Climatic Factors Influencing the Anthrax Outbreak of 2016 in Siberia,Russia

In 2016, an outbreak of anthrax killing thousands of reindeer and affecting dozens of humans occurred on the Yamal peninsula, Northwest Siberia, after 70 years of epidemiological situation without outbreaks. The trigger of the outbreak has been ascribed to the activation of spores due to permafrost thaw that was accelerated during the summer heat wave. The focus of our study is on the dynamics of local environmental factors in connection with the observed anthrax revival. We show that permafrost was thawing rapidly for already 6 years before the outbreak. During 2011–2016, relatively warm years were followed by cold years with a thick snow cover, preventing freezing of the soil. Furthermore, the spread of anthrax was likely intensified by an extremely dry summer of 2016. Concurrent with the long-term decreasing trend in the regional annual precipitation, the rainfall in July 2016 was less than 10% of its 30-year mean value. We conclude that epidemiological situation of anthrax in the previously contaminated Arctic regions requires monitoring of climatic factors such as warming and precipitation extremes.

     

Effects of individual variability on the outcome of competition between cladoceran species

Simulation modeling was performed to study the impact of individual variability on the population dynamics of particular cladoceran populations and the outcome of interspecific competition at low and high temperatures. The study was performed on one species of small size (Ceriodaphnia quadrangula O.F. Müller) and one species of large size (Simocephalus vetulus O.F. Müller). Laboratory experiments were performed to estimate the average values of principal demographic parameters of these species and their coefficients of variability at two temperatures, 18 and 27°C. Population dynamics of the two species in mono- and mixed cultures was simulated with and without accounting for individual variability using available published data and our own data on demographic parameters. Individual variability was shown to help populations survive unfavorable trophic conditions and to give competitive advantage over populations in which all individuals of the same age are identical. Individual variability decreased with rising temperatures due to probable acceleration of physiological processes.