Resilience and resistance: powers help phytoplankton to keep spatial heterogeneity during long-term intermittent water diversion

How phytoplankton respond to changes in water resource allocations, and whether water diversion cause phytoplankton homogenization remain no incontestable conclusion. Herein the changing rules of phytoplankton communities faced to water diversion were unveiled based on long-term (2011–2019) time-series observation and analysis of algae data of three regulating lakes on the eastern route of the South-to-North Water Diversion Project in China. We found that phytoplankton composition had dramatic differences before and after water transfer; however, after long-term planned water diversion the algal structure — especially for abundant species — gradually became similar to that found in 2014, revealing the community structure was changed by water mixing, and reverted slowly to the initial state after water diversion. Phytoplankton communities exhibited greater fragility when they firstly experienced human-mediated disturbance, while gradually adapted to more interferences and obtained stronger stability. More importantly, we found that the community composition had no homogenization across three lakes after water diversion and resistance and recovery are underlying mechanisms to maintain the community heterogeneity and stability. Moreover, the altered phytoplankton communities in round lakes re-established stable states, while strip-shaped Nansi Lake not, reflecting the strip-shaped lake had slower response and less resilience to the disturbance than the round lakes.