Blooming in the Anthropocene: Perspectives on the development of freshwater blooms, changing phytoplankton communities, and mitigation strategies.

Freshwater is a declining natural resource sensitive to anthropogenic impacts on the environment, now exacerbated by climate change and elevated global temperatures. Among modern predicaments associated with the Anthropocene are nuisance and harmful algal blooms (HABs), which typically correlate with eutrophication resulting in the rapid growth and overabundance of planktonic microalgae, including cyanobacteria. Regions of hypoxia are common following bloom collapse, and some species of microalgae produce potent toxins, intensifying environmental impacts. While there has been some success implementing mitigation strategies against common bloom-forming microalgae, their responses to treatments are inconsistent. Routine mitigation can be incredibly costly while not being entirely effective, warranting innovation in mitigation strategies. Ultimately, a significant reduction in nutrient loading has the greatest potential for successful mitigation yet is not feasible due to societal requirements. At present, eutrophication and water pollution associated with bloom events are treated on a case-by-case basis, which can be unique depending on the microalgae present. This review provides a comprehensive summary of nuisance and harmful bloom-forming taxa, driving environmental factors, and existing mitigation strategies unique to freshwater microalgae. The major groups of bloom-forming microalgae are discussed, integrating factors responsible for increasing blooms in a rapidly changing climate, including potential treatment strategies.