Effect of delay on nutrient cycling in phytoplankton–zooplankton interactions in estuarine system

Phytoplankton–zooplankton interactions with delayed nutrient cycling from senescence and mortality of phytoplankton in Hooghly-Matla estuarine system are considered in this present study. Average numbers of zooplankton interacting with phytoplankton follow Poisson distribution (random zooplankton grazing). The condition for asymptotic stability of steady state is derived. The length of the delay preserving the stability is also estimated. The criterion for existence of Hopf-type small amplitude periodic oscillations of phytoplankton and zooplankton biomass is derived. Delay in the decomposition process of dead phytoplankton from senescence and other mortalities do not affect the stability of the system. All analytical results are interpreted ecologically.