Abstract
Temporary water bodies, especially vernal pools, are the most sensitive to climate change, yet the least studied aquatic environments. Their functioning largely depends on the phytoplankton communities structure. This study aimed to determine how temperature and photoperiod length (simulating inundation in different parts of the year under six climate scenarios) affect the succession and the structure of phytoplankton communities soon after inundation. For longer photoperiods and at lower temperatures in vernal pool microcosms (simulating a cold spring after a warm snowless winter), the phytoplankton community evolved into chlorophytes and cryptophytes. At short photoperiod (inudation in winter, followed by freezing of the water surface) the communities evolved into the euglenoids. Medium temperatures and long photoperiods (late inundation during cool spring) promoted the development of chlorophytes, with high total phytoplankton abundance as well as species richness and diversity. The lack of cyanobacteria dominance, suggests that they will not be the leading group in vernal pools in the temperate zone with progressive global warming. Our study shows that climate change will result in the seasonal shifts of the species abundance or even in their disappearance, and finally in strong changes in the biodiversity and food web of aquatic ecosystems in the future.