Cyanobacterial blooms are becoming increasingly frequent and intense globally, driven by nutrient over-enrichment, climate change, and anthropogenic disturbances to aquatic ecosystems. These harmful algal blooms (HABs) not only deteriorate water quality but also significantly disrupt aquatic food webs and threaten vital ecosystem services, including fisheries, potable water supply, biodiversity conservation, and recreational opportunities. This chapter provides a comprehensive examination of the ecological and socioeconomic impacts of cyanobacterial blooms, emphasizing their cascading effects across trophic levels and their role in destabilizing ecosystem resilience. Through ecological analysis and global case studies such as those from Lake Erie, Lake Taihu, the Baltic Sea, and the Murray Darling Basin, the chapter offers a holistic perspective on bloom dynamics and their broader environmental implications. The primary aim is to assess the influence of cyanobacterial blooms on aquatic food webs and ecosystem services. Objectives include investigating trophic disruptions, evaluating bloom-related ecosystem degradation in different regions, reviewing modern monitoring and assessment tools, and presenting integrated strategies for management and research. Key findings reveal that cyanobacterial blooms result in biodiversity loss, disrupted nutrient cycling, toxin transfer across food chains, oxygen depletion, and fisheries collapse. They impair provisioning, regulating, and cultural ecosystem services, with case studies illustrating both regional variability and common ecological impacts. The chapter recommends future research focus on long-term ecological monitoring, multitrophic ecological modeling, climate-linked bloom forecasting, and the incorporation of ecosystem services into water governance. Adaptive, precautionary, and cross-sectoral management strategies are essential. In conclusion, cyanobacterial blooms represent a multifaceted environmental challenge. Mitigating their impacts requires an ecosystem-based approach that bridges scientific understanding, technological innovation, and policy integration to ensure the sustainability and resilience of aquatic ecosystems in a changing global climate.