Surface Temperature Influences the Population of Limnothrissa miodon in Lake Kariba

Abstract

Global warming is a serious world problem where earth’s temperature has been reported to increase over the years; the aquatic ecosystems are also not the exceptions. But, the effects of this phenomenon on the aquatic ecosystems are not well understood. This study aims to understand the influence of surface temperature on the population density of Limnothrissa miodon in Lake Kariba. We constructed a mathematical model on the population dynamics of Limnothrissa miodon with nutrients, phytoplankton, zooplankton, and Hydrocynus vittatus. Lake surface water temperature was modelled by a cosine function, and the parameters were estimated from data fitting. Numerical simulations were used to determine the stability of the nonautonomous model. Numerical simulation results of the nonautonomous model showed a stable periodic orbit for varying initial conditions, and therefore, instability. Numerical techniques were used to investigate the influence of surface water temperature on Limnothrissa miodon. Results from the model with fitted lake surface water temperature data showed that a shift in the optimal temperature for phytoplankton growth from 25°C to 34°C, corresponding to dominance of Cyanophyceae over Chlorophyceae, resulted in a decline in the population density of Limnothrissa miodon. Numerical results showed that the population density of Limnothrissa miodon declines after an optimum temperature of 30°C for phytoplankton growth. Numerical simulation results suggested that warming of the lake may lead to a decline in Limnothrissa miodon population density in Lake Kariba.