This study investigates the effects of time delays and stochastic environmental disturbances on plankton dynamics. To this, we propose and analyze a stochastic model consisting of two toxin-producing phytoplankton-one zooplankton model. The model incorporates nonlinear white noise, (L \(\acute{e}\) vy) noise, and regime switching to characterize environmental variability. Theoretical analyses establish conditions for persistence in the mean and stochastic extinction, while global sensitivity analysis identifies the key parameters affecting plankton density. Numerical results reveal that time delays and environmental fluctuations strongly influence plankton dynamics. Specifically, increased time delay induces a bubble effect, whereas reduced time delay weakens the destabilizing impact of toxin release rates. Strong white noise (L \(\acute{e}\) vy) noise can drive phytoplankton to extinction, while regime switching mitigates this risk and promotes persistence of plankton. Moreover, variations in the growth rate of toxin-producing phytoplankton suppress delay-induced oscillations, suggesting a potential mechanism for controlling phytoplankton blooms. These findings enhance our understanding of plankton persistence, extinction, and bloom formation in fluctuating environments and provide useful insights for ecological management.
