Temperature as a factor affecting fluctuations and predictability of the abundance of lake bacterioplankton

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 themselves. 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 populations, 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 bacterioplankton and temperature time series we show that the chaotic bacterioplankton oscillations are synchronized with water temperature oscillations, while chaotic fluctuations of the phytoplankton abundance are not synchronized with the temperature oscillations in Lake Naroch and Lake Myastro in contrast to the phytoplankton fluctuations in Lake Batorino, the smallest of the Naroch Lakes, where phytoplankton fluctuations are phase-locked by the temperature oscillations. We conclude that temperature is the factor that has significant impact on predictability of the bacterioplankton fluctuations, while dynamics and predictability of phytoplankton dynamics can apparently be controlled not only by the temperature but also by trophic interactions and nutrient supply.