The rate of biodiversity loss in aquatic ecosystems in general, and freshwater ecosystems in particular, has increased dramatically over the last several decades. One of the major drivers for changes in biodiversity composition has been climate change. Consequently, the responses of lakes to the effects of global warming are of particular interest for conservation and management. We analyzed long-term observational time series of key properties of a Central European shallow polymictic lake. These data cover a wide range of temporal scales, from the sub-daily to the multi-decadal. We used the data to examine the extent and emporal scale of climate driven changes in water temperature and the resulting effects on the physical and biological properties of these lakes.
Results/Conclusions
After ordering and grouping the data according to their average annual and seasonal warming rates, we found that changes were independently distributed from around mean lake values. We also found no ecological memory effects in shallow lakes, with short-term variabilities of climate and weather conditions having stronger effects on key lake properties than long-term climate trends. These effects were examined by spectral analysis of air temperature and humidity and water temperature. The characterisitic 1/f pattern was interrupted at frequencies corresponding to synoptic weather conditions (ca. 8 days). For time scales under one year the variabilities of the resulting frequency distributions were well explained by log-log regression of variability (power) against frequency ( R2 values of 0.95, 0.94 and 0.92, respectively). We will demonstrate implications of these results for conservation and management issues of shallow lakes under the risk of global change.
