
6000
1990 1995 2000 2005 2010
Ab
un
dan
ce (f
ish
h
a-1
)
Year
Warmer water
Reduction in zooplankton
Increase in roach
Increase in phytoplankton
Reduction in Arctic charr
Reduction in oxygen at
depth
Stronger stratification
Increased internal P-
load
Planktivores
Zooplankton
Phytoplankton
Chemistry
Physics
Changes in Pike diet
Carnivores
Echoes in the ecosystem
Climate change
Creating the model 10 km2 Database and Atlas of Freshwater Fish (1973-1989) + Met Office UKCP09
daily 5 km2 gridded observed mean air temperature (1973-
1989)
Generalised Linear Model (GLM) with binomial
response
Probability of roach presence
Testing the model
Compared model prediction with observed presence (1990-2006; new sites in yellow) using gridded air temperature from that period
Predicted response Percentage
Presence/absence correct 81.9%
Wrongly predicted presence 7.3%
Wrongly predicted absence 10.9%
A probability threshold of 0.876 was optimal for classifying presence or absence of roach
Predicted expansion of Roach habitat
Probability of presence
Air temperature increase (°C)
1 2 4 3
Changed predation on zooplankton?
Pre
dat
ors
G
raze
rs
Foo
d/T
emp
erat
ure
The hypothesis
Climate change
Warmer water
Reduction in zooplankton
Increase in roach
Increase in phytoplankton
Reduction in Arctic charr
Reduction in oxygen at
depth
Prolonged stratification
Increased internal P-
load
Planktivores
Zooplankton
Phytoplankton
Chemistry
Physics
Changes in Pike diet
Carnivores
Mean zooplankton (No. dm-3
)
0
2
4
6
8
10
12
14
16
18
1950 1970 1990 2010
North Basin
South Basin
Bo
tto
m-u
p
Top
-do
wn
Data from 1991-2010 Modelling using GAMS on de-seasonalised data with
each driver allowed to interact with month
Top-down and bottom-up effects on Eudiaptomus
Seas
on
ally
dtr
end
ed E
ud
iap
tom
us
abu
nd
ance
Seasonally detrended fish consumption
Seasonally detrended chlorophyll concn
Top model assessed using
AIC
Changing fish populations
Water temperature
Roach numbers
Zooplankton
density in summer
Phytoplankton (Chla) in summer
Arctic charr numbers
Oxygen concentration
at depth
Arctic charr numbers
30%
4%
12%
6%
Path-analysis for the North Basin (Bayesian belief
network implemented in Winbugs)
Effects on the top predator of changing fish populations?
The hypothesis
Climate change
Warmer water
Reduction in zooplankton
Increase in roach
Increase in phytoplankton
Reduction in Arctic charr
Reduction in oxygen at
depth
Prolonged stratification
Increased internal P-
load
Planktivores
Zooplankton
Phytoplankton
Chemistry
Physics
Changes in Pike diet
Carnivores
The changing diet of pike
Pike percent diet composition in the 1970s and 2000s
• Historically eutrophication has been the major stressor on Windermere
• Currently climate change is altering niches and creating both top-down and bottom-up effects in the lake
• Warming water has ‘echoed through the ecosystem’ increasing the niche for roach with knock-on effects at different levels in the food web
• Climate change is a global phenomenon and so cannot be managed locally. Further nutrient reduction may ameliorate some of the effects of climate change but species at the southern-end of their geographic range are likely to be lost and species at the northern-end will become more abundant.
• There are likely to be ecological surprises as the complex interactions between the external environment and different components of the lake unfold.
Summary
Acknowledgements
• This work was funded by NERC Grant NE/H000208/1: “Whole lake responses to species invasion mediated by climate change” (http://www.windermere-science.org.uk/).
• Many thanks to everyone involved in maintaining the Cumbrian Lakes long-term monitoring programme, past and present.
• Thank you for your attention!
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