Phytoplankton blooms recur across lakes, reservoirs, rivers, coastal oceans, and cryospheric systems, with life cycles shaped by system-specific environmental drivers. This review synthesizes how five universal stages—recruitment, proliferation, persistence, decline, and fate—are expressed across systems, highlighting overlooked contrasts. Recruitment is temperature-driven in stratified lakes but governed by hydrodynamic relaxation in rivers and reservoirs. Proliferation is phosphorus-driven in freshwaters and iron-limited in offshore marine systems, where it can also trigger cysteine synthase-mediated neurotoxin production in diatoms. Persistence reflects more than physiological tolerance: bloom-associated microbiomes buffer nutrient supply and may harbor antibiotic resistance genes under warming. Decline is shaped by residence time: slow-retention systems favor viral lysis and internal recycling, whereas fast-flowing systems favor physical export. Bloom fate is reshaped by plastisphere-associated microbial interactions altering organic matter remineralization and carbon export efficiency. In cryospheric environments, blooms are governed by ice physics rather than liquid-water dynamics: recruitment follows ice-melt release, proliferation depends on light duration under meltwater stratification, decline is triggered by refreezing, and fate is amplified through ice-albedo feedbacks. Despite system-specific controls, bloom progression follows five generalized ecological laws: threshold activation, resource-retention optimization, feedback stabilization, disturbance-driven reset, and ecological legacy propagation. Critical gaps remain—quantitative stage-transition thresholds are poorly constrained, phytoplankton physiological plasticity is rarely incorporated into models, and no framework resolves all five stages across the land-sea continuum. Addressing these gaps require trait-based parameterization, high-frequency observational networks, and coupled lake-river-estuary-coastal forecasting models. This framework provides a mechanistic foundation for transferable bloom prediction under climate change and hydrological regulation.