The document discusses the ecological responses of Windermere, England's largest lake, to various environmental stressors such as nutrient enrichment, climate change, and invasive species over the last 65 years. It highlights how these factors have impacted the lake's food web and resource conversion into algae, complicating conservation and water quality objectives. Acknowledgments are given for the long-term data collected and funding received for this research project.

1. Echoes in the ecosystem: top-down &
bottom-up responses of Windermere to
environmental perturbation
Stephen Maberly, Ian Jones, Stephen
Thackeray, Ian Winfield & Peter Henrys
Lake Ecosystem Group
Centre for Ecology & Hydrology, Lancaster UK
NERC project in association with:
Jonathan Grey & Peter Smyntek- Queen Mary University of London
Project partners:
Mike Dobson- FBA
Chris Harrod- Queen’s University Belfast

2. Windermere
• 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 planned
for Jan or Feb 2012
Photos from
FBA Image
Archive

3. Multiple stressors
Natural variability in weather Schematic of changes in multiple
stressors in Windermere
Acidification Nutrient enrichment
Climate change Invasion of non-native species
Tertiary Detectable
Climate change Sew age w orks
installed
Sulfate
loading treatment change in w ater
Acid declines temperature
(& nutrients) Large No.s of
1 roach detected
Nutrients
(& toxins) 0.8
0.6
Stress
0.4
0.2
0
1940 1950 1960 1970 1980 1990 2000 2010
Year

4. Publications on invasive species & freshwater
Search on Web of Science, May 2011

5. Response to changing P
40
Mean winter TP (mg m-3) Mean Chla (mg m )
-3
35 12
30 10
25
8
20
6
15
10 4
North Basin
5 2 North Basin
South Basin
0 South Basin
0
1950 1960 1970 1980 1990 2000 2010
1950 1960 1970 1980 1990 2000 2010
Year
Year
10
-3 Min O2 at depth (g m-3)
Mean winter SRP (mg m )
30 Max pH
10
8
25 North Basin
South Basin
20 6
9
15
4
10 8
2
North Basin North Basin
5
South Basin South Basin
7 0
0
1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010
1950 1960 1970 1980 1990 2000 2010 Year Year
Year

6. Seasonal patterns of phytoplankton change
Spring Summer
20 North Basin South Basin 20
16 16
Chla in M,A,M (mg m-3)
Chla in J,J,A (mg m-3)
12 12
8 8
4 4
0 0
1960 1970 1980 1990 2000 2010 1960 1970 1980 1990 2000 2010
Year Year
Lines are 3-year moving averages

7. Zooplankton
40 North Basin
18 -3
Mean zooplankton (No. dm ) 1977-1991
16
Mean Zooplankton (No. dm )
1993-2007
-3
14
30
12
10
8 20
6
4 North Basin
2 South Basin 10
0
1950 1970 1990 2010
0
0 3 6 9 12
Month

8. Fish predation?
6000
CPUE (fish (Fish 100 m net-1day ) -1)
50
CPUE 100 m net-1 day
-1
Abundance (fish ha )-1)
5000
40
Abundance (fish ha
-1
4000
30
2
2
3000 20
2000 10
1000 0
1995 2000 2005 2010
Year
0
1990 1995 2000 2005 2010
Year
Largely roach

9. Climate change and roach invasion?
Maitland 1972
Roach
distribution
Mean surface temperature (oC)
12
10
Davies et al. 2004
8
North Basin
South Basin
6 ‘It is not unlikely that these
had been brought as live-
1950 1970 1990 2010 bait for pike, as live-baiting
Year is occasionally done by
strangers.’
(Watson, 1925)

10. Possible consequences for Arctic charr
Catch per unit effort on spawning grounds
100 100 20
North Basin North Basin
Catch per unit effort on spawning grounds
90 90 18
Summer zooplankton (No. dm-3)
80 80 16
70 70 14
60 60 12
50 50 10
40 40 8
30 30 6
20 20 4
Arctic charr
10 Arctic charr 10 2
Summer zooplankton
0 0 0
1950 1960 1970 1980 1990 2000 2010 1950 1960 1970 1980 1990 2000 2010
Year Year

11. • Echoes in the ecosystem
Carnivores
Changes in
Pike diet
Planktivores Increase in Reduction in
roach Arctic charr
Zooplankton Reduction in
zooplankton
Increase in
Phytoplankton phytoplankton
Chemistry Increased Reduction
internal P- in oxygen at
Climate load depth
change
Warmer Stronger
water stratification Physics

12. Mixed layer depth & light availability
Day of year
0
50 70 90 110 130 150
-5
-10
-15
seventies
Depth (m)
-20 eighties
-25 nineties
naughties
-30
-35
-40
seventies
naughties
-45
South Basin

13. Phytoplankton edibility changes?
1000000000
1000000000
Biolvol in JJA of algae < or >50 µm (µm3 cm-3)
>50 um
Average biovolume in JJA (µm3 cm-3)
100000000
100000000 y = 1E+07e-0.152x P<0.05
<50 um R² = 0.155
10000000
10000000
1000000
1000000
100000
100000
10000
y = 306565e-0.065x
R² = 0.174 P<0.05
1000 10000
1950 1970 1990 2010 0 5 10 15 20
Year Zooplankton density in JJA (No. dm-3)
North Basin

14. Path-analysis for the North Basin (Bayesian belief
network implemented in Winbugs)
Roach Arctic charr
numbers numbers
4%
Zooplankton
density in
summer
12%
Phytoplankton
(Chla) in
summer
Oxygen
concentration
Water at depth
temperature 6%
30%

15. Conclusions
• Multiple stressors have affected Windermere over the
last 65 years via top-down and bottom-up processes- the
response of a complicated ecosystem to perturbation is
complex
• Nutrient enrichment has had the major impact but more
recently climate change interacting with expansion of a
non-native species has started to alter the food-web and
the way the lakes converts resources into algae
• Climate change is likely to make the achievement of
water quality and conservation objectives more difficult
and nutrient targets will have to be more stringent

16. Acknowledgements
• We thank the FBA (1945 to 1989) and our
colleagues in CEH/IFE (1989-present) for
(1989-
collecting the long-term data analysed here
long-
• This work was funded by a NERC EHFI grant to
CEH and QMUL
• See our web-page: http://www.windermere-
web- http://www.windermere-
science.org.uk/home