Tuesday, July 24th, 10:30 Room: C8.2.15 Parallel Session Ecology II DIRECT AND INDIRECT EFFECTS OF TEMPERATURE ON THE DYNAMICS OF LAKE PLANKTON Alexander Medvinsky alexander medvinsky@yahoo.com Institute of Theoretical and Experimental Biophysics, Pushchino, Russia Joint work with Boris Adamovich (Biology Faculty, Belarussian State University, Minsk, Belarus), Rubin Aliev (Institute of Theoretical and Experimental Biophysics, Pushchino, Russia), Amit Chakraborty (Central University of Rajastan, Bandar-Sindri, Rajastan, India), Elena Lukyanova (Biology Faculty, Belarussian State University, Minsk, Belarus), Tamara Mikheyeva (Biology Faculty, Belarussian State University, Minsk, Belarus), Ljudmila Nikitina (Biology Faculty, Belarussian State University, Minsk, Belarus), Nailya Nurieva (Institute of Theoretical and Experimental Biophysics, Pushchino, Russia), Alexey Rusakov (Institute of Theoretical and Experimental Biophysics, Pushchino, Russia) and Tatyana Zhukova (Naroch Biological Station, Belarussian State University, Naroch, Belarus). Keywords : Bacterioplankton, Phytoplankton, Temperature, Chaos, Predictability. Prediction implies the estimation of future states of dynamical systems on the basis of time series. Unavoidable uncertainty in making predictions stems from errors and fluctuations associated with making measurements, and also from the complexity of the dynamics them- selves. To be predicted, the time series have to contain some kind of repeatability, which can be exploited in the course of forecasting. In particular, even irregular time series are often characterized by the repeatability that implies fuzzy recurrences of the states of the system under study. Recently, the recurrence quantification analysis was used in order to assess numerically the horizon of predictability of chaotic fluctuations of the phytoplankton abundance in the Naroch Lakes system consisting of three reservoirs, Lake Naroch, Lake Myastro and Lake Batorino (Medvinsky et al., 2015. Chaos far away from the edge of chaos: A recurrence quantification analysis of plankton time series. Ecol. Complex., 23, 61–67). Here, we present the results of the analysis of the dynamics of bacterioplankton popula- tions, which inhabit the Naroch Lakes. We demonstrate that the dynamics are chaotic. The horizons of predictability of the bacterioplankton dynamics are shown to be equal to 4.8 months for Small Stretch of Lake Naroch, 4.6 months for Large Stretch of Lake Naroch, 4.7 months for Lake Myastro, and 3.4 months for Lake Batorino. Chaoticity of fluctuations in population abundance can be either an immanent feature of the dynamics or be related to environmental influences. In order to evaluate the action of changes in the environment on plankton dynamics, we assessed numerically the extent to which chaotic fluctuations of bacterioplankton and phytoplankton abundances in the Naroch Lakes were synchronized with temperature oscillations. With the use of the analysis of phase relations between