Lakes at risk under climate change: Climate variability matters
Final Report Abstract
Variability in water temperature: Variability in water temperature is not inherently associated with levels of average water temperatures, but tends to higher in summer than in winter at temporal scales from days to years. Variability in ecosystem respiration: The relationship between daily variance in Schmidt stability was consistently positively related to ER (ecosystem respiration) model parameter variance. Wind speed in the range of about 0.8 – 3m s^-1 were consistent predictors of high variance for both GPP and ER model parameter variance, with greater uncertainty in eutrophic lakes. These findings can be used to reduce ecosystem metabolism model parameter uncertainty and identify potential sources of that uncertainty. Cyanobacteria bloom formation: Our results emphasized that not average temperature increase but changes in short-term meteorological variability will determine whether cyanobacteria will bloom more often in a future warmer world. Surpassed critical thresholds in the length of thermally stratified periods determine whether cyanobacteria dominate phytoplankton communities in polymictic lakes. Temporal scale of zooplankton dynamics: Below the 1 year scale, we found evidence for resource competition to be ongoing and zooplankton species may exhibit compensatory dynamics via their temporal partitioning of the growing season. Above 1 year competitive exclusion and zooplankton species replacement may be important processes driving compensatory dynamics. Our results suggest that the processes driving compensatory dynamics may be local in their extent, while those generating synchronous dynamics operate at much larger scales. Overall, results from our performed case studies within LakeRisk confirm the importance of temporal scale in identifying, critical time scales and critical thresholds in order to understand variability in ecosystem responses on various systems levels; temperature, propagating effects on phytoplankton, zooplankton, and lake metabolism.
