Search

This paper is an outcome of a Lake Modelling Workshop held at Griffith University from 18 to 19 October 2017 and funded through an 'Area of Strategic Investment' in Water Science at Griffith University. We thank the reviewers for constructive comments. M.F. and D.H. conceived the study; M.F. wrote the first draft of the paper. All authors contributed in further writing, reviewing and editing the manuscript. Except from the lead-author and last author, authors are listed in alphabetic order.

Cyanobacteria of the order Nostocales found in lakes in temperate regions are generally assumed to benefit from climate change. To predict their future development under varying environmental conditions, we developed a mathematical model that simulates their entire life cycle. Cylindrospermopsis raciborskii, a tropical species which spread to the northern temperate zone during the last decades, was used as the model organism. We calibrated and validated the model using a 13-year data set on the species' population dynamics gathered in a shallow lake in northern Germany. The predicted values were consistent with the observed data. We used sensitivity studies and Hasse diagrams based on partial order theory to rank the impact of different model parameters on life cycle dynamics. Our results show that the seasonal dynamics of C. raciborskii are mainly determined by the optimum growth temperature of its vegetative cells. The dynamics of pelagic populations in the water and akinete populations (resting stages) in the sediment is highly dependent on lake water temperature and underwater light intensity and, thus, on climatic conditions. Therefore, any future increase in lake water temperature will presumably lead to an increase in the size of C. raciborskii populations in particular and of Nostocales populations in general.