This chapter addresses the growing problem of harmful cyanobacterial blooms (HABs) and their ecotoxicological impacts, emphasizing nonchemical agents. Ecotoxicology, which initially focused on chemical agents, now also considers physical and biological factors responsible for these blooms, such as the uncontrolled growth of cyanobacteria. High temperatures, changes in nutrients, and hydrological changes, aggravated by human activities, intensify the effects of HABs. Rising temperatures, changes in nutrient levels, and modifications in hydrological patterns, exacerbated by anthropogenic activities, significantly amplify the impacts of harmful cyanobacterial blooms (HABs), intensifying their adverse effects on aquatic ecosystems and associated ecosystem services. The chapter discusses how factors such as temperature, precipitation, wind, and solar radiation influence the growth of cyanobacteria and the importance of biological interactions such as allelopathy. Mitigation involves predictive models and bioremediation with microorganisms and aquatic plants. The need for integration between limnology, environmental toxicology, and ecological modeling is highlighted, along with public policies and environmental awareness to prevent the intensification of blooms.