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Maberly et al 2013 SIL presentation
Climate change is altering the ecosystem of Windermere lake in the following ways: Warming water temperatures have reduced zooplankton populations and increased the numbers and range of roach fish. This has led to bottom-up effects of increased phytoplankton and top-down impacts such as reduced Arctic charr fish and lower oxygen levels at depth. Path analysis indicates the changes have rippled through the food web, impacting top predators like pike fish, whose diets have shifted over time. Climate change represents a global stressor that cannot be managed locally, and further surprises are expected as species ranges shift in the lake's complex interacting system.
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Maberly et al 2013 SIL presentation
- 1. Stephen Maberly, AlexElliott, 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
- 2. Top-down & bottom-upmultiple stressors Maberly & Elliott (2012) Freshwater Biology 57, 233-243 Nutrients (& toxins) Acid (& nutrients) Climate change Natural variability in weather Bottom-up Top-down
- 3. 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)
- 4. Windermere as amodel 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 2010 Year 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 Abundance(fishha-1) Year
- 5. Warmer water Reduction in zooplankton Increase in roach Increasein 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
- 6. Creating the model 10km2 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
- 7. Testing the model Comparedmodel 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
- 8. Predicted expansion ofRoach habitat Probability of presence Air temperature increase (°C) 1 2 43
- 9. Changed predation onzooplankton? PredatorsGrazersFood/Temperature The hypothesis Climate change Warmer water Reductionin zooplankton Increasein roach Increasein phytoplankton Reductionin Arcticcharr Reduction in oxygen at depth Prolonged stratification Increased internalP- load Planktivores Zooplankton Phytoplankton Chemistry Physics Changesin 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 Bottom-up Top-down Data from 1991-2010 Modelling using GAMS on de-seasonalised data with each driver allowed to interact with month
- 10. Top-down and bottom-upeffects on Eudiaptomus SeasonallydtrendedEudiaptomusabundance Seasonally detrended fish consumption Seasonally detrended chlorophyll concn Top model assessed using AIC
- 11.
- 12. Water temperature Roach numbers Zooplankton density in summer Phytoplankton (Chla) in summer Arcticcharr numbers Oxygen concentration at depth Arctic charr numbers 30% 4% 12% 6% Path-analysis for the North Basin (Bayesian belief network implemented in Winbugs)
- 13. Effects on thetop predator of changing fish populations? The hypothesis Climate change Warmer water Reductionin zooplankton Increasein roach Increasein phytoplankton Reductionin Arcticcharr Reduction in oxygen at depth Prolonged stratification Increased internalP- load Planktivores Zooplankton Phytoplankton Chemistry Physics Changesin Pike diet Carnivores
- 14. The changing dietof pike Pike percent diet composition in the 1970s and 2000s
- 15. • Historically eutrophicationhas 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
- 16. Acknowledgements • This workwas 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!