We analyzed the effects of stratification changes due to wind on the vertical cyanobacteria distribution and microcystin-LR concentrations in a reservoir and assessed the implications for water management. Under stratified conditions, the highest microcystin concentrations (up to 4.16 µg/L) and toxic cyanobacteria biovolume occurred in the epilimnion (~ 1 m). The lowest microcystin concentrations were between 0.02 and 1.28 µg/L and occurred in the hypolimnion (~ 20 m). A cold front passage associated with high wind velocities induced water column mixing, promoting the redistribution of microcystin-LR and cyanobacteria throughout the water column and increasing their concentrations in deeper zones. Microcystin-LR concentration was positively correlated with cyanobacteria biovolume (r = 0.747) and chlorophyll a concentration (r = 0.798). Changes in thermal profile due to wind would imply a greater challenge for drinking water treatment plants, since high cyanobacterial and microcystin concentrations could reach deep-water intakes.

Variación anual de larvas del mejillón dorado (Limnoperna fortunei) en sistemas de refrigeración de centrales hidroeléctricas en embalses del Río Negro, Uruguay Annual variation of golden mussel larvae (Limnoperna fortunei) in refrigeration systems of hydroelectric power plants in Río Negro reservoirs, Uruguay Variação anual das larvas do mexilhão dourado (Limnoperna fortunei) nos sistemas de refrigeração de usinas hidrelétricas em reservatorios do Río Negro, Uruguai