Climate induced changes in phenology of lake plankton communities: Implications for the match / mismatch of species interactions
Final Report Abstract
Recent climate warming has induced substantial changes in lake ecosystems across the world. Within the AQUASHIFT project ‘Climate induced changes in phenology of lake plankton communities: Implications for the match/mismatch of species interactions’ (PIs: Rita Adrian and Dieter Gerten) we quantified the extent to which abiotic and biotic lake processes follow abrupt or more gradual patterns of response to climatic changes. The project also addressed the question as to how responses follow a hierarchy, i.e. whether responses of lake physical variables occur rapidly, with more gradual and time lagged responses along the trophic cascade (abiota biota trophic level). Furthermore, we separated direct temperature effects from indirect effects such as changes in ice formation and mixis regime, and separated overlapping effects of climate-independent forces, in order to better understand observed long-term changes in phenology, abundances and composition of plankton communities. We used Müggelsee, a polymictic lake in Berlin, Germany as a case study site. Contrary to current theory long-term response pattern did not follow a hierarchy – the complexity of response at the single system level manifested themselves, however, in clear chronological regime shifts, abiota biota trophic level in spring and, to a lesser extent, in summer. Variables displaying no long-term changes pointed to compensation processes caused by e.g. simultaneously acting forces of warming trends and climate-independent changes in trophic state. In spring, e.g. strong climate-induced shifts in phytoplankton phenology were later influenced by changes in trophic state with a qualitative switch between mechanisms from a bottom-up to a top-down driven collapse of the spring algal bloom. Climate warming is anticipated to favour nuisance blooms of cyanobacteria. We were able to quantify critical thresholds for changes in thermal regime and stability beyond which cyanobacteria bloom formation is indeed supported; given sufficient nutrient availability. Those thresholds can be generally used to mark projections of cyanobacteria bloom formations under future climate scenarios. Our findings also indicate that the plankton response to climate warming, particularly to heat waves, is critically dependent on the detailed system related temporal pattern of elevated water temperatures; e.g. summer zooplankton populations responded to periods of warming in relation to events in the plankton annual cycle rather than to warming at a fixed time in the season. Overall, besides general warming trends the detailed seasonal timing of warming seems to be crucial for plankton community performance in the context of current and future global change. It sure matters when it hits.
Publications
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2006. Life-history traits of lake plankton species may govern their phenological responses to climate warming. Global Change Biology 12:652-661
Adrian, R., Wilhelm, S., Gerten, D.
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2007. Long-term response of Dreissena polymorpha larvae to physical and biological forcing in a shallow lake. Oecologia 151: 104-114
Wilhelm, S. & R. Adrian
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2008. Impact of summer warming on the thermal characteristics of a polymictic lake: Consequences for oxygen, nutrients and phytoplankton. Freshwater Biology 53: 226-237
Wilhelm S. & R. Adrian
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2008. Phytoplankton response to climate warming modified by trophic state. Limnology and Oceanography, 53 (1): 1-13
Huber V., R. Adrian, D. Gerten
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2009. Cyanobacteria blooms: Quantifying the effects of climate change. Limnology and Oceanography 54(6): 2460-2468
Wagner, C., Adrian R.
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2009. Exploring lake ecosystems: hierarchy responses to long-term change? Global Change Biology 15: 1104-1115
Wagner, C., R. Adrian
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2009. Periodically forced food chain dynamics: model predictions and experimental validation. Ecology 90(11): 3099-3107
Steiner, C.F., A.S. Schwaderer, V. Huber, C.A. Klausmeier and E. Litchman
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Lake ecosystem responses to climate warming. PhD thesis, Free University Berlin; May 2009
Wagner Carola
