Hydroclimatic drivers associated with an unusual bloom of Microcystis aeruginosa and increase of CyanoHABs in a deep oligotrophic lake

Hydroclimatic and anthropogenic factors in climate change scenarios contribute to ecological changes of harmful cyanobacterial algal blooms in lakes. This study describes the variability of the bathymetric and temporal distribution of cyanobacterial communities in a deep oligotrophic lake. An increase of two to nine in the detection of CyanoHABs potential was observed, likely linked to nitrogen contributions to Lake Rupanco during the last 36 years related to changes in land use and the cultivation of salmonids. We recorded an unusual bloom of Microcystis aeruginosa in winter, 2017 at 30 m during the total mixing period of the lake, associated with the highest N/P index (16.24), the increase of total nitrogen (75 μg/L) and climatic conditions that favored the availability of nitrogen of this cyanobacterium. This study provides information on the causes of increased cyanobacteria in a deep oligotrophic lake. Long-term information on the composition of cyanobacterial communities is very helpful in determining ecological changes.