Water column stability driving the succession of phytoplankton functional groups in karst hydroelectric reservoirs

[Display omitted] •Phytoplankton functional group concept was applied in hydroelectric reservoirs.•Phytoplankton community succession exhibits obvious spatial–temporal variation.•RWCS was the key factor for the succession of functional groups. Hydrological conditions are a critical factor for phytoplankton ecology in hydroelectric reservoirs, and how this factor contributes to the succession of phytoplankton functional groups is still unclear. Therefore, we investigated the phytoplankton functional groups, relative water column stability, and related environmental factors in the Wujiang cascade reservoirs to understand this process. Altogether five phyla and thirteen functional groups were identified, and they showed evident variations across space and time. The B, D, P, and J groups were dominant, and the Lo and X1 groups existed only in the reservoirs. Relative water column stability rather than nutrient availability affects the succession and distribution of phytoplankton functional groups in the study area, and high relative water column stability usually increases phytoplankton biomass. This indicates that hydrologic conditions are an important factor controlling phytoplankton composition in hydroelectric reservoirs, and this study enriches the understanding of reservoir phytoplankton ecology.