Bloom-forming cyanobacteria and dinoflagellates in five Argentinian reservoirs: Multi-year sampling

Abstract

Harmful algal blooms are important threats to reservoir condition. Over a 15-year period, we sampled fiveArgentinian reservoirs to identify the responsible species for harmful algal blooms and determine the waterquality factors driving their occurrence. These reservoirs exhibit diverse morphological and hydrological characteristics and are distributed across varying climatic zones. Cyanobacterial blooms included an array of species,including toxin producers such as Raphidiopsis raciborskii, Aphanizomenon gracile, and Microcystis aeruginosa. Incontrast, dinoflagellate blooms were predominantly characterized by Ceratium. The cyanobacterial blooms primarily occurred in the shallower reservoirs located in warmer regions, whereas dinoflagellate blooms occurredwhere temperatures were lower. The most intense blooms occurred during the summer, and although cyanobacterial and chlorophyte blooms co-occurred, they never coexisted with dinoflagellate blooms. We identifiedcyanotoxins in the reservoirs over the past three years, a phenomenon previously unreported in the region. Giventhat these reservoirs are drinking water sources for human populations, ongoing and systematic monitoring isneeded to protect public health. Controlling the proliferation of algae and cyanobacteria in reservoirs requiresresource management at the watershed level, and in the case of the Itiyuro and El Limon, requires binational management with Bolivia.