<p>Plankton, comprising phytoplankton and zooplankton, are foundational to marine food webs and biogeochemical cycles, serving as key indicators of ocean health. They drive primary productivity, sustain marine life, and shape distinct ocean regimes. This systematic review, based on literature from 2014 to 2024, applied narrative synthesis to qualitatively examine patterns and themes across studies, aiming to consolidate current understanding of plankton’s role in supporting marine ecosystem function and biodiversity. By analyzing 127 studies from diverse global habitats, we highlighted the critical roles of plankton in supporting fish populations, contributing to mariculture, and maintaining ecosystem balance. Zooplankton species are widely utilized as live feed for cultured fish, underscoring their importance in aquaculture. Environmental stressors, particularly rising ocean temperatures, consistently negatively impact plankton communities. Additional factors, such as hypoxia, altered water currents, and nutrient fluxes—often exacerbated by climate change, significantly affect fish populations and other marine organism’s dependent on plankton for sustenance. This review emphasizes the need for continued monitoring and research to understand the complex dynamics of plankton communities amid accelerating environmental changes.</p>