Impacts of a changing environment on a stoichiometric producer-grazer system: a stochastic modelling approach

Internal and external factors on a producer-grazer system are important because these systems underpin many food chains and changes in them are therefore significant for many animal species. In particular, alterations between phytoplankton and zooplankton are important because they represent a vast source of nutriments for aquatic species. However, the impacts of different intrinsic and extrinsic noise on phytoplankton and zooplankton population dynamics are still missing. By applying stochastic methods to a popular stoichiometric model, the influence of internal and external factors on the system are explored, culminating with a proposition of how noise in the system can be used to examine the latitudinal spatial distribution of phytoplankton. This is achieved by expanding the stoichiometric model to account for macro environmental factors that induce noise in the system. First, the population dynamics under the influence of factors, such as predation, wind gusts and temperature, are individually documented in the paper. Thereafter, using the macro environmental factors such as climate change, stochastic simulations generate a spatial distribution in a latitudinal sense of phytoplankton where it is observed that the phytoplankton clusters are blooming at a higher than expected latitude. Therefore, the latitudinal distribution of phytoplankton of these clusters gives further evidence of the influence of arctic amplification.